text:
\section{\label{sec:SI} Supporting Information (SI)}
the exact dimensions of the three-tiered container are listed below.

\redcomment{find new word instead of activity}

\redcomment{With a robotic collective, it is possible to create a material which could generate multiple desired responses, lessening dependence on single use design paradigms}

\section*{Conflicts of interest}
In accordance with our policy on \href{http://www.rsc.org/journals-books-databases/journal-authors-reviewers/author-responsibilities/#code-of-conduct}{Conflicts of interest} please ensure that a conflicts of interest statement is included in your manuscript here.  Please note that this statement is required for all submitted manuscripts.  If no conflicts exist, please state that ``There are no conflicts to declare''.

\section*{Acknowledgements}
We thank Akash Vardhan for experimental assistance, Dana Randall, Andr\'{e}a W.~Richa, and Paul Umbanhowar for helpful discussions.

\balance

\section*{}
\vspace{-1cm}

\footnotetext{\textit{$^{\ast}$~School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA. E-mail: daniel.goldman@physics.gatech.edu}}

\footnotetext{\dag~Electronic Supplementary Information (ESI) available: [details of any supplementary information available should be included here]. See DOI: 10.1039/cXsm00000x/}

\section*{}
\vspace{-1cm}

\footnotetext{\textit{$^{a}$School of Physics, Georgia Institute of Technology, Atlanta, GA 30318}}
\footnotetext{\textit{$^{b}$School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30318 E-mail: daniel.goldman@physics.gatech.edu}}

\footnotetext{\dag~Electronic Supplementary Information (ESI) available: [details of any supplementary information available should be included here]. See DOI: xx.xxxxx/xxxxxxxx/}

\footnotetext{\ddag~These authors contributed equally to this work.}

\begin{figure}[h!]
\centering
    \includegraphics[width=\hsize]{A_Fig01_simExpWormsPics.jpg}
    \caption[Smarticles in simulation and experiment] {\textbf{Smarticles in simulation, biological, and robophysical experiments.} (a) The coordinate system and size designations used for the smarticles. (b) An individual California blackworm (\textit{Lumbriculus variegatus}). (c) An entangled pile of smarticles in simulation. (d) A group of 20 individual blackworms forming a physically-entangled blob. (e) Front view of robotic smarticle used in experiment. Scale bar is 1 cm. (f) Smarticles in experiment.}

    \label{fig:simAndExpPics}
\end{figure}

\section{Introduction}

Physically entangled active matter is an emerging area of both living and man-made systems, where mechano-functionality of the collective emerges through physical interaction of individual elements. These are different from flocks of birds or swarms of fish that are not physically connected into an amorphous emergent material~\cite{2016Hu}. Biological examples includes cellular slime molds, insect assemblages and worm blobs, where the dynamics of the individual agent (cell, ant or worm) contributes to emergent functionality of the collective (slugs, rafts or blobs)~\cite{2012Reid,Mlot2011,2021Ozkan-Aydin}. Synthetic or biohybrid systems include xenobots~\cite{2021blackiston,2020kriegman}, acto-myosin assemblies~\cite{2014Dumont,1997Ndelec,2001Surrey}, granular materials~\cite{Gravish2012}, stochastic robot collectives~\cite{2021boudet,2019Li}, and super-smarticles~\cite{2019Savoie}. In contrast to biological counter-parts, robotic active matter systems are limited to spheroidal elements (low-aspect ratio), low density, non-interacting particles, or weakly actuating elements.
Thus, P.W. Anderson's famous observation that 'More is different' remains true, and foundational understanding through both theory and experiments that can guide bottom-up mechano-functional entangled active matter systems remains tantalizingly elusive~\cite{1980Anderson}.

In soft condensed matter systems composed of particle ensembles, it is known that particle shape can influence rheological and structural properties like viscosity~\cite{Hsueh2010,Brown2011,Egres2005}, yield-stress~\cite{Brown2011,Kramb2011,murphy2019,nelson2019}, packing density~\cite{Man2005,Desmond2006,Miskin2014,Trepanier2010,Blouwolff2006}, and packing stiffness~\cite{miskin2013}. In granular media for example, there has been some research in the evolution of the macroscopic state dynamics. Most research was performed with external loading~\cite{Gravish2012,murphy2019}; however, less is known about how structural properties evolve as particle shape evolves, despite such transitions existing in nature (as in ant systems, in cytoskeleton and f-actin, in polymer rheology, and in aquatic worm blobs)~\cite{Gardel2003,foster2014,Mlot2012,mcleish2008,lieleg2009, 2021Ozkan-Aydin, 2021Nguyen, 2020aDeblais, 2020bDeblais}. In this work, we focus on an active matter system composed of shape-changing particles, where as we demonstrate below, rich and non-intuitive material physics can be uncovered. How macroscopic material properties are affected by the microscopic movements of its constituents is under-studied\cite{henein2007}. Moreover, for many-agent systems where elements can actuate, much of the research is either limited to planar systems\cite{garcimartin2015,zheng2009}, or are low density or non-interacting three-dimensional systems \cite{michael2006,kelley2013}. Yet as both computational units and actuating elements become smaller and cheaper, smaller and more highly interactive robotic systems may become more commonplace.

In this paper, we seek to discover and understand the independent formation of solid or semi-solid structures by an
open-loop dynamic collective. Using simulation, we examine how material properties change for a collective composed of dynamic particles whose form (a three-linked two degree-of-freedom shape) is based on the robotic particle called smarticles~\cite{Savoie2019,Savoie2018}. By implementing different shape-altering procedures, and probing the final structures, we gain insight into possible material properties attainable for future real-world robotic systems. Using stress-strain tests on an entangled chain of smarticles, we discover various properties related to their emergent auxeticity. Finally, we compare a few of these properties to biological experiment using California blackworms (\textit{Lumbriculus variegatus)}, whose collectives demonstrate a non-trivial macroscopic rheological analogue with features and properties from microscopic entanglement~\cite{2022Tuazon, 2021Ozkan-Aydin, 2021Nguyen}.

\section{Materials and methods}
To test the material properties of non-convex granular aggregates, we constructed a three-link robot in simulation Fig.~\ref{fig:simAndExpPics}(a,c) in robophysical experiments Fig.~\ref{fig:simAndExpPics}(e,f), and compared it to the entangled collective behavior demonstrated by blackworms Fig.~\ref{fig:simAndExpPics}(b,d).

\subsection{Multibody simulation of smarticles}
\label{sec:smartSim}
We developed a multibody simulated model of many staple-shaped three-link particles (henceforth called ``smarticles''), Fig.~\ref{fig:simAndExpPics}(a), capable of actuating their outer links. The smarticle's form was inspired by Purcell's three-link swimmer~\cite{Purcell1977,hatton2013} and the size was inspired by previous work from Gravish et al.~\cite{Gravish2012}. Two outer links (or barbs) are connected to a middle segment by rotational actuators, making the smarticle a planar system with two degrees-of-freedom. The middle link is of width $w=1.17$ cm and the barbs are of length $l=[0-1.1]w$ (all simulation parameters are shown in Tab.~\ref{tab:simPars}). The multibody simulation was implemented using ProjectChrono~\cite{ChronoWebsite,Tasora2015}, an open-source physics dynamics engine.

Since smarticles can actuate their barbs to specific positions, each motor is velocity-controlled with a maximum allowable torque. Smarticle barbs are controlled to move with an angular velocity of $\omega = 6$ rad$/$s. The maximum allowable torque, $\tau_{max}$, was set to the torque required to lift a mass equivalent to a smarticle of $l/w=0.7$, a distance $w$ away from the actuator's axis. For $\tau_i \geq \tau_{max}$, the $i$th barb's movement was halted until the first time step where the condition $\tau_i<\tau_{max}$ was satisfied.

Each simulation consisted of three phases: a deposition phase Fig.~\ref{fig:2a}(a), an activity phase, and a final testing phase for certain simulations. A relaxation period was added between each activity phase (when energy is added to the system) and testing phase. During this period, no activity is added to the system. We chose a relaxation period of 0.5 seconds, which was we determined to provide sufficient amount of time for the system to settle. In the deposition phase, smarticles were given a random initial and rotation position, and were released to fall by gravity into a hollow cylinder of radius $r=2w$. All barbs were held static at the position: $(\alpha_1,\alpha_2)=(\pi/2,\pi/2)$ during this phase (see Fig.~\ref{fig:simAndExpPics}(a)). The activity phase began once all smarticles were deposited in the system. This phase was responsible for changing the material properties of the collective by affecting the average entanglement between smarticles Fig.~\ref{fig:2a}(a,b). We define entanglement as the interpenetration of concave particles.

