Schematic representation of a sensor: a force acting on the nipple (gray) deforms the connected membrane (red), changing the capacitance to the electrodes (blue). Credit: ETH Zurich / Johannes Weichart

One of the many special human qualities is the ability to handle objects with skill and precision. All this is due to our sense of touch, which is especially sharp at our fingertips. Using our hands, we are able to explore the shape and composition of objects and feel the texture of their surface – and all this without even slapping our eyes on them.

Our sense of touch is incredibly subtle. Just try to take a robot to achieve a similar degree of nuance. Production robots, for example, can lift and move objects with impressive dexterity. However, to do this, they must first know where the object is located or need additional visual information to help with orientation. Ideally, they should also know how strong an object is and its composition before catching it.

Hundreds of sensors

Johannes Weihart has an idea that can make robots much more adept at handling objects. Weichart, a PhD student in the Micro- and Nanosystems Group (MNS) at ETH Zurich, has developed artificial leather that emulates the sensation of touch in the human finger. He believes that this can give robots the ability to touch and feel. Moreover, artificial leather is flexible, which means that it can be used to cover soft and unevenly shaped materials – such as a robotic grapple in the shape of a human finger.

Like its human equivalent, Weichart’s artificial skin is equipped with a wide range of receptors. “You need about one sensor per square millimeter,” he explains. Each sensor consists of different layers. Two of them are a conductive membrane and adjacent electrodes, which the springs are kept at a distance of three to four micrometers. Changes in the distance between them cause changes in the electrical signal captured by the electrodes.

Credit: ETH Zürich

Sophisticated sense of touch

A small grain is connected to the conductive membrane. When pressure is applied to the nipple, the membrane deforms – and with it the signal measured by the sensor.

Half of the sensors are equipped with three electrodes, not one. They measure not only the amount of force applied to the grain at each point, but also the angle of application. This gives the skin a much more nuanced touch. “This means you can feel the quality and texture of the surface and recognize when an object is sliding on the surface of the skin by taking samples from the sensors at high enough frequencies,” explains Weichart.

Too much raw data

Weichart spent the first three years of his doctorate, demonstrating that his idea worked in principle. The challenge now is to make the skin healthier and, crucially, suitable for specific applications. This still requires some work. “In order to be able to use artificial leather in everyday contexts, the sensors require a protective layer that we developed,” says Weichart. “And we also need to radically simplify the output signal. All this raw input would overwhelm the robot. Besides, even humans don’t perceive the output of each individual receptor. We just register the overall impression.”

Despite the work ahead, the project already looks promising. No wonder then that Weichart was among the nominees for the Spark Award, which was presented last week.

Helps robots feel more human

Electron microscope image of a sensor showing the membrane and the nipple attached to it. Credit: ETH Zurich / Johannes Weichart

Non-standard approach

Weichart tends to prefer the left-hand approach – as his desk easily reveals. Unlike the functional workspaces of his fellow students, his is literally surrounded by a mini jungle of houseplants.

He also quickly backed away from the original proposal of his boss, Christopher Hierold, and his adviser, Cosmin Roman. The idea was to develop silicon-based touch sensors. But Weichart chose to embed the sensors in a flexible substrate. This will make it easier to mount them on soft and uneven surfaces. “My advisers were a little skeptical at first,” he grinned. “But looking back, I think that was the right decision!”

From fusion to sensor technology

In the end, bureaucratic problems pushed Weichart to faux leather. Having just graduated from ETH Zurich with a degree in mechanical engineering, he first joined Evatec AG, where he worked on plasma processes for coating and etching integrated circuits. However, at the end of three years, the time seems ripe to return to research.

His work in the industry aroused interest in synthesis technologies. “But because I come from Liechtenstein, it was difficult for me to be considered a participant in national research programs,” he explains. In search of information, he turned to Hierold, who is leading his master’s thesis. To his delight, Hierold offered to start his project on tactile sensor technology.

Helps robots feel more human

Flexible leather can be mounted on any surface. The small grains that put pressure on the sensitive membrane are clearly visible. Credit: ETH Zurich / Johannes Weichart

“My experience in the industry has been really valuable,” says Weihart. “You don’t always have to rediscover the wheel – in fact, it’s often better to build on familiar technology.” Instead of striving for academic excellence, he strives for practical relevance: “That’s what makes me tick.” And relying on established technology can be an advantage when it comes to commercializing a new development, he says. “As a startup, you can never control the whole process chain. There are always some parts that you have to outsource.”

So far, his entrepreneurial ambitions have been halted. “I still have another year as a PhD student, and then I’ll start thinking about my next move.” If he were to continue the project on his own – perhaps as a Pioneer Fellow – he would have to think very carefully about which area to focus on. It spies on potential applications in various fields, including medical robotics, telerobotics, storage robotics, and prosthetics. But there is no way he can justify all these options at this stage of development.

The eyes of the award

Staying focused can be his biggest challenge in the coming months. “I’m not obsessed with details,” he admits, “and I can quickly start chasing new ideas. But that may soon be out of control. ” As it is, he already has a lot on his plate: microtechnology, electronics, precision mechanics, data processing, material integration and AI pattern recognition – all of these areas will be his focus for a while.

Regular activity outside the lab helps him keep his eyes on the award. “I go cycling and skiing in the mountains, I swim in the lake in the winter and I do boxing and mixed martial arts to help coordinate and be self-confident,” he says. This frees my head and helps me focus on my work.

The electronic skin anticipates and perceives for the first time touch from different directions

Quote: Faux leather can give robots a human-like touch (2022, May 3), extracted on May 5, 2022 from

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