The students of College of Engineering Trivandrum had the rare opportunity to interact with the CEO of NEX Robotics Dr.Anant Malewar on January 15th 2014 at Seminar Hall of Department of Electrical and Electronics Engineering College of Engineering Trivandrum
The session began by a prayer and then the Chapter Advisor of IEEE RAS student Chapter College of Engineering Trivandrum Dr. Jisha V.R delivered the welcome address.
Next was the talk on State of Art of the robotics by Dr. Anant Malewar CEO of Nex Robotics. He highlighted the need to bridge the gap with robotics and academics in India. He also mentioned about the topic Mobile Robots –Past, Present, Future, and also demonstrated the different kind of robots and their working . He added that the Nex Robotics system has a good future in INDIA and mentioned about the career in Nex Robotics. The talk was highly inspirational for all Robotics enthusiastic students in the student chapter. And the talk was concluded with the question and answering session.
The students were introduced to git, the most popular revision control system. Students cloned a repository and made pull requests to another repository. They also understood important concepts such as branches and merging..
The annual general body meeting of IEEE CET Student Branch was held on 5th March 2014 in CETA hall, CET at 12:30 PM. The event was presided over by the Student Branch Counselor, Dr. Suresh Kumaraswamy and the Robotics and Automation Society Advisor Ms Jisha V R and witnessed a gathering of over 40 members of the IEEE Student Branch. The event started with the entire IEEE gathering reading the code of ethics. After which Dr Suresh and Ms Jina both expressed their views on the IEEE Student Branch. The annual report including the achievements and events conducted and the annual budget report were presented. The new executive committee for CET Student Branch for the year 2014 to 2015 was announced during the occasion..
Taking apart the shattered power station and its three melted nuclear cores will require advanced robotics
A radiation-proof superhero could make sense of Japan’s Fukushima Daiichi nuclear power plant in an afternoon. Our champion would pick through the rubble to reactor 1, slosh through the pooled water inside the building, lift the massive steel dome of the protective containment vessel, and peek into the pressure vessel that holds the nuclear fuel. A dive to the bottom would reveal the debris of the meltdown: a hardened blob of metals with fat strands of radioactive goop dripping through holes in the pressure vessel to the floor of the containment vessel below. Then, with a clear understanding of the situation, the superhero could figure out how to clean up this mess.
Unfortunately, mere mortals can’t get anywhere near that pressure vessel, and Japan’s top nuclear experts thus have only the vaguest idea of where the melted fuel ended up in reactor 1. The operation floor at the top level of the building is too radioactive for human occupancy: The dose rate is 54 millisieverts per hour in some areas, a year’s allowable dose for a cleanup worker. Yet, somehow, workers must take apart not just the radioactive wreck of reactor 1 but also the five other reactors at the ruined plant.
This decommissioning project is one of the biggest engineering challenges of our time: It will likely take 40 years to complete and cost US $15 billion. The operation will involve squadrons of advanced robots, the likes of which we have never seen.
Nothing has been the same in Japan since 11 March 2011, when one of history’s worst tsunamis flooded Fukushima Daiichi, crippled its emergency power systems, and triggered a series of explosions and meltdowns that damaged four reactors. A plume of radioactive material drifted over northeast Japan and settled on towns, forests, and fields, while plant workers scrambled to pour water over the nuclear cores to prevent further radioactive releases. Nine months later, the Tokyo Electric Power Co. (TEPCO), the utility company that operates the plant, declared the situation stable.
Stability is a relative concept: Although conditions at Fukushima Daiichi aren’t getting worse, the plant is an ongoing disaster scene. The damaged reactor cores continue to glow with infernal heat, so plant employees must keep spraying them with water to cool them and prevent another meltdown. But the pressure vessels and containment vessels are riddled with holes, and those leaks allow radioactive water to stream into basements. TEPCO is struggling to capture that water and to contain it by erecting endless storage tanks. The reactors are kept in check only by ceaseless vigilance.
TEPCO’s job isn’t just to deal with the immediate threat. To placate the furious Japanese public, the company must clean up the site and try to remove every trace of the facility from the landscape. The ruin is a constant reminder of technological and managerial failure on the grand scale, and it requires a proportionally grand gesture of repentance. TEPCO officials have admitted frankly that they don’t yet know how to accomplish the tasks on their 40-year road map, a detailed plan for decommissioning the plant’s six reactors. But they know one thing: Much of the work will be done by an army of advanced robots, which Japan’s biggest technology companies are now rushing to invent and build.
