High sensitivity wrist-worn pulse active sensor made from tellurium dioxide microwires.

We have demonstrated the practicality of an ultrasensitive wrist-wear pulse active sensor that was first made using tellurium dioxide triangular microwires. The unusual growth direction of the α-TeO 2 triangular microwires was governed by a [110] axis. The α-TeO 2 microwires belong to the tetragonal structure with a space group of P4 1 2 1 2. Due to the gravitational force effect, the triangular microwires were encapsulated by polydimethylsiloxane (PDMS) and underwent a natural gravity-driven settling process during the PDMS solidification process, leading to the triangular microwires being placed on the substrate with a randomly horizontal orientation. When a compressive stress was applied to the α-TeO 2 –PDMS composite film, the shear forces were formed on the microwires׳ surface along with the [110] and/or [ 1 ¯ 1 ¯ 0] poling axis. As a result of the antisymmetric element of e 14 and − e 25 in the α-TeO 2 structure, the triangular microwires have created an obviously piezoelectric potential (piezopotential) ~3.2 V that was perpendicularly established along with the poling axis. On the basis of the unique triangular morphology and its physical properties, the piezopotential of the α-TeO 2 will not be canceled out even if the microwires׳ tips are pointed towards each other. Thus, the piezopotential can be accumulated across the top and bottom electrodes of the nanogenerator (active sensor). The α-TeO 2 triangular microwires can be acted upon as a useful active sensor for detecting the tiny physical motions, for instance, a pulse driven sensor, air pressure, and touchless control of smart devices. [ABSTRACT FROM AUTHOR]