No abstract

Screen-printed piezoelectric shoe-insole energy harvester using an improved flexible PZT-polymer composites Abstract. This paper reports improved screen-printed piezoelectric composites that can be printed on fabrics or flexible substrates. The materials are flexible and are processed at lower temperature (130°C). One main PZT particle size (2µm) was mixed separately with smaller piezoelectric particles (0.1, 0.3 and 0.8µm) with different weight ratios to investigate the piezoelectric property d 33 . The blended PZT powder was then mixed with 40% polymer binder and printed on Alumina substrates. The applied poling field, temperature and time were 8MV/m, 160°C and 10min, respectively. The optimum material gives a d 33 of 36pC/N with particle sizes of 2µm and 0.8µm and mixed percentages of 82% and 18%, respectively. A screen-printed piezoelectric shoe-insoles (PSI) has been developed as a self-powered force mapping sensor. The PSI was simulated, fabricated and tested. ANSYS results show that one element of PSI sole can produce an open-circuit voltage of 3V when a human of average weight of 70kg makes a gait strike. Experimental results show that one element produced 2V which is less than the simulated results because of the reduction of poling field for the practical device.

Abstract. This paper introduces a new flexible PZT/polymer composite material that can be screen-printed onto fabrics and flexible substrates, and investigates the clamping effect of these substrates on the characterization of the piezoelectric material. Experimental results showed that the optimum blend of PZT/polymer binder with a weight ratio of 12:1 which provides a dielectric constant of 146. The measured value of the piezoelectric coefficient d 33 was found to depend on the substrate used. Measured d 33clp values of 70, 40, 36 pC/N were obtained from the optimum formulation printed on Polyester-cotton with an interface layer, Kapton and alumina substrates, respectively. The variation in the measured d 33clp values occurs because of the effect of the mechanical boundary conditions of the substrate. The piezoelectric film is mechanically bonded to the surface of the substrate and this constrains the film in the plane of the substrate (the 1-direction). This constraint means that the perpendicular forces (applied in the 3-direction) used to measure d 33 introduce a strain in the 1-direction that produces a charge of the opposite polarity to that induced by the d 33 effect. This is due to the negative sign of the d 31 coefficient and has the effect of reducing the measured d 33 value. Theoretical and experimental investigations confirm a reduction of 13%, 50% and 55% in the estimated freestanding d 33fs values (80 pC/N) on Polyester-cotton, Kapton and alumina substrates, respectively. These results demonstrate the effect of the boundary conditions of the substrate/PZT interface on the piezoelectric response of the PZT/polymer film and in particular the reduced effect of fabric substrates due to their lowered stiffness. IntroductionMechanical boundary conditions can affect the mechanical performance of the piezoelectric material and its measured piezoelectric response. This paper explores the effect of the substrate mechanical boundary condition on the measured properties of printed polymer piezoelectric films. The magnitude of this effect is dominated by the mechanical properties of the substrate and the influence of three different substrates (textile plus interface layer, Kapton and alumina) is presented. This enables a comparison between rigid ceramic, flexible polymer and flexible textile substrates.

This paper describes the development of screen printed vibration energy harvesters developed at the University of Southampton. The mark 1 harvester developed very low levels of power (2 mW) due to the poor piezoelectric properties of the printed film. Properties were improved by blending particle sizes and optimising firing and poling conditions. The new piezoelectric paste was applied to harvesters developed for the EU funded project TRIADE. Power outputs have improved to 240 mW from an excitation vibration of 0?29g rms (g59?8 m s 22 ) at 67 Hz. Multilayer structures also demonstrate further improvements, and the harvester has been demonstrated powering an autonomous wireless sensor system for condition monitoring.

No abstract