Kristopher Sturgis

The university announced that the new pressure sensor was designed in the form of a flat, flexible material that could be molded into artificial skin for prosthetics, providing users with a sense of touch and feel unlike ever before.

The new plastic skin was created to help users detect how hard it is being pressed against a surface by generating an electrical signal that can be delivered directly into brain cells. Zhenan Bao, professor of chemical engineering at Stanford and lead researcher on the project, spoke to the university about how the technology is among the first of its kind to detect and transmit pressure signals to the brain.

"This is the first time a flexible, skin-like material has been able to detect pressure and also transmit a signal to a component of the nervous system," she said. "We have a lot of work to take this from experimental to practical applications, but after spending many years in this work, I now see a clear path where we can take our artificial skin."

The goal of Bao and her team was to replicate the sensory mechanism that enables us to distinguish pressure differences. The sensor consists of a two-ply plastic construct where the top layer serves as the sensing mechanism, and the bottom layer acts as the circuit to transport electrical signals, and translate them into biochemical stimuli that are compatible with nerve cells.

The group's latest design features a new top layer sensor that can detect pressure over the same range as that of normal human skin -- providing users the ability to discern the difference in pressure from a light finger tap to a firm handshake.

The group was able to create these pressure-sensing capabilities electronically through the use of billions of carbon nanotubes scattered into the tiny plastic sensors. When the plastic sensor is pressed or squeezed, all those tiny nanotubes compress and close together, enabling them to conduct electricity. The idea was that this could mimic how human skin senses touch by transmitting pressure information to the brain through short pulses of electricity.

The group theorized that as more pressure is applied to their new sensor, the carbon nanotubes will squeeze closer together, allowing more electricity to flow through the sensor, and those varied impulses can be sent as short pulses to the sensing mechanism. Once some of the pressure is removed, the carbon nanotubes space out and the flow of pulses relaxes, indicating a lighter sense of touch. Once all pressure is removed, the flow of pulses to the sensing mechanism stop altogether.

So far the sensor has yet to be tested on humans, as the group has only worked with the technology using a mouse brain in vitro -- a necessary step to ensure the sensor could communicate with neurons. Eventually the group is hopeful that the sensor can be used to channel information into the peripheral nerves that were once connected to a lost hand.

While the future of prosthetics looks promising, the group acknowledges that they are not yet at a point where they can fully recreate natural touch. The team hopes to eventually create an interface between the prosthetic and patient that will allow users to communicate with their muscles and nerves to provide an unparalleled sense of touch and control to prosthetics.  

Kristopher Sturgis is a contributor to Qmed and MPMN.

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