A wireless implantable drug delivery device with hydrogel microvalves controlled by field-frequency tuning

This paper reports a micromachined implantable drug delivery device that is wirelessly operated using radiofrequency magnetic fields. Frequency-dependent induction heating is used to control the actuation of thermoresponsive hydrogel microvalves for drug release. The hydrogel microvalves are formed on a passive inductor-capacitor tank with a size of 8.4×6.1-mm2, which serves as a wireless resonant heater that can be activated by tuning the field frequency to the resonant frequency of the tank for the microvalve actuation that unplugs the release holes created in a wall of the device's reservoir. An in-situ photo-polymerization technique is developed to form the hydrogel microvalves self-aligned to the release holes. The fabricated device shows no detectable leak for at least 12 hours. Frequency-controlled temporal release is experimentally demonstrated using a fluorescein-loaded device with the resonant frequency of 65 MHz in deionized water and a magnetic field with ~800-mW output power.