A low power, microvalve regulated architecture for drug delivery systems

This paper describes an actively-controlled architecture for drug delivery systems that offers high performance and volume efficiency through the use of micromachined components. The system uses a controlled valve to regulate dosing by throttling flow from a mechanically pressurized reservoir, thereby eliminating the need for a pump. To this end, the valve is fabricated from a glass wafer and silicon-on-insulator wafer for sensor integration. The valve draws a maximum power of 1.68 mu W (averaged over time); with the existing packaging scheme, it has a volume of 2.475 cm(3). The reservoirs are assembled by compressing polyethylene terephthalate polymer balloons with metal springs. The metal springs are fabricated from Elgiloy (R) using photochemical etching. The springs pressurize the contents of 37 mL chambers up to 15 kPa. The system is integrated with batteries and a control circuit board within a 113 cm(3) metal casing. This system has been evaluated in different control modes to mimic clinical applications. Bolus deliveries of 1.5 mL have been regulated as well as continuous flows of 0.15 mL/day with accuracies of 3.22%. The results suggest that this device can be used in an implant to regulate intrathecal drug delivery.