An 87-$\hbox{mA}\cdot \min$ Iontophoresis Controller IC With Dual-Mode Impedance Sensor for Patch-Type Transdermal Drug Delivery System

A bio-feedback iontophoresis controller IC is implemented into a fabric patch for transdermal drug delivery. An iontophoresis stimulator front-end (ISFE) can provide programmable stimulation current in the range of 16-512-μA amplitude, DC-500-Hz frequency, and 3% -100% duty cycle for controllable drug delivery. For safe and robust electrical stimulation, a failure detection circuit monitors the stimulation current to prevent overcurrent and stimulation voltage saturation. For bio-feedback operation, a dual-mode impedance sensor (DMIS) measures load and tissue impedances in the range of 5-50 kΩ and 5 Ω-1 kΩ, respectively. In the DMIS, the gain of a programmable gain amplifier and the injected current level of a chopper-modulated current source are automatically controlled to minimize power consumption. The proposed IC occupies 2.35 mm × 2.35 mm including pads in a 0.11-μm 1P6M CMOS technology and dissipates a peak power of 2.2 mW. The proposed IC is directly integrated on a 9 cm × 4 cm fabric circuit board together with a 6.2-mAh coin battery for convenient iontophoresis treatment. The proposed system provides a maximum dosage range of 87 mA·min, which is larger range than the 80- mA·min dosage range of a commercial iontophoresis patch. Using a reconfigurable tetra-polar electrode configuration, load and tissue impedances are measured during the iontophoresis treatment to provide bio-feedback. The proposed iontophoresis system is successfully verified by both in-vitro and in-vivo tests.