Here’s some more bad news: Chernobyl and Three Mile Island, the only other commercial-scale nuclear accidents, can’t teach Japan much about how to clean up Fukushima Daiichi. The Chernobyl reactor wasn’t dismantled; it was entombed in concrete. The Three Mile Island reactor was defueled, but Lake Barrett, who served as site director during that decommissioning process, says the magnitude of the challenge was different. At Three Mile Island the buildings were intact, and the one melted nuclear core remained inside its pressure vessel. “At Fukushima you have wrecked infrastructure, three melted cores, and you have some core on the floor, ex-vessel,” Barrett says. Nothing like Fukushima, he declares, has ever happened before.
Barrett, who is now a consultant for the Fukushima cleanup, says TEPCO is taking the only approach that makes sense: “You work from the outside in,” he says, dealing with all the peripheral problems in the buildings before tackling the heart of the matter, the melted nuclear cores. During the first three years of the cleanup, TEPCO has been surveying the site to create maps of radiation levels. The next step is removing radioactive debris and scrubbing radioactive materials off walls and floors. Spent fuel must be removed from the pools in the reactor buildings; leaks must be plugged. Only then will workers be able to flood the containment structures so that the melted globs of nuclear fuel can safely be broken up, transferred to casks, and carted away.
Many of the technologies necessary for the decommissioning already exist in some form, but they must be adapted to fit the unique circumstances of Fukushima Daiichi. “It’s like in the 1960s, when we wanted to put a man on the moon,” says Barrett. “We had rocketry, we had physics, but we had never put all the technologies together.” Just as with the moon shot, there is no guarantee that this epic project can be accomplished. But faced with the wrath of the Japanese people, TEPCO has no choice but to try.
To begin the first step—inspection—TEPCO sent in robots to map the invisible hot spots throughout the smashed reactor buildings. The first to arrive were the U.S.-made PackBot and Warrior, hastily shipped over from iRobot Corp. of Bedford, Mass. But Japan is justly proud of its own robotics industry, so the question arose, Why didn’t TEPCO have robots ready to respond in a nuclear emergency? Yoshihiko Nakamura, a University of Tokyo robotics professor, has the dispiriting answer. The government did fund a program on robotics for nuclear facilities in 2000, following a deadly accident at a uranium reprocessing facility. But that project was shut down after a year. “[The government] said this technology is immature, and it is not applicable for the nuclear systems, and the nuclear systems are already 100 percent safe,” Nakamura explains. “They didn’t want to admit that the technology should be prepared in case of accident.”
Still, some roboticists in Japan carried on their own research despite the government’s indifference. In the lab of Tomoaki Yoshida, a roboticist at the Chiba Institute of Technology, near Tokyo, robots have learned to crawl over rubble and to climb up and down steps. These small tanks roll on a flexible series of treads, which can be lifted or lowered individually to allow the bot to manage stairs.
After the Fukushima accident, Yoshida’s academic research became very relevant. With seed money from the government, he constructed two narrow metal staircases proportioned like the 5-floor staircases inside the Fukushima Daiichi reactor buildings. This allowed Yoshida to determine whether his bots could navigate those cramped stairs and tight turns. His acrobatic Quince robots proved themselves able, and after hundreds of tests they received TEPCO’s clearance for field operations. In the summer of 2011, the Quince bots became the first Japanese robots to survey the reactor buildings.
The Quinces were equipped with cameras and dosimeters to identify radioactive hot spots. But the robots struggled with a communication issue: The nuclear plant’s massive steel and concrete structures interfere with wireless communication, so the Quinces had to unspool cables behind them to receive commands and transmit data to their operators. The drawback of that approach soon became apparent. One Quince’s cable got tangled and damaged on the third floor of reactor 2, and the lonely bot is still sitting there to this day, waiting for commands that can’t reach it.
Back at Yoshida’s lab, where modest bunk beds bespeak the dedication of his students, the team is currently working on a new and improved survey bot namedSakura. To guard against future tangles, Sakura not only unspools cable behind, it also automatically takes up the slack when it changes direction. It’s waterproof enough to roll through puddles, and it can carry a heavy camera capable of detecting gamma radiation. The bot can tolerate that radiation: Yoshida’s team tested its electronics (the CPU, microcontrollers, and sensors) and found that they’re radiation-tolerant enough to perform about 100 missions before any component is likely to fail. However, the robot itself becomes too radioactive for workers to handle. Sakura must therefore take care of itself: It recharges its batteries by rolling up to a socket and plugging itself in.