In the activity phase, activity was added to the system in one of three ways, where each active procedure represented a categorically different type of motion: an external sinusoidal oscillation of the confining cylinder (``externally oscillated'') Fig.~\ref{fig:2a}(c), a single cycle of a large angular change of each particles' barbs (``shape-change'') Fig.~\ref{fig:2a}(d), and finally, many small amplitude oscillations of each particles' barbs (``internally oscillated'') Fig.~\ref{fig:2a}(e). In the externally oscillated procedure, the container was shaken with a peak acceleration $\Gamma=2$ (in units of gravitational acceleration $g$) at $f = 30$~Hz and oscillated for 20~s (600 cycles) Fig.~\ref{fig:2a}(c). The shape-change procedure represented large amplitude movements. In shape-change simulations, the barbs were given 1.5 s to actuate from $(\alpha_1,\alpha_2)=(90^{\circ},90^{\circ})$ to $(\alpha_1,\alpha_2)=(0^{\circ},0^{\circ})$, then another $1.5$ s to actuate back to their original position $(\alpha_1,\alpha_2)=(90^{\circ},90^{\circ})$ (Fig.~\ref{fig:2a}(d)). The internally oscillated procedure represents small amplitude vibrational motion. The arc length traveled by the barbs' tips, for a given degree amplitude $\theta$, was constant for all $l/w$ in the internally oscillated trials. Each barb's tip displaced a distance equivalent to the arc length traveled by an arm of length $l$ with $l/w=0.7$ an amount $\theta=\pm [5^{\circ},30^{\circ}]/2$ (Fig.~\ref{fig:2a}(e)) from the original $(90^\circ,90^\circ)$ position. This ensured that the arc length traced by the barb tip was equal, for all $l/w$, at a single oscillation amplitude $\theta$.
The activity phase in the internally oscillated procedure lasts 5 s before any subsequent procedures start. These various methods were used to encourage higher entanglement than that achieved from only deposition. Following the activity phase was a testing phase.

In the testing phase, we performed a casting test, which examined qualitative material properties of a collective after smarticle activations. In summary, after smarticles were deposited in a container of a certain shape and activated, the container walls were removed for testing.

In all the simulations, the range of aspect ratios tested in the smarticle system for all procedures was  $l/w \in [0.4,1.1]$. For the internally oscillated system, the oscillation amplitude was $\theta \in [5^\circ,30^\circ]$.

\begin{figure}[h!]
\centering
    \includegraphics[width=\hsize]{A_Fig02_procedures}
    \caption[System entanglement procedures]{\textbf{Various smarticle activation procedures, internal and external.} (a) Render of simulated smarticle system deposited into a closed container of radius $r=2w$, one side is shown open to enhance visualization. (b) Rendering of 4 smarticles entangled together, here $\langle N\rangle=1.5$. (c) Externally oscillated procedure, particles are deposited into system and container is shaken sinusoidally, parallel to gravity, such that $z(t)=A \sin{(2\pi ft)}$. (d) In the shape-change procedure, smarticle barbs travel $\pi/2$ outwards and return back to the original position, this position change happens a single time in this procedure. (e) Internal oscillation procedure, particle barbs oscillate an amplitude $\theta$ centered around $(\alpha_1,\alpha_2)=(\pi/2,\pi/2)$.}
\label{fig:2a}
\end{figure}

\begin{table}
\small
\caption[Smarticle chain simulation parameters]{simulation parameters}
\label{tab:simPars}
\begin{tabular*}{0.48\textwidth}{@{\extracolsep{\fill}}ll}
\hline
parameter & value  \\
\hline
$w$ & 1.17 cm  \\
$dt$ & $2 \times 10^{-4}$ s  \\
$f$ & 30 Hz \\
$\Gamma$ & 2 \\
$\rho$ & 7850 kg/m$^3$\\
$\tau$ & 1  \\
$\omega$ &  6 rads$/$s\\
$t_1$ & 1.27 mm\\
$t_2$ & 0.5 mm \\
$\mu_{particle-wall}$ & 0.4\\
$\mu_{particle-particle}$ & 0.4\\
$r$ & 2$w$\\
$H_T(t_i)$ & $20 t_2$\\
$H_B(t_i)$ & $10 t_2$\\
\hline
\end{tabular*}
\end{table}

\subsection{Robophysical experiments of smarticles}
To test the physical attributes of a configurable chain of non-convex granular materials, three-link robots were built~\cite{Savoie2018,Savoie2019}. These robots, called ``smarticles'', are shown in Fig.~\ref{fig:simAndExpPics}(c,d,f). The arms are controlled by two servos (Power HD, HD-1440A) to a precision of ($<1^{\circ})$ and with an accuracy of $\pm6^{\circ}$. All processing and servo control is handled by an Arduino Pro Mini 328 - 3.3 V 8 MHz. Each robot is powered by a $3.7$~V $150$~mAh $30$~C LiPo battery (Venom;Rathdrum, ID.).

Due to the size of the servos and the thickness of the body Fig.~\ref{fig:simAndExpPics}(e,f), the dimensions of the smarticles prevented it from performing 3D entangling tests mentioned in Sec.~\ref{sec:smartSim}; the thickness of a robotic smarticle's center link limits the number of simultaneous particle interpenetrations, Fig.~\ref{fig:simAndExpPics}(e) and Fig.~\ref{fig:2a}(b).
Despite this shortcoming, we found interesting results for these smarticle robots in 2D tests which depend on their non-convex nature.

The u-shaped particles, when strained, produce auxetic behavior because of their concave shape. Furthermore, the strength of a ``chain'' of smarticles, defined by its resistance to fracturing under strain, is affected by the confinement of the chain.

\subsection{Comparing multibody simulations to nature}
\label{sec:worms}
We compared smarticle simulations to emergent physically-entangled behaviors demonstrated by blackworms. Outside of their natural granular or detritivorous habitat, these worms entangle together forming a highly dense worm blob (Fig.1d) due to their thigmotactic behavior~\cite{2015Timm, 1990Drewes}. Furthermore, depending on the oxygenation of their surrounding, blackworms can disentangle their tails from the collective and lift it up to supplement respiration in hypoxic, or low dissolved oxygen (DO), conditions~\cite{1990Drewes, 2015Timm}. By altering the dissolved oxygen in a container, we can vary the entanglement strength displayed by a worm blob and observe its emergent dynamics. We define low and high DO as <2 mg/L and >8 mg/L, respectively.

\subsubsection{Animals}

We purchased, reared, and habituated blackworms as described in Tuazon, et al. The experimental setup and data analysis is also the same \cite{2022Tuazon}. For the toppling experiment, blackworms were placed in a 250 mL cell culture flask with 100 mL of filtered water. We used MATLAB to generate the kymographs that tracts its center-of-mass (CoM) height as a function of time. Using blackworms for experiments do not require approval by an institutional animal care committee.

\section{Results and Discussion}
\subsection{Simulation}
\label{sec:sim}
\subsubsection{Packing fraction for an externally forced smarticle collective}

\begin{figure}[!ht]
\centering
    \includegraphics[width=\hsize]{A_Fig03_ExtOscPhi}
    \caption[External oscillation packing fraction and simulation calibration]{\textbf{Packing fraction and packing evolution as a function of smarticle aspect ratio.} (a) $\phi$ vs. time for various smarticles aspect ratios. The inset is a zoomed in version of the data from $l/w=1.1$ over a 0.25 s domain.

    (b) $\phi$ as a function of aspect ratio in experiment (orange) and simulation (blue). The bottom two curves represent the volume fraction before activity was added to the system $\phi_0$ in both simulation and experiment. The top two curves are the volume fraction after external forcing $\phi_f$. The orange curves were taken from data used in Gravish et al.~\cite{Gravish2012}}.
    \label{fig:externalPhi}
\end{figure}

We began by testing how smarticle collectives pack when subjected to an external vibration. In granular material studies, compaction, or volume fraction, is a commonly measured material property~\cite{Callister2014}. Volume fraction, or $\phi$, is defined by $\phi=V_p/V$, where $V_p$ is the solid particle volume and $V$ is the volume of the collective. $\phi$ can greatly affect how a granular collective reacts to external perturbations~\cite{Gravish2014,Agarwal2019}. For a non-ordered system of spherical particles, $\phi$ will generally be in the range between random loose packing (rlp) and random close packing (rcp) values. $\phi_{rlp}\simeq 0.56$ is the lowest density arrangement of spheres that is capable of enduring stresses~\cite{Scott1969,Andreotti2013}, and $\phi_{rcp}\simeq0.64$ is the highest possible value for randomly packed systems~\cite{Onoda1990,Andreotti2013}. The highest possible packing for ordered mono-disperse collections is  $\phi_{max}=\frac{\pi}{3\sqrt{2}}\simeq 0.74$~\cite{wells1991}.

We tested how $\phi$ evolves for a collective undergoing external oscillation. Fig.~\ref{fig:externalPhi}(a) shows how $\phi$ evolved over time for different aspect ratios. As $l/w$ increases, the initial and final volume fraction, $\phi_0$ and $\phi_f$ respectively, also increases. The inset in Fig.~\ref{fig:externalPhi}(a) shows $l/w=1.1$ with $t\in [12.375 s,12.625 s]$, the oscillations in the inset are consistent with the applied oscillation frequency $f=30$ Hz. Furthermore, the rate at which $\phi$ increases, as a function of $l/w$, is faster than linear, which is illustrated more clearly in Fig.~\ref{fig:externalPhi}(b). This is true for both the $\phi_0$ and $\phi_f$. Fig.~\ref{fig:externalPhi}(b) shows a comparison of our simulation to results from a similar experimental system~\cite{Gravish2012}. Both $\phi_0$ and $\phi_f$ are monotonically decreasing functions of $l/w$. Our simulation results agree with the experimental system.

\begin{figure*}[ht]
\centering
\includegraphics[width= 174mm]{A_Fig04_SCandVibFill}
\caption[Packing behavior for different procedures]{\textbf{Packing behavior distinctions between two different active procedures.} (a) Renders of a shape-change trial at three times. (b) The center-of-mass (CoM), $\frac{h(t)}{h_0}$,  in the z-plane of the shape-change collective, the times of the renders in (1,2,3) are highlighted with black points $[1s, 2.5s, 4.5s]$. (c) Renders of an internally oscillated trial at three times. (d) The CoM in the z-plane of the internally oscillated collective, the times of the renders in (1,2,3) are highlighted with black points $[1s, 3.5s, 6s]$.}
\label{fig:activePacking}
\end{figure*}

\subsubsection{Packing fraction for a smarticle collectives with internal degrees-of-freedom}

In the following trials, we examine packing evolution for internally activated smarticles. In Fig.~\ref{fig:activePacking} we introduce the effects of internal activations by showing the time evolution of a single trial for the different activation procedures. In Fig.~\ref{fig:activePacking}, we show three different frames from a shape-change activation procedure. In Fig.~\ref{fig:activePacking}(b), we show both the CoM height in addition to the inset containing the volume fraction. In the shape-change procedure, the final collective's shape fills the container differently with time as shown in Fig.~\ref{fig:activePacking}(a.1-3). The dynamics of the procedure are better captured by both the CoM height and $\phi$ evolution in the shape-change procedure. As the shape-change is initiated, we see a rapid increase of $h$. This increase results from the smarticles straightening. As the second shape-change phase happens, there is an initial decrease in height as smarticles curl into the u-shape.

