A flexible strain sensor from polypyrrole-coated fabrics

Conductive-polymer coated fabrics have been investigated as intelligent materials in the past years. In this paper, a flexible strain sensor from polypyrrole-coated fabrics which is featured with high sensitivity, good stability is reported. The strategies used for enhancing the sensitivity and stability of the sensor include: (a) the formation of thin coatings of polypyrrole (PPy) on the surface of fabrics using the chemical vapor deposition (CVD) method, (b) low temperature polymerization of pyrrole, (c) introduction of large docecyl benzene sulfonate anion in PPy film and (d) annealing of the PPy-coated conductive fabrics. The conductivity-strain tests reveal that the developed sensor exhibits a high strain sensitivity of ∼80 for a deformation as large as 50%, while its good stability is supported by the small changes in conductivity and sensitivity over a storage time of 9 months. The effect of the temperature and humidity on the conductivity of the strain sensor is investigated.