The second step in the Fukushima decommissioning is decontamination, because only when that is complete will workers be able to get inside to tackle more complex tasks. The explosions that shattered several of the reactor structures sprayed radioactive materials throughout the buildings, and the best protective suits for workers in hot zones are of little use against the resulting gamma radiation—a worker would have to be covered from head to toe in lead as thick as the width of a hand.
After the accident, the Japanese government called for robots that could work on decontamination, and several of Japan’s leading companies rose to the challenge. Toshiba and Hitachi have designed robots that use jets of high-pressure water and dry ice to abrade the surfaces of walls and floors; the robots will scour away radioactive materials along with top layers of paint or concrete and vacuum up the resulting sludge. But the robots’ range is defined by their own communication cables, and they can carry only limited amounts of their cleaning agents. Another bot, the Raccoon, has already begun nosing across the floor in reactor building 2, trailing long hoses behind it to supply water and suction.
To clear a path for the robotic janitors, another class of robots has been invented to pick up debris and cut through obstacles. The ASTACO-SoRa, from Hitachi, has two arms that can reach 2.5 meters and lift 150 kilograms each. The tools on the ends of the arms—grippers, cutting blades, and a drill—can be exchanged to suit the task. However, Hitachi’s versatile bot is limited to work on the first floor, as it can’t climb stairs.
Removing spent fuel rods is the third step. Each reactor building holds hundreds of spent fuel assemblies in a pool on its top floor. These unshielded pools, perfectly safe when filled with water, became a focus of public fear during the Fukushima Daiichi accident. After reactor building 4 exploded on 15 March, many experts worried that the blast had damaged the structural integrity of that building’s pool and allowed the water to drain out. The pool was soon determined to be full of water, but not before the chairman of the U.S. Nuclear Regulatory Commission had caused an international panic bydeclaring it dry and dangerous. The reactor 4 pool became one of TEPCO’s urgent decommissioning priorities, not only because it’s a real vulnerability but also because it’s a potent reminder of the accident’s terrifying first days.
The process of emptying that poolbegan in November 2013. TEPCO workers use a newly installed cranelike machine to lower a cask into the pool, then long mechanical arms pack the submerged container with fuel assemblies. The transport cask, fortified with shielding to block the nuclear fuel’s radiation, is lowered to a truck and brought to a common pool in a more intact building. The building 4 pool contains 1533 fuel assemblies, and moving them all to safety is expected to take a year. The same procedure must be performed at the highly radioactive reactors 1, 2, and 3 and the undamaged (and less challenging) reactors 5 and 6.
Containing the radioactive water that flows freely through the site is the fourth step. Every day, about 400 metric tons of groundwater streams into the basements of Fukushima Daiichi’s broken buildings, where it mixes with radioactive cooling water from the leaky reactor vessels. TEPCO treats that water to remove most of its radioactive elements, but it can’t be rendered entirely pure—and as a result local fishermen have protested plans to release it into the sea. To store the accumulating water, TEPCO has installed more than 1000 massive tanks, which themselves must be monitored vigilantly for leaks.
TEPCO hopes to stop the flow of groundwater with a series of pumps and underground walls, including an “ice wall” made of frozen soil. Still, at some point the Japanese public must grapple with a difficult question: Can the stored water ever be released into the sea? Barrett, the former site director of Three Mile Island, has argued publicly that the processed water is safe, as contamination is limited to trace amounts of tritium, a radioactive isotope of hydrogen. Tritium is less dangerous than other radioactive materials because it passes quickly through the body; after it’s diluted in the Pacific, Barrett says, it would pose a negligible threat. “But releasing that water is an emotional issue, and it would be a public relations disaster,” he says. The alternative is to follow the Three Mile Island example and gradually dispose of the water through evaporation, a process that would take many years.
TEPCO must also plug the holes in the reactor vessels that allow radioactive cooling water to flow out. Many of the leaks are thought to be in the suppression chambers, doughnut-shaped structures that ring the containment vessel and typically hold water, which is used to regulate temperature and pressure inside the pressure vessel during normal operations. Shunichi Suzuki, TEPCO’s general manager of R&D for the Fukushima Daiichi decommissioning, explains that one of his priorities is developing technologies to find the leak points in the suppression chambers.
