Soft and stretchable tactile sensor using MWCNT-elastomer nanocomposite and anisotropic electrical impedance tomography

Abstract

In the related fields of robotics, there is a need for an inexpensive, durable, wide-area covering, and stretchable skin-like tactile sensor that measure both pressure and stretch. Although many tactile sensing technologies have been introduced, large area deployment and durability were key issues in practical applications including wearable artificial skins and robotic skins. Technically, difficulty to fabricate large number of electrical wires in elastomeric substrates was a major problem because electrical wires need to be stretchable in order to sustain stable attachment to the elastomeric substrate. An alternative approach was using electrical impedance tomography (EIT) technique which resolves large area deployment and durability by using electrodes only installed on the boundary of the sensor. Although previous EIT based tactile sensors can be stretchable to cover highly stretching area such as the area near to rotational joints, stretch of the sensor also affected tactile sensing performances. In this dissertation, anisotropic electrical impedance tomography (aEIT) based tactile sensing technique is introduced to achieve stretchable, large area deploying, and durable tactile sensor. Particularly, multi-walled carbon nanotubes (MWCNTs) with silicone elastomer is used to fabricate the sensing element. Anisotropic piezoresistivity of the material was examined while the material is stretched in lateral direction and indented in surface normal direction. A mathematical formulation of aEIT is introduced and detailed information to implement hardware circuitry and finite element based computation model is introduced. As final results, development of stretch measurable tactile sensor is presented and performances of the sensor is evaluated.