Some of that investment went to Herr’s most prominent invention, a bionic ankle designed for people who have lost one or both legs below the knees. Known as the BiOM and sold by Herr’s company iWalk (there are a lot of lowercase “i’s” floating around the prosthetics industry these days), the device—fitted with sensors, multiple microprocessors and a battery—propels users forward with each step, helping amputees regain lost energy as they walk. Roy Aaron, a professor of orthopedic surgery at Brown University and the director of the Brown/VA Center for Restorative and Regenerative Medicine, says people who use a BiOM compare it to striding on a moving walkway at an airport.
Herr envisions a future where prosthetics such as the BiOM can be merged with the human body. Amputees who sometimes have to endure chafing and sores while wearing their devices might one day be able to attach their artificial limbs directly to their bones with a titanium rod.
Michael McLoughlin, the engineer leading development of advanced prosthetics at the Johns Hopkins University Applied Physics Laboratory, also wants to see bionic limbs that are more integrated with the human body. The Modular Prosthetic Limb (MPL), an artificial arm-and-hand mechanism that was built by the Johns Hopkins lab, has 26 joints controlled by 17 separate motors and “can do just about everything a normal limb can do,” says McLoughlin. But the MPL’s sophisticated movements are limited by the level of technology available for interfacing with the body’s nervous system. (It’s comparable to owning a top-of-the-line personal computer that’s hooked up to a slow Internet connection.) What’s needed is a way to increase the data flow—possibly by establishing a direct uplink to the brain itself.
In April 2011, researchers at Brown achieved just that when they connected a robotic arm directly into the mind of Cathy Hutchinson, a 58-year-old quadriplegic who is unable to move her arms and legs. The results, captured on video, are astounding: Cathy can pick up a bottle and lift it to her mouth to drink.
This feat was made possible when neurosurgeons created a small hole in Cathy’s skull and implanted a sensor the size of a baby aspirin into her motor cortex, which controls body movements. On the outside of the sensor are 96 hair-thin electrodes that can detect electrical signals emitted by neurons. When a person thinks about performing a specific physical task—such as lifting her left arm or grabbing a bottle with her right hand—the neurons emit a distinct pattern of electrical pulses associated with that motion. In Hutchinson’s case, neuroscientists first asked her to imagine a series of body movements; with each mental effort, the electrodes implanted in her brain picked up the electrical pattern generated by the neurons and transmitted it through a cable to an external computer near her wheelchair. Next, the researchers translated each pattern into a command code for a robotic arm mounted on the computer, allowing her to control the mechanical hand with her mind. “The whole study is embodied in one frame of the video, and that is Cathy’s smile when she puts the bottle down,” says Brown neuroscientist John Donoghue, who co-directs the research program.
Donoghue hopes this study will eventually make it possible for the brain to form a direct interface with bionic limbs. Another goal is to develop an implant that can record and transmit data wirelessly. Doing so would eliminate the cord that presently connects the brain to the computer, allowing mobility for the user and lowering the risk of infection that results from wires passing through the skin.
Perhaps the toughest challenge faced by inventors of artificial organs is the body’s defense system. “If you put something in, the whole body’s immune system will try to isolate it,” says Joan Taylor, a professor of pharmaceutics at De Montfort University in England, who is developing an artificial pancreas. Her ingenious device contains no circuitry, batteries or moving parts. Instead, a reservoir of insulin is regulated by a unique gel barrier that Taylor invented. When glucose levels rise, the excess glucose in the body’s tissues infuse the gel, causing it to soften and release insulin. Then, as glucose levels drop, the gel re-hardens, reducing the release of insulin. The artificial pancreas, which would be implanted between the lowest rib and the hip, is connected by two thin catheters to a port that lies just beneath the skin’s surface. Every few weeks, the reservoir of insulin would be refilled using a
syringe that fits into the port.
The challenge is, when Taylor tested the device in pigs, the animals’ immune system responded by forming scar tissue known as adhesions. “They are like glue on internal organs,” Taylor says, “causing constrictions that can be painful and lead to serious problems.” Still, diabetes is such a widespread problem—as many as 26 million Americans are afflicted—that Taylor is testing the artificial pancreas in animals with an eye toward solving the rejection problem before beginning clinical trials with people.
For some manufacturers of artificial organs, the main problem is blood. When it encounters something foreign, it clots. It’s a particular obstacle to crafting an effective artificial lung, which must pass blood through tiny synthetic tubes. Taylor and other researchers are teaming up with biomaterial specialists and surgeons who are developing new coatings and techniques to improve the body’s acceptance of foreign material. “I think with more experience and expert help, it can be done,” she says. But before Taylor can continue her research, she says she needs to find a partner to provide more funding.
And private investors can be hard to come by, since it may take years to achieve the technological breakthroughs that make an invention profitable. SynCardia Systems, an Arizona company that makes an artificial heart device capable of pumping up to 2.5 gallons of blood per minute, was founded in 2001 but wasn’t in the black until 2011. It recently developed a portable battery-powered compressor weighing only 13.5 pounds that allows a patient to leave the confines of a hospital. The FDA has approved the SynCardia Total Artificial Heart for patients with end-stage biventricular failure who are waiting for a heart transplant.