In this research, two wearable surface stimulation systems have been developed for use in wound electrotherapy. These self-contained, battery-powered bandages have been demonstrated in-vivo using both a rat chronic wound model and a pig infected wound model and provide a new means to investigate the physiological mechanisms of wound healing.
The first stimulation bandage was designed for use with a rat wound model and consists of a stimulator PCB module and plastic electrode bandage. The PCB is constructed from discrete COTS components and is powered by a small button cell battery providing at least seven days of continuous use. This voltage-mode device generates stimulation pulses that are 10 - 90 V in amplitude, 10 - 200 µs in width, and 12 – 25 Hz in frequency. Stimulation was typically applied to wounds for 10 minutes every hour for one week, and then the device and wound dressings were replaced.
An ASIC has been developed using the OnSemi 0.7-µm I2T100 process and is
capable of operation up to 100 V. A high-gain, current-mode boost converter addresses challenges associated with efficient generation of the large amplitude compliance voltage (up to 90 V) from a small battery with limited output current capability. A biphasic current mode stimulator was demonstrated with ±21-mA output range, 0.33-mA resolution, and a voltage headroom requirement of 3.5 V at full scale output.
The second stimulation bandage uses this ASIC and was designed for use on larger wounds, up to 6 cm in diameter. A rechargeable lithium polymer battery allows a single stimulator module to be used for an entire 28-day study. The disposable electrode bandage portion of the device is easily replaced in-situ by the clinician. Continuous monitoring of the delivered stimulation current while the device is in place on an animal is achieved using a microcontroller with a built-in Bluetooth Low Energy radio. Performance information from up to six devices is recorded to a wireless base station located outside the animal pen and may also be remotely accessed by research personnel.