Abstract
The electroactive polymer polyvinylidene fluoride (PVDF) has gained much interest in smart materials research with a wide application range for industry and consumer applications due to the low cost, flexibility, chemical resistance, non-toxicity, and light weight. In this work, we present an α-phase PVDF cantilever that exploits electrostriction as the main transducer mechanism for excitation. We realize thin PVDF films with a thickness of ∼190 nm and a low roughness (∼19 nm RMS). Electrostrictive cantilevers need high electric fields to achieve amplitudes comparable to piezoelectric counterparts. At thinner films, lower voltage levels are requested for comparable electric fields, thus making electrostrictive PVDF cantilevers a viable route and subsequently allowing broader use of PVDF in MEMS devices. We use an asymmetric electrode design that has the advantage of shifting the neutral axis out of the PVDF without enhancing cantilever thickness with a supporting device layer. In addition, these devices can be produced by CMOS compatible micromachining techniques. We measured the electrostrictive and piezoelectric actuation signal with laser-Doppler vibrometry and showed the frequency spectrum and curvature of such α-phase PVDF cantilevers. The cantilevers have a curvate of up to 120 m−1 at 1500 kV/cm. We demonstrate that the electrostrictive actuation has a low temperature dependency in the range from 25 up to 130 °C. A typical cantilever exhibits a geometry dependent low spring constant (k ∼ 0.3 N m−1) and a low quality factor (Q ∼ 75) in air.
Highlights
Extensive research was conducted in the polymer community in order to fully use the potential of polyvinylidene fluoride (PVDF) as a reliable and cheap transducer material.[1]
We fabricated and characterized an α-phase PVDF microelectromechanical systems (MEMS) cantilever, whereas the functional polymer is spin-on coated on a pre-heated chuck
The PVDF film thickness was about 190 nm, which allows the realization of high electric fields at lower voltage levels
Summary
Extensive research was conducted in the polymer community in order to fully use the potential of polyvinylidene fluoride (PVDF) as a reliable and cheap transducer material.[1]. Research has focused on materials with high electrostrictive coefficients like near-percolated networks of reduced graphene oxide as conducting fillers dispersed in a polydimethylsiloxane matrix.[19] Another approach is to make the PVDF film as thin as possible, so that at even lower voltage levels the same electric field strength results as in thicker layers. When targeting lower voltage levels for the actuation of high amplitudes due to a low PVDF film thickness while ensuring simultaneously high breakdown field strengths, electrostrictive PVDF thin films represent a promising transducer material for MEMS applications. For the synchronized measurement of the time-resolved mechanical response A(t) at different locations on
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