Pushing the Limits for Microactuators Based on Electroactive Polymers

Abstract

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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(\sim 110\ \mu\hbox{m})$</tex></formula> . 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> . We then employed a laser ablation technique to fabricate microsized EAP actuators as small as 200 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> in length and 50 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu\hbox{m}$</tex></formula> 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 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$850\ \mu\hbox{m} \times 250\ \mu\hbox{m} \times 126\ \mu\hbox{m}$</tex></formula> and as small as <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$200\ \mu\hbox{m} \times 50\ \mu\hbox{m} \times 48\ \mu\hbox{m}$</tex></formula> and 2) to evaluate their performance metrics. <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\hfill$</tex></formula> [2011-0250]