Hiroaki Kitada

Pressure-Sensitive Touch Panel Based on Piezoelectric Poly(L-lactic acid) Film

Poly(lactic acid) (PLA) is a widely used biomass-derived polymer. It is chiral because the lactic acid monomer has an asymmetric carbon. If the L-lactide is polymerized, then the PLA polymer is an L-type PLA or poly(L-lactic acid) (PLLA); if the D-lactide in PLA is polymerized, then the polymer is a D-type PLA (PDLA). When these polymers undergo drawing or elongation, they exhibit shear piezoelectricity. PLA films are highly transparent and do not exhibit pyroelectricity because of the lack of intrinsic polarization. Therefore, if a PLLA film is used for a touch panel, which is operated by pressure, there is no spurious signal due to heating from the fingers. This suggests that PLLA films may be suitable for touch panels using pressure detection. We used PLLA as the base film of a projected capacitive touch panel with multiple electrodes, and demonstrated a multitouch gesture screen that was sensitive to pressure applied on the screen. This touch panel technology has potential applications for smart phones and tablet personal computers.

New human machine interface devices using a piezoelectric poly(L-lactic acid) film

Poly(lactic acid) (PLA) is a well-known, environmentally-friendly polymer. Piezoelectric poly(L-lactic acid) (PLLA), a type of chiral polymer, exhibits a high shear piezoelectric constant, is highly transparent, and is not pyroelectric. New human machine interface devices with intuitive control can be fabricated using piezoelectric PLLA as a deformation sensor. Specifically, for projected capacitive touch panels widely used in smartphone technology, the PLLA film as a pressure sensor with multiple electrodes allows pressure-sensitive functions to be added to the touch panel display.