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, actuationmoment, 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.