Mechanoelectrical Force Sensors Using Twisted Yarns of Carbon Nanotubes

Yarns spun by twisting multiwalled carbon nanotubes (MWNTs) have been reported. Here, we report the application of these yarns as mechanical force sensors. When electrochemically charged, the yarns can respond to a change in the applied tension by generating a change in the cell current (up to about 1.2 nA/MPa per centimeter length of the yarn) or the open-circuit potential of the cell (up to 0.013 mV/MPa per centimeter length of the yarn) corresponding to the applied tension force. The MWNT yarns are mechanically strong with tensile strengths reaching 1 GPa. These properties together make them prime candidates for many applications as fast and efficient sensors. Their sensitivity as mechanical strain sensors is about 0.5 V/micorstrain, which is comparable to the sensitivity of metal film strain gauge sensors. The sensitivity is expected to improve by using thicker bundles of yarns.