A carbon nanotube based temperature independent strain sensor on a flexible polymer

Structured and vertically aligned carbon nanotubes (CNTs) are investigated for their applicability as strain gauges. The CNTs are grown onto an oxidized Si substrate, passivated by a polymer and transferred to a flexible film. This sensor material has a high gauge factor up to 11.5 but also a negative temperature dependence of resistance (TCR with α_CNT = -500 ppm/K). For TCR compensation, thin film Pt resistors are added in series on either side of the CNT carpet. Due to the positive TCR of Pt the total TCR can be turned to zero by an appropriate layout of the Pt resistors.