Human vital signs such as the heartbeat and respiration are important physiological parameters for public health care. Precisely monitoring these very minute and complex time-dependent signals in a simple, low-cost way is still a challenge. This study shows a novel fabrication of vertically well-aligned piezoelectric nanowire arrays with preferential polarization orientation as highly sensitive self-powered sensors for monitoring vital signs. The process realizes in situ poling of the P(VDF-TrFE) nanowires within the nanopores of the anodized aluminium oxide (AAO) template to yield a preferential alignment of both nanowires and the polymer chains required for superior sensitivity in one step. The resulting self-powered flexible sensor shows high sensitivity, good stability and strong power-generating performance. Under bending conditions, the device exhibits a maximum voltage of ∼4.8 V and a current density of ∼0.11 μA cm⁻². The fabricated self-powered sensor shows a linear relationship of output voltage versus compressive force with a high sensitivity, and the piezoelectric voltage of the P(VDF-TrFE) nanowire array is enhanced 9 times that of conventional spin-coated bulk films. Furthermore, the highly sensitive vertically well-aligned nanowire array can be applied as a self-powered sensor for detecting some tiny human activities including breath, heartbeat pulse, and finger movements, which may possibly serve for medical diagnostics as sensors, robotics and smart electronic devices.

A patterned electrohydrodynamic pulling technology was first proposed to fabricate a new self-connected, vertically integrated nanogenerator with a well-bridged electrode pair.

Formation of thick, high energy density, flexible solid supercapacitors is challenging because of difficulties infilling gel electrolytes into porous electrodes. Incomplete infilling results in a low capacitance and poor mechanical properties. Here we report a bottom-up infilling method to overcome these challenges. Electrodes up to 500 μm thick, formed from multi-walled carbon nanotubes and a composite of poly(3,4-ethylenedioxythiophene), polystyrene sulfonate and multi-walled carbon nanotubes are successfully infilled with a polyvinyl alcohol/phosphoric acid gel electrolyte. The exceptional mechanical properties of the multi-walled carbon nanotube-based electrode enable it to be rolled into a radius of curvature as small as 0.5 mm without cracking and retain 95% of its initial capacitance after 5000 bending cycles. The areal capacitance of our 500 μm thick poly(3,4-ethylenedioxythiophene), polystyrene sulfonate, multi-walled carbon nanotube-based flexible solid supercapacitor is 2662 mF cm^–2 at 2 mV s^–1, at least five times greater than current flexible supercapacitors.