Worlds in Your Hand
To build a mechanical eyesay, a camerayou need to study optics. To build a receiver, you need to understand acoustics and how these work with the human ear. Similarly, if you expect to build an artificial handor even a finger that perceives tactile sensationyou need to understand skin biomechanics.
At the MIT Touch Lab, where numerous projects in the realm of haptics are running at any given time, one project seeks to mimic the skin sensitivity of the primate fingertip as closely as possible, concentrating on having it react to touch as the human finger would.
The research is painstaking and exacting, involving, for example, precise friction and compressibility measurements of the fingerpads of human subjects. Fingertip dents and bends in response to edges, corners, and surfaces have provided additional data. At the same time, magnetic resonance imaging (MRI) and high-frequency ultrasound show how skin behaves in response to these stimuli on the physical plane.
Not satisfied with the close-ups that they could get from available devices, the team developed a new tool, the Ultrasound Backscatter Microscope (UBM), which shows the papillary ridges of the fingertip and the layers of skin underneath in far greater detail than an MRI.
As researchers test reactions to surfaces from human and monkey participants, the data they gather is mapped and recorded to emerging 2D and 3D fingertip models. At this MIT project and elsewhere, human and robot tactile sensing is simulated by means of an array of mechanosensors presented in some medium that can be pushed, pressed, or bent.