Balloon-equipped ‘wearable robot’ could help stroke survivors

A first-of-its-kind, soft, vest-like wearable designed by Harvard researchers could help stroke survivors and people living with ALS regain crucial upper limb movement. The researchers call the device a “wearable robot,” which uses inflatable balloons positioned under a patient’s arm that  bulge and contract based on the desired movement. A combination of machine learning software and a separate physics-based model helps the robot interpret the patient’s intended movements and personalize actions accordingly.

In testing, the robot was able to correctly identify the user’s intended shoulder movement 94.2 percent of the time. After the device activates, it helped reduce the amount of force a patient needed to exert to lower their arm back down 31.9 percent compared to an earlier model. That means less exertion and fatigue for patients. 

The study included five people who had experienced a stroke and four living with ALS, a nervous system disease also known as Lou Gherig’s disease. Overall, each participant reported improvements in shoulder elevation and wrist extension, as well as a decrease in fatigue when asked to perform tasks like reaching for or holding objects.

These results suggest the wearable could play an important role in augmenting physical therapy for patients working to regain mobility. For some with severe limb impairment, it could offer a path toward regaining the ability to perform everyday tasks like brushing their teeth or simply taking a sip of water. The findings of the experimental study were published recently  in Nature Communications.

The fabric-based device is worn over the upper body like a long-sleeve vest and powered cordlessly by a battery. Multiple sensors collectively powered by a machine learning model are embedded across the device’s surface.. The sensors detect subtle movements made by the wearer. Then, the machine learning model  determines whether each movement was intentional or not. That determination is sent back to the device, which inflates or deflates balloons with air to assist in raising or lowering the arm.

“This technology is quite simple in its essence,” Harvard professor Tommaso Proietti said in a statement earlier this year. “It’s basically a shirt with some inflatable, balloon-like actuators under the armpit. The pressurized balloon helps the wearer combat gravity to move their upper arm and shoulder.”

The version of the wearable robot featured in the new Nature Communications study improves on a previous model shown earlier this year by incorporating what the researchers call an additional physics-based model. This second model calculates the minimum pressure needed to hold a patient’s limb in place, making the assistance feel less rigid and more natural for movement. In theory, that should make the device less awkward to use for people using it in rehabilitative settings. 

Related: [Robotic Exoskeletons Are Here, And They’re Changing Lives] 

To test this, the team asked the study participants to wear the device and attempt various arm movements. They measured the device’s performance using a motion capture system similar to those used in body tracking for video games and movies. Overall, the motion capture data showed a notable increase in range of motion around the shoulders, wrists, and elbows. This increased mobility also meant patients were less likely to overexert themselves by twisting or shifting other parts of their body to compensate for the movement of their impaired limb. 

Kate Nycz, one of the study’s  volunteers who has ALS, said the researchers also listened to and incorporated feedback from the device’s users.

“They’re not sitting in the lab just playing with the robot,” Nycz said in a statement. “I felt like they were really engaged with me. I didn’t feel like a lab rat or a cog in a wheel.” 

A softer, more accessible exoskeleton

Larger, more rigid body-assistance devices, broadly referred to as “exoskeletons”, are already being used to help some people regain limb functionality. Initially proposed by the Pentagon’s Defense Advanced Research Projects Agency (DARPA) as a way to help soldiers lift heavy objects, the technology has since been adopted by multiple researchers and private companies focusing  on improving mobility for a wider audience. These devices have proven effective in helping patients with disabilities improve their walking abilities. They also have the potential to help prevent falls in older adults by functioning like a high-tech, sci-fi-inspired walker.

The soft wearable robot explored by the Harvard researchers is less complicated (and less capable) than a full-body exosuit, but that may also be part of its appeal. By trading in metal backbones for a soft familiar-feeling vest, the wearable robot offers a more cost-effective and approachable solution for the millions of individuals worldwide who could possibly benefit from moderate limb support.

 

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