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The technique is being used for a variety of procedures, from gallbladder removal to heart valve repair. It offers patients reduced pain and blood loss, minimal muscular damage, and shorter recovery times. However, one drawback is the surgeons inability to directly feel internal organs and their resistance to the scalpel.To remedy this problem, force feedback and tactile sensing are being added to surgi- cal robots, with encouraging results. At the Harvard BioRobotics Laboratory, Robert Howe and his colleagues monitored medical stu- dents as they used a telerobotic system to expose a simulated artery, a common type of surgical task.Adding force feedback to visual feed- back did not improve the speed or precision of the operations, but it did enable the students to perform the procedures less forcefully.This reduced the rate of inadvertent damage or nickingof the artery by some 75 percent compared to remote surgery using visual feedback alone.

The Harvard group is also finding ways to help surgeons remotely search for internal lumps, not easy to do through a small incision. Howe likens it to trying to find a pea inside a bowl of jello using chopsticks.The solution is a robotic fingertip consisting of 64 pres- sure sensors in a square array, inserted in the body. Each sensor is connected to a motorized pin outside the body, and the surgeons finger rests against this array of pins. As the robot fingertip moves within the body and encounters a lump, the pressure readings on the sensors change and the corresponding pins move in proportion.The end result is that the array of external pins maps the shape of the lump, which can then be felt by the surgeons finger resting on the pins.

Other approaches could eliminate separate sensors to yield artifi- cial skin or muscles with built-in haptic senses.For example, research- ers at the STMicroelectronics Corporation and the University of Bologna have mounted a grid of fine electrically conducting wires in a soft substrate. Pressure on the material changes the electrical inter- actions among the wires.This information is turned into a map that gives the shape of the object causing the deformation. And at the Polytechnic University of Cartagena,Toribio Otero and Maria Cortés have used a plastic called polypyrrole to make a touch-sensitive muscle. Like other smart materials used for artificial muscles, theirs alters its

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