New ‘skin’ gives robots human touch

By Stephen Beech

A new synthetic "skin" gives robots the human touch.

The low-cost, durable and highly-sensitive material can be added to robotic hands just like a glove, say scientists.

It enables automatons to detect information about their surroundings in a way that’s similar to humans, according to research published in the journal Science Robotics.

The research team, from the University of Cambridge and University College London (UCL), developed the flexible, conductive skin, which is easy to fabricate and can be melted down and formed into multiple shapes.

They say the new technology senses and processes various physical inputs, allowing robots to interact with the physical world in a more meaningful way.

Unlike other solutions for robotic touch, which usually work via sensors embedded in small areas and require different sensors to detect different types of touch, the entirety of the electronic skin developed by the British team is a sensor, bringing it closer to human skin.

Previously, signals from different sensors could interfere with each other, and the materials were easily damaged.

Although the new robotic skin is not as sensitive as human skin, the researchers say it can detect signals from more than 860,000 tiny pathways in the material.

That enables it to recognise different types of touch and pressure, such as the tap of a finger, a hot or cold surface, damage caused by cutting or stabbing, or multiple points being touched at once, in a single material.

The research team used a combination of physical tests and machine learning techniques to help the robotic skin "learn" which of these pathways matter most, so it can sense different types of contact more efficiently.

As well as the potential for humanoid robots or human prosthetics where a sense of touch is vital, the researchers say the robotic skin could be useful in industry and even disaster relief.

Study lead author Dr. David Hardman, from Cambridge’s Department of Engineering, said: "Having different sensors for different types of touch leads to materials that are complex to make.

“We wanted to develop a solution that can detect multiple types of touch at once, but in a single material.”

Co-author Dr. Thomas George Thuruthel, of UCL, said: “At the same time, we need something that’s cheap and durable, so that it’s suitable for widespread use.”

Their solution uses a type of sensor that reacts differently to different types of touch, known as multi-modal sensing.

While it’s challenging to separate out the cause of each signal, the researchers explained that multi-modal sensing materials are easier to make and more robust.

The team melted down a soft, stretchy and electrically conductive gelatine-based hydrogel, and cast it into the shape of a human hand.

They tested several different electrode configurations to determine which gave them the most useful information about different types of touch.

From 32 electrodes placed at the wrist, they were able to collect more than 1.7 million pieces of information over the whole hand, thanks to the tiny pathways in the conductive material.

The skin was then tested on different types of touch.

The researchers blasted it with a heat gun, pressed it with their fingers and a robotic arm, gently touched it with their fingers, and even cut it open with a scalpel.

They then used the data gathered during testing to train a machine learning model so the hand would recognise what the different types of touch meant.

Dr. Hardman said: “We’re able to squeeze a lot of information from these materials – they can take thousands of measurements very quickly.

“They’re measuring lots of different things at once, over a large surface area.”

Dr. Thuruthel added: “We’re not quite at the level where the robotic skin is as good as human skin, but we think it’s better than anything else out there at the moment.

“Our method is flexible and easier to build than traditional sensors, and we’re able to calibrate it using human touch for a range of tasks.”

The team is now hoping to improve the durability of the electronic skin and to carry out further tests involving real-world robotic tasks.