The net result of this amalgamation of hardware, software and mechanisms was that the procedure felt intuitively right: easy through the skin, resistance as the needle popped through the blood vessel wall, and a feeling of release as the needle reached the bloodstream. Even my ears were engaged, as my maiden foray into catheterization elicited jarring “ouches” from the computer’s speakers: cries of pain from the violated virtual man.But, hey, I’d done it. Feeling good, I decided to take a stab at something more challenging: pediatrics. But after my third try at easing a thin-gauge catheter into a vein on a newborn baby’s virtual forehead, I gave up. My angle was too low. The resistance in the needle told me as much. The virtual baby told me, too, as shrieks rattled the speakers. Maybe I wasn’t meant to be a doctor after all.
Merril characterizes the hardware components of his company’s simulators as novel uses for existing mechanical and robotic components. With combinations of electromagnetic brakes, motors, cables and other devices, he says it’s possible to convey a wide range of tactile sensations. What makes it seem “like you are really sticking the needle in…and that you are feeling a force that corresponds to what you are seeing, is a computer model of the skin,” Merril says.
Using critiques from doctors and nurses who have done the real thing many times, software engineers tweak the simulators to improve the fidelity of the haptic sensations. “We know how much force it takes for the surface of the skin to break, and when that happens in the simulator, it tells the machine to let up on the brake,” which feels like a sudden reduction of resistance on the ingoing catheter, Merril says. Rabkin adds that today’s best devices are still a bit jerky, and just short of real time on the visual side.
After wielding a needle, I wanted to try a fancier-looking bronchoscopy simulator, which mimics the device used to inspect the bronchial passages of the lungs. I inserted a straw-thin flexible tube through a nostril of an artificial face staring at the ceiling from a stand. This time, the haptic interface was a free-floating, joystick-like controller-identical to the real medical device-not unlike a bartender’s multiple-button, soda-dispensing head. As I snaked the camera- and tool-tipped tube inward, a computer monitor displayed strikingly realistic visual and haptic simulations of the lung’s bronchial tree; the simulated airways even convulsed when my “patient” coughed (I forgot to “apply” local anesthetic). I felt particularly doctorly when a menacing mass suddenly became visible. Using a clawlike tool controlled with the haptic interface, I performed a virtual biopsy. A “bloody” spot instantly appeared where I had extracted tissue.
Such were my first encounters with so-called haptic rendering. They undoubtedly won’t be the last. These simulators presage haptic things to come in arenas ranging from product design to remotely operated robotic tools, perhaps even hands-on museums where you can rub a virtual Rembrandt. The collective aim of haptics researchers is nothing less than to encode and re-create the world’s tactile features with the same breadth and fidelity that has made digital visual and audio rendering so realistic and versatile. To this research community, the tactile surface of the world-real or imagined-is something they can capture, replay, even synthesize from scratch with a combination of computers and handheld gadgetry.
Although there are lots of potential applications on the horizon, medical training appears slated to become the first killer app of haptics. The initial waves of products are already diffusing into medical settings, where students can learn procedures under normal, novel, and unexpected conditions. In the past two years, Immersion Medical says it has shipped approximately 400 medical simulators to hospitals and medical schools. “It’s common sense-if that individual can rehearse that circumstance, he will be better able to deal with it when it really happens,” says E. James Britt, professor of pulmonary and clinical medicine at the University of Maryland and a consultant to the company.