Polypyrrole-coated Fabric Strain Sensor with High Sensitivity and Good Stability

The sensitivity and stability are mainly factors to hold back the practical applications of Polypyrrole coated fabrics. In this paper, a flexible fabric strain sensor with high sensitivity, good stability and large deformation is reported. It is fabricated by depositing a nano-layer (200nm to 300nm) of polypyrrole on the fabric substrate at low temperature. Thickness and morphology of the conducting thin film on the surface of the fibers were examined by scanning probe microscopy (SPM) and scanning electron microscopy (SEM). The measurement of the conductivity change with strain shows the fabrics so prepared exhibits a high strain sensitivity of ~160 for a deformation as large as 50%, while its good stability is indicated by a small loss of conductivity after the thermal and humidity aging tests, and supported by the slight change in conductivity and sensitivity over a storage of eighteen months. The flexible strain sensor is expected to be a promising "soft" smart material with good sensing properties in the preparation of smart garment, wearable hardware and biomedical applications