Dual drug delivery device for chronic pain management using micromachined elastic metal structures and silicon microvalves

This paper describes a dual-chamber drug delivery microsystem that provides regulated flow from two spring- pressurized balloon reservoirs using independent microvalves. A preliminary prototype has been constructed with the primary components. Micromachined bulk metal springs (Co-Ni-Cr alloy), with an in-plane spring constant exceeding 300 N/m, are used in conjunction with 18.8 mL reservoirs, and provide 15 kPA pressure when the balloons are fully inflated. A piezoresistive pressure sensor that is embedded in the microvalves monitors reservoir pressure with a sensitivity of 250 ppm/kPa, and is used to regulate bolus delivery. Two control plans for the valve and their respective limitations are presented. In a demonstration of regulated bolus delivery, 1.5 mL bolus doses are delivered at different rates.