Flexible, Wearable Mechano-Acoustic Sensors for Real-Time, Wireless Monitoring of Low Frequency Body Sounds

Measurements of low-frequency physiological signals, such as heart rate and pulse waves, play an essential role in biomedical applications for the early diagnosis of abnormal cardiovascular activities. Recent advances in flexible mechanical electronics represent a novel concept of miniaturized, wearable sensors for heart rate measurement that can be used in ambulatory environments. However, most mechanical sensors require the sensing element to be placed directly on the skin surface, which can lead to performance degradation or device damage due to significant skin deformation or external forces from skin-object interactions. This work addresses this challenge by developing soft, stretchable mechano-acoustic sensing platforms where all sensing components are not directly subjected to skin movement or deformation. Instead, this design allows cardiovascular pulse waves to propagate through a hollow, flexible microchannel, to vibrate the piezoresistive sensing element. Experimental studies demonstrate a complete wireless sensing system capable of detecting pulse waves and heart rates, with results consistent with those of commercially available devices. The proposed sensing concept allows for the develop of other wireless and flexible sensing systems such as a flexible air-channel pad for detecting swallowing patterns from users’ laryngeal movements, facilitating a non-invasive and remote platform for potential monitoring, and assessment of dysphagia.