“There are some ideas for a submersible robot,” Suzuki says, “but it will be very difficult for them to find the location of the leaks.” He notes that both the suppression chambers and the rooms that surround them are now filled with water, so there’s no easy way to spot the ruptures; it’s not like finding the hole in a leaky pipe that’s spraying water into the air. Among the robot designs submitted by Hitachi, Mitsubishi, and Toshiba is one bot that would crawl through the turbid water and use an ultrasonic sensor to find the breaches in the suppression chambers’ walls.
If robots prove impractical, TEPCO may take a more heavy-handed approach and start pouring concrete into the suppression chamber or the pipes that lead to it. “If it’s possible to make a seal between the containment vessel and the suppression chamber, then the leaks don’t matter,” Suzuki says. One way or another, TEPCO hopes to have all the leaks stopped up within three years. Sealing the leaks is a necessary precondition for the final and most daunting task.
Removing the three damagednuclear cores is the last big step in the decommissioning. As long as that melted fuel glows inside reactors 1, 2, and 3, Fukushima Daiichi will remain Japan’s ongoing nightmare. Only once the fuel is safely packed up and carted away can the memory begin to fade. But it will be no easy task: TEPCO estimates that removing the three melted cores will take 20 years or more.
First, workers will flood the containment vessels to the top so that the water will shield the radioactive fuel. Then submersible robots will map the slumped fuel assemblies within the pressure vessels; these bots may be created by adapting those used by the petroleum industry to inspect deep-sea oil wells. Next, enormously long drills will go into action. They must be capable of reaching 25 meters down to the bottoms of the pressure vessels and breaking up the metal pooled there. Other machines will lift the debris into radiation-shielded transport casks to be taken away.
Making the task more complicated is the design of the reactors. They have control rods that project through the bottom of the pressure vessels, and the entry point for each of those control rods is a weak spot. Experts believe that most of the fuel in reactor 1, and some in reactors 2 and 3, leaked down through those shafts to pool on the floor of the containment vessel below. To reach that fuel, some 35 meters down, TEPCO workers will have to drill through the steel of the pressure vessel and work around a forest of wires and pipes.
Before TEPCO can even develop the proper fuel-handling tools, Suzuki says, the company must get a better understanding of the properties of the corium—the technical term for the mess of metals left behind after a meltdown. The company can’t just copy the drills that broke up the melted core of the Three Mile Island reactor, says Suzuki. “At Three Mile Island, [the core] remained in the pressure vessel,” he says. “In our case, it goes through the pressure vessel, so it melted stainless steel. So our fuel debris must be harder.” The melted fuel may also have a lavalike consistency, with a hard crust on top but softer materials inside. TEPCO is now working with computer models and is planning to make an actual batch of corium in a laboratory to study its properties.
When the core material is broken up and contained, it will be whisked away to some to-be-determined storage facility. Over the decades its radioactivity will gradually fade, along with the Japanese public’s memory of the accident. It’s a shame that those twisted blobs of corium are too dangerous to be displayed in a museum, where a placard could explain that we human beings are so clever, we’re capable of building machines we can’t control.
Depending on whom you ask, nuclear power stations like Fukushima Daiichi are exemplars of either humanity’s ingenuity or hubris. But, the museum placard might add, these metallic blobs, plucked from the heart of an industrial horror, prove something else—that we humans also have the grit and perseverance to clean up our mistakes.
Molecules manipulate electron spin to increase light emission without the aid of iridium
A new way of coaxing light out of an organic LED may make for cheaper displays and could even provide a way to see magnetic fields.
By choosing a molecule of a particular shape, a team of German and American researchers designed a new type of OLED that has the potential to emit as much light as a commercial OLED, but without the rare metals normally added to make the devices efficient. If manufacturers could leave out metals such as iridium or platinum, they might not have to worry about potential shortages of these elements. This would allow them to bring down the costs of OLEDs, which are increasingly being used in the screens of smartphones and televisions, as well as in solid-state lighting.
OLEDs convert only a fraction of the electrical current they receive into light. That’s because of a quantum mechanical property of the electrons and their positive quasiparticle counterpart holes, called spin. Spin is what gives rise to magnetism; when the spins of a majority of electrons in a material point in the same direction, the material is magnetic. Each electron and each hole can exist in one of two spin states, so when they pair up there are four possible states, three of which dissipate their energy as heat rather than light. This means that only a quarter of the electricity put into the device produces light. OLED makers add metal to the hydrocarbon molecules in their devices to mix up the spin states and increase the number of light-generating combinations.
