Restoring movement

Amyotrophic lateral sclerosis (ALS) is the most common form of motor neurone disease (MND), a neurological condition that affects an individual’s motor neurons – the nerve cells in the brain and spinal cord that control our ability to move our muscles. The disease gets worse over time: as the motor neurons degenerate, they stop sending messages to the muscles, which means the muscles twitch and waste away. In the later stages of the illness, it becomes impossible for the patient to control their muscles, so they cannot walk, eat or speak, and eventually require a ventilator to breathe. Typically, patients die within three-to-five years of diagnosis, though some live for longer – the late physicist Stephen Hawking being the most well-known example.

In the US, about 30,000 people have the condition at any one time, while in the UK, the figure is about 5,000. While there is no cure for ALS, could there be a way of using mechanical means to help patients retain muscle movement? This is the question that Conor Walsh, professor of engineering and applied sciences at Harvard University, and founder of the Harvard Biodesign Lab, set out to answer.

Walsh’s lab brings together researchers from different disciplines (engineering, industrial design, medicine and business) to develop robotic technologies. These include wearable robotic devices that can help restore and improve mobility in individuals with, for example, gait deficits. One of its major areas of research is in exosuits – soft, wearable robotics designed to improve mobility in people with muscle weakness. The components, which are extremely light, are much more comfortable than traditional exoskeletons and minimise the suit’s interference with the body’s natural biomechanics. The exosuits can also help improve movement in healthy people – one of the lab’s spin-outs, Verve Motion, has launched the SafeLift suit, which reduces the strain on workers performing physically strenuous tasks in different industries.

When Walsh and his colleagues decided to create a device that could help with arm movement in people suffering from paralysis, it was, he says, “with broad use across a range of application areas in mind”. Initially, they hoped to use it for stroke rehabilitation. The Covid-19 pandemic prevented them from carrying out human subject testing, however, putting the stroke plans on hold. The team then switched focus to ALS, enabling them to apply for the newly launched Cullen Education and Research Fund (CERF), which awards prizes for research that helps people with ALS lead a more normal life. They went on, in 2022, to win the prize, worth €500,000, in collaboration with the BrainGate team at Brown University.

An inflatable actuator

When Tommaso Proietti, an assistant professor at the Biorobotics Institute of Scuola Superiore Sant’Anna, Italy, joined the team as a research fellow, he brought with him expertise in upper limb robotics. Two of his colleagues, Ciaran O’Neill, with a specialism in engineering, and Kristin Nuckols, an occupational therapist, worked with Proietti on the project. Working with clinical and patient communities to understand the requirements and get feedback on early prototypes, the team set about creating the assistive device.

The final prototype, which is powered cordlessly by a battery, consists of a shirt with an inflatable actuator resembling a balloon under the armpit. A sensor system that can detect angle, velocity and acceleration is integrated into the shirt. After a 30-second calibration period in which it detects the strength and mobility of the individual patient, it inflates the balloon accordingly, moving the arm in a way that appears smooth and natural. If, for example, an individual with ALS is normally able to move their arm to 40 or 50 degrees of elevation, once they reach this angle, the robot assists them to raise it further.

Proietti, who spent three years in the Harvard lab working on the technology, says it “seems like a very simple idea to use inflatable balloons to assist the shoulder”. The biggest challenge, he says, was to “understand how to anchor the textile to the body in a smart way that would allow maximising the torque transfer from the pressurised actuator to the limb”. They used a combination of extensible and inextensible textile in the design of the shirt – the inextensible to transfer the torque, and the extensible to make the shirt more comfortable and adjustable to different body sizes.

Another challenge was to find a pump that could pressurise the necessary flow, but was not too heavy, bulky or noisy. There are not many companies making pumps for health care. “We were able to find one very exceptional device, that is very silent and provides a good flow,” Proietti says. The team bought three prototypes but were then told that the company would only sell the pumps in batches of at least 100. Fortunately, there has since been a change of heart, and the company is now selling the pumps individually at a cost of about $3,000 each.

Significant improvements in function

Once the prototype was complete in the summer of 2021, the researchers were able to test it on 10 patients with ALS at different stages of the disease. One advantage they observed was ease of use: participants were able to learn how to use it in under 15 minutes. Despite the relative simplicity of the design, they saw “significant improvements in function”, says Walsh, and patients were able to increase arm movement by 30–40%. As well as improving their range of motion, the device reduced muscle fatigue and improved the performance of tasks such as reaching for objects.

The participants were “very excited” to use the robot, Proietti says: “All of them asked me once we were done where they could buy this, or if we could give them a version of it, because they felt it could be really useful for their everyday life.” As Walsh points out, the user-friendliness of the technology is a major benefit: “The apparel-based nature of the approach lends itself to something that can be worn throughout the day at home and be made affordable.” The device can, however, only be used by those who have some residual movement in their arm. Those who have reached the late stages of ALS and cannot move at all would not benefit from the device.

Having had this initial success, what next? “We are continuing to refine the technology,” says Walsh. “This involves developing better sensing and control strategies so we can have the device work intuitively and synergistically with the wearer. Also, we want to improve the design of the inflatable structures so they can better support a large range of arm motions.”

Using brain signals to drive the soft robotics

Walsh is now working with their CERF prize collaborators at Brown University to integrate its BrainGate technology. The two teams are working together to create wearable soft robotics that maintain the function of the arm and hand, and – in a crucial difference from the original prototype – can be controlled entirely by a patient’s intention to move.

Whereas the original required the patient to have some residual movement in the arm, the new device will be combined with the BrainGate system, an array of electrodes able to decode signals from the brain’s motor cortex. The signals from the brain will drive the soft robotics created by the Harvard team. Using the same balloon principle, Walsh and his colleagues have created a glove that can perform hand movements. By decoding the signals from the brain, the robotics can restore, for example, a patient’s ability to grasp a coffee cup. This would be beneficial not just for ALS patients, but for patients with stroke or any other condition that impairs their ability to move.

Walsh is hopeful about the possibilities opened up by the BrainGate collaboration. “The current prototype is only capable of functioning on study participants who still had some residual movements in their shoulder area,” he says. “ALS, however, typically progresses rapidly within two to five years, rendering patients unable to move. With the BrainGate team, we are exploring potential versions of assistive wearables whose movements could be controlled by signals in the brain.”

For ALS patients suffering from a gradual deterioration in their ability to control their movements, the technology could prove transformative. Walsh believes it won’t be too long before it is commercially available: “It is still in the research phase, but we would hope we might bring it to market in two to four years.”