Generation of direct current (DC) from mechanical kinetic energies is crucial for realizing self-powered wearable electronics. Here, we report a flexible textile-based DC generator based on the tribovoltaic effect at a dynamic metal-semiconducting polymer interface. The tribovoltaic effect refers to a phenomenon in which an energy "quantum" is released once an atom−atom bond is formed at the dynamic interface of two contacting materials; such released "binding" energy excites electron−hole pairs at metal−semiconductor interfaces or semiconductor−semiconductor pn junctions. This textile DC generator, based on the dynamic Schottky junction between an Al slider and a poly(3,4-ethylenedioxythiophene)-coated textile, can output a voltage of approximately 0.45−0.70 V. The voltage and current can be increased by simply connecting multiple generators in series or in parallel. Seven generators in series can power an electronic watch constantly without any conditioning circuit. These findings offer an efficient strategy for harvesting mechanical energies and realizing selfpowered electronics.

In this paper, star-shaped honeycombs are analyzed in terms of their equivalent mechanical behaviors and band gap properties. Firstly, by applying Castigliano’s second theorem, the effective Young’s modulus and Poisson’s ratio are derived by an analytical method used in structural mechanics. On the basis of Bloch’s theorem, the dispersion characteristics are then analyzed by the dynamic matrix in conjunction with the Wittrick–Williams (W–W) algorithm. It should be noted that the presented method can form a more simple stiffness and mass matrices of the proposed structures, compared with the traditional finite element (FE) method. Thereafter, the effects of the geometrical parameters on the effective constants and band gaps are investigated and discussed. Numerical results demonstrate that the negative Poisson’s ratio provides an enhanced effective Young’s modulus of the considered honeycombs. Furthermore, the band gap exists in a much lower frequency region with an unchanged summing band gap width when the Poisson’s ratio is in negative values. In general, the work can serve as a guide for the optimal design of cellular structures.

No abstract