Scientists at the University of Cambridge’s Bio-Inspired Robotics Lab have taken a step closer to creating an artificial human-like skin with tactile properties. The hydrogel-based skin can be used on humanoid robots and gives them a human sense of touch.
In the scientific paper “Tactile perception in hydrogel-based robotic skins using data-driven electrical impedance tomography”, which is published in Materials Today, the researchers describe how tactile stimuli can be reconstructed using electrodes and a model-free computational approach.
Soft robots are safe to use, says David Hardman, one of the researchers involved in the study. They do not damage items they handle and can undertake tasks that rigid robots cannot. To do this, however, they need tactile sensors, which must also be soft.
Model-free approach
The sensor material developed by Hardman and his colleagues is based on hydrogel, a water-insoluble gel that also contains water. The skin is adaptable, very stretchy and biodegradable. “We couple it to electrical impedance tomography (EIT) hardware, which uses electrodes to apply currents to the edge of the skin and measure voltages that give us information about the condition of the skin. Using these voltages, we try to find out where the skin was touched or if it’s damaged,” says Hardman, explaining how the artificial skin works. This approach contradicts methods that analyze data collected using neural networks with electrodes.
In one experiment, the scientists tested the artificial skin and had it scanned by a robotic arm. Electrodes placed around the skin provided the necessary data. From this, the researchers created deformation maps. Only a small amount of real data was required. They found that this model-free approach is clearly superior to an artificial skin based on a conventional neural network. The average resolution of their skin is 12.1mm on a circular area 170mm in diameter.
“Sentient” artificial skin
Researchers also tested the hydrogel skin in three real-world applications: damage detection and localization, environmental monitoring, and detection of various tactile stimuli. The system achieved good results in all three areas. This suggests that it could be used in soft robotic systems.
The scientists see the advantage in the simplicity of their system that the tactile skin can be used over an entire robot. This is not feasible with an analytical approach.
The researchers are now working on improving the shape and size of the artificial skin. The goal: It should be able to process and recognize even more complex stimuli. For example, it should not only recognize the location and strength of a touch on a robot hand, but also the position of the finger and whether the hand is damaged.
(olb)
