Multi-modal biofeedback electrical stimulator for wearable healthcare application

Abstract

Wearable healthcare is a promising research field which leads to shift the healthcare paradigm from the expensive and low quality of life (QoL) hospital-centric healthcare to the low-cost and high QoL patient-centric healthcare. Until now, previous wearable healthcare systems have been developed in two separate ways: 1) wearable sensors to monitor the patient’s health condition

and 2) wearable stimulators to provide electrical stimulation for remedial value. Consequently, optimized and safe electrical stimulation cannot be guaranteed. To solve these problems, this dissertation proposes two multi-modal biofeedback electrical stimu-lation ICs which contain both sensor circuit and stimulation circuit together for closed-loop controlled weara-ble healthcare. The proposed three ICs can measure the patient’s status or treatment status during the electrical stimulation for optimized and efficient treatment. The first IC is multi-modal feedback electro-acupuncture (EA) controller IC. The proposed EA con-troller IC measures the electromyography (EMG) and the skin temperature to analyze the stimulation status as well as supplies programmable stimulation current ($40 \mu A$ - 1 mA) with five different stimulation modes. The large time constant (LTC) sample and hold (S/H) current matching technique achieves the high-precision charge balancing (< 10 nA) for the patient’s safety. The proposed EA controller IC consumes 6.8 mW at 1.2 V supporting 32 different current levels. Based on EMG and skin temperature analyses, the practitioner can adaptively change the stimulation parameters for the optimal treatment value. The second IC is dual-impedance feedback iontophoresis controller IC. An iontophoresis stimulator front-end provides programmable stimulation current ($16 \mu A$ - $512 \mu A$ amplitude, DC - 500Hz frequency, and 3 % - 100 % duty cycle) for controllable drug delivery. For biofeedback operation, a dual-mode imped-ance sensor measures load and tissue impedances. The proposed IC consumes peak power of 2.2 mW. From the measured tissue impedance, the delivered drug dosage can be estimated. The user adaptively controls the stimulation parameters for optimized and accurate drug delivery. The third IC is the revised iontophoresis controller IC which contains the Bluetooth interface for wide compatibility with various smart devices. These three ICs are integrated into fabric patches using planar-fashionable circuit board (P-FCB) tech-nology for comfortable feeling to the skin. In order to implement compact fabric patch, multi-layer P-FCB technology is adopted. Thanks to two multi-modal biofeedback electrical stimulation systems with three ICs, more functional, safe, and convenient treatments can be achieved. The proposed multi-modal biofeedback electrical stimulation systems are fully implemented and verified by both in-vitro and in-vivo experiments.