Self-powered sensing elements based on direct-write, highly flexible piezoelectric polymeric nano/microfibers

We have developed a general purpose self-powered sensing elements (SSE) based on polymeric piezoelectric nano/microfibers (NMFs). The applications are demonstrated through two promising devices. The first demonstration is the dual purposes micro-cantilevers act as a self-powered air flow sensor and a wind-driven energy harvester. The second demonstration is to integrate the proposed SSE as the embedded sensor/cyber garment for monitoring the muscular movement and knee/elbow joint rehabilitation. For the self-sustained flow-sensing device, the extremely high flow sensing sensitivity of 83.3 mV/(m/s) is obtained, as compared with previously published MEMS (micro-electro-mechanical system) device. The output voltage and optimized power matching to the load resistance of 1.5 MΩ are measured as 0.64 V and 136.54 nW respectively at flow velocity of 19.8 m/s. The corresponding power density is as large as 7,111 μW/cm3. For the embedded sensor/cyber garment device, the assembled PVDF piezoelectric NMFs are demonstrated to detect various forms of human motions such as skin wrinkle/eye blink and knee/ elbow bending movement. In contrast to conventional sensors such as translational/rotary encoders subjected to specific motion restriction and required continuously power supply, the proposed device are highly versatile in implementation and could be beneficially promising for monitoring the progress of human rehabilitation.