Tattoo Assisted Optical Sensor System for Multimodal Discrete Physiological Sensing.

This work introduces a novel method for recording electrophysiological signals and sensing physiological events using an optical tattoo sensor (OTS), eliminating the need for integrating electronics on the skin. Traditional sensors face challenges due to the mechanical mismatch between rigid silicon-based circuits and soft, stretchable sensors, leading to poor performance and interface failures. The OTS, which can be applied as a conventional temporary tattoo, eliminates scattered light from beneath the skin. When used with a handheld speckle sensing device, it improves signal-to-noise ratio and stability in capturing physiological activities beneath the skin. Using the tattoo assisted portable optical sensing system, different types of electrophysiological signal recording and physiological events sensing, including electrocardiography (ECG), electromyography (EMG), seismocardiography (SCG), respiration rate, and pulses, are performed. A shallow neural network is developed to convert the detected skin motions into electrophysiological signals such as ECG. The electrophysiological recording using OTS shows consistency with electrically measured signals.