Wearable multimode sensors with amplified piezoelectricity due to the multi local strain using 3D textile structure for detecting human body signals

In this study, a new wearable multi-local strain sensor (MLS-sensor) based on 3D textile structure with pre-strained monofilament was proposed, which features two modes. First, the vibration mode detects bio-signals from voice printing, respiration and blood pulse. Second, the tensile and compression mode, which detects signals from body movement based on pressure of fingertip and gait, four movement of neck, and joint movement (elbow and knee). Previous research studies mainly focused on investigation on how to enhance the output performance of piezoelectric PVDF film via nanostructure. However, this study explores how macro-sized 3D textile structure can improve the piezoelectric performance of PVDF film. Whereas, 3D textile structure has been commonly utilized as a pressure absorber due to the space caused by the monofilament that exhibits viscoelastic behavior. The MLS-sensor utilizes the pre-strained monofilament of 3D textile structure as a pressure transmitter to create amplified strain resulting from multi-local strain (MLS) in PVDF film in order to improve the PVDF piezoelectric performance. The MLS-sensor was shown to amplify the piezoelectric output voltage (4.6 V) up to 5 times (25.6 V) using the same pressure.