A Microcontroller-Based Portable Transcutaneous Electrical Nerve Stimulator via Ultra-comfortable Tattoo Electrodes for Haptic Feedback

The non-invasive electrical stimulation of nerves requires neural stimulators with high voltage compliance to pass current through the skin and reach the targeted nerves. This study proposes a low-cost, microcontroller-based, wearable, high-voltage compliant current stimulator with four independent channels based on Components-Off-The-Shelf (COTS). The proposed system implements a voltage-current converter capable of generating custom stimulating waveforms with microseconds temporal resolution. The ±90 V voltage compliance enables the system to adapt to the possible variations in electrode-skin impedance during a daily life activity, allowing it to stimulate with currents up to 9 mA. The system was preliminary tested on humans using ultra-conformable Parylene-C based tattoo electrodes, showing the possibility of stimulating median and ulnar nerves and evoking sensation on the hand through more-than-wearable and completely unobtrusive technology.