An electrochemically actuated drug delivery device with in-situ dosage sensing

Very few conventional micro-electro-mechanical systems as drug delivery devices have in-situ dosage monitoring sensors, this thus brings inaccurate released dose, which results in either inefficient pharmaceutical effects or over-dose induced side effects. In this work, we integrate a low-cost piezoresistive sensor with an electrochemically actuated drug delivery device, and investigate its dosage monitoring performance. Different from the conventional sensor fabrication based on mixing conductive particles into liquid polymer, our proposed sensor is constructed from solidified carbon ink film embedded in a polydimethylsiloxane (PDMS) membrane, which can obtain an optimum tradeoff between the gauge factor and maximum achievable displacement. An electrolytic reaction induces the electrolysis-bubble in the actuator chamber with an increase in pressure, which causes displacement of the PDMS sealing membrane. This provides the actuation force to deliver the drug solution. The displacement of the PDMS membrane that determines the pumped volume of the drug solution is quantified through a resistance change of the embedded piezoresistive sensor. We report a single pumping volume of up to 7 μl, which is monitored by the resistance change ratio (ΔR/R), ranging from 2% to 12% with a dosage sensing accuracy of 6.5%.