Conjugated Polymer Films for Piezoresistive Stress Sensing

The changes in the electrical conductivity of an indium-tin-oxide/poly [2-methoxy-5-(2´-ethylhexyloxy)-1,4-phyenylenevinylene] (MEH-PPV)/Al structure under compressive stresses were measured. The current recorded at 3 V showed a nearly linear characteristic response between 0.25 and 1.1 MPa with a sensitivity of 5.0 muA/KPa and a maximal piezoresistance coefficient of ~1.1 times 10^-4 Pa^-1. The devices under compression exhibited resistive switching above a threshold voltage with a resistance ratio of five, suggesting that the formation of nanofilamentary chains may be another mechanism in addition to increased intermolecular electron hopping contributing to the stress-induced current changes. The single-layer MEH-PPV sensors also exemplified good stability and repeatability, and appear to be promising for tactile sensing applications.