Paraffin-pdms Composite Thermo Microactuator with Large Vertical Displacement Capability

We have micromachined and tested the first paraffin–PDMS composite thermal microactuator having multi shot large vertical displacement capabilities (~160 μm for 1 mm diameter device). A solid to liquid phase change of trapped paraffin into the PDMS is used to create a large volume dilatation of the composite (18%, for a temperature varied from 20 to 80 °C). The elasticity of the PDMS ensures the reversibility of the actuation. The paraffin-PDMS composite also facilitates fabrication and confines the melted paraffin when the device is actuated. This actuator has large force capabilities illustrated in our demonstrator by lifting a heavy mass for microsystems (60 mg). The actuator consists of a glass cavity filled with a paraffin-PDMS composite, a micro hotplate at the bottom of the cavity, and a nozzle-like silicon structure sealing the top of the cavity. The polyimide-aluminium microhotplate bonded to the bottom of the cavity heats (160 mW @ 2 V) the composite to obtain up to 160 μm out of plane vertical displacement.