But it’s also possible for some of the spins to switch to the more light-friendly version on their own, says John Lupton, a physicist at the University of Regensburg, in Germany, who was part of the team that did the work. “You just have to wait long enough for this spin state to spontaneously relax,” he says.
If an electron-hole pair can be held in its electrically excited state long enough for one spin to flip, when it drops to a lower energy state it’ll emit the extra energy as a photon rather than as heat, Lupton explains. “Long enough” is measured in milliseconds, compared with the nanoseconds it usually takes for emission to occur, a difference of six orders of magnitude.
The trick, which the researchers from Regensburg, the University of Bonn, the University of Utah, and MIT explain in a paper published online byAngewandte Chemie, lies in the shape of the organic molecules used in the LED. The researchers developed two kinds of polycyclic aromatic hydrocarbons (carbon-based molecules having multiple ring-shaped components): one called phenazine and the other triphenylene. The atomic structures of the molecules were such that they trapped the charge carriers long enough for the spontaneous change to occur. A peculiarity of the molecule–the researchers speculate that it may have to do with different energy characteristics in different areas of the molecule–prevents the extra energy from being released as heat before the spin can flip. “Because of their shape, you can localize the electron density and therefore the spin density in specific areas in the molecules,” Lupton says, adding that the result was surprising to the researchers, who were actually studying other facets of OLEDs. “If you look at textbooks of physical chemistry, this should not have actually worked,” he says.
Last year another group, led by Chihaya Adachi at Kyushu University, in Japan, demonstrated its own method for making OLEDs without the use of metal. The researchers designed a molecule that relies on fluorescence for light emission, instead of the phosphorescence used in most metal-reliant OLEDs. Their mechanism, called thermally activated delayed fluorescence, takes the heat released by some of the charge carriers and uses it to bump up the energy level of others to the point that they emit light instead of heat when they relax. The Kyushu scientists say their material has an internal efficiency of nearly 100 percent, which translates into about 14 percent of the electricity pumped into the OLED reemerging as light, compared with about 20 percent in commercial OLEDs that use metal.
Alán Aspuru-Guzik, a chemist at Harvard, sees the work by Adachi and Lupton as developments “that could lead to a breakthrough in the field of OLEDs.” The work both groups are doing could lead to better emission in the blue end of the spectrum in particular. Blue organic light emitters have been the most difficult to develop.
At the moment, the price of rare metals needed in OLED manufacturing is so low that manufacturers are unlikely to need either trick soon. And this new method doesn’t actually improve OLED efficiency over what existing devices can deliver, says Lupton. But it could prove appealing to OLED manufacturers if the price of iridium goes up.
Far more interesting may be another aspect of Lupton’s discovery: The spins of the charge carriers in this type of OLED control the wavelength of the light emitted. “You can actually measure the spin of the electron within your OLED by using the color,” Lupton says. And because spin on the quantum level translates into magnetism in the macro world, “if you design this in the right way you could make it incredibly sensitive to magnetic fields,” Lupton says. “That will actually allow us to use the color of the OLED as a compass.” He says such a device could be more sensitive than Hall effect devices, which are common in smartphone navigation systems and in automobiles, where they measure the rotation of the wheels.
The research might even provide a new clue to how birds navigate using Earth’s magnetic field. While the exact mechanism is still debated, some scientists suspect that their eyes let them see shifts in the field as subtle variations of color. Lupton says they may be sensitive to color changes caused by alterations in the spins of electrons.
Dustin Shillcox fully embraced the vast landscape of his native Wyoming. He loved snowmobiling, waterskiing, and riding four-wheelers near his hometown of Green River. But on 26 August 2010, when he was 26 years old, that active lifestyle was ripped away. While Shillcox was driving a work van back to the family store, a tire blew out, flipping the vehicle over the median and ejecting Shillcox, who wasn’t wearing a seat belt. He broke his back, sternum, elbow, and four ribs, and his lungs collapsed.
Through his five months of hospitalization, Shillcox’s family remained hopeful. His parents lived out of a camper they’d parked outside the Salt Lake City hospital where he was being treated so they could visit him daily. His sister, Ashley Mullaney, implored friends and family on her blog to pray for a miracle. She delighted in one of her first postaccident communications with her brother: He wrote “beer” on a piece of paper. But as Shillcox’s infections cleared and his bones healed, it became obvious that he was paralyzed from the chest down. He had control of his arms, but his legs were useless.