The smarticle collective's height does not decrease to the initial height of $h_0$, despite all constituents being in the same shape as deposited. Since the number of smarticles does not change during a trial, the change in height suggests that the procedure has changed the macroscopic state. After performing the shape-change procedure, the smarticles were not as well-molded or sculpted to the container as before. This suggests that the shape-change activation tends to force the smarticles away from the container wall as they transition back to the final u-shape. This inwardly-directed movement during the activation indicates an inwardly pointing attractive force. We suspect that the origin of the force arises from the geometry of the smarticle's final shape, as well as from the confining walls. The now excluded volume between the outer walls and curled smarticles drives the collective upwards, increasing its height after the initial drop after point 2 in Fig.~\ref{fig:activePacking}(b).

The internally oscillated smarticles affect the collective differently than the shape-change procedure, Fig.~\ref{fig:activePacking}(c). As the smarticles vibrate their barbs, the smarticles interact with their neighbors, which causes them to rotate and displace. This allows particles to siphon into empty spaces that may exist between neighbors. Since gravitational force points downward, most rearrangement tends to lead to the compaction of particles until an equivalent $\phi_{rcp}$ for the smarticle shape is approached. As the general action fills voids, the collective tends to decrease in height and becomes denser. This increase in density means that the smarticle collective is molding more closely to the container boundary; thereby producing a final height of less than $h_0$. In Fig.~\ref{fig:activePacking}(d), we see that the majority of the compaction happens rapidly, in fact, the first 50\% of the final compaction is reached after only $\approx12\%$ of the total activation time has elapsed.

Next, we look at how the geometry of the smarticles, as well as the amplitude of their movements, affects the packing state of each system. In the shape-change procedure, $\phi$ generally decreases as the aspect ratio increases (Fig.~\ref{fig:SCphiEvolution}). Past $l/w>0.6$, $\phi$ monotonically increases (rather than increasing for a short time) then decreases. This behavior suggests at the existence of a critical packing fraction, which likely existing between $0.7<l/w_{crit}<0.6$.

The internally oscillated procedure is affected similarly as the shape-change with regards to the aspect ratio $l/w$. In Fig.~\ref{fig:VibPhiEvolution}(a) $\theta=10^\circ$ is held constant, and just as with the shape-change procedure, $\phi$ of the internally oscillated procedure decreases with increasing $l/w$. $\Delta \phi=\phi_f-\phi_0$ also increases with increasing $l/w$. For a given smarticle in a collective, as the barbs get longer, the number of neighboring smarticles it interacts with will generally increase. During internally-activated procedures, longer barbs tend to create more overall motion in, and of, the collective. The increased motion, or collective ``temperature'', tends to rearrange smarticles when space is available. For the simulation, at a given $\theta$, the arc length traveled by barb tips is constant for all $l/w$. This explains why the oscillations in $\phi$ tend to decrease as $l/w$ the oscillation frequency increases as $l/w$ increases.

Given a constant $l/w=0.7$, in Fig.~\ref{fig:VibPhiEvolution}(b) we vary oscillation amplitude $\theta$. We find that $\phi$ decreases as $\theta$ increases. As oscillation amplitude increases, larger vacancies form between neighbors, but the larger $\theta$ hinders flow into the temporary vacancies made by the barb motion. While $\theta$ increases, $\Delta \phi$ decreases as well.

Finally we compare how $\phi_f$ varies with $l/w$ for all activation procedures (Fig.~\ref{fig:phiCompareAll}(a-b)). The internally oscillated procedure tends to pack more densely, whereas shape-change tends to pack the least densely Fig.~\ref{fig:phiCompareAll}(a). Among various oscillation amplitudes, lower amplitudes tend to pack more tightly than larger amplitudes Fig.~\ref{fig:phiCompareAll}(b). Indeed, the largest amplitude shows only a marginal increase in $\phi$ compared to the static system, where there is no smarticle activation after the deposition phase (Fig.~\ref{fig:phiCompareAll}(a)).

\begin{figure}[!t]
\centering
    \includegraphics[width=\hsize]{A_Fig05_SCphiEvo}
    \caption[Evolution of packing fraction at different aspect ratios for the shape-change procedure]{\textbf{Evolution of $\phi$ at different $l/w$ for the shape-change procedure.} Time evolution of $\phi$ for varying $l/w$ performing the shape-change procedure. The vertical dashed line represents denotes when the "straight" to "u" configuration change begins.}
    \hfill \break
    \label{fig:SCphiEvolution}
\end{figure}

\begin{figure}[t!]
\centering
    \includegraphics[width=\hsize]{A_Fig06_VibPhi}
    \caption[Evolution of packing fraction at different aspect ratios]{\textbf{Evolution of $\phi$ at different $l/w$ for the internally oscillated system.} Time evolution of $\phi$ for for various $l/w$ (a) and $\theta$ (b) for the internally oscillated procedure. (a) $l/w$ is varied  while $\theta=10^\circ$ is held constant. (b) $\theta$ is varied while $l/w=0.7$ is held constant.}
    \label{fig:VibPhiEvolution}
\end{figure}

\begin{figure}[t!]
\centering
    \includegraphics[width=\hsize]{A_Fig07_AllPhi}
    \caption[final packing fraction for all system procedures]{\textbf{$\phi_f$ fraction for the various procedures.} (a) $\phi_f$ versus $l/w$ for all procedures. For the internally oscillated procedure, $\theta=10^\circ$ was used. (b) $\phi_f$ versus aspect ratio for the internally oscillated system, each line is has a different $\theta$.}
    \label{fig:phiCompareAll}
\end{figure}

\subsubsection{Energy comparison between procedures}
To clarify the cost of each procedure in terms of energy input to packing output, we measured the energy necessary to complete each procedure. This test was performed for smarticles of varying aspect ratio. Each simulation was performed three times for each preparation style at each aspect ratio and oscillation amplitude when applicable.
To calculate the energy of the active procedures,  the following calculation was performed at each time step,
\begin{equation}
E=\int_{\alpha_1(t)}^{\alpha_1(t+dt)}\tau_1 d\alpha_1 + \int_{\alpha_2(t)}^{\alpha_2(t+dt)}\tau_2 d\alpha_2
\end{equation}
where the subscripts correspond to the barbs on each smarticle. Here, $\tau_i$ is the motor reaction torque on barb $i$. Since the energy is added into the system for the externally oscillated system,  we sum

\begin{equation}
E=\int_{z(t)}^{z(t+dt)}F(t)dz
\end{equation}
over each time step during the shaking process. Here $F(t)$ is the reaction force on the linear actuator (which controls the height of the container with the smarticles) motor at time $t$, and $z(t)$ is the distance traveled by the cylinder at time $t$. The contribution of the container's weight was removed from the force calculation.

Fig.~\ref{fig:sysCompare}(a) reveals that the shape-change procedure requires the most energy to perform, regardless of the aspect ratio. Indeed, shape-change required greater than an order of magnitude increase in energy compared to the internally oscillated procedure, which required generally the lowest amount of energy. Plotted in Fig.~\ref{fig:sysCompare}(a) are all oscillation amplitudes in the internally oscillated procedure. As $\theta$ increases, the energy required to perform the procedure also increases. Similarly, the energy to perform the procedure increases with $l/w$ with the exception of local maxima at $l/w=0.9$.
Plotted in Fig.~\ref{fig:sysCompare}(b) is the energy as a function of oscillation amplitude for various aspect ratios. Apart from
$l/w=0.9$, energy tends to increase with amplitude. Next, given each procedure's energy expenditure, we measure how the average entanglement in the collective varies for each procedure.

\begin{figure}[!ht]
\centering
    \includegraphics[width=\hsize]{A_Fig08_Energy}
    \caption[Comparing energy usage between procedures]{\textbf{Comparing energy usage between procedures.} (a) Comparisons of energy output for different procedures as a function aspect ratio. The internally oscillated data are the unlabeled lines where $\theta$ is varied. All data points are averaged from three trials. (b) Energy usage for the internal oscillation procedure as a function of $\theta$ with a constant $l/w=0.7$.

