Binary-Blended Polylactic Acid Multilayer Film Exhibits Super Piezoelectric Effect

Teijin’s New Films Development Section in conjunction with Professor Yoshiro Tajitsu, Faculty of Engineering Science at Kansai University, unveiled what it is calling a flexible, transparent piezoelectric material that demonstrates unprecedented piezoelectric effects. A piezoelectric material generates electric power (voltage, current) in proportion to pressure applied to it. Consequently, an inverse piezoelectric effect occurs by applying electric power instead of pressure to a piezoelectric material.

Tajitsu forms the material by alternately laminating two types of polylactic acid (PLA) films: poly-L-lactic acid (PLLA) and optical isomer poly-D-lactic acid (PDLA) (Fig. 1). The professor’s research indicates that piezoelectricity improves dramatically when PLA exceeds a certain level of purity.

1. Exhibiting super piezoelectric properties, the unique material consists of alternate layers of poly-L-lactic acid (PLLA) and optical isomer poly-D-lactic acid (PDLA).

Using high-purity PLLA and PLDA with Teijin’s advanced PLA refining technology, the unique multilayer film demonstrates superior piezoelectric performance. According to its makers, it emerges as the world’s first binary-blended PLA multilayer film with piezoelectric performance that outpaces industry-standard lead zirconate titanate (PZT).

Using a simple coextrusion method, manufacturing of the film consists of alternately inserting positive and negative electrodes between PLLA and PDLA films. In the presence of an electrical field, these materials exhibit piezoelectricity motion in opposite directions. Therefore, piezoelectricity motion can align in the same direction. Piezo performance is also controllable by varying the number of layers, enabling custom designs.

According to the researchers, this material is environmentally friendly. Future use forecasts larger but lighter products, a feature thought to be difficult to achieve in the past. Moving ahead, the Teijin and Kansai University team will continue research and development on the material (Fig. 2).

Also of note, the piezo material proves to be quite flexible. Future applications include pressure, vibration, and impact sensors, as well as ultrasonic motors, ultrasonic transducers for medical care, and actuators, which sounds promising.