At first, going out in public in his wheelchair was difficult, Shillcox says, and getting together with friends was awkward. There was always a staircase or a restroom or a vehicle to negotiate, which required a friend to carry him. “They were more than happy to help. The problem was my own self-confidence,” he says.
A few months after being discharged from the hospital, in May 2011, Shillcox saw a news report announcing that researchers had for the first time enabled a paralyzed person to stand on his own. Neuroscientist Susan Harkema at the University of Louisville, in Kentucky, used electrical stimulation to “awaken” the man’s lower spinal cord, and on the first day of the experiments he stood up, able to support all of his weight with just some minor assistance to stay balanced. The stimulation also enabled the subject, 23-year-old Rob Summers, to voluntarily move his legs in other ways. Later, he regained some control of his bladder, bowel, and sexual functions, even when the electrodes were turned off.
The breakthrough, published in The Lancet, shocked doctors who had previously tried electrically stimulating the spinal nerves of experimental animals and people with spinal-cord injuries. In decades of research, they had come nowhere near this level of success. “This had never been shown before—ever,” says Grégoire Courtine, who heads a lab focused on spinal-cord repairat the Swiss Federal Institute of Technology in Lausanne and was not involved with the project. “Rob’s is a pioneer recovery. And what was surprising to me was that his was better than what we’ve seen in rats. It was really exciting for me to see.”
The report brought renewed hope for people living with paralysis. The prognosis is normally grim for someone like Shillcox, who has a“motor complete” spinal-cord injury. That level of damage usually results in a total loss of function below the injury site.
Teams of scientists have been working on transplanting stem cells for neural repair and modifying the spinal cord in other ways to encourage it to grow new neurons, but these long-term approachesremain mostly in the lab. Harkema’s breakthrough, however, produced a real human success story and gives hope to paralyzed people everywhere. It presents a viable means of regaining bowel, bladder, and sexual functions, and maybe—just maybe—points the way toward treatments that could give paralyzed people the ability to walk again.
But Harkema’s first experiment involved only one patient, and many researchers wondered whether the improvement they saw in Summers was an anomaly. “The next big question was, Will you ever see these things in more than one subject?” says neurobiologist V. Reggie Edgerton of the University of California, Los Angeles, a collaborator in the Louisville experiments.
The U.S. Food and Drug Administration (FDA) had given Harkema the go-ahead to try the technique in four more paralyzed people. Shillcox put his name in the pool the night he saw the news report. He was selected, and in July 2012 he packed his wheelchair into his retrofitted Dodge Journey and drove himself from Green River to Louisville to begin 18 months of experiments.
The circuitry of the lower spinal cord is impressively sophisticated. Neuroscientists believe that the brain merely provides high-level commands for major functions, like walking. Then the dense neural bundles in the lower spinal cord take over the details of coordinating the muscles, allowing the brain to focus on other things. That division of labor is what lets you navigate a party and focus on the conversation rather than on your steps. After aspinal-cord injury, damage prevents the high-level signal from the brain from reaching the neurons below. Yet those neural bundles remain intact and are just waiting to receive a signal to start the muscles working. Stimulating the lower spinal cord with electrodes can awaken that circuitry and get it functioning, astonishingly, without instructions from the brain.
It has been known since the mid-1970s that direct stimulation of the spinal cord can actually induce the legs to move as if they were taking steps, without any input from the brain. Edgerton and other researchers have demonstrated the concept definitively in paralyzed cats, rats, and a few humans. But in most of these demonstrations, researchers were blasting a large amount of electrical current into the body to force the muscles to move. “Everyone, including us, was hung up on the idea that you have to stimulate at this high level to induce the movement,” says Edgerton. What they missed was that the stimulation was essentially overwhelming the neurons in the lower spinal cord and was actually interfering with their ability to process sensory information that can help the body move on its own.
The neurons in the spinal cord don’t only receive signals from the brain; they also process sensory feedback from the body as the muscles move and balance shifts. The importance of that sensory feedback gradually emerged with some animal experiments Edgerton reported in Nature Neuroscience in 2009. The study suggested that sensory input could actually control the motor commands produced by the spinal cord.
Harkema, a former student of Edgerton’s, ran with that concept. In her experiments with Summers, she stimulated his spinal cord just enough to wake it up and then let the sensory input do its thing. “It’s like putting a hearing aid on the spinal cord,” says Edgerton. “We’ve changed the physiological properties of the neural network so that now it can ‘hear’ the sensory information much better and can learn what to do with it.”
