A sub-10nA DC-balanced adaptive stimulator IC with multimodal sensor for compact electro-acupuncture system

Electro-acupuncture (EA), a combination of acupuncture and electrical stimulation, has been widely used for its effectiveness in pain relief since the 1970s [1] and later for treatment of various diseases such as depression, addiction, and gastrointestinal disorders [2], and non-medical applications including obesity treatment [3]. For stimulation, most EA systems use a pair of needles with long, thick wires connected to an external power supply to form a closed current loop. The thin (φ=2mm) needle may suffer from the inconvenient and unstable connection to the thick wire and if there are many needles, it is difficult to supply power to all needles [4]. Recently, a wirelessly-powered EA system was proposed in [4] to remove the wire connections for convenient treatment, but its wireless power harvesting generated only 8μW which is not enough for various applications [1-3]. Most EA systems use bi-phase stimulation to reduce tissue damage, electrolysis, and electrolytic degradation [5]. However, the high-precision balancing of a bi-phase current pulse is difficult to achieve because the required offset, <;10nA [6], is only on the order of 10<;sup>;-5<;/sup>; of the stimulation current level, ~1mA. Furthermore, none of the previous EA systems have any feedback mechanism to enable adaptive stimulation by showing the real-time status of the EA stimulation to the patient.