Development of piezoelectric PVDF sensor integrated textile yarn

Since the invention of micro-electromechanical systems (MEMSs), scientists have found it possible to introduce novel functional textiles and garments that are very close in appearance to conventional textile products. In addition to this, wireless communication technology will enable a flow of information between devices, human body and the external environment. In the last decade, the micro system technologies have focused on flexibility apart from the size. The large area available in these products provides the space to integrate micro systems and still offer enough flexibility in the fabrics to make them wearable as well. Piezoelectric material is a smart and flexible material capable of generating electrical polarisation under applied mechanical stress. Therefore piezoelectric PVDF films are such material candidates using which smart textiles can be created and can be shaped easily into many wearable electronic products or forms. The purpose of this study is to encapsulate piezoelectric PVDF material in/onto a textile yarn in order to create intelligent yarns. The encapsulation of piezoelectric material in/onto yarn would enable them to be placed, using conventional textile manufacturing processes, in textiles in order to measure mechanical stimulations on them. The piezofilm sensor size was cut to 1 x 10mm to bring it close to textile yarn dimensions. A soft encapsulation material was utilised in order to create an encapsulation area as soft as yarn also providing washability and tumble drying. In order to transport the data generated by these PVDF sensing yarns, carbon loaded monofilament yarns, in the form of conductive pathways in the fabrics, were attached to the piezofilm by creating a conductive and strong bond. Manufactured Piezofilm Yarn Sensors (PYSs) were characterised by conducting tensile, pressure, buckling, long term cyclic and breakage tests, showing good voltage generation and linearity. The PYS samples were knitted along with textile yarns for the creation of smart structures. Human body experiments showed that the knitted PYSs are able to measure both respiration and heart beat signals at static or ambulatory conditions. Therefore the newly created PYS could play an important role towards the advancement of wearable health monitoring systems.