Microfluidic preparation of highly stretchable natural rubber microfiber containing CNT/PEDOT:PSS hybrid for fabric-sewable wearable strain sensor

Soft strain sensors have received considerable attention because of their promising applications in human motion detection, soft robotics, and smart clothing. Mechanically strong and highly conductive strain sensors with a wide working range, high linearity, and fast response are in high demand. To fulfill these requirements, in this study, we prepared mechanically tough and stretchable elastomer microfibers comprising natural rubber, poly (3,4-ethylenedioxythiophene):poly (styrene sulfonate) (PEDOT:PSS), and multi-walled carbon nanotubes (CNTs) using a microfluidic device composed of coaxially aligned micro-capillaries. The strain sensors fabricated with these elastomer microfibers demonstrated high stretchability with a wide sensing range up to an elongation of 1275% and a high linearity of 1000%, with a very low response time of ~63 ms and a high resolution of 0.05%. The PEDOT:PSS functions as “bridges” to connect the CNTs, leading to the improved conductivity and linearity of the sensor. Furthermore, the strain sensor could be readily sewn on fabric and demonstrated excellent real-time detection of various human motions such as finger or elbow bending, walking, jumping, and phonation.