    }
    \label{fig:sysCompare}
\end{figure}

\begin{figure}[!]
\centering
    \includegraphics[width=\hsize]{A_Fig09_Entangle}
    \caption[Comparing entangling procedures]{\textbf{Comparing entangling procedures.} (a) Comparisons of entanglements for all procedures at various aspect ratios. The internal oscillation line for each point has an amplitude $\theta=10^{\circ}$. (b) Entanglement with respect to $l/w$ for the internally oscillated system. (c) Entanglement as a function of $\theta$ for internally oscillated systems.}
\label{fig:systemEntangles}
\end{figure}

\subsubsection{Entanglement}
Since entanglement is affected by aspect ratio in externally activated procedures, we examine how it changes for internally activated procedures. After the collective has performed a procedure, the average number of entanglements, $\langle N\rangle$, between smarticles was measured. $\langle N\rangle$ was measured for the non-actuated (or static) procedure, the shape-change procedure, and the internally and externally oscillated procedures. $\langle N\rangle$ was determined as follows: for each smarticle A, there exists a plane defined by its 3 links. The number of smarticle links, not belonging to A, which intercepts smarticle A's plane is $N$. The mean of all $N$, over all smarticles in a single timestep, is $\langle N \rangle$ (see Fig.~\ref{fig:systemEntangles}(a) inset).

While entanglement is largely independent of aspect ratio in the static, or inactive, procedure, it is more dependent on aspect ratio in the active procedures Fig.~\ref{fig:systemEntangles}(a). Apart from the shape-change procedure, all other active procedures tend to display a maximum of $l/w \approx 1.0$. As $l/w$ increases, the barbs increase in size, thereby requiring more movement between two entangled components to become disentangled. Larger barbs make disentangling more difficult, this is true for an even greater degree in confined systems. Although smarticles with larger $l/w$ will remain entangled more readily, they are less likely to become entangled~\cite{Gravish2012}. The shape-change system does not have this issue: the entangling action happens during the straight to u-shape transition. During this time, a barb's length does not act to restrict a new entanglement from arising, as the smarticle shape starts from a convex (straight) shape. Therefore, higher values of $l/w$ increase the likelihood of entanglements happening in the shape-change system, as the area defining interpenetration is larger.

\begin{figure*}[ht]
\centering
    \includegraphics[width= 174mm]{A_Fig10_SCandVibRemove}
    \caption[Falling behavior for different ]{\textbf{Melting behavior for active procedures.}(a,c) Renders of a shape-change trial and internally oscillated trial, respectively, at three instants. (b,d) The center of mass (CoM), in the z-plane, of the collective; the three renders from (a,c) are indicated with black points.}
    \label{fig:activeWallRemove}
\end{figure*}

\begin{figure*}[!hb]
\centering
    \includegraphics[width= 174mm]{A_Fig11_sculpting}
    \caption[Smarticle aggregate sculpting capabilities]{\textbf{Smarticle aggregate sculpting capabilities.} (a) Particles are deposited a three-tiered system with $l/w=0.8$ with each tier smaller than the one below. In (b), after the activation state has occurred, (top is internally oscillated at $\theta=10^\circ$ and bottom is the shape-change) the outer walls are removed. After the particles are activated, the walls are removed. (c) The piles one second after the container is removed for the internally oscillated (top) and shape-change (bottom).

    }
    \label{fig:sculpting}
\end{figure*}

Now we examine how $\theta$ and $l/w$ affect $\langle N \rangle$ in the internally oscillated system. In these trials, we measured entanglements over $\theta=[5^\circ- 30^\circ]$ for all $l/w$ in Fig.~\ref{fig:systemEntangles}(b). At $l/w<0.7$, as $\theta$ increases, the number of entanglements decreases. At larger $l/w$, $\langle N\rangle$ becomes more independent of $l/w$. The functional form of entanglement, as a function of amplitude, changes as aspect ratio increase. At low aspect ratios, $l/w=[0.4-0.5]$, the curve is monotonically decreasing. However as $l/w$ increases, the curve is no longer monotonic: the peak forms between $\theta=[10^\circ-15^\circ$]. As barbs increase in size, the location of the peak increases too. Furthermore, the peak's relative amplitude to the rest of the curve also increases. We posit that this is related to the argument stated before: at low $l/w$, there is an increased likelihood to both entangle and to disentangle; the barbs can break the entanglements faster than new ones are generated. However, if the arms are longer, the same arc length traveled will not tend to disentangle an existing connection. The amplitude, as well as the energy threshold that is necessary to break pre-existing bonds, is larger.

The static system (not shown in the energy plot) has zero energy input, and the $\langle N\rangle$ is the lowest for all aspect ratios measured. The internally and externally oscillated procedures have similar energy inputs; although the internally driven system is slightly lower. In the internally driven system, however, the number of entanglements measured after the deposition phase is noticeably higher. Aside from requiring different amounts of energy to prepare each procedure, each procedure also tends to impart different collective attributes. Since entangling allows a collective to support tensile loads, next we test how well each procedure allows a collective to both sculpt in a cast, and keep its shape after the cast is removed.

\subsubsection{Melting behavior}
We check the qualitative differences between collections of smarticles after each procedure was performed and after the confining walls were removed. Inspired by heat-treatment annealing procedures in metallurgy and their effects on a metal's final hardness properties during fast and slow cooling, respectively, we test how shape-change and internal oscillation change the properties of the collective~\cite{Callister2014}. Furthermore, we study how these preparation procedures allowed cohesive smarticle collectives to be sculpted by the container.

After the deposition and activation of smarticle collectives, in Fig.~\ref{fig:activeWallRemove}(a-d) we removed the outer boundary and examine how the unconfined collective settles. The shape-change system, Fig.~\ref{fig:activeWallRemove}(a-b), does not break apart nor do the particles on the periphery disengage from the collective: the collective holds firmly together. Since shape-change narrows the base and increases the height, this procedure tends to produce less stable structures. Indeed, in the illustrated example, the structure falls onto its side in Fig.~\ref{fig:activeWallRemove}(a.3). The internally oscillated system reacts differently than the shape-change system when the confinement is removed. Since the internally oscillated procedure increases in $\phi$, lowering the height of the collective and keeping the initial width, the stability of the final collective is improved compared to the initial state after deposition. However, because the amount of entanglement was lower than in the shape-change procedure after the walls were removed, some smarticles on the outer edge slough off as they are not entangled tightly with neighbors in the structure. In the next section, we will look in more detail at structure forming using these two procedures.

\afterpage{\FloatBarrier}
\afterpage{\clearpage}

\subsubsection{Casting}
Here, we show how certain shapes are formed or sculpted through the activity of the smarticles in the collective. Starting in the u-shape position, we deposited smarticles into a three-tiered empty structure with each tier smaller than the one below (Fig.~\ref{fig:sculpting}(a). After depositing the smarticles, the smarticles are activated using the two aforementioned internal activation procedures: internal oscillation in Fig.~\ref{fig:sculpting}(b-top) and shape-change in Fig.~\ref{fig:sculpting}(b-lower). The container serves to define the final shape.

While activation procedures tend to compact a collection, they do so in distinct ways; these distinctions lead to the macroscopic differences visible in the remaining structure after the container is removed. Internal oscillation imparts the fluid-like property of being able to fill its container, and the activity tends to help smarticles flow into voids. While the container is filled more completely (as shown by the increase in $\phi$), this does not imply increases in entanglement. This is evident in Fig.~\ref{fig:sculpting}(b) in the instant the walls are removed. The system has the shape of the container but, shortly afterward, the overhangs tend to fall apart. For the shape-change procedure, while the particles become more compact, it is not due to an improved container space usage. The walls serve to give a basic tubular shape, but the particle structure consolidates inward and grows upward rather than outward. Previously, we showed the resulting effects caused by the number of entanglements produced by the different procedures (Fig.~\ref{fig:systemEntangles}). Shape-change produces a higher entanglement allowing particles to stay together more readily, but it does not sculpt to the container as easily as the internally oscillated procedure. After the activation procedure completion in the shape-change procedure, the system exhibits properties of a hardened structure, whereas the internally oscillated procedure tends to flow apart and is comparably softer, eroding at its surface after the removal of the walls.  We find analogies between the shape-change and internal oscillation procedure and rapid and slow quenching in metallic systems. In metals, rapid temperature reduction in the quenching process tends to leave a metal harder but more brittle, with a great deal of internal stress. Conversely, a slowly quenched metal will see a reduction in the internal stress as well as becoming softer~\cite{Callister2014}. These effects are further supported through quantitative tests in the simulated fracture tests performed in the next section.

\subsubsection{Tensile loading and fracture}

To determine the relationship between entanglement and tensile loading ability, we measured the force required to raise a hook embedded in the various smarticle preparations as shown in Fig.~\ref{fig:3a}(a-c). Specifically, we measure the force as a function of aspect ratio, $F(l/w)$. The force required to raise the top hook was measured three times for each aspect ratio.

