In the mid-1970s, when scientists in a popular TV series rebuilt a gravely wounded test pilot as the world's first bionic man - making him "better, stronger, faster" - medical bionics was the stuff of science fiction. No longer. Last week, at Experimental Biology 2006 in the US, some of the leading scientists in the rapidly expanding field explained how much of what was once fiction is today at least partial reality - including electronically-powered legs, arms, and eyes like those given the Six Million Dollar Man over 30 years ago. The symposium on "The $6 Billion (Hu)Man" was part of the program of the American Association of Anatomists. Bionics, a word that merges biology with electronics, means replacing or enhancing anatomical structures or physiological processes with electronic or mechanical components. Unlike prostheses, a bionic implant actually mimics the original function, sometimes surpassing the power of the original organ or body part. Bionics takes place at the interface between bioengineering and anatomy. The AAA scientific program at Experimental Biology also included a symposium on tissue engineering - another means of replacing organs or organ function. Dr. William Craelius, Rutgers University, created the first multifinger prosthesis, combining new understanding of musculoskeletal signaling with advances in human-to-machine communication. In recent years, prosthetic limbs have been transformed from the unwieldy designs of the last century into more life-like substitutes that give users a more intuitive feel. The bionic hand system (Dextra) produced by Craelius and his colleagues uses existing nerve pathways to control individual computer-driven mechanical fingers. Dextra consists of a standard plastic socket and silicone sensor sleeve that encases an amputee's limb below the elbow. After a brief training period, operating the fingers is biomimetic - as if the user were commanding his natural fingers. Dextra relies on the fact that much of the musculo-tendon control structures that originally operated the fingers are still present and can be tapped by sensors. As long as the user remembers how to activate his phantom fingers, he can mentally command the new robot digits. Thus far, users have been able to play slow piano pieces with Dextra, as demonstrated at Epcot Center for the Discover Magazine Innovation of the Year Award ceremony. IN DR. SCOTT DELP'S Neuromuscular Biomechanics Laboratory at Stanford, digital humans walk across the computer screen, their visible musculoskeletal system revealing the complex interplay of muscles, bones, momentum and gravity that makes up human movement. A few alterations to the program that controls the form and function of these mechanisms, and the movements of the previously healthy, agile human on the screen change into those caused by neuromuscular disorders such as stroke, osteoarthritis or Parkinson's. Delp, now chairman of bioengineering at Stanford, helped establish the lab, which makes its computerized simulations of biological systems, ranging from molecules to entire organisms, available to scientists and clinicians studying neuromuscular disease. The simulations also are invaluable in the education of bioengineers and physicians, and in the development of new surgeries and medical devices. Delp originated the system that adapts the computerized models to different diseases, even to individual patients. His own work at the interface of bioengineering and medicine illustrates the simulations' widespread applications; he collaborates with physicians at a children's hospital in devising new treatments for patients with cerebral palsy. DR. HOMAYOON KAZEROONI of the University of California at Berkeley, is the creator of BLEEX, a wearable robotic system that turns its wearer into a man or woman of incredible strength, able to carry up to 85 kilos with no more effort than it would take to carry five (see photo, Page 1). Kazerooni started his work by understanding the human gait. Then, through the design of a novel actuation system, a network of sensors, a pair of computer controlled strap-on robotic legs, and an intelligent algorithm, he created the BLEEX to follow the wearer's gait faithfully while carrying major loads. As the wearer walks and runs normally on ascending and descending slopes and stairs, the embedded sensors and computers in the robotic legs function like an extension of his or her own nervous system, gathering information on the direction being moved and continually redistributing the weight to make it feel like a barely perceptible burden. BLEEX created a sensation when it first appeared. The New York Times recognized it as one of the best ideas of 2004, and the military hopes the research will not only help soldiers carry heavy loads for long distances but eventually also help create super-human combat gear. Kazerooni, who directs the Berkeley Robotics and Human Engineering Laboratory at UC Berkeley, regards BLEEX as having wide range applications in the work force and service industry, adding power while preventing back and other injuries. The beauty of this type of exoskeleton, he says, is that it combines the intellect of humans and the strength of machines. His laboratory is currently improving the system's speed and flexibility. DR. TIMOTHY MARLER describes Santos - a new kind of complete whole-body virtual (computer-based) human model developed at the University of Iowa's Virtual Soldier Research laboratory. Santos combines a highly realistic appearance, real-time simulations, and a relatively complex musculoskeletal structure. Because he will think, move and act like a real human, he provides both a unique tool to scientists studying the human body and feedback to engineers designing and improving products. Unlike virtual mannequins, Santos actually predicts human motion and behavior based on human performance measures, such as energy, joint torque, or discomfort. That means that when trying out a new product, whether protective military clothing or new army tanks, he can answer questions such as: Is this comfortable? Can I reach this? Am I strong enough to pull this lever? His motion is "task-based," like that of real humans, says Marler. "We move differently when dodging bullets than we do when sipping tea," he says, "and we can model this difference in Santos." Advances in understanding anatomy and physics are having substantial impact for a wide variety of peace-time industries as well as those in the military. Currently the Virtual Soldier Research Laboratory is working with TACOM (the department of the Army that designs tractor vehicles), Natick Soldier systems (that works with everything on the dismounted soldier, including clothing), Caterpillar, Rockwell, and Honda. Dr. Daniel Palanker, a physicist in Stanford's Department of Ophthalmology and Hansen Experimental Physics Laboratory, leads the team that recently designed a bionic eye. The eye, actually a retinal prosthesis system, consists of a portable wallet-sized computer processor, a solar or RF-powered battery implanted in the eye, a threemillimeter (half the size of a grain of rice) light-sensing chip implanted in the retina, and a tiny video camera mounted on virtual-reality-style pulsed infrared goggles. The system is designed to do what the eye's own photoreceptors do - or no longer do, in patients with degenerative retinal diseases - which is to stimulate cells in the retina to perceive images. When tested in rats, the retinal neurons migrate into the porous interface with the subretinal implant, and thus provide intimate proximity between the stimulation sites and the neural cells, which is essential for high-resolution stimulation. The first generation of the system is designed for visual acuity of 20/400, the second for 20/200, and the ultimate target is 20/80 vision. For humans who have lost vision through retinitis pigmentosa, age-related macular degeneration and other diseases that destroy the body's own photoreceptors, 20/80 vision would mean being able to recognize faces and read large print. Currently there are no effective treatments for these diseases. Human trials of the first generation are expected to begin within two years.