Bulk Micromachined Electrothermal Hydraulic Microactuator and Its Applications

Paraffin wax exhibits a volumetric expansion of ~15%, at around its melting point. By exploiting this expansion, electrothermal hydraulic microactuators have been demonstrated. The paraffin wax is contained within a bulk micromachined silicon container. The container is sealed using a PDMS diaphragm. The paraffin wax in the container is melted by a gold microheater on a glass substrate. All the layers used to make up the containers are bonded together using an overglaze and PDMS. Four applications of the microactuator have been demonstrated. The realization of a prototype refreshable Braille cell (3times2 dot, 7times8.5times2 mm³) is presented. Other applications are microvalves and micropipettes for microfluidics, and the two types of microgrippers. All the devices have been successfully demonstrated and operate at either 10 or 15 V DC.