To investigate how materials properties are affected, we performed vaious fracture tests. In Fig.~\ref{fig:forceDiffSys}(a) for the three procedures, the peak force output and the entanglements (Fig.~\ref{fig:systemEntangles}(a)) do not keep the same ordering. The shape-change system shows the highest peak force output, whereas internal oscillation displays the least amount of tensile strength. There is agreement between force generated as a function of internal oscillation as shown in Fig.~\ref{fig:forceDiffSys}(b) and in the number of entanglements for a given oscillation amplitude as shown in Fig.~\ref{fig:systemEntangles}(b). Using this simulated system, we found a connection between tensile strength, measured through a fracture test, and the number of entanglements. Next, we examine emergent properties arising in a planar fracture setup with smarticles in an experiment.

\begin{figure}[h!]
\centering
\includegraphics[width=\hsize]{A_Fig12_tensilePic}
\caption[Tensile loading in simulation]{\textbf{Tensile loading in simulation.} Measuring force as a function of entanglement procedure. Two hooks, colored red, are embedded in an already entangled pile. The force necessary to raise the top hook out of the pile is measured, while the bottom hook is kept fixed}
\label{fig:3a}
\end{figure}

\begin{figure}[h!]
\centering
\includegraphics[width=\hsize]{A_Fig13_FractureForce}
\caption[Fracture force versus time for different systems]{\textbf{Tensile force measurements for the various preparation procedures.} Force shown here is a unitless quantity scaled by $W_s$, the weight of the smarticles, and $n$, the number of smarticles in the trial. Each line is averaged over 3 trials. (a) Force versus time for the various procedures at $l/w=0.7$, (b-c) Force versus time for the internally oscillated system.  In (b), $l/w=0.7$ and $\theta$ is varied, and (c) $\theta=10^\circ$ as $l/w$ varies.
}
\label{fig:forceDiffSys}
\end{figure}

\subsection{Robophysical Experiment}
Strain tests are a common method to test the elastic, plastic and yielding properties of materials. Here, we perform a strain test for a chain of smarticles. In all trials, smarticles were initially centered between the confining walls Fig.~\ref{fig:frac2-6}(a). The positions of each smarticle in the chain were randomized between each trial to account for any variance in the servos' strength due to manufacturing differences or general wear that may accumulate over time. Experiments are performed with two different amounts of smarticles, $n=[2,6]$. The chains were arranged as shown in Fig.~\ref{fig:frac2-6}(a,b) in a repeating $\sqcup-\sqcap-\sqcup-\sqcap$... pattern, where a ``$\sqcap$'' is the same shape as a ``$\sqcup$'' but rotated by $\pi$ rads. This pattern interlocks adjacent smarticles together. For chains of $n>1$, stress was transmitted between smarticles  via the entanglement between their barbs. The barbs on the ends of the chain that are not in contact with an adjacent smarticle were connected to the apparatus via a string. On one side the chain is a force sensor which is affixed to a static part of the apparatus' structure on the other side. The force sensor was connected on the side of the chain where the strain was imparted.
The force sensor was a custom device with strain gauges in a full-Wheatstone bridge configuration. All force measurements, F(t), were sampled at 1 kHz. The strain was imparted by a modified linear actuator kit (OpenBuilds; Monroeville, NJ.) as shown in Fig.~\ref{fig:timeSeq}(a-c). All strains were performed at a strain-rate $v=[5$ mm/s$]$. The strain was measured by tracking infrared markers on the smarticles, where all positions and orientations of the smarticles were tracked using an infrared video recording hardware/software suite (OptiTrack; Corvallis, OR).

\begin{figure}[!h]
\centering
\includegraphics[width=\hsize]{A_Fig14_System2-6}
\caption[n=6 and n=2 image]{\textbf{smarticle chains of varying size, $n=6$ and $n=2$.}
(a) Top view of an $n=6$ system, (b) top view of an $n=2$ system.}
\label{fig:frac2-6}
\end{figure}

\begin{figure}[!h]
\centering
    \includegraphics[width=\hsize]{A_Fig15_fractureTimePics}
    \caption[Fracture time sequence in experiment]{\textbf{Time sequence of chain fractures in experiment.}
    (a-c) 3 snapshots of an $n=6$ chain of smarticle. (a) shows the chain before strain starts, (b) shows right before fracture, and (c) shows immediately after fracture.}
    \label{fig:timeSeq}
\end{figure}

\begin{figure}
\centering
    \includegraphics[width=\hsize]{A_Fig16_fracture}
    \caption[Single fracture trial for n=2 and n=6 smarticle chains]{\textbf{Single fracture trial for n=2 and n=6 smarticles.} Single trials of force as a function of strain for smarticle chain at different $n$, both strains were continued until the chain fractured.}
    \label{fig:fracture}
\end{figure}

\begin{figure}[t!]
\centering
    \includegraphics[width=\hsize]{A_Fig17_confinement}
    \caption[Auxetic behavior in smarticle chain]{\textbf{Auxetic behavior in smarticle chain and dependency on number.} (a) Peak force before fracture (b) peak strain before fracture. (c) Schematic of smarticle chain setup. (d) Configuration after smarticle chain has been strained. $h_f>h_i$.}
    \label{fig:confinement}
\end{figure}

We begin the investigation of some of the elastic properties of our system. With two types of trials, one for each value of $n$, we measure force as a function of strain for the chain.
There is a small decrease in force at a strain of $\epsilon=0.2$, for $n=2$ and $\epsilon=0.4$ for $n=6$ (see Fig.~\ref{fig:fracture}), the same mechanism causes the decrease in both systems. The decrease in force happens as a result of a sudden and rapid increase in the chain's length. This sudden change in length corresponds to the yield stress, the point at which rearrangement in the chain occurs. Surpassing the yield stress indicates a material has undergone plastic deformation. After reaching this yield stress point during a cyclic strain test, the force as a function of strain will produce a different curve than in cycles before the yield point was reached. As $n$ increases, force also increases but elongation decreases. When arranged in a chain, the PD-controlled servos can be expected to act approximately as a chain of springs for small strains. Therefore, the force should increase linearly with strain distance.

Fracture is defined as the separation of a body into two or more pieces in response to an imposed stress~\cite{Callister2014}. Fracture tests insight into when materials plastically deform and fail. For our second experiment, we measure properties related to fracture in the chain system, namely, the peak force and strain before fracture. Trials were run with $n=[2,6]$ smarticles and the smarticle order was rearranged between each trial. All trials were repeated 5 times for confinement widths between $h/H=[0.52-0.65]$,
where $h=6.2$~cm is the initial width of the smarticle chain.
\begin{figure*}[ht!]
\centering
    \includegraphics[width=\hsize]{A_Fig18_BlobOnAStick.jpg}
    \caption[Blob-on-a-stick]{\textbf{Assessing internal mechanical stress} Measuring position of center of mass height (H$_{CoM}$) of worm blob structure as a function of time in two dissolved oxygen environments. Using a 3D-printed serrated endpiece, worm blobs are lifted up by 15 mm using a linear actuator. (a) In low DO ($<$2.0 mg/L), they display less internal mechanical stress by entangling loosely with one another. In high DO ($>$8.0 mg/L) (b), they show increased amounts of internal mechanical stress, enough to be lifted using the endpiece. (c) Position of the H$_{CoM}$ as a function of time in both environments. Shaded region corresponds to the span of $n=5$ trials. Reused from Tuazon, et al. with permission~\cite{2022Tuazon}.}
    \label{fig:blobstick}
\end{figure*}

In the chain system, the fracture mechanism is related to the arm opening angle and friction. When the chain is strained, the barbs' angle is forcefully increased beyond the $\sqcup$-shape or $\alpha_i=90^{\circ}$. As $\alpha_i$ increases with stress, the barb's contact with the adjacent smarticle will begin to slip away from the adjacent smarticle in a direction lateral to the strain direction. The chain fails, or fractures, when the expansion reaches a certain threshold such that the static friction is overcome and adjacent barbs slip lose contact. As the smarticles slip, due to their geometry, they displace outwards. The phenomenon of dilation in the direction lateral to the strain is called auxeticity~\cite{Callister2014}. The width of the chain as it is strained can change, but the system is bounded and has a maximum of $H$ (see Fig.~\ref{fig:confinement}(a)). In trials where the chain width expands to equal the confining width $H$ before it fractures, the maximum force before the fracture is affected. Some of the stress from the chain is offloaded and supported by the walls, effectively reducing the load on the arms as shown in Fig.~\ref{fig:confinement}(a-b). As the confinement increases, ($H$ decreases), the maximal force measured before a fracture will increase. The force increases linearly with the confinement fraction. Moreover, the functional form of an $n=2$ and $n=6$ smarticle chain is qualitatively similar and only the magnitude changes. We find similar results in Fig.~\ref{fig:confinement}(b) for the maximum strain at fracture. As confinement increases, maximum possible strain increases as well. This is consistent with the spring chain approximation of the servo chain.

In our smarticle system, based on ``smarticle cloud'' results ~\cite{Savoie2019}, we hypothesize the existence of gaits which can reliably produce contraction as well as an expansion for a smarticle cloud system. In a contracting case, smarticles at the center of the pile experience confinement. With that as our motivation, we tested how confinement affected fracture. We found that the maximum force before fracture steadily increases with confinement fraction, similarly, we found the maximal strain distance before fracture increases as well. By leveraging future capabilities of smarticle swarms, we could effectively employ other smarticles to enforce the confinement conditions, allowing a chain to exhibit improved tensile strength performance on command. Finally, we compare emergent properties that arises from simulations to physically entangled collective behavior found in biology.

\begin{figure*}[ht!]
\centering
    \includegraphics[width= \hsize]{A_Fig19_Wormtumble.jpg}
    \caption[Falling behavior worms.]{\textbf{Tumbling behavior of a worm blob.}(a) Timelapse of a tumbling worm blob ($\sim$2 g) at three instances. At t=0, a short burst of UV 365nm light caused worms to retract their tails. The yellow dot represents the estimated projected center of mass (CoM) (b) CoM XY position as a function of time. (c) Heat map depicting the CoM Y-axis pixel intensities as a function of time. Shaded region corresponds to the span of $n=1$ trials.}
    \label{fig:blobtumble}
\end{figure*}

\subsection{Biological Experiment}
Here, inspired by the results from simulations, we conducted experiments using an analogous entangled system found in nature. Similar to how smarticles display the metallurgical dynamics of annealing, worm blobs can emergently display a few of these behaviors from their entanglement. Of course, we note that in contrast to smarticles, blackworms are highly flexible with aspects ratios >40~\cite{2021Nguyen} that can generate thrust using muscles across its body length~\cite{1989Drewes, 1999Drewes}. Additionally, worms can display a wide range of length as it extends and contracts its body.

