The rapidly developing field of polymeric electronic and microelectromechanical (MEMS) devices has attracted much attention in recent years. Applications of polymeric MEMS devices include thin film transistors, waveguides for optical sensors, stretchable electronics as well as electroactive polymers (EAP) and dielectric elastomers actuators (DEAs). Polymeric actuators are distinguished by their very low fabrication cost, are often biocompatible, demonstrate large strain under small forces, exhibit fast response times, relatively large actuation forces and high efficiency. Because the electric fields required for the actuation of these devices are relatively high, of the order of tens or even hundreds of V/mm, reduction of the thickness of the polymeric layers is crucial for toreducing operational voltages. Thin layers of polymeric materials in MEMS devices are typically formed by spin-coating using diluted solutions of the uncured polymer. However, the spin-coating of polymers into micron scale films is challenging as there are strict requirements for film thickness, uniformity, process integration and defect density.

In this work we report on a novel fabrication process based on thermal imprinting for the formation of micron-scale, freestanding, layers of two polymeric materials, the dielectric elastomer poly(dimethylsiloxane) (PDMS) and the electroactive relaxor P(VDF-TrFE-CFE). We have fabricated freestanding, smooth, defect-free membranes with thicknesses in the range of 0.4–4.8 μm and with diameters of several millimeters . Since the ability to detach the membrane from the chips after imprinting is critical for the production of freestanding layers, the adhesion between the polymers and the silicon (Si) stamp and the Si substrate is reduced by the deposition of a hydrophobic dodecyl-trichlorosilane monolayer on the chips prior to imprinting. We demonstrate the feasibility of patterning the devices at the time of imprinting to create freestanding patterned micron-scale structures. A simple device made up of a freestanding circular membrane with electrodes on the circumference demonstrating the application of the method is presented . The results of the device’s electromechanical characterization revealed that a free-standing PDMS membrane 1 mm in diameter and 5.3 mm thick demonstrated displacements of 5 mm at an actuation voltage of 300 V.

 

This project was supported by Arkema/Piezotech . P(VDF-TrFE-CFE) materials were supplied by Piezotech S.A.S