The Brave New World of Bionics

In the 1970s TV series The Six Million Dollar Man, former astronaut Steve Austin became the world's first bionic man. Two artificial legs, an arm, and an eye transformed him from "a man barely alive" into a super-human intelligence agent who was "better, stronger, faster" than ever before.

Bionics is defined as the replacement of body parts with mechanical versions which can closely mimic, or surpass, the body's natural function. Today, it has moved from the realm of science fiction into that of research and medicine.

Bionics Today

Cochlear Implants

Cochlear implants, or bionic ears, are one of the most advanced bionic devices currently available. The device has external parts which pick up, filter, and transmit sound, and internal parts which convert sound signals into electrical impulses, and then stimulate the auditory nerves inside the cochlea. Unlike hearing aids, which only amplify sound, cochlear implants can help people who are completely deaf.

Cochlear implants are useful for patients who have lost their hearing later in life and for pre-lingually deaf children (i.e., those born with insufficient hearing to acquire speech normally, or those who lost their hearing before acquiring speech). Many patients with cochlear implants are able to carry on conversations without lip-reading, talk on the phone, and enjoy music. About 100,000 people around the world have received cochlear implants, roughly half of which are adults and half children, including British Member of Parliament Jack Ashley and US radio talk show host Rush Limbaugh.

Artificial Hearts

The quest for an artificial heart that works as well as the real thing began in the 1950s, and remains one of the Holy Grails of modern medicine. Currently, they are only used to prolong the life of patients who are waiting for heart transplants, and the longest-lasting artificial heart implant was a CardioWest Total Artificial Heart (CW-TAH), which lasted 602 days.

The first completely self-contained replacement heart was the AbioCor, produced by the ABIOMED company. In September of 2006, the device received FDA approval for commercial use under a Humanitarian Device Exemption.

Thanks to ongoing advances in cardiac research, computer science, electronics, and other fields, most researchers believe that a long-lasting artificial heart will become a reality during our lifetime.

Hands

A team of researchers headed by Dr. William Craelius of Rutgers University in New Jersey, has created a bionic hand system called Dextra. Many amputees retain the muscles and tendons that were once used to control their own hands, and Dextra has a silicone sensor sleeve that picks up electrical signals generated by those muscles. The signals are then transmitted to a portable computer worn by the user, which directs the movements of five artificial fingers. After training, amputees wearing Dextra have been able to type and to play slow pieces on the piano.

Super-Human Suits

Ever dreamed of lifting loads heavier than yourself and performing other astonishing feats? You may soon be able to with the help of a robotic exoskeleton. Several experimental models have been built, including BLEEX, the Berkeley Lower Extremity Exoskeleton, which is designed to help soldiers and other personnel carry heavy loads. Endearing himself to nurses everywhere, Keijiro Yamamoto from the Kanagawa Institute of Technology of Japan built a prototype Power Assist Suit to help nurses and physical therapists lift their patients.

The world's most advanced robotic suit is probably HAL (hybrid assistive limb), designed by Yoshiyuki Sankai of the University of Tsukuba in Japan. Slightly reminiscent of Peter Weller's RoboCop costume, HAL can help its wearer lift 40 kilograms (88 pounds) more than they can manage without assistance, and is available in either a full-body or lower-body only version. The best part of HAL is that it actually responds to your commands the same way your own muscles do. Before you take a step, your brain sends a nerve signal to your muscles, which generates an electric current on the skin's surface. HAL picks up those currents through bioelectric sensors attached to the skin, and then transmits the signal to the electric motors located at the hips and knees of the exoskeleton. This process takes only a fraction of a second, and HAL can actually respond faster to the brain's commands than the wearer's own muscles!

HAL has many potential applications for laborers, disabled people, and the elderly. A commercial version of the suit is expected to be available soon from Cyberdyne, Inc.

Bionics of Tomorrow

Bionic Eyes

Scientists at Stanford University are working on developing a retinal implant that could restore limited sight to the blind. The retina is a thin layer of cells at the back of the eyeball that responds to light. A variety of diseases, such as macular degeneration, cone-rod dystrophy (CORD), and retinopathy can damage the retina and rob a person of their sight. In order to restore vision, a retinal implant must break down visual information into patterns of electrical stimulation, and then pass the signals onto nerve cells so that they can be interpreted by the brain.

