Ultrasensitivity of self-powered wireless triboelectric vibration sensor for operating in underwater environment based on surface functionalization of rice husks

We demonstrate the self-powered wireless triboelectric vibration sensor as made from the naturally nanoporous SiO2 particles for allowing the detection of the vibrations and movement in the underwater environment. The nanoporous SiO2 particles are directly converted from the rice husks (referred to as RHsiO2), which exhibit strongly interacting surface hydroxyl groups. Through the enzymatic treatments, the surface potential of the RHsiO2 particles can be modulated to obtain either an extremely low or strongly high electronegativity. Specifically, by adding fluorinated groups using fluoroalkylsilane (FOTS) treatment to obtain RHsiO2-F, the charge density of the RHsiO2-F triboelectric nanogenerator (TENG) can be enhanced similar to 56.67-fold as compared to the untreated RHsiO2-TENG. The power density of the RHsiO2-F TENG is increased from 0.077 mWm(-2) to 261 mWm(-2). The RHsiO2-F particles are encapsulated in a quartz cube to fabricate a self-powered wireless sensor that can be stabilized for operating in an underwater environment at various temperatures. The theoretical calculation further demonstrates that the triboelectric potential is dramatically established between the surface functionalized RHsiO2-F particles and the quartz's surface. With porous nature of rice husks covered with nano-Si is of a high functionality for designing a new-type TENG which has a great potential to apply in the environmental monitoring.