A miniature, single use, skin-adhered, low-voltage, electroosmotic pumping-based subcutaneous infusion system

Abstract

A programmable, skin-attached, 36 × 30 × 8 mm system for subcutaneous infusion of 1.2 mL of a drug solution is described. The system is intended to be replaced daily. It comprises a 20 × 14 × 8 mm electronic controller and power source, an 8 mm diameter 2 mm thick electroosmotic pump, a two-compartment reservoir for a pumped water and a drug solution, an adhesive tape for attachment to the skin, and a 6 mm long 27 gauge needle. Its removable electronic controller programs the dose rate and dose and is re-used. The electroosmotic pump consists of a porous ceramic membrane sandwiched between a pair of Ag/Ag₂O plated carbon paper electrodes. It operates below 1.23 V, the thermodynamic threshold for water electrolysis without gassing. The flow rate can be adjusted between 4 and 30 μL min⁻¹ by setting either by the voltage (0.2–0.8 V) or the current (30–200 μA). For average flow rates below 4 μL min⁻¹, the pump is turned on and off intermittently. For example, a flow rate of 160 μL day⁻¹, i.e., 0.13 μL min⁻¹ for basal insulin infusion in type 1 diabetes management, is obtained when 10 s pulses of 75 μA is applied every 15 min. High flow rates of 10–30 μL min⁻¹, required for prandial insulin administration, are obtained when the pump operates at 50–200 μA. To prevent fouling by the drug, only pure water passes the pump; the water pushes a drop of oil, which, in turn, pushes the drug solution.