Since the human retina is only half a millimeter (0.02 inches) thick, one challenge to creating an artificial retina is the size constraint. Using state-of-the-art technology, the Stanford team has developed a three-millimeter (0.1 inches) light-sensing chip and a solar or RF-powered battery, both of which are small enough to be implanted in the retina. Other components of the bionic eye include a portable computer the size of a wallet, and a tiny video camera mounted in a pair of pulsed infrared goggles.

A second challenge to duplicating vision is the fact that the human eye and cameras see things in very different ways. Cameras detect the total amount of light available, and respond to changes in the total amount of light. The human eye, however, works in a much more complicated fashion. Ganglion cells in our retinas compare signals from hundreds of photoreceptors, and detect changes in both the total amount of light, and percentage differences between different areas. This is an adaptation which allows us to see in a variety of light conditions, ranging from bright sunlight to dim starlight. In order to overcome this problem, the Stanford team is trying to copy the retina's neural circuits with computer transistor circuits.

The group has seen promising results in rats, where the rat's own neurons grew into the retinal implant, enabling the bionic eye to transmit signals to the brain. Human trials are expected to begin in the near future. The first generation of bionic eyes are designed for visual acuity of 20/400. Ultimately, the group wants to achieve 20/80 vision, which would allow users to recognize faces and read large print type.

Cells, Tissues, and "Unobtanium"

Although the technology hasn't yet been developed, some scientists have already started speculating about bionics at the cellular level. Robert Freitas, a senior research fellow at the Institute for Molecular Manufacturing in Palo Alto, California, has published several papers on how nano-machines might one day replace the cells that circulate throughout our blood. His proposals include respirocytes in place of red blood cells, clottocytes in place of platelets, and microbivores in place of white blood cells.

Many researchers are also working to develop materials that could mimic the action of human muscles and tissues. In 2004, the Pentagon issued this challenge to scientists: Create a smart material that could self-heal, self-replicate, and turn invisible. Other criteria included the ability to generate its own power, store and transmit huge amounts of data, and to shrivel up and pass through a crack in a wall, then regain its original shape. If discovered, such a material could be made into anything from artificial organs to bridges and aircraft. Researchers have made many advances in the past two years, but there is no single material which comes close to fulfilling all of the Pentagon's criteria. In fact, the quest is so difficult that the material has already been dubbed "unobtanium."

In the case of artificial muscles, scientists have created a number of materials that can contract in response to electrical stimulation or changes in ion levels – just like real muscles do. However, they are still a long ways from being able to duplicate the fine degree of motor control that living muscles and nerves produce. For example, electroactive polymers are one of the most promising muscle-like materials, yet robotic arms made with the material regularly lose in arm-wrestling contests when pitted against real humans.

Re-growing Bone

Years down the road, broken bones may be treated with an injection of plastic liquid instead of old-fashioned casts. Researchers are exploring ways of using plastic scaffolding to promote the growth of new bone. Ideally, the plastic would be injected into the site, thus avoiding invasive surgery, then harden to offer support while the bone heals. The plastic scaffolding would also be laced with growth factors, proteins that will attract blood vessels to the area, bringing the nutrients that the new bone tissue needs to survive. Finally, the plastic scaffolding will be biodegradable, so that it could slowly disintegrate as new bone grows, leaving no trace of itself behind.

These plastic scaffoldings may be particularly useful when large sections of bone need to be replaced, when the bone needs to grow into a particular shape, or when radiation therapy has compromised the body's own ability to re-grow bone tissue. Dr. Michael Miller from MD Anderson Cancer Center in Houston, Texas, has tried to tackle all of these problems in one experiment. His approach has shown promising results in sheep, and involves cutting plastic molds into the desired shapes, seeding them with ground-up bone fragments from the patient's own hip, and implanting the molds near the patient's hip. After new bone has filled the plastic mold, it can be removed again and implanted into the correct site in the body. Since the new bone is growing next to healthy tissue, this approach may overcome the hurdle posed by radiation treatments. Another experimental approach to re-growing bone following radiation therapy is to seed scaffolds with both growth factors and stem cells.

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Unlike the sci-fi writers of the 70s who gave Steve Austin metal limbs that would have been quickly rejected and a nuclear power source that guaranteed radiation poisoning, today's bionics researchers realize that they must work with the body's natural systems to succeed. However, their aims are no less ambitious than those of any sci-fi author: restore sight to the blind, design robotic suits that grant the wearer super-human strength, and create artificial hearts that give patients a new lease on life.

Incidentally, the price tag has gone up since the days of The Six Million Dollar Man. The 2006 Experimental Biology convention in San Francisco included some of the leading scientists in the field of bionics. The name of their symposium? The $6 Billion (Hu)Man.

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