Through three-dimensional (3D) printing, we attempted to fabricate 3D solid objects with piezoelectricity. By optimizing the conditions of 3D printing, we realized the fabrication of a piezoelectric object by 3D printing. In fact, we could produce a poly(L-lactide) (PLLA) object similar to a smart phone case fabricated by 3D printing, the molded body of which has button sensors at the desired sites by exploiting the piezoelectric properties of PLLA. Finally, we confirmed that the PLLA object behaved as a fully functional sensor.

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.