21 April 2006

Bionics: The Six Million Dollar Question

By Rusty Rockets

You won't hear much about bionics outside medical conferences these days, but when The Six Million Dollar Man hit the airwaves during the 70s, it was a hot topic of conversation around the water cooler. Actor Lee Majors played astronaut Col. Steve Austin, who had various body parts replaced with bionic prosthetics after a nasty plane crash. The bionic prosthetics that Austin received made him "better… stronger… faster," but the claim that he was "a man barely alive," in reference to his cyborg existence, also raised poignant and prophetic questions of what it means to be human. Today, against a backdrop sketched by nanotech futurists such as Ray Kurzweil, bionics is about to take center stage once more, but this time it'll be for real. The six million dollar question is: how do the bionics of today stack up against Col. Austin's fictional bionics conceived 30 years ago? Could someone equipped with today's bionics go mano a mano against Col. Austin and come out on top?

Early this month, at an Experimental Biology 2006 symposium on "The $6 Billion (Hu)Man", a group of prominent scientists explained how bionic prosthetics and enhancements are finally going to become a reality. Bionics is on the cutting-edge of both biology and electronics, and can be explained as the substitution of organic anatomical structures or physiological processes with mechanical or electronic versions designed to replicate or enhance original function. Col. Austin, for example, had a bionic eye with a zoom lens and night vision, a bionic arm as powerful as a bulldozer, and two bionic legs that gave him the speed of a cheetah in full flight and the ability to leap over tall buildings in a single bound (or was that Superman?). But while researching some of the latest bionic devices currently under development, it seems that there is some latitude given in regard to the replacement and enhancement definition of bionics. The gray area is the fact that some "bionics" seem more like add-ons akin to glasses, hearing aids or cars. Yes, cars, as there are some who argue that we have already reached "cyborg" status as we use machines that enhance our innate human abilities.

Putting the difficulty of definitions to one side, the first challenger to Col. Austin comes from Dr. William Craelius of Rutgers University, who has created the first hand that comes with multi-fingered function. "Bionic technologies can be adapted for restoring some degree of almost any lost function," claims Dr. Craelius. The doctor says that bionics' biggest hurdle has so far been human-machine communication; so finding innovative new ways to cross this barrier is paramount to success. This is why Dr. Craelius' bionic hand is considered something of a coup among his peers, because his technology combines a unique understanding of musculoskeletal signaling with advances in human-to-machine communication. "Communication is key," he emphasized, while modestly adding: "it is getting easier."

Craelius' bionic hand system, dubbed Dextra, uses existing nerve pathways to control individual computer-driven mechanical fingers. The system is interesting in that it relies on the presence of what is known as a "phantom limb," where an amputee can still "feel" the presence of their lost appendage. This means that the movement of the hand is biomimetic, or activated by normal volitional thinking, just as the amputee would do if they were controlling their original hand.

Scientists working on another bionic hand project have also had some promising results in respect to human-machine communication. Coordinated by Professor Paolo Dario and Professor Maria Chiara Carrozza, the Cyberhand project is looking to hard-wire a prosthetic hand directly into the nervous system, which will allow sensory feedback from the hand to reach the brain, and vice versa. Like Dextra, Cyberhand has five fully operational fingers. Cyberhand has 16 degrees-of-freedom powered by six tiny motors, and a self-adaptive grasp made possible by a single cable connected to the cables operating the phalanges. The main cable and the cables (representing a tendons) operating the phalanges mimic a real hand by running through a Teflon sheath pulled by a DC motor. This approach, say the researchers, is referred to as underactuation, and it gives more degrees-of-freedom than degrees-of-movement (effectively the number of motors). "This is a fundamental feature of the Cyberhand prosthesis because only a limited number of control signals are available for user's voluntary control," says project manager, Dr Lucia Beccai. Importantly, it also means less user effort is required to control the hand during use.

Scientists are gradually overcoming other limitations of bionics, such as the size of bionic components. Craelius gives the example of a wireless implant the size of a grain of rice, currently under development at UCLA under the watchful eye of Dr. Gerald Loeb. The implant is injected under the skin and acts as an interface between nerves and bionic devices. While over 1000 connections may be needed to communicate data between nerves and a bionic device, Craelius believes it is achievable. "Miniaturization of components will soon bring even that processing inside the body," said Craelius. "The number of transistors we can fit onto an integrated circuit doubles about every 18 months," he said in reference to Moore's law. "At this pace, within the decade, the processing for complex bionic activity will be implantable in the brain or elsewhere in the body."

The Cyberhand team is also looking to improve comfort for the wearer of bionic devices. Currently, the Cyberhand prototype uses Longitudinal IntraFascicular Electrodes (LIFEs) to connect the hand to the nervous system, but like Craelius, the team is trying to make the bionic components less invasive and cumbersome, so they're trialing a new type of electrode that has been developed to improve performance and fitting: the Thin Film LIFE (tfLIFE). Cyberhand will not hit the market until 2011-2014, and so far, while impressive, users of Dextra have only been able to play slow piano pieces. This means it may be some time before users are able to single-handedly pick up a grand piano and hurl it at bad guys. "Right now we are miniaturizing the human-machine interface to help make Dextra feel more natural," Craelius said.

