# Contacting Layer Affects Properties of Piezoelectric Poly-L-Lactide Biomaterial

## TL;DR

Using different contacting layers during high-temperature processing of a polymer improves its piezoelectric properties and affects cell behavior.

## Contribution

The novel use of contacting layers during high-temperature drawing enhances PLLA's piezoelectric properties and cell response.

## Key findings

- Contacting layers like PTFE, cellulose, and polyimide influence PLLA's crystallization and molecular orientation.
- These layers improve piezoelectric properties and cell response through cytoskeleton activation and directional migration.
- The method is solvent-free, economical, and expands high-temperature drawing applications.

## Abstract

The main limitations of using a high-temperature drawing approach to tailor poly-l-lactide (PLLA) crystallization and molecular orientation for ultrasound-active piezoelectric structures stem from the intrinsic properties of the processed polymer, including low melting/softening elasticity and slow crystallization kinetics. Here, we found that applying different contacting layers, including polytetrafluoroethylene (PTFE) (as Teflon and Teflon S), cellulose (Paper) or polyimide (Kapton) deposited at the surface of PLLA, significantly affects the drawing process and tailors its oriented crystallization and molecular chain orientation. Consequently, the contacting layers contribute to the piezoelectric properties of PLLA (alone or with added morphologically anisotropic hydroxyapatite (HAp) filler), affecting its activation via ultrasound and generated electro-signal. Human keratinocytes (HaCaT cells) stimulated on these surfaces are shown to receive and respond to the transferred stimuli via the activation of the cytoskeleton and directional migration. The high-temperature (250 °C) drawing approach with contacting layers is a simple, solvent-free and economically viable way of broadening the applications of classical high-temperature drawing, opening new possibilities for further tailoring the piezoelectricity of organic piezoelectrics.