What if, instead of X-rays or ultrasound, we could view the insides of human bodies and electrical gadgets using touch? Researchers show a bionic finger that can produce 3D maps of the interior forms and textures of complicated objects by touching their outer surface in a paper published in the journal Cell Reports Physical Science on February 15.
“We were inspired by human fingertips, which have the most delicate touch sensibility that we know of,” explains senior author and Wuyi University professor Jianyi Luo. “For example, when we use our fingers to touch our own bodies, we can feel not only the texture of our skin, but also the contour of the bone underneath it.”
“Our bionic finger goes beyond prior artificial sensors that could only recognise and discriminate between exterior forms, surface textures, and hardness,” explains co-author and Wuyi University professor Zhiming Chen.
The bionic finger “scans” an item by moving over it and applying pressure—imagine a continuous stream of prods or pokes. The carbon fibres compress with each poke, and the degree to which they compress indicates the object’s relative stiffness or softness. Depending on the substance of the item, it may compress when prodded by the bionic finger: hard things retain their shape, whilst soft objects deform when enough pressure is applied. This data, together with the location at which it was collected, is sent to a computer and shown onscreen as a 3D map.
The researchers put the bionic finger to the test by mapping out the internal and exterior properties of complicated things composed of various materials, such as a solid “letter A” buried under a layer of soft silicon, as well as more abstractly structured items. When they used it to scan a small compound object made of three different materials—a rigid internal material, a soft internal material, and a soft outer coating—the bionic finger could distinguish not only between the soft outer coating and the internal hard ridges, but also between the soft outer coating and the soft material that filled the internal grooves.
The researchers next assessed the finger’s capacity to detect and photograph synthetic human tissue. Scientists used 3D printing to make this tissue, which consists of a skeleton component comprised of three layers of hard polymer and a soft silicone “muscle” layer. The bionic finger was able to recreate a three-dimensional profile of the tissue’s structure and detect a synthetic blood artery underneath the muscle layer.
The scientists also investigated the bionic finger’s potential to identify problems in electrical gadgets without having to open them up. The researchers were able to create a map of the internal electrical components of a defective electronic device and pinpoint the location where the circuit was disconnected, as well as a mis-drilled hole, without breaking through the encapsulating layer by scanning the surface with the bionic finger.
“Our tactile technique enables nondestructive testing of the human body and flexible electronics,” explains Luo. “Next, we aim to improve the bionic finger’s ability to detect omnidirectionally with varied surface materials.”
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