As an analogy to shape-change, worms blobs can display either very high or very low entanglement in steady state environmental parameters. As a comparison to the smarticles simulations, very low levels of entanglement occurs when worms are extended (Fig.~\ref{fig:simAndExpPics}b), similar to when the barbs travel $\pi/2$ outwards (Fig.~\ref{fig:2a}d). However, when transitioning between levels of environmental parameters, worms can reversibly vary their activity levels and change their level of entanglement, an analogy for internal oscillations.
For example, according to Tuazon, et. al, worm blobs show less activity and less structural exposed surface area in high DO (>8 mg/L) as opposed to hypoxic conditions (<2 mg/L)~\cite{2022Tuazon}. Furthermore, worm blobs in high DO shows higher internal mechanical stress, which was demonstrated by lifting worm blobs using a 3D serrated endpiece (Fig.~\ref{fig:blobstick}a-c) in two extreme levels of DO. Additionally, according to Ozkan-Aydin, et al.~\cite{2021Ozkan-Aydin}, a highly entangled, "solid-like" blob was observed in lower temperatures (T<25$^\circ$C). However, when exposed to higher temperatures T>25$^\circ$C, the blob slowly disentangled into a "fluid-like" aggregate: demonstrating that higher temperature leads to higher internal oscillations followed by full disentanglement. In short, worm blobs in low temperatures or high DO tend to display solid-like structural properties and vice versa.

In a new behavioral observation not found in literature, we observe that blackworms can collectively alter its CoM using the air-water interface as support. As previously discussed, blackworms supplement respiration by lifting their tails up. If the water level is low enough, tails can reach the air-water interface at a 90$^\circ$ and break surface tension. Drewes, et al. deduced that blackworm tails can break surface tension due to hydrophobic material properties found on its skin's surface~\cite{1990Drewes}. We hypothesize that this hydrophobic effect exerts an upward force against buoyancy and gravitational forces which helps to "latch'' and stabilize the tail onto the interface. As worms in a blob reach up and latch their tails on the interface at low DO, its CoM shifts upwards, creating an "inward and grows upward rather than outward'' with a narrow base structure, similar to the shape in the sculpting simulations Fig.~\ref{fig:sculpting}a. We believe that the shift in CoM is due increased internal mechanical stress and higher level of entanglement from a combination of access to higher DO concentrations and from thigmotaxis.

When we stimulated blackworm's negative phototaxis behavior~\cite{2021Ozkan-Aydin, 1990Drewes} using a short burst of UV 395 nm light, individuals immediately retracted their tails, unlatching from the interface and causing the collective to topple over on its side (Fig.~\ref{fig:blobtumble}a-c). This result is analogous to the melting and sculpting experiments for the shape-change trials after the stabilizing structure was removed. Similar to the shape-change results, the structure topples over, due to its unstable conformation from having a narrow base and high CoM, but maintains its overall entanglement.

\section{Conclusions}
We have performed, to our knowledge, the first study of time-dependent material-properties of soft amorphous entangled matter through simulations, robotics and living systems. Despite the seemingly complex interactions which comprise the material properties of a collective, we found entanglement, which encodes much of the material properties, is controllable. Building upon previous studies of entangleable materials, we found that fracture force increased with the degree of entanglement in a simulation. Next, we performed a 2D fracture test analog and found that the peak fracture force increased as a function of confinement due to the auxetic nature of the smarticle chain. Finally, we compared our simulations to the physically-entangled collective behavior blackworms and found that by controlling the ambient DO, worm blobs can display solid-like material properties and tumble from an unstable conformation.

In the future, we envision an adaptable material capable of maximal or minimal entanglement in response to stimuli (i.e. fire ants' raft formations in the presence of flooding~\cite{Mlot2011,Mlot2012}). This entanglement response should be able to spread through the collective ``organically'', or via local communication, rather than through a global or centralized mechanism. We believe that another major insight from this study is that the choice of how limbs may be activated to alter entanglement is optimizable as a function of energy cost. Due to improvements in the field of rheology over the last century, there has been an explosion in the number of goods with designed material properties based on their purpose: from detergents, to plastics, to hydrophobic clothing~\cite{barnes1989}. We posit that by improving our understanding of the emergent collective dynamics of mutable active particles, it will represent a major step forward in the race towards adaptive, shape-shifting and task-capable soft, super-materials~\cite{Mcevoy2015}.

\section*{Author Contributions}
W.S. designed and carried out the smarticles experiments, analyzed, and interpreted the results. H.T. observed, designed, and carried out the biological experiments, analyzed, and interpreted the results. D.I.G. and M.S.B. reviewed the design and execution of experiments, the data analysis, the interpretations, and the manuscript. All authors contributed to writing the manuscript.

\section*{Conflicts of interest}
There are no conflicts to declare.

\section*{Acknowledgements}
H.T. acknowledges funding support from the NSF graduate research fellowship program (GRFP) and Georgia Tech's President's Fellowship. D.I.G. acknowledges funding support from ARO MURI award (W911NF-19-1-023), NSF Physics of Living Systems Grant (PHY-1205878), and the Dunn Family Professorship award. M.S.B. acknowledges funding support from NIH Grant R35GM142588 and NSF Grants CAREER 1941933 and 1817334.

We thank members of the Bhamla lab and Goldman lab for useful discussions. We especially want thank Akash Vardhan for experimental assistance, Dana Randall, Andr\'{e}a W.~Richa, and Paul Umbanhowar for helpful discussions. Finally, we thank Dr. Prateek Seghal for assisting with the image analysis of the biological experiment.

\balance

\renewcommand\refname{References}

redpajama_set_name: RedPajamaArXiv


As you might have read our previous article on How to Earn From Home Without Any Investment, we had mentioned Blogging on the number one point and this tutorial is going to help you for that. Setting up a custom domain on blogger is very easy and it doesn't take more than 5-10 minutes to complete the process. We all know that Blogger is a platform by Google which is free of cost and doesn't cost anything, which means you are free from any Web-Hosting fees that you pay on a monthly basis.
Blogger is very fast in terms of accessing and the images that you upload are stored through the mean of CDN which signifies as content delivery network (CDN) which is a system of distributed networks and delivers the content of the article to the user based on the geographic location, this makes the access to the website very quickly.
Bigrock is a domain registrar based in India that provides domains for a very reasonable rate, that is why we have picked Bigrock and are going to write this tutorial to set up the custom domain on blogger for free.
Leave name column blank use above IP in Destination IPv4 Address and use TTL value 28800.
www in the Name box and put Value ghs.google.com and TTL 28800 and save your cname record.
Go to Setting Tab >> Then Basic >> Publishing Blog Address >> Add Custom Domain name >> Switch To Advance Settings now type your domain name in the box and click on save button.
Then your blog asks you to verify authority on that domain name. Now you have to create another cname record in Domain DNS to verify.
First code in the Name box and Second long code in Value Box of Cname and add TTL 28800.
Now, after following all above steps carefully, it may take few hours to updates DNS settings and blog verification. After few hours add domain name again by switching custom settings in your blogs.


Richard Walker has been appointed business development director for Osprey Flight Solutions, a brand new company which is introducing a major step change in aviation security expertise.
Effective immediately, based out of Leeds, UK, Richard's day to day role will include building the sales pipeline, closing deals and increasing brand awareness of Osprey and its innovative technology, airport and airspace intelligence.
With over 25 years' international sales and marketing experience in the aviation industry, Richard started his aviation career with British Airways' franchise Maersk Air selling charters on Boeing 737s. Since then, he has worked for OEMs including Bombardier, operators such as VistaJet and PrivatAir, and charter specialist and leasing company AXON Aviation.
Richard comes to Osprey Flight Solutions from a UK HondaJet dealership, where he built up a strong pipeline for the aircraft across his territory. He has also spent time in a business development role for UAS International Trip Support, where he was responsible for growing the business in northern Europe across all sectors of aviation, including commercial and cargo airlines, business aviation and military operators.


