Piezoelectricity of fluorine-system porous electret and its application

Abstract

We developed a piezoelectric polymer film that was an electret using a porous poly(tetrafluoroethylene) (p-PTFE) film with high piezoelectricity and high heat resistance. First, we found that the p-PTFE electret had a piezoelectric constant d 33 of 100 pC/N after the optimization of its pore size. This value was about five times as large as that of poly(vinylidene fluoride) (PVDF) and was retained up to a temperature of as high as 120 °C.Then a new device using the laminated film with perfluoroalkoxy (PFA) laminated on one side of the p-PTFE electret was developed for the demonstration of pressure sensing. A new flexible device with a large area was realized. Then, for the demonstration of pressure sensing, a plastic touch pen for a touch panel was traced on the surface of the device at a constant speed of 80 mm/s under a compressive load of 0.05 N. The results confirmed that the device exhibited superior sensing responsiveness.

Application of piezoelectric electrets to an energy-harvesting system

“…First, we prepared many p-PTFE films with a thickness of 12 μm and various pore sizes. In the previous study, 31) tetrafluoroethylene-hexafluoropropylene copolymer (FEP) films with a thickness of 6 μm were laminated on both surfaces of each p-PTFE film (FEP/p-PTFE/FEP film) by hot pressing. However, in the previous method, 31) the FEP films laminated in the surface roughness direction produced surface waviness owing to the pores near the surfaces of the p-PTFE film.…”

“…[27][28][29][30] Instead, we attempted to fabricate electrets from poly(tetrafluoroethylene) (PTFE), which has excellent environmental resistance and high heat resistance. 31) Finally, we realized a p-PTFE electret with a large d 33 and good environmental resistance up to a high temperature. Also, it is generally difficult to realize a p-PTFE film with a flat surface by controlling the surface roughness because of the many pores of various sizes on the top surface of the film.…”

Piezoelectric characteristics of three-dimensional solid object of poly(l-lactide) fabricated by three-dimensional printing

“…Piezoelectric polymers with excellent properties such as flexibility, lightness, and transparency have attracted attention as materials for wearable sensing devices. [1][2][3][4][5][6][7][8][9] In particular, because poly(Llactide) (PLLA) is non-pyroelectric, it is expected to be used as a piezoelectric material for wearable devices. [10][11][12][13][14][15] The existence of pyroelectricity is a very important factor in human-machine-interface (HMI) applications.…”