Working mechanisms of strain sensors utilizing aligned carbon nanotube network and aerosol jet printed electrodes

This paper reports on highly sensitive aligned carbon nanotube network (CNTN)-based strain sensors produced by aerosol jet printed electrodes and polyimide substrates. Two types of sensing mechanisms were revealed. Type A sensors, whose electrodes were directly printed on the CNTNs and embedded in epoxy resin, take advantage of the intrinsic piezoresistive properties of highly oriented carbon nanotube bundles and exhibited large positive gauge factor. Type B sensors, whose electrodes were printed on the polyimide substrate, utilize the effects of applied strains on the contact resistances between layers of the CNTN structure and between CNTN and the electrodes, exhibited large negative gauge factors. Type A and B sensors achieved positive and negative gauge factors up to 20 and 40 in magnitude, respectively. The high performance and flexible nature of the sensors, combined with the capability of scalable manufacturing processes, exhibits promising application potentials.