Researchers at the University of Washington and University of California, Los Angeles have developed a flexible “skin” that can be applied to a prosthetic limb. The skin can sense vibrations and can also measure shear force, such as the feeling when your finger slides along a table or when an object slips out of your grasp. This technology could help prosthetic devices to act more like real limbs, or maybe even help surgical robots to better sense their environment and so surgical instruments more safely and accurately.
So far, artificial skin for prosthetics has not been able to sense a full range of tactile information. “Traditionally, tactile sensor designs have focused on sensing individual modalities: normal forces, shear forces or vibration exclusively. However, dexterous manipulation is a dynamic process that requires a multimodal approach. Our latest skin prototype incorporates all three modalities,” says Veronica Santos, a researcher involved in this study.
The technology developed by Santos and her colleagues is bioinspired, as it mimics the way human skin undergoes tension and compression when experiencing force. Their electronic skin consists of silicone rubber, the kind that is used in swimming goggles. The rubber layer contains tiny microfluidic channels filled with liquid metal that conducts electricity. As the skin experiences shear force, some of the channels stretch out, while others are compressed, causing changes in electrical resistance that allow the skin to accurately measure the applied force.
“It’s really following the cues of human biology,” said Jianzhu Yin, another researcher involved in the study. “Our electronic skin bulges to one side just like the human finger does and the sensors that measure the shear forces are physically located where the nailbed would be, which results in a sensor with similar performance to human fingers.”