The world currently has some awesome prosthetics. We have low-cost 3D-printed ones, prosthetics based on Metal Gear Solid aesthetics that send emails, and slick-looking hands that (finally) come in more than one size.
Yet despite this proliferation of designs, but researchers are still working towards one holy grail in the prosthetic-making sphere: How can we endow them with a sense of touch so that users will be able to feel the world around them?
Researchers from the Ecole Polytechnique Federale de Lausanne (EPFL) and the Scuola Superiore Sant'Anna (SSSA), say they've created an artificial fingertip that lets amputees differentiate between smooth and rough surfaces in real-time.
"The touch sensation is quite close to what you would feel with your normal finger," says amputee Dennis Aavo Sorenson in a video released by EPFL. For the video, Sorenson is tasked with sensing if he can feel the ridges on a small rectangular piece of material that the artificial finger is passed along. "You can feel the coarseness of the plates, and the different gaps and ribs," he notes.
In a study published Tuesday in the journal eLife, the researchers describe surgically connecting the artificial fingertip, replete with sensors, to electrodes implanted in the peripheral nervous system in Sorensen's left arm stump. They believe that their invention could accelerate the development of prostheses equipped with advanced sensory feedback features in the future. The main aim is for wearers to be able to regain an understanding of the weight, surface texture, and temperatures of the objects that surround them.
To test the bionic finger, the researchers chose four healthy non-amputee volunteers alongside Sorensen to act as control subjects. They connected the artificial fingertip to them via an electrode inserted into a nerve in their arm. The fingertip was then moved over a piece of plastic engraved with smooth and rough surfaces, making the sensors produce "patterns of electrical pulses that stimulated the nerve," according to their paper.
They found that the control volunteers were able to distinguish between different textures 77 percent of the time; Sorensen answered correctly 96 percent of the time. The researchers also compared brain wave activity captured through an EEG device between non-amputee and amputee reactions, and found that the same brain regions were activated. These findings confirmed that different texture surfaces could indeed be distinguished by amputees, paving the way for a study involving more participants and advanced prototypes of the bionic finger.
While it might still be early days, there are high hopes that touch-sensitive systems will have applications not just for prosthetics, but also for robotics used in surgery, rescue and manufacturing. For example, humanoid rescue robots with tactile sensors in their feet could be able to sense what kind of terrain they were on, and adjust their balance accordingly.