YouTube has a new design, and a new logo to accompany it. In fact, it's the company's first new logo in 12 years.
Logo aside, we've seen most of the new look already. YouTube has been testing its new design for months, opening it up for anyone to try back in May. It's immediately cleaner, more in the vein of material design and its ample use of whitespace. There's also a dark mode for those of us that prefer not to watch video surrounded by eye-searing whiteness.
There a few useful features wrapped up in the update too. You can finally adjust video playback speed on mobile devices, and the app will soon dynamically change shape to match your videos aspect ratio – something that was first shown off in June. But my favorite bit is that the dark mode is also coming to smartphones as well.


text:
Q: Aesthetics Plotly - Title in the offline mode I have a basic question, tried many variations and couldn´t get it right. I am trying to put a title in a plotly barchart printes offline in a jupyter notebook. I am using python.
Without the title I can get the graph ok:
from plotly.offline import iplot, init_notebook_mode
init_notebook_mode()
import plotly.graph_objs as go

trace_2 = go.Bar(x=['Jan','Feb','Mar'],
              y = [1,2,3],
               text = [1,2,3],
               textposition = 'auto',
                   marker=dict(
                    color='rgb(158,202,225)'),)
data_2 = [trace_2]

fig_2 = go.Figure(data=data_2)

iplot(fig_2)

When I try to put the title in, as in the tutorial, I get a lot of unexpected errors. How can I put the title "Count of the month" on top of the Graph?
tks

A: You need to use the title property of layout object, which you then pass to fig object, please refer the below example. Also please checkout the official docs for `plotly layout title.
from plotly.offline import iplot, init_notebook_mode
init_notebook_mode()
import plotly.graph_objs as go

trace_2 = go.Bar(x=['Jan','Feb','Mar'],
              y = [1,2,3],
               text = [1,2,3],
               textposition = 'auto',
                   marker=dict(
                    color='rgb(158,202,225)'),)
data_2 = [trace_2]
layout = {'title': 'Count of the month'}

fig_2 = go.Figure(data=data_2, layout = layout )

iplot(fig_2)

redpajama_set_name: RedPajamaStackExchange


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The first test suggests suitable therapies based on your symptoms; the second does so based on your personality and lifestyle.
You can, of course do both tests.
They might not both make the identical suggestions but they should both provide useful guidance that will narrow down the choice and point you in the right direction.


By now we can all agree that all hair is not created equal. Just like your hair type determines which shampoo and conditioner is right for you, your unique texture should dictate the temperature of your hot tools, too. That's right, just because your curling iron goes up to 450 degrees does not mean you have to max it out – it won't make hair curl faster or stay curled longer. (You've seen the YouTube video of the girl who sizzled her hair off during a tutorial — don't let it happen to you.) We asked T3 Lead Stylist David Lopez, who's responsible for Chrissy Teigen's gorgeous mane, to give us the 411 on hot tool temperatures based on hair type. Here's what he had to say.
And please, please, please don't forget to use a heat protecting spray. All hair types will benefit from it, but Lopez suggests a heat protecting serum for coarser hair types. "I love the Platinum Blow Dry Serum from from Kenra Professional and the Damage Manager spray from Kevin Murphy," he adds.


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Q: Javascript - Cómo borrar el div clonado...? Tengo un código de práctica donde estoy clonando un div de la izquierda a la derecha, y estoy tratando de borrar SOLO EL DIV CLONADO, pero se me borra el original y no es lo que estoy buscando.
Alguna idea...?
DEMO

A: puedes hacerlo haciendo referencia a this osea al elemento clickeado luego buscas al parentElement que es el cont-2-producto-# y entonces si le aplicas el display:none;
ejemplo:

 $(document).ready(function() {
      $("#copiar-1").click(function(){
        $("#cont-1-producto-1").clone().appendTo(".derecha");
      });

      // =============

      $("#copiar-2").click(function(){
        $("#cont-2-producto-2").clone().appendTo(".derecha");
      });
});
html{background-color:#eee;}
body{margin:0 auto;color:#323232;max-width: 100%;line-height:1.5;padding:1em 3em;background-color:#fff;font-family:'Roboto',serif}

/* ===================== */
#copiar-1,#copiar-2{width:120px;height:30px;margin-top:15px;background:grey;padding:10px 0 5px;text-align:center;vertical-align:middle;color:#fff;cursor:pointer}

.izquierda{border:solid 2px black;height:200px;width:200px;float:left;text-align:center;padding:10px 0}

.derecha{border:solid 2px red;height:auto;width:200px;float:right;text-align:center;padding:10px 0}

#producto-1,#producto-2{display:inline-block;width:100px;margin:10px auto;padding:5px}
#producto-1{background:green;color:#fff}
#producto-2{background:lightblue;color:#000}

#equis-1,#equis-2{display:inline-block;width:24px;height:24px;vertical-align:middle;text-align:center;background:red;color:#fff;margin-left:10px;border-radius:3px;cursor:pointer}

/* ===================== */

.izquierda #equis-1,.izquierda #equis-2{display:none}

/*.izquierda #cont-producto-1 {display:none}*/

Div Original

Producto 1

X

Producto 2

X

Div Copia

Copiar 1

Copiar 2


In recent days, we have all been rightly shocked and appalled by the threat of terrorism on our shores perpetrated by those who adhere to the twisted and repugnant ideology of extremists.
The fear and anger that it has provoked is understandable, but in some cases, it has led us to act and speak in a manner which is contrary to our ethics and ideals.
Whilst we must be unanimous in unequivocally condemning these crimes and denouncing the invocation of religion to justify them, we must also be vigilant not to promote hostility towards any religion based on the violent actions of extremists and recognise that all of our religious communities continue to be actively, responsibly and positively integrated into mainstream Australian society.
Our nation takes great pride in its multicultural composition which is at the heart of our national identity and is intrinsic to our history and character.
Indeed, Australia's vigour and cohesion rests upon the right for all of us to foster our cultural identity and to receive equal treatment, regardless of race, culture or religion.
Of course, we have our differences. How could it be otherwise, given the rich diversity of our nation?
But these differences need to be celebrated and recognised as a source of social wealth and dynamism and as a key driver of our national prosperity.
The reality of everyday life in multicultural Australia is that we all have family members, friends, colleagues and neighbours who come from widely diverse origins.
And each us of want to be accepted as Australians and have a firm commitment to the institutional framework of our political and legal system.
We, as a society, need to build on these shared values rather than perpetuate superficial differences which benefits no one and tarnishes everyone.
We cannot succumb to the divisiveness of suspicion and mistrust.
If barriers exist within ourselves then those who wish to do us harm succeed.
So long as our national identity is defined by our differences, we will empower those who promote division rather than the cooperation that lift up the values of understanding and mutual respect.
This is an issue that I believe we cannot afford to simply ignore.
To do so would give credence to a profoundly distorted view of our tenets as a nation.
We must disown incendiary language and actions which only serve to denigrate both the greatness and the goodness of our nation.
And we must also promote the unity and harmony that we all cherish.
If we are going to uphold our proud tradition as a multicultural nation, our values must be guarded and vitalised anew by each generation of Australians.
Next month I will be partaking in the 'Walk Together' event being held right across Australia.
The event invites all Australians to come together in a celebration of our diversity.
Its theme of "common people with common dreams" highlights that our national harmony and aspirations are stronger than anything that drives us apart.
Here we have an example, repeated throughout Australia, in which persons of differing ethnic, cultural and linguistic heritages are able to relate to each other on equal terms; in which people are judged by what they say and do and not by what they look like and in which an Australian is not someone who conforms to a particular stereotype but whose citizenship is based upon their commitment to the social and moral values which underpin our society.
Our multiculturalism is about inclusion, not division. It is about interaction not isolation. It is about a melting pot of cultures embracing common values which enrich all Australians.
We, as a nation, need to turn to each other, not against each other and reaffirm our commitment to an Australia bound together by tolerance and consensus, rather than torn and divided by bigotry and confrontation.


text:
Office - 949-544-1410
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info@elitespeakersinternational.com
PETE KOCH
Keynote speaker to numerous organizations including Fortune 500 companies and the NFL, Pete Koch is a former NFL defensive lineman with extensive training in strength development, general fitness, weight loss, life extension and holistic wellness.
Pete is a Keynote Speaker who speaks to Corporations, the NFL, Associations, Government Agencies, Not For Profits, Sports Teams, Educators, and to our Military on Motivational Leadership, Team Building, Story-Selling and Safety, customizing his message to your purpose, including:
Championship Team Development: Pete was the Captain of his Championship High School team, his Maryland Championship team and a leader on his Kansas City Chiefs playoff team. Teamwork and leadership must be rooted in positive psychology and reinforced consistently to develop true Champions.
The Keys to Achieving Exceptional Health, Fitness and Wellness: Having worked for more than a decade with world renowned 'non-surgical' weight loss doctor Robert "Dr H" Huizenga MD (Biggest Loser, Raiders) Pete has established himself as a leader in fitness program design and wellness programing in a clinical setting. His presentation is entertaining, fact based and motivational.
Pete developed his FAST Fitness principles to help people optimize their bodies, inside and out. This combined with his Four Quarters of Personal Excellence allow the audience to experience what it takes to live a live of personal excellence.
Born on Long Island, NY Pete began playing contact football at the age of seven and didn't stop for twenty years. Along the way he captained his winning New Hyde Park High School team, then his University of Maryland team to the ACC Championship and appearance in the prestigious Citrus Bowl. Pete received All ACC and All-American Honorable Mention honors. Pete was a First Round selection (sixteenth overall) in the 1984 NFL Draft; selected by the Cincinnati Bengals. Pete spent four years with the Kansas City Chiefs, notably starting at right defensive end in their playoff run of 1986. Pete wrapped up his six-year NFL run with the Los Angeles Raiders teaming with future Hall of Famers Howie Long, Marcus Allen and Mike Haines.
Upon retirement from the NFL, Pete transitioned into a successful fitness modeling and acting career starring along side Clint Eastwood in Heartbreak Ridge, Burt Reynolds in Heat and Evening Shade, Patrick Dempsey in Loverboy and others totaling more than 120 Hollywood productions.
Throughout the years, Pete has remained deeply committed to maintaining his strength, flexibility, conditioning and overall health through regular workouts. A natural curiosity and commitment to ongoing education, drives Pete's continuous research in the field of Athlete Performance. Self preservation factors into the zeal Pete brings to his studies and training, initiated by five orthopedic surgeries (due to 20 years of contact football). Pete's early exposure and relationships with internationally renown strength and conditioning experts Dr. Fred Hatfield and Frank Costello motivated him to continue his exploration of cutting edge training methods and techniques. He successfully rehabilitated from two spine surgeries, which helped him to solidify his ideas on the importance of spinal stability/core conditioning.
In 2004 Pete Developed a system of training that he calls Functional Advanced Sports Training or FAST, a melding of numerous scientifically proven training methodologies to optimize neuromuscular control and maximize athletic performance. Pete was then called on to direct the training of a number of Hollywood luminaries including Tobey Maguire, Joseph Fiennes and Academy Award winner Benicio Del Toro. Currently certified by the National Academy of Sports Medicine as a Sports Fitness Specialist and a Certified Strength and Conditioning Coach by the National Strength and Conditioning Association.
His FAST Company trains people of all ages and levels of physical condition to help them achieve their fitness and conditioning goals. A University of Maryland graduate, Pete remains committed to ongoing education and research in a life long commitment to maximizing human performance and health in people of all ages.
For booking information contact:
Stacy Anderson
info@theelitespeakersbureau.com
Outreach Radio
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redpajama_set_name: RedPajamaCommonCrawl


