A piezoelectric swallow patch sensor and its correlation to the physiological swallowing processes

Abstract Current studies on wearable devices have demonstrated that swallowing can be detected by attaching the sensor to the larynx area. However, most reports only perform demonstration studies, with limited efforts to investigate the correlations between the detected signals and the swallowing process. From the physiology standpoint, the movements of the hyoid bone (HY) and thyroid cartilage (TH) play essential roles in swallowing, such as epiglottic inversion, glottic closure, and the opening of the upper esophageal sphincter. Because HY and TH move underneath the larynx skin, we can monitor their actions by attaching a wearable sensor on the skin along their routes. However, a stiff sensor can restrict the skin deformation induced by the HY and TH movements and cause complications. Thus, we developed an ultra-compliant piezoelectric swallow patch sensor (SPS) that uses P(VDF-TrFE) microfibers as the sensor core and encapsulated inside a silicone rubber. The compliant design allows the SPS to track swallow-induced skin deformation caused by HY and TH, and the SPS signal can reflect their actual contribution to the swallowing process. The optimal SPS locations to monitor HY and TH are presented. The correlations between the SPS signal and the HY and TH movements are verified using a laryngeal ultrasound imaging system. The experimental studies verified that the SPS can determine the temporal and spatial movements of HY and TH, which can be utilized to monitor the swallowing process. Applying the SPS, we demonstrate that it can identify the >50-year-old male group has a longer TH moving time and slower TH rising velocity than the 18-to-25-year-old male group. In summary, we developed a novel SPS that can accurately monitor HY and TH movements for non-invasive screening of the swallowing process. Furthermore, our studies can serve as a guideline for designing a wearable device for swallow monitoring.