Thermally driven microactuator containing thermal isolation structure with polyimide and its application to microvalve

We have developed a thermally /spl middot/ isolated bimorph structure based on a silicon (Si) /nickel (Ni) pair. A 2.5-mm-long beam of the bimorph was thermally isolated by a polyimide comb from the rest of the Si structure. The Si and Ni layers of the bimorph were 30 /spl mu/m and 25 /spl mu/m thick, respectively. This geometry enabled us to generate the bending displacement (the stroke) of the free end of the bimorph up to 100 /spl mu/m at about 100 /spl deg/C with a generated force of about 15 mN. A low-voltage actuation (<3V) and low-energy consumption (<0.2W) were achieved. Besides, the miniaturized Si/Ni bimorph actuator was incorporated into the valve structure. The actual size of the fabricated valve is 7.3/spl times/5.8/spl times/1.2 mm/sup 3/. The flow rate from 0 to 500 ml/min at the air pressure of 47 kPa with low leakage rate of 0.03 ml/min and good linearity of the air pressure control were achieved.