Babita Gaihre

Pushing the Limits for Microactuators Based on Electroactive Polymers

We have previously reported on the fabrication and displacement output of electroactive polymer (EAP) microactuators less than 1 mm in length. The main limiting factor hindering their further miniaturization and their displacement output was the thickness of the commercially available polyvinylidene fluoride (PVDF) membrane used (~ 110 μm). In this study, we have reduced the thickness of the PVDF layer using a spin-coating technique and then electrochemically deposited polypyrrole layers on both sides of this thin film to make ultrathin-film EAP substrates with a thickness of 48 μm. We then employed a laser ablation technique to fabricate microsized EAP actuators as small as 200 μm in length and 50 μm in width that can operate in both dry and aqueous media. This is the minimum-size EAP microactuator to be reported in the literature. Based on the operation principle of these actuators, we model them as a microcantilever beam under a uniformly distributed load. We then establish bending displacement and blocking force models to perform the following: (1) to estimate the actuation force, actuation moment, tip deflection, flexural rigidity, and strain energies per unit volume and mass for a set of microactuators as big as 850 μm × 250 μm × 126 μm and as small as 200 μm × 50 μm × 48 μm and (2) to evaluate their performance metrics.

Methods developed for the fabrication of a thermally-induced polypyrrole bilayer micro/nanoactuator

This paper presents preliminary results on the development of methods for the fabrication of a thermally-induced polypyrrole bilayer microactuator using a combination of electropolymerisation and focused ion beam techniques. A thin polypyrrole film doped with trifluoromethanesulfonimide (TFSI) featuring high thermal and environmental stability, laminated with a thin gold layer is used as an active structure for the electrothermal actuator. A cantilever-shaped polypyrrole actuator of micrometer-sized was successfully fabricated by focused ion beam (FIB) milling and deposition with high dimensional precision, minimal damage and a short processing time. The feasibility of FIB in the fabrication of this actuator marks its potential as a micro/nanofabrication tool to produce micro/nanodevices and prototypes that require no mask, resist or multi-step etching.