Harkema’s group uses an off-the-shelf neurostimulation system—made by Minneapolis-based Medtronic—that’s FDA approved for pain management. The system’s array of 16 electrodes is surgically implanted in the epidural space next to the outermost protective layer of the spinal cord. The array is then connected to a pulse generator (which resembles a pacemaker) that’s implanted nearby. Finally, the pulse generator receives a wireless signal from a programming device outside the body.
The array spans approximately six spinal-cord segments, the ones generally responsible for movement in the lower half of the body. By placing the electrodes over them, the researchers can generate a response in the corresponding muscle groups. Electrode 5, for example, is located near a segment of the spinal cord that controls hip muscles. Electrode 10 is located at the bottom of the array, over the segment that controls the lower leg.
Each of the array’s 16 electrodes can be set to act as a cathode or an anode or be completely shut off. Stimulation intensities can range from 0 to 10.5 volts with pulses sent at frequencies ranging from 2 to 100 hertz, although the researchers usually don’t go beyond 45 Hz. Picking the right combination of electrodes and stimulation parameters to generate a simple response in a single muscle is relatively straightforward. But generating a complex behavior like standing, which involves many muscle groups and a considerable amount of sensory feedback, is far more difficult. Choosing the right electrode configurations for standing requires both a tremendous amount of intuition and plenty of trial and error. “That’s the challenge: to create the electrical field that’s going to give you the desired behavior,” says Harkema.
On a Wednesday in February of this year, Shillcox arrived at theFrazier Rehab Institute in downtown Louisville for one of his first stimulation sessions. The array and pulse generator had been implanted a few weeks before. He wore Nike sneakers and black gym shorts, revealing thin legs atrophied from lack of use.
Shillcox joined Harkema and her team in a large room equipped with custom rehabilitation equipment. He wheeled himself to a three-sided stand Harkema had made out of metal pipes that she’d bolted to a piece of plywood. Researchers taped 14 sensors to Shillcox’s legs. Usingelectromyography (EMG), these sensors would measure the electrical activity produced by his muscles and indicate how Shillcox was responding to the stimulation. Two trainers hoisted Shillcox from his wheelchair onto his feet and into the stand. Then they took their positions to keep him upright—one in front of Shillcox with both hands pushing against his knees and the other behind, steadying his hips. Shillcox held onto the stand with his hands, and a bungee cord supported him from behind.
That day, Harkema planned to test new stimulation configurations to see whether one of them would allow Shillcox to stand on his own. She took a seat in front of a screen displaying the EMG signals while two other researchers helped monitor the data from other screens. To start the session, Harkema called out the electrode settings: “1+, 2+, 3+, 9+, 14+, 12+, 13+, 6+, 7–, 8–, 4–, 10–.” This configuration used 12 of the 16 electrodes, 8 of them as anodes (positively charged) and 4 of them as cathodes (negatively charged). Harkema instructed her team to set the pulsation frequency at 30 Hz and the initial intensity at 1 V and to ramp up by a tenth of a volt at a time. “Left independent,” a trainer called out when the stimulation reached 1.5 V. Shillcox bore his weight on his left leg without assistance for about 30 seconds.
Harkema jotted in her lab book and instructed the team to turn off electrode 10, the one targeting Shillcox’s lower leg. “Going to zero,” a researcher called out. He powered down the system, punched in the new electrode configuration without electrode 10, and ramped it up again. At 2.6 V, Shillcox’s knees buckled. “It shot me out,” Shillcox said. The electrodes hadn’t sent the signal to the legs to stand straight but had twitched his knees forward instead. The stimulation pattern and parameters weren’t quite right.
Harkema tried more configurations, but each time Shillcox felt nothing until Harkema hit a particular voltage threshold, at which point Shillcox’s knees would give way. After 75 minutes, on the 10th and last try, Harkema removed the bungee supporting Shillcox from behind. The muscle activity on the EMG monitors skyrocketed. He’d been balancing so perfectly with the bungee cord that he hadn’t been getting enough external sensory information to activate his muscles, Harkema concluded, so there had been little input flowing back to the lower spinal cord. She instructed her team to devote the next few sessions to the last electrode pattern of the day, but without the bungee.
