As the finger slides over a textured surface, the skin vibrates in characteristic ways. The skin even has fingerprints on its surface, greatly enhancing its sensitivity to vibration. These vibrations are detected by a hydrophone inside the bone-like core of the finger. Capable of other human sensations, the sensor can also tell where and in which direction forces are applied to the fingertip and even the thermal properties of an object being touched. It also used a newly designed algorithm to make decisions about how to explore the outside world by imitating human strategies. The robot was equipped with a new type of tactile sensor built to mimic the human fingertip. The human finger uses similar vibrations to identify textures, but the robot finger is even more sensitive Like the human finger, the group's BioTac® sensor has a soft, flexible skin over a liquid filling.
A famous theorem by 18th century mathematician Thomas Bayes describes how decisions might be made from the information obtained during these movements. "
Built by Fishel, the specialized robot was trained on 117 common materials gathered from fabric, stationery and hardware stores. The article, authored by Professor of Biomedical Engineering Gerald Loeb and recently graduated doctoral student Jeremy Fishel, describes their new theorem for solving this general problem as "Bayesian Exploration. When confronted with one material at random, the robot could correctly identify the material 95% of the time, after intelligently selecting and making an average of five exploratory movements. When humans try to identify an object by touch, they use a wide range of exploratory movements based on their prior experience with similar objects. Until now, however, there was no way to decide which exploratory movement to make next. It was only rarely confused by pairs of similar textures that human subjects making their own exploratory movements could not distinguish at all
So, is touch another task that humans will outsource to robots? Fishel and Loeb point out that while their robot is very good at identifying which textures are similar to each other, it has no way to tell what textures people will prefer. Instead, they say this robot touch technology could be used in human prostheses or to assist companies who employ experts to assess the feel of consumer products and even human skin.
Loeb and Fishel are partners in SynTouch LLC, which develops and manufactures tactile sensors for mechatronic systems that mimic the human hand. Founded in 2008 by researchers from USC's Medical Device Development Facility, the start-up is now selling their BioTac sensors to other researchers and manufacturers of industrial robots and prosthetic hands.