the second sensor node is placed on the shoulder of the user, according to embodiments of the present disclosure, and to FIG. 13C, which is a schematic illustration of a screenshot of a smartphone application displaying data received from wireless sensor nodes on the shoulder and wrist (shown as nodes 4 and 5 respectively on the application) via propagation of Bluetooth signals along the metamaterial textile, according to embodiments of the present disclosure. 

[00152] According to some embodiments, it was desired to demonstrate that wireless, battery-free sensors may be interconnected within the presently disclosed platform, accordingly, wirelessly powered Bluetooth sensor nodes may be placed on the shoulder and on the wrist of a user along the metamaterial textile. The sensor circuit is powered by a custom wireless energy harvesting unit and integrates a temperature sensor, a humidity sensor and a Bluetooth module that wirelessly transmits data to a smartphone placed near the body. Touching the sensors results in an increase in temperature and humidity, which may be detected by the respective sensors and displayed by an application on a smartphone. The distributed and synchronized capabilities of such wireless sensor networks could be used to monitor clinically important physiological signals such as pulse pressure propagation and electrical activity. 

[00153] The interaction of surface waves with nearby objects also provides sensing capabilities in analogy to optical plasmonic sensors. The potential of metamaterial textiles of the present disclosure for human-machine interaction, an interactive smartphone application that changes the display image when an abrupt change in Bluetooth RSSI is detected, may be created. When the smartphone is placed near a metamaterial textile on which a Bluetooth signal is propagating, the display image can be changed by touching the textile with the index finger, even if the smartphone and the finger are not both in physical contact with the textile. Measurements show that the proximity of the textiles to biological tissue decreases the transmission by up to 6 dB, due to interaction with the surface wave. By tailoring the geometry of the metamaterial structure to modify the localization of the surface plasmons, this sensitivity to the proximity of biological tissue could be suppressed to improve robustness to environmental effects, or further enhanced for applications in gesture sensing, proximity detection and physiological monitoring. The conductive textiles according to the present disclosure may have conductivities between 2 * 10 5 to 5 * 10 5 S/m. 

[00154] According to the present disclosure, the energy-efficient and secure interconnection of wireless sensor networks by confining radio-waves emitted by standard wireless devices onto metamaterial textiles, has been demonstrated. It is illustrated that the transmission efficiency of a wireless network may be enhanced by over three orders of magnitude compared to conventional radiative networks without metamaterial textile. Furthermore, it has been demonstrated that the 

