Design and Optimization of a Wearable Sonomyography Sensor for Dynamic Muscle Activity Monitoring

Sonomyography is a non-invasive modality that uses ultrasound for sensing muscle activity. The ability of this modality to robustly sense muscle activity with good resolution makes it suitable as a biomechatronic control interface. However, the most sonomyography-based studies utilize B-mode ultrasound imaging which require large form-factor clinical ultrasound imaging devices. In order to extend the utility of sonomyography techniques to wearable systems, the size of the ultrasound system and associated sensors needs to be greatly reduced. In this paper, we design and optimize the performance of a wearable ultrasound sensor for muscle activity monitoring applications. We fabricated a custom ultrasound transducer with a backing layer by mixing varying amounts of Tungsten powder to epoxy resin to optimize the bandwidth of the transducer. Our results showed that increasing the proportion of Tungsten improves the bandwidth of the transducers. Following optimization of the transducer design, we developed a wearable sonomyography sensor and demonstrated real-time measurement of dynamic muscle activity during hand open-close movement.