The technological limitations of the stimulation system make these trials unnecessarily difficult. Each time Harkema changes the configuration of electrodes, she has to turn off the electric field they generate and start over at 0 V. It’s a safety feature of this off-the-shelf stimulator, but it destroys the body’s neural momentum. “You can get really close, and you think the person is almost standing independently, and if you could just shift the field a little you would have it. But you can’t. You have to go to zero. And then everything starts over,” says Harkema. The limitation makes it especially difficult to induce a stepping motion in her patients. “It’s a left-to-right problem. If we get the right leg to step, the left is doing nothing,” she says.
It doesn’t help that there are something like 4.3 x 107 possible electrode patterns she can try and that each can be tried with a range of frequencies and voltages. Without an algorithm to help her choose parameters, Harkema must rely on her experience, some limited neural mapping data, and what she sees on her monitors. “I have to look at the EMG data whizzing by and then make decisions about what I can change out of these 4.3 x 107 combinations to get it better,” says Harkema. She’s gotten pretty good at making adjustments, but she acknowledges that no one can fully interpret the nuances of all that EMG data.
To do better, Harkema has enlisted the help of a handful of engineers who say they can build a stimulation system specifically for her research. At the California Institute of Technology, mechanical engineer Joel Burdick is developing a machine-learning algorithm that aims to take some of the guesswork out of choosing stimulation parameters.
The algorithm is based on statistical methods that predict the patient’s likely response to stimulation patterns—even those that haven’t been tested yet. The prediction part is crucial because there’s no way to try out all the options: There are millions of electrode configurations, and every patient is different. And just to make things even more complicated, patients’ spinal cords change during the course of the stimulation experiments. “The amount of time it would take to test that space is beyond a patient’s lifetime,” says Burdick. So the algorithm has to learn quickly. It must apply reasonable stimulation patterns and then use the patient’s EMG responses to choose better configurations.
Burdick’s team is working with Edgerton’s lab at UCLA to test the algorithm on paralyzed rats. The researchers are starting simply, using just a couple of electrodes and trying to maximize the response in a particular muscle. The first step is to make sure the algorithm is making reasonable decisions. The team has also begun a small human pilot study, Burdick says.
Meanwhile, John Naber, an electrical engineer at the University of Louisville, and a team of engineers are developing a stimulation system that would give Harkema independent control of all 16 electrodes in Medtronic’s array. The design would allow her to transition from one configuration to the next without shutting off the current. The team is building a new pulse generator using off-the-shelf components, and they’ve already written the code and roughed out a design. The challenge, Naber says, will be getting it approved by the FDA in a reasonable amount of time. “It’s not like a commercial integrated circuit or product, because of the FDA requirements for human implants,” Naber says.
The lingering question is whether Medtronic’s 16-electrode array is the best one for Harkema’s work. It was designed to treat pain, so the current diffuses rather broadly. Yu-Chong Tai, an electrical engineer at Caltech, thinks that an array with smaller electrodes arranged more densely might offer the precise stimulation needed after spinal-cord injury. The prototype he’s testing in rats has 27 electrodes arranged over a 2-centimeter-long array. A human version would be similar in size to Medtronic’s (about 5 cm long) but would contain hundreds of electrodes. Of course, more electrodes would mean exponentially more configuration options. “If we give them more electrodes, they will need a smart algorithm,” says Tai.
Until Naber and Tai’s prototypes can be approved by the FDA and Burdick’s algorithm can be fine-tuned, the Medtronic system will have to suffice. That may limit what Harkema can achieve when she puts Shillcox and her other research subjects on the stimulator, especially in terms of stepping. Even so, Shillcox has reason to hope that the experiments will boost his quality of life. Rob Summers, Harkema’s first subject, says his perspective on life has greatly improved since he regained bladder, bowel, and sexual functions. “This project has given me my freedom back,” he says.
Research subjects No. 2 and No. 3 have completed their initial trials. Like Summers, both were able to stand while on the stimulator, as Harkema and her colleagues reported at a Society for Neuroscience meeting in 2012. The researchers have not publicly announced whether other voluntary movement and physiological functions, such as bladder control, have returned for those individuals.
Shillcox—subject No. 4—remains hopeful, but he’s trying to keep his expectations realistic. “I don’t want to be too optimistic, and I’m trying to be prepared for no results at all,” he says. “I hope that whatever they find from this research will at least benefit other people.” Shillcox will likely complete his training by the end of the year, and Harkema says she cannot yet publicly reveal their preliminary results. Whatever the medical benefits ultimately prove to be, working with Harkema as a pioneer on an experimental treatment for spinal-cord injury has boosted Shillcox’s confidence around others. “I have no problem asking for help now,” he says.