Stretchable Composite Acoustic Transducer for Wearable Monitoring of Vital Signs

We report a highly flexible, stretchable, and mechanically robust low-cost soft composite consisting of silicone polymers and water (or hydrogels). When combined with conventional acoustic transducers, the materials reported enable high performance real-time monitoring of heart and respiratory patterns over layers of clothing (or furry skin of animals) without the need for direct contact with the skin. Our approach enables an entirely new method of fabrication that involves encapsulation of water and hydrogels with silicones and exploits the ability of sound waves to travel through the body. The system proposed outperforms commercial, metal-based stethoscopes for the auscultation of the heart when worn over clothing and is less susceptible to motion artefacts. We have tested the system both with human and furry animal subjects ( i.e. dogs), primarily focusing on monitoring the heart, however, we also present initial results on monitoring breathing. Our work is especially important because it is the first demonstration of a stretchable sensor that is suitable for use with furry animals and do not require shaving of the animal for data acquisition.