Vital Sign Measurement Using Covered FBG Sensor Embedded into Knitted Fabric for Smart Textile

It is desirable that a medical system should begin therapy before diseases reach severe stages. To realize such a system, vital signs should be monitored continuously. As an approach, we have worked on smart textiles for monitoring vital signs. In particular, a fiber Bragg grating (FBG) sensor is an excellent device because of its high performance, low cost, and fiber-or yarn-like form that is considered to be suitable for textile processes. In this study, we examined the measurement signal intensity for calculated blood pressure using a covered FBG sensor embedded into knitted fabric. An FBG sensor covered with silk thread was developed and embedded into tubular knitted fabric using inlay knitting technology. Next, a pulse wave signal was measured using this covered FBG sensor embedded into knitted fabric. Results showed that clothing pressure changed according to the number of wales of the knitted fabric and clothing pressure strongly influenced the detection of the pulse wave signal. Even though there is scope for improving this sensor as a wearable system, we found that it is possible to use the sensor in smart textiles for monitoring vital signs.