Design and pressure analysis for bulk-micromachined electrothermal hydraulic microactuators using a PCM

Paraffin wax exhibits a volumetric expansion of ∼15%, at around its melting point. By exploiting this phenomenon, high performance bulkachined electrothermal hydraulic microactuators have been demonstrated. The microactuators have been integrated into microfluidic valves, icrogrippers and micropipettes. The paraffin wax is confined within a bulk-micromachined silicon container. This container is sealed using an elasic diaphragm of PDMS, while it is heated via gold microheaters located on an underlying glass substrate. All the layers used to make up the containers re bonded together using a unique combination of overglaze paste and PDMS. The hydraulic pressure of expanding paraffin wax was determined sing the deflection theory of a circular plate. For the first time, the hydraulic pressure of expanding paraffin wax was calculated using the theory of arge deflections for a circular plate and measured data from the type-A microgripper. This theory has been exploited for the deflection analysis of icromachined thin elastic diaphragms. In order to calculate the hydraulic pressure, the theory of large deflections of a circular plate is calculated sing the measured actuation height, the PDMS diaphragm dimension of the microgripper (type-A) and mechanical properties of the PDMS. The ydraulic pressure was calculated to be approximately 0.12 MPa. All the devices were successfully demonstrated and operated at either 10 or 15 V. 2006 Elsevier B.V. All rights reserved.