One of the most featured aspects of Col. Austin's cyborg body was his bionic eye, and let's face it, who wouldn't want to have the ability to see great distances with your zoom lens or use your night-vision to see into the black of night? But Dr. Daniel Palanker, a physicist in Stanford's Department of Ophthalmology and Hansen Experimental Physics Laboratory, has had bigger problems in his endeavor to develop the first bionic eye other than fiddling around with zoom lenses and night vision. "Zooming is easy. Replacing retina is much harder," he said. Comprised of over 100 million photoreceptors, the eye, explains Palanker, is a vastly complex machine. "If we compare it to modern digital cameras, for example, it will be 100 megapixels. We buy cameras usually of three megapixels, maybe four." We also take for granted the fact that a great deal of processing occurs before an image even reaches our brains via the million axons that comprise the optic nerve. "We have a built-in processor in the eye. Before it goes into the brain, the image is significantly processed," said Palanker.

Palanker's eye resides in the gray area between prosthesis and bionics. It consists of a pocket-sized CPU, retinal prosthesis system, a solar or RF-powered battery implanted in the eye, a 3-millimeter (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 infrared goggles.

It's designed to help restore a level of sight for people with incurable retinal degenerative diseases, which ultimately cause blindness. "Currently, there is no effective treatment for most patients with retinitis pigmentosa," writes Palanker in his research paper. "However, if one could bypass the photoreceptors and directly stimulate the inner retina with visual signals, one might be able to restore some degree of sight." This is one of the most amazing aspects of Palanker's system as he really does manage to get the retinal neurons to cooperate and integrate with his retinal implant. However, the more scientists advance in this field, the more limitations become apparent. Currently, such an eye could only really reach a level of acuity around 20/80. This is enough to allow people to view distant objects and view a computer screen, but would not qualify them for a California driver's license where acuity of 20/40 is required.

Palanker explains that his work on the bionic eye is basic research, but adds that nothing should be discounted out of hand. "Artificial organs and parts of organs are coming. Electronic cochlear implants, electronic reading and transmission of thoughts is a reality already, so slowly we are getting there. Mother Nature built an exquisitely fine machine [our body], and our technology in many aspects is still far behind... Maybe one day," he said. Palanker's research and comments show that Col. Austin's eye was sophisticated in ways that perhaps most people, dazzled by a simple zoom lens and night-vision, did not consider, as just having a normally functioning eye is by far the most complex thing to recreate artificially.

The next item on the agenda seemed to capture the imaginations of journalists everywhere, and represents the most likely bionic device likely to give Col. Austin a run for his money. Though strictly speaking, it is again a moot point as to its true bionic status. The Bleex robotic exoskeleton was created by Dr. Homayoon Kazerooni, University of California, Berkeley, and backed by the US Defense Advanced Research Projects Agency (DARPA). The exoskeleton renders its wearer super strong and able to carry up to 200 pounds the same way they would carry 10. Kazerooni explains that the exoskeleton utilizes a unique actuation system comprised of a network of sensors, a pair of computer controlled strap-on robotic legs, and an intelligent algorithm. "The beauty of this type of exoskeleton," says Dr. Kazerooni, "is that it combines the intellect of humans and the strength of machines."

The Bleex system faithfully follows the wearers every movement as they carry otherwise backbreaking loads. The sensors embedded into the Bleex system ostensibly act as an extension of the wearers own nervous system, which allows them a good deal of freedom as they run up hills, climb stairs or even run. As a result it's no surprise that the military are interested, hoping to use the technology to develop super-human combat gear.

Ok, so we have the strength of Col. Austin's legs, but what about the speed? Apparently the Bionic Man could run at least 60 mph, as shown in the opening credits, so would a bionic man of today be able to beat Col. Austin in a cyber-foot race? Well, perhaps not just yet, but we think that in the not too distant future this could certainly be a possibility. This optimism stems from the fact that a team of researchers at MIT is working on an actuation system theory that would make the speed of robotic muscles 1000 times faster than human muscles.

Professor Sidney Yip, a professor of nuclear engineering and materials science and engineering, and his associates think they have improved upon previous attempts at using conjugated polymers for muscles. "Conjugated polymers are also called conducting polymers because they can carry an electric current, just like a metal wire," says Xi Lin, a postdoctoral associate in Yip's lab. This means that conjugated polymers can actuate on demand if a charge can be sent to a specific location in the polymer chain in the form of "solitons," or charge density waves. Scientists already knew about this, but the breakthrough came when Yip realized that the polymer did not need the ions that scientists added to give it extra strength. Along with a lighter polymer also came lightning speeds. The point to be made here is that if muscles made from these polymers were integrated with the Dextra, Cyberhand or exoskeleton would the result be super-speed? If so, we could be well on our way to seeing science fiction becoming science fact.

So, today's bionic man (or woman) may not be much chop compared to Col. Austin, but we do seem to be well on the way. And anyway, after some consideration it may not be such a bad thing that we are not going to get there too rapidly. One of the criticisms leveled at Futurist Ray Kurzweil and his notion of us reaching a technological singularity (where humankind as it exists today will be superseded) is that he does not focus enough on the negatives of such a development. In writer Martin Caidin's original version of the TV show, the Bionic Man was a ruthless killer, with a titanium skull and a CO2 powered index finger that shot poisonous darts. And DARPA's interest in super-human combat gear does not inspire hope in a peaceful future. Other less ominous possibilities for bionics might mean that they are the next step in body modification, a trend already embraced by many young people. How about eyes at the back of your head, X-ray eyes or an extra appendage? The modifications might be easy, but could we make the cognitive leaps necessary to accommodate such changes? What will it mean to be human in the not too distant future and who will set the parameters that define a human?