Electronic fingertip enhances surgeons sense of touch

A flexible electronic circuit that can be worn on fingertips may improve surgeons' touch as they operate.

"Imagine the ability to sense the electrical properties of tissue and then locally remove that tissue, precisely by local ablation, all via the fingertips using smart surgical gloves. Alternatively, or perhaps in addition, ultrasound imaging could be possible," said John Rogers, co-author of the study recently published in the journal Nanotechnology. Rogers, the Lee J. Flory Founder Chair in Engineering and professor of materials science and engineering at Illinois, worked on the technology with colleagues at Northwestern University and Dalian University of Technology in China.

The researchers explained the sensor utilizes gold electrodes just a few nanometers thick encased in a "nanomembrane" on a finger-shaped tube of silicone rubber that puts one side of the circuit in contact with the wearer's fingertips.

The wearer receives electrotactile stimulation from the sensor, a tingling sensation caused by a small voltage applied to the skin, they said.

Surgical gloves are one potential application, Rogers added, as gloves fitted with the nanomembrane could sense the thickness or composition of tissue via its electrical properties. A surgeon could also remove tissue using a high-frequency alternating current supplied by a battery attached at the wrist and delivered via the nanomembrane itself.

Offering guidelines to the creation of these electrotactile stimulation devices for use on surgeons’ fingertips, their paper is said to describe the materials, fabrication strategies and device designs using ultra-thin, stretchable, silicon-based electronics and soft sensors that can be mounted onto an artificial ‘skin’ and fitted to fingertips.

The electronic circuit on the ‘skin’ is made of patterns of gold conductive lines and ultra-thin sheets of silicon, integrated onto polyimide. The sheet is then etched into an open-mesh geometry and transferred to a thin sheet of silicone rubber moulded into the precise shape of a finger. This electronic ‘skin’, or finger cuff, was designed to measure the stresses and strains at the fingertip by measuring the change in capacitance of pairs of microelectrodes in the circuit. Applied forces decreased the spacing in the skin, which in turn increased the capacitance.

The fingertip device could also be fitted with sensors for measuring motion and temperature, with small-scale heaters as actuators for ablation and other related operations. The researchers suggest that the new technology could open up possibilities for surgical robots that can interact, in a soft contacting mode, with their surroundings through touch.

They believe that, because the device exploits materials and fabrication techniques adopted from the established semiconductor industry, the processes can be scaled for realistic use at reasonable cost.

"Perhaps the most important result is that we are able to incorporate multifunctional silicon semiconductor device technologies into the form of soft, three-dimensional, form-fitting skins, suitable for integration not only with the fingertips but also other parts of the body,: said Rogers.

The researchers now intend to create a ‘skin’ for integration on other parts of the body, such as the heart. In this case, a device would envelop the entire 3D surface of the heart to provide various sensing and actuating functions, providing advanced surgical and diagnostic devices relevant to cardiac arrhythmias. Future challenges include creating materials and schemes to provide the device with wireless data and power.
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Editor's note: Portions of this story were excerpted from previously published articles.

Contact: John Rogers, Department of Materials Science and Engineering, 217/244-4979.

If you have any questions about the College of Engineering, or other story ideas, contact Rick Kubetz, editor, Engineering Communications Office, University of Illinois at Urbana-Champaign, 217/244-7716.