Design, fabrication and testing of piezoelectric polymer PVDF microactuators

Abstract

Piezoelectric polymers are increasingly considered as favorable materials for microactuatorapplications due to their fast response, low operating voltages and greaterefficiencies of operation. However, the difficulty of forming structures and shapeshas so far limited the range of mechanical design. In this work, the design andfabrication of a unimorph piezoelectric cantilever actuator using piezoelectricpolymer polyvinylidene fluoride (PVDF) with an electroplated layer of nickel iron(permalloy) alloy is described. The modeling and simulation of the compositecantilever was performed using CoventorWare to optimize the design parameters inorder to achieve large tip deflections. These simulation results indicated that thethicknesses of both the piezo and non-piezo layers of the composite cantilever affect themagnitude of deflection of the cantilever. It was shown that the tip deflection ofsuch a cantilever with a length of 5 mm and a width of 1 mm can reach up to70 µm, when simulation wascarried out using a 28 µm thick PVDF layer at a non-piezo layer thickness of5 µm. A PVDF polymer cantilever is fabricated using a simple punching technique based onmicroembossing. The permalloy layer was electroplated on one side of the PVDF to form acomposite cantilever. The tip deflection of the cantilever was observed and measuredunder an optical microscope. The experimental results showed deflection valueswhich are 20% less than those predicted by the simulation and analytical results.The thickness non-uniformity, residual stresses and possible difference in Young’smodulus values of the bulk material to that of electroplated permalloy film areidentified as some of the potential issues that might have caused this difference.