Piezoelectric Motion of Multilayer Film with Alternate Rows of Optical Isomers of Chiral Polymer Film

Abstract

We realized a multilayer film laminated alternately with poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA) films in order to improve the piezoelectric performance of the PLLA film. In the fabrication processes, the thicknesses of PLLA and PDLA films were reduced to improve the effective electric field, and a multilayer composed of more than 100 layers (PDLA/PLLA multilayer film) was realized to improve the piezoelectric performance. In general, a single PLLA film has a piezoelectric constant of about 5 pC/N, and it is difficult to observe the piezoelectric resonance in this film of centimeter-order size using a commercial impedance analyzer because of its small Q-value. In contrast, the PDLA/PLLA multilayer film of centimeter-order size has a piezoelectric performance equivalent to that of the piezoelectric material with a piezoelectric constant of 100 pC/N, and also, the piezoelectric resonance can be observed in this film. On the basis of these results, we confirmed that even an object of 259 g mass is made to vibrate under the piezoelectric resonance vibration of this PDLA/PLLA multilayer film. In other words, necessary quantities for actual work as an actuator could be obtained in the PDLA/PLLA multilayer film.

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“…In order to induce piezoelectricity, the chains must be thermally stretched to transform the a-crystalline form into the b-crystalline form, which represents a change from randomly oriented molecular chains to molecular chains being aligned along the stretched direction. 78,79 It is noted that elongated PLLA lms have no…”

“…PLLA is a transparent and very exible polymeric material, and thus is used for applications in mobile devices as an environmentally friendly, exible, transparent, piezoelectric thin lm. 78,79 Fig. 2 presents PLLA in the a-crystalline form which is thermodynamically stable conformation.…”

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“…PLLA is more widely utilized for making piezoelectric devices while PDLA is often used as an agent to improve the piezoelectric and thermo‐mechanical properties of PLLA. [ 35,111–114 ]…”

“…PLLA is more widely utilized for making piezoelectric devices while PDLA is often used as an agent to improve the piezoelectric and thermo-mechanical properties of PLLA. [35,[111][112][113][114] Compared with PVDF, PLLA exhibits a higher shear piezoelectric coefficient value (d 14 ) of ≈12 pm V −1 . [115] Studies have demonstrated that the chirality of the asymmetric carbon atoms in PLLA affects its shear piezoelectric constant.…”

Skin‐Adhesive Flexible Force Sensors Based on Piezoelectric Poly(l‐lactic acid) for Human Behavior Recognition

“…[20,21] Therein, the sustainable growth of shear piezoelectric signals gives the PLLA great application potential in the field of actuators and sensors. [21][22][23][24][25] In addition, PLLA is biodegradable and can be decomposed in a hydrolytic or enzymatic condition, [26,27] it is a kind of environmentally friendly biomaterial, which has been applied in flexible electronics and wearable sensors due to excellent biocompatibility. [28][29][30] Currently, greater progress has been made in flexible sensors based on elastic polymers.…”