Layered Double Hydroxide Based Self-Powered Triboelectric Sensor for Biomechanical Motions

Sensing of biomechanical motions is advantageous for biomedical health monitoring. Here, we propose a layered double hydroxide (LDH) based triboelectric sensor (TES) for monitoring biomechanical motions. The triboelectric sensor is based on initially triboelectrification between the friction pair of LDH and aluminum and subsequently electrostatic induction in an external electric circuit due to the contact-separation of the two friction layers. To realize the triboelectric sensor, ZnAl-LDH is synthesized using an in-situ hydrothermal method resulting in a nanostructured ZnAl-LDH with high surface-to-volume ratio. The triboelectric sensor is self-powered as it generates a peak-to-peak output voltage (Vo) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 11$</tex> V across a load resistance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$1\mathrm{M}\Omega$</tex> and a short circuit current (I<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">SC</inf>) of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sim 2.5\mu\mathrm{A}$</tex> in response to hand tapping. Since the triboelectric pulses (high voltages and very low currents) are not suited for conventional electronics, a two-stage-amplifier based interface circuit is designed to interface the sensor to a microcontroller. As proof of concept, the self-powered triboelectric sensor is interfaced with Arduino Mega 2560 microcontroller through the interface circuit. The sensorial system monitored the contact-separation induced by hand tapping and the counting information was displayed on a digital LCD. The self-powered LDH based triboelectric sensor along with the two-stage-amplifier based interface circuit provides a platform for monitoring various biomechanical motions including walking with applications in biomedical health monitoring.