Tactile skin gives prosthetics and robots a flexible touch

May 19, 2014 // By Julien Happich
Under its Fellowship for Growth programme, the UK's Engineering and Physical Sciences Research Council (EPSRC) has just granted £1.07 million of funding to support the creation of ultra-flexible tactile skin for robotics and prosthetics.

Dr Ravinder S. Dahiya, who joined the University of Glasgow last year as a senior lecturer in electronic and nanoscale engineering, will be leading the four-year research programme.

“To date, no robotics scientist has been able to create ultra-flexible tactile skin. Either the sensors have been too big or the electronics not sufficiently flexible”, explains Dr Dahiya who wants to get away from discrete and bulky silicon devices.

“Often, you see discrete components soldered on flexible PCBs, or hard component islands grafted onto flexible substrates. Some sensors may be flexible, but you need to connect them to electronic processing modules away from the sensing area, hidden in the robot’s housing” says Dr Dahiya whose vision is to integrate ultra-thin and flexible silicon-based electronics onto flexible polymers, in effect, forming sheets of distributed electronics along the sensors.

Printed organic electronics is typically seen as a good candidate for low-cost flexible sensing applications, but they have low charge carrier mobility, typically three orders of magnitude lower than that of single crystal silicon. Their short lifetime also makes organic electronics more suitable to low-cost disposable applications. These are real drawbacks if one is to rely on fast transistor switching speed for efficient data processing or communication needs, hence the researcher’s focus on using ultra-thin silicon-based devices.

In previous research, Dr Dahiya has developed tactile sensing chips, forming 5x5 arrays of Piezoelectric Oxide Semiconductor Field Effect Transistor (POSFET) pressure and temperature sensors, about 15x15mm in size.

 

Fig. 1: In the top close-up photo, serpentine shaped metal lines make up a passive device on two 15×22mm flex–chips, shown placed on 18mm and 30mm diameter cylinders.

 

Measuring 1x1mm, each POSFET tactile pixel in the arrays were obtained by spin coating piezoelectric polymer films directly onto the gate area of Metal Oxide Semiconductor (MOS) transistors. They were designed to yield human like spatial acuity, each tactile pixel being about 1mm apart.