  Materials that respond to external stimuli by expanding or contracting
provide a transduction route that integrates sensing and actuation powered
directly by the stimuli. This motivates us to build colloidal scale robots
using these materials that can morph into arbitrary configurations. For
intelligent use of global stimuli in robotic systems, computation ability needs
to be incorporated within them. The challenge is to design an architecture that
is compact, material agnostic, stable under stochastic forces and can employ
stimuli-responsive materials. We present an architecture that computes
combinatorial logic using mechanical gates that use muscle-like response -
expansion and contraction - as circuit signal with additional benefits of logic
circuitry being physically flexible and able to be retrofit to arbitrary robot
bodies. We mathematically analyze gate geometry and discuss tuning it for the
given requirements of signal dimension and magnitude. We validate the function
and stability of the design at the colloidal scale using Brownian dynamics
simulations. We also demonstrate the gate design using a 3D printed model.
Finally, we simulate a complete robot that folds into Tetris shapes.

Robotics;Applied Physics