A stretchable and transparent SWNT strain sensor encapsulated in thin PDMS films

In this paper, a stretchable and transparent strain sensor made of an ultrathin film of single-walled carbon nanotubes (SWNTs) encapsulated inside poly(dimethyl siloxane) (PDMS) films is presented. A surface plasma treatment, followed by a solution based, low temperature drop casting process was developed and utilized to fabricate the strain sensor. The fabricated SWNTs strain sensor functions as a two-terminal resistor which changes its resistance when the sensor is stretched. The strain sensor was tested with 10% tensile cyclic strain and was found to handle strains of up to 35%. With PDMS encapsulation, the effect of environmental gases to the response of the SWNT strain sensors was eliminated. The electrical response of the SWNT strain sensor was highly reversible and repeatable after the initial conditioning step. The reliability of this sensor was evaluated up to 200 cycles at 4% strain. Our results demonstrate the possibility of using ultrathin SWNT films as a stretchable, transparent and reliable strain sensor.