While Duhamel is talking about casting for a movie that doesn't even have a script yet, Badass Digest has some more believable news regarding the plans for the sequel. The movie will be a true sequel and follow the events of Transformers: Dark of the Moon but the "reboot" aspect comes from changing the point-of-view from Sam Witwicky to the Transformers. That's not a horrible idea and it's a worthwhile approach provided they write strong characters. If you end up writing transformers like Skids and Mudflap, the movie will be unbearable.
Additionally, a source tells BD that the movie will be more like the last hour of Transformers: Dark of the Moon. That means a lot more action (if that's even possible, but I'm sure Bay will find a way) and a lot less silly humor. Since intentional humor hasn't really been the series' strong suit (although there were plenty of fun moments in the first movie), I wouldn't mind cutting back on stuff that doesn't work. Stuff that did work: Jon Voight's pronunciation of the word "robot".
Of course, filming is still a ways off so all of this can change, but these non-casting rumors are at least beginning to get me back on board with a new Transformers movie.
"Michael realized it needs to be more like the last hour [of Dark of the Moon]," this source told me. So expect lots of big action, lots of carnage, lots of military badasses, very few silly bits.


text:
Once in a lifetime challenge for Banbury students
Jaguar Swallow Sidecar restoration that Banbury and Bicester College students will undertake NNL-190105-092824001
Published: 16:37 Thursday 02 May 2019
Students from Banbury and Bicester College will get a chance to restore a rare and beautiful piece of the UK's motoring history.
The college has joined forces with Jaguar Daimler Heritage Trust for a project which will see classic vehicle restoration students working on dismantled components of a Swallow sidecar to restore it into a fully assembled, finished product to a high standard. The components are believed to be from a very early Swallow Sidecar dating from around 1922/1923.
The project was officially launched by Michael Quinn, grandson of Jaguar founder Sir William Lyons, at the Activate Learning Technology Campus in Oxford on Tuesday.
Michael Quinn said: "I am delighted to be able to lend my support to this inspirational initiative.
"The skills and experience gained in the restoration of this example of my grandfather's heritage will be invaluable to the students' development, and I am pleased that the Jaguar Daimler Heritage Trust is in a position to be so closely involved in this way."
Jaguar Heritage Trust has loaned the Swallow Sidecar to support classic vehicle restoration students' learning at Banbury and Bicester College.
This key partnership project will see students try to retain the character of the original sidecar as they restore the former vehicle.
Lee Jamieson, director of curriculum for technology at Activate Learning, said: "This is a once in a lifetime opportunity for our classic restoration students.
"Thanks to our partnership with Jaguar Daimler Heritage Trust, our students can develop industry standard restoration skills by working, hands on, to rebuild this important icon of UK motoring.
"This partnership will contribute two things to the vehicle restoration sector: an original Swallow Sidecar will be preserved for future generations to enjoy, and a new wave of young, enthusiastic engineers will enter an industry in short supply of skilled restoration talent."
The vehicle requires extensive restoration work and will challenge the students' knowledge and abilities while working with the dismantled components provided.
Sunshine Centre continues to shine
To infinity and beyond for Banbury students
See who from Banburyshire has appeared before magistrates in Oxford


text:
We are uncommon
We are a creative business that delivers unique merchandise solutions from concept to fulfilment.
Our inventiveness sets us apart from the rest. We think on our feet and defy convention.
We are agile yet focused, fun yet reliable, creative yet grounded: thinkers AND doers.
This is Uncommon.
Paul Preuveneers | CEO + Founder
With a successful career leading merchandise, licensing, retail and e-commerce teams in B2B and B2C organisations, Paul is a strong leader with a truly global network. Well-respected and trusted across the motorsport industry, he has strategically authored some of the most successful motorsports licensing and merchandising agreements in auto racing.
As CEO of Branded, Paul led PUMA's strategic Sports Licensing & Merchandising business for iconic global brands including Ferrari, Mercedes AMGP F1, Red Bull and Arsenal FC. He then headed up the e-commerce and merchandise retail arm of The Motorsport Network, as Executive Director and Board member. His broad experience in branded product creation, licensing and multi-channel distribution, combined with a creative, open-minded approach, are what make Uncommon uncommon.
Olivia Brook | General Manager
Olivia has a wealth of global marketing and operational experience across automotive, motorsport and beyond. She joined Uncommon from Jaguar Land Rover where she held a number of prominent roles in global marketing and PR over the last decade. Olivia is well-versed in leading teams from all over the world, and has spent the last 20 years working in the UK and overseas project managing product launches, marketing campaigns, agency transitions and rebrands. Working with several key international partnership activations, Olivia has strong knowledge of experiential marketing and how brands are perceived by customers through at-event activation, such as Rugby World Cup, Extreme Sailing Series and NASCAR.
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I'm Happy With That


text:
Thread: National Kit Car Show
Lucky@LeMans
Got there early today, met up with a couple of people, had a chat about the Formosa to a few interested parties and that was about it.
Down to just one hall this year and that was spaced out and sparse . The club areas are much reduced and spread out .
The "show" was running down by about 2.30 so it was time to go !
There was a German bloke who parked next to me in a Seven style car. He had come all the way to visit the show, don't know what he thought but he left before me !
A bit of a let down really, I think this type of show has had its day. The older halls that were once used as an area for selling your car are now taken by a company making prefab buildings. Much of the site has been handed over to HS2. Other parts of the site are run down and in a mess !
The organisers would do better by integrating with one of the larger "classic" shows, Stoneleigh as a venue has run its course.
Last edited by Lucky@LeMans; 30th August 2021 at 00:19..
Find all posts by Lucky@LeMans


text:
Hospitals Prepare for Coronavirus Surge Following July 4th Holiday
By Estephany Escobar North Carolina
UPDATED 5:30 AM ET Jul. 14, 2020 PUBLISHED 10:46 PM ET Jul. 13, 2020 PUBLISHED 10:46 PM EDT Jul. 13, 2020
CHARLOTTE, N.C. -- Nearly 80 percent of hospital and intensive care unit beds in North Carolina are currently in use amid the COVID-19 pandemic. Some health care officials in North Carolina are concerned that the number will rise.
On July 11, the state reported 2,462 COVID-19 cases, which is the highest one-day number of laboratory-confirmed cases. Hospitalizations have also reached a record high with 1,093 patients. Currently, Atrium Health and Novant Health have 20 percent of hospital beds and intensive care unit beds available. Both healthcare systems have been working to prepare for the surge by increasing bed capacity and reinforcing supply chains.
Novant Health Chief Clinical Officer for the Greater Charlotte Market Dr. Sid Fletcher says the healthcare system has not added extra beds but it could, if needed.
"We put pencil to paper and worked very hard at developing some robust surge plans that would allow over 60 percent above our current license bed capacity," Fletcher said.
Fletcher adds at Novant Health Presbyterian Medical Center in Charlotte, over 10 percent of those hospitalized are being treated for COVID-19. He considers it a high number.
"We have concerns that that number is going to rise over the upcoming weeks, post the July 4th holiday, just given that businesses and other things have reopened. We recognize people have tired of staying inside and they are seeking outdoor activities or seeking activities with other people," he said.
Centers for Disease Control Director Robert Redfield, who visited Charlotte on Monday to discuss Mecklenburg County's COVID-19 tracing and response, says the public can help stop the spread of the virus.
"We are not defenseless against this virus," Redfield said. "The most powerful weapon that we have, that I know of, is wearing face coverings when you are in public. We ask the American public to all fully embrace the use of face coverings when you are in public. The second thing we have is the importance is hand hygiene and the third is the importance of social distancing."
Fletcher gives the same recommendations for community members. He says he's concerned about having an exponential growth in number of hospitalizations, similar to those impacting other cities.
"There's always the risk of having a situation where you don't have the system resources to be able to manage, not only those who have COVID, but your other patients that have underlying health conditions that occur regardless there's a worldwide pandemic going on," Fletcher says.
Both Atrium Health and Novant Health have also noticed an increasing trend of younger patients admitted to the hospital for COVID-19 treatment. Mecklenburg County anticipates both health care systems will be able to handle a surge in hospitalizations without needing a field hospital. The health care systems are not planning to postpone non-emergent appointments or elective surgeries for now.