Artificial ‘skin’ gives robotic hand a sense of touch

September 22, 2017

University of Houston researchers have reported a development in stretchable electronics that can serve as artificial skin for a robotic hand and biomedical devices (credit: University of Houston)

A team of researchers from the University of Houston has reported a development in stretchable electronics that can serve as an artificial skin, allowing a robotic hand to sense the difference between hot and cold, and also offering advantages for a wide range of biomedical devices.

The work, reported in the open-access journal Science Advances, describes a new mechanism for producing stretchable electronics, a process that relies upon readily available materials and could be scaled up for commercial production.

Cunjiang Yu, Bill D. Cook Assistant Professor of mechanical engineering and lead author of the paper, said the work is the first to create a semiconductor in a rubber composite format, designed to allow the electronic components to retain functionality even after the material is stretched by 50 percent.

He noted that traditional semiconductors are brittle and using them in otherwise stretchable materials has required a complicated system of mechanical accommodations. That’s both more complex and less stable than the new discovery, as well as more expensive, he said. “Our strategy has advantages for simple fabrication, scalable manufacturing, high-density integration, large strain tolerance, and low cost,” he said.

Photograph of a robotic hand with intrinsically stretchable rubbery sensors (credit: Hae-Jin Kim et al./Science Advances)

The team used the skin to demonstrate that a robotic hand could sense the temperature of hot and iced water in a cup. The skin also was able to interpret computer signals sent to the hand and reproduce the signals as American Sign Language.

Uses of the stretchable skin include soft wearable electronics such as health monitors, medical implants, and human-machine interfaces.

The stretchable composite semiconductor was prepared by using a silicon-based polymer known as polydimethylsiloxane (PDMS) and tiny nanowires to create a solution that was then hardened into a material that used the nanowires to transport electric current.

Abstract of Rubbery electronics and sensors from intrinsically stretchable elastomeric composites of semiconductors and conductors

A general strategy to impart mechanical stretchability to stretchable electronics involves engineering materials into special architectures to accommodate or eliminate the mechanical strain in nonstretchable electronic materials while stretched. We introduce an all solution–processed type of electronics and sensors that are rubbery and intrinsically stretchable as an outcome from all the elastomeric materials in percolated composite formats with P3HT-NFs [poly(3-hexylthiophene-2,5-diyl) nanofibrils] and AuNP-AgNW (Au nanoparticles with conformally coated silver nanowires) in PDMS (polydimethylsiloxane). The fabricated thin-film transistors retain their electrical performances by more than 55% upon 50% stretching and exhibit one of the highest P3HT-based field-effect mobilities of 1.4 cm2/V∙s, owing to crystallinity improvement. Rubbery sensors, which include strain, pressure, and temperature sensors, show reliable sensing capabilities and are exploited as smart skins that enable gesture translation for sign language alphabet and haptic sensing for robotics to illustrate one of the applications of the sensors.