Electronic glove that gives robots a feeling of touch

Electronic glove that gives robots a feeling of touch

Stanford engineers have developed an electronic glove containing sensors that could someday give robotic hands the kind of dexterity that humans take for granted.

Image caption: The sensor shown in this photo is sensitive enough to allow the finger to hold a blueberry without crushing it. In the future, all the fingers and the palm will have similar electronic sensors that mimic the biological sensors of our skin. (Image credit: Courtesy of Bao Lab)

Stanford researchers have developed skin-shaped touch sensors that allow this robotic hand to provide the amount of pressure needed to lift and move a ping-pong ball without crushing it.

In an article published November 21 in Science Robotics, chemical engineer Zhenan Bao and his team demonstrated that the sensors worked well enough to allow a robotic hand to touch a delicate berry and manipulate a ping pong ball without reduce.

"This technology puts us on the track to give robots the kind of detection capabilities found in human skin," Bao said.

According to Bao, sensors located at the fingertips simultaneously measure the intensity and direction of pressure, two qualities essential to manual dexterity. Researchers have yet to perfect the technology to automatically control these sensors, but in this case, a robot carrying the glove could have the dexterity to hold an egg between thumb and forefinger without breaking it or letting it slip.

Electronics imitating life

The electronic glove mimics how layers of human skin work together to give our hands extraordinary sensitivity.

Our outer skin layer is impregnated with sensors to detect pressure, heat and other stimuli. Our fingers and palms are particularly rich in tactile sensors. These sensors work in conjunction with a sub-layer of skin called spinosum, a rugged microscopic terrain consisting of hills and valleys.

These bumps are critical. When our finger touches an object, the outer layer of the skin gets closer to the spinosum. A light touch is felt mainly by the sensors near the vertices. More intense pressure forces the outer skin into the spinosum valleys, causing more intense tactile sensations.

But measuring the intensity of the pressure is only part of what the spinosum allows. This embossed underlayer also helps to reveal the direction of pressure, or shear force. A finger that presses the north, for example, creates powerful signals on the southern slopes of these microscopic hills. This ability to feel the shear force is part of what helps us hold an egg between thumb and forefinger in a gentle but firm way.

Postdoctoral researcher Clémentine Boutry and master student Marc Negre led the development of electronic sensors that mimic this human mechanism. Each sensor on the robotic glove finger is composed of three flexible layers that work together. The upper and lower layers are electrically active. The researchers placed a grid of power lines on each of the two facing surfaces, like lines in a field, and rotated these lines perpendicularly to create a dense network of small detection pixels. They also made the bottom layer bumpy like spinosum.

The centrally located rubber insulator simply separated the top and bottom layers of the electrodes. But this separation was essential because electrodes close to each other can store electrical energy. When the robotic finger was depressed, by squeezing the upper electrodes closer to the bottom, the stored energy increased. The hills and valleys of the lower layer were used to map the intensity and direction of pressure at specific points of the perpendicular grates, much like human skin.

Delicate touch

To test their technology, the researchers placed their three-layer sensors on the fingers of a rubber glove and then on a robotic hand. Ultimately, the goal is to integrate sensors directly into a skin type coating for robotic hands. In an experiment, they programmed the robotic hand wearing gloves to gently touch a bay without damaging it. They also programmed the gloved hand to lift and move a ping pong ball without crushing it, using the sensor to detect the proper shear force to grab the ball without dropping it.

Bao said that with good programming, a robotic hand carrying the current tactile sensing glove could perform a repetitive task, such as lifting eggs from a treadmill and placing them in cartons. The technology could also have applications in robot-assisted surgery, where precise touch control is essential. But the ultimate goal of Bao is to develop an advanced version of the glove that automatically applies the force needed to handle an object safely without prior programming.

"We can program a robotic hand to touch a raspberry without crushing it, but we're still far from being able to touch and detect that it's a raspberry and allow the robot to seize, "she said.

Zhenan Bao, KK Professor Lee at the School of Engineering, Professor of Chemical Engineering, Senior Member of the Precourt Institute for Energy, Member of Stanford Bio-X, Affiliate Member of the Institute for Stanford Woods' environment and member of the Wu Tsai Neurosciences Institute. Other Stanford co-authors include Osama Khatib, a professor of computer science; postdoctoral researcher Orestis Vardoulis; and doctoral student Mikael Jorda.

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