Melt electrowriting of poly(vinylidene fluoride‐co‐trifluoroethylene)

Juliane C Kade,Robert Luxenhofer,Dario Pisignano,Jan Weichhold,Biranche Tandon,Paul D Dalton,Luana Persano

doi:10.1002/pi.6272

Abstract

AbstractPoly(vinylidene fluoride‐co‐trifluoroethylene) (P(VDF‐co‐TrFE)) is an electroactive polymer with growing interest for applications in biomedical materials and flexible electronics. In this study, a solvent‐free additive manufacturing technique called melt electrowriting (MEW) has been utilized to fabricate well‐defined microperiodic structures of the copolymer (P(VDF‐co‐TrFE)). MEW of the highly viscous polymer melt was initiated using a heated collector at temperatures above 120 °C and required remarkably slow collector speeds below 100 mm min−1. The fiber surface morphology was affected by the collector speed and an increase in β‐phase was observed for scaffolds compared to the unprocessed powder. Videography shows vibrations of the P(VDF‐co‐TrFE) jet previously unseen during MEW, probably due to repeated charge buildup and discharge. Furthermore, piezo‐force microscopy measurements demonstrated the electromechanical response of MEW‐fabricated fibers. This research therefore achieves the melt electrohydrodynamic processing of fibers with micrometer resolution into defined structures with an important electroactive polymer. © 2021 The Authors. Polymer International published by John Wiley & Sons Ltd on behalf of Society of Industrial Chemistry.

Highlights

Electroactive polymers with piezoelectric properties are of increasing interest for biomedical applications, in particular for the electrical stimulation of cells without the need for an external power supply [1, 2]
Poly(vinylidene fluoride) (PVDF) is piezoelectric in the β-phase conformation, the content of which can be increased at the expense of the α-phase by stretching, poling or annealing of the raw material [8]
This study investigates processing of P(VDF-co-TrFE) using melt electrowriting (MEW) and determines the printability of the copolymer with this technique

Summary

Introduction

Electroactive polymers with piezoelectric properties are of increasing interest for biomedical applications, in particular for the electrical stimulation of cells without the need for an external power supply [1, 2]. The sinusoidal formation starts to appear when the collector temperature reaches about 70-80°C at the glass slide and 80-90°C for the set-temperature of the heated collector (Supporting Video S5) and could be connected to the Curie transition temperature during cooling as judged from the DSC thermograms (Figure S1B) These structural variations could be due to changes in the recrystallization process during solidification and residual thermal strain, which are known to be highly dependent on the cooling rate [32]. MEW-processing the P(VDF-co-TrFE) with a heated collector could be seen as an in situ annealing process and annealing temperatures close to the Curie temperature can provide sufficient energy for chain reorientation and, can lead to an increase in β-phase formation compared to unprocessed material [24]. Dipoles are sensitive to the direction of the applied field and exhibit a phase shift when the external bias is inverted (i.e. the positive bias is applied to the sample and the tip is grounded) as reported in Figure S6 B-C

Fiber fabrication

Conclusion

Fiber diameter