indication of the subject’sheartbeat using a light-emitting diode (LED) coupled to a resistive pressure sensor and powered by an energy harvesting circuit. [00100] Reference is now made to FIG. 4C, which is a schematic illustration of contactless sensing of finger proximity at distance d from the metamaterial textile, according to embodiments of the present disclosure. That is, according to FIG. 4C, sensing may be performed even when no actual contact is made between the user and the sensor/metamaterial textile. [00101] Reference is now made to FIG. 4D, which is a schematic illustration of pulse detection and FED indication by the wireless sensor. Recorded ECG is shown for comparison. According to Fig. 4D, the transmitter was placed on the shoulder of the user and the output power set to 20~dBm (l00~mW, equivalent to a typical Wi-Fi transmitter). Monitoring the FED brightness during wireless power transfer revealed pulses that corresponded temporally with periodic cardiac activity recorded by electrocardiography (ECG). The transfer efficiency in this configuration was estimated to be 10.5% to the loop antenna and, including losses due to the rectifier, 3.5% to the FED. These power levels meet requirements for broad classes of low-power sensors, including temperature, pH, and other physiological markers, which consume less than l~mW. [00102] Reference is now made to FIG. 4E, which is a schematic illustration of sensing of finger proximity from the metamaterial textile. FED light intensity is modulated by the dependence of the transmission efficiency of the waveguide (inset) on finger distance. The interaction of surface waves with nearby objects also provides sensing capabilities in analogy to optical plasmonic sensors. As a proof-of-principle, FIG. 4E illustrates that placement of the index finger close to the metamaterial textile (less than 2 cm) during wireless powering of a FED resulted in a visually detectable decrease in FED brightness. This decrease can be attributed to the drop in transmission (FIG. 4E inset) that occurs when the field interacts with biological tissue, which exhibits high dielectric permittivity and absorption at radio frequencies. By tailoring the geometry of the metamaterial structure to change the localization of the surface plasmons, this sensitivity could be suppressed to improve robustness to environmental effects or further enhanced for applications in gesture sensing, proximity detection, and physiological monitoring. [00103] Reference is now made to FIG. 5A(l), which is a schematic illustration of the metamaterial textile indicating various dimensions that may be controlled during the metamaterial textile design, according to embodiments of the present disclosure. According to some embodiments, ’a’denotes the width of the comb shaped base 120 (FIG. 1B), ’h’denotes the length of each comb shaped tooth 122, ’b’denotes the width of each tooth 122, and ’d’denotes the width of each tooth (’b’)