shoulder, and a smartphone worn over the shirt above the abdomen using a waistband. The smartphone recorded the receive signal strength during indoor physiological activity (standing, walking and running) in 5 min trials with a 2 min rest period in between each trial. Controls were performed by repeating the activity protocol with an un-patterned athletic shirt. Evaluation of the wirelessly powered sensor was performed with one healthy volunteer. The subject was asked sit back and relax on a chair while a custom pulse sensor was attached to a wrist and electrodes on the arm (Red Dot Electrodes, 3M). The antenna was attached on a long-sleeved sweater integrated with metamaterial textiles at the shoulder and driven with a continuous-wave signal. For quantification, the light intensity from the pulse sensor was measured by using optical fibre connected to a Si amplifier detector (PDA26A-EC, Thorlabs). ECG measurements were simultaneously obtained from the electrodes using a custom amplifier. ECG and optical data were simultaneously recorded using a digital oscilloscope (PicoScope 6402D, Pico Technology). 

[00137] According to some embodiments, the Pressure sensor was fabricated as follows: Micro structured pyramid films were fabricated from a 20: 1mixture of polydimethylsiloxane (PDMS) elastomer base and curing agent (Sylgard 184, Dow Corning). Polyethylene terephthalate (PET) film with 12 pm thickness was used as the substrate. The PDMS mixture was mixed for 1 min at 2,500 r.p.m. using a SpeedMixer (FlackTek) and transferred onto a silicon wafer mould pretreated with octadecyltrichlorosilane. The mixture was spin-coated on the mould at 1,000 r.p.m. for 30 s. A plasma-treated PET film substrate was placed on top of the degassed PDMS film and thermally cured for 4 h. The moulded PDMS film on the PET substrate was plasma-treated and coated with a thin layer of PEDOT:PSS (CLEVIOS PH1000; Heraues) that was premixed with 5 wt% DMSO and 0.1 wt% Zonyl FS-300. The conductive layer was dried in a 70°C oven for 30 min before use. The pressure sensor was placed on top of the etched copper electrodes and sealed. 

[00138] According to some embodiments, the Wirelessly powered, battery-free Bluetooth sensors were fabricated as follows: The sensor nodes were made from commercial BLE sensors (CYALKIT- E02) with an integrated power management component (S6AE103A) and temperature and humility sensors (Si7020-A20). The output terminals of the rectifier in the wireless energy harvesting unit were connected to the input of the power management component on the back side of the sensor. The sensors were attached onto the metamaterial textile with the antenna of the energy harvesting unit facing down and configured to transmit sensor data via BLE immediately when powered on. The data were wirelessly received using a smartphone and displayed using an application. 

[00139] Reference is now made to FIG. 6A, which is a schematic illustration of an electric field profile of the metamaterial textile with transmitter (horizontal electric dipole, 5 mm length) 

