A Flexible Pressure Sensor With Sandwiched Carpets of Vertically Aligned Carbon Nanotubes Partially Embedded in Polydimethylsiloxane Substrates

This paper presents a flexible pressure sensor composed of two face-to-face electrodes of vertically aligned carbon nanotubes (VACNTs) carpets partially embedded in polydimethylsiloxane(PDMS) substrates. VACNTs were grown using atmospheric pressure chemical vapor deposition (APCVD) on a Si/SiO2 substrate and transferred onto PDMS for partial embedment. This unique synthesis permitted a rapid and facile integration of a flexible and stretchable platform for the pressure sensor. The change of resistance occurs due to the external pressure applied orthogonal to the surface. The substrate was stretched to 180% and bent at bending radii of 87 mm and 105 mm. The pressure sensor exhibited the response times of 40 ms during loading and 60 ms during unloading. As a proof-of-concept, the sensor was attached on human skin; the heart rate, muscle flexing, and walking signals of an individual have been measured. In respect to durability, this sensor also showed a stable performance for 10,000 loading/unloading cycles with a resistance retention of 82% demonstrating its long-term use for repeated cycles toward practical applications.