A strain gauge that uses carbon black and carbon nanotube doped silicone oil encapsulated in a PDMS microchannel

We present a piezoresistive strain gauge fabricated using electrically conductive silicone oil encapsulated in a close volume polydimethylsiloxane (PDMS) microchannel. The conductive silicone oil is made using carbon black and carbon nanotube to dope the silicone oil to become conductive. A characteristic of the electrical resistance versus the applied pulling force was measured. The non-linear behavior was due to the large deformation of the strain gauge, which makes the second order term of the increasing gauge length can not be ignored. An exponentially decrease of the resistance was found when applying a biasing voltage without exerting a force. It is caused by the reorganization of the carbon black particles in the silicone oil with applying electrical field. Temperature change also gave effect on the strain gauge with positive and negative temperature coefficients (PTC and NTC) with turning point at 55°C.