In the related fields of prosthetics and robotics there is a need for an inexpensive, durable, wide-area, flexible, and stretchable skin-like material that can sense both pressure and shear. While a variety of tactile skins exist with excellent sensitivity, resolution, and integration, the best devices are micro-fabricated electronic arrays that are complex, expensive and delicate. This work addresses these issues by developing two sensing skin designs that can be fabricated out of molded silicone rubber.
First, arrays of sensors based on piezoresistive PDMS / carbon black composite are investigated. This technology allows piezoresistive sensors, insulators, and conductors to be molded into stretchable skins or directly onto cloth. After a thorough characterization of the material, sensors capable of sensing pressure, shear, and elongation are demonstrated.
The second technology, novel for tactile skins, is a distributed sensor based on microwave transmission lines. Pressure applied to the sensor deforms the soft silicone rubber dielectric creating an impedance discontinuity, which can be used to determine the location and degree of deformation. An algorithm is presented which reconstructs a map of the deformation of the sensor from swept impedance measurements in real time. Pressure sensors are fabricated that have 10 mm spacial resolution and can sense depressions less then 20 um deep, corresponding to a calculated pressure sensitivity of less than 10 kPa, the accepted human pressure sensation threshold. A shear sensitive device, based on two parallel transmission lines, is also demonstrated. All the devices are flexible, stretchable, manufactured using simple molding techniques, and require at most two electrical connections to supporting electronics.
Prof. Jeffrey Lang (supervisor)
Prof. Vladimir Bulovic
Prof. David Trumper