Exoskeletons: As if by magic

30 minutes by car southwest of Zurich: On the edge of the forest of the tranquil town of Affoltern is the Children Rehab Switzerland. A modern concrete building. Outside on the playground, children spend the afternoon with their parents. Inside, Professor Hubertus van Hedel and his team are working on a major technical development: a hand exoskeleton.

These are "systems that follow the shape of the human body," explains van Hedel, "and are connected to the hand from the outside, just like ours. This "external skeleton" ensures that certain movements can be performed with the human hand.

Anything but futuristic

Van Hedel's research team has developed a first-of-its-kind, fully motorized and wearable hand exoskeleton: Unscrewing bottles, cutting bread, picking up buttons from the floor and holding playing cards using robotics. The device is designed specifically for children and young people with congenital or acquired brain damage that limits their ability to move their hands.

Pexo - as the device is called - looks anything but futuristic: Each finger consists of three thin leaf springs on the upper side that function like tendons and are connected to a motor via cables. The device is activated by voice control or a blue button. Then the movable leaf springs exert a slight pressure on the human fingers and the patient's biological hand closes or opens. The electronics, motors and battery are housed in a back module weighing about two kilograms.

Pexo the crocodile

The bright green hand module resembles a crocodile. That's because the design is intended to meet children's needs, as Jan Dittli, an engineer at ETH Zurich, explains: "We developed different sizes to offer children between the ages of five and 18 a suitable size."

But the exoskeleton still has mechanical limitations: Fingers cannot be controlled individually. Only the thumb and the remaining four fingers together can be activated separately to open or close the hand. Playing the piano: No way. But this is the only way the low weight of the exoskeleton is possible from an engineering point of view. The hand module weighs about 120 grams, which is less than a smartphone.

Beginnings of the research

Van Hedel's team has deliberately avoided sensor technology or even control via connections to nerves or the brain. Although this is medically exciting, research is still in its infancy. Until now, therapeutic robotic devices have been very bulky, heavy and large. With Pexo, children and young people can easily practice movements with everyday objects and lift things that weigh up to half a kilogram. A large bar of chocolate is no problem, but a full carton of milk is borderline.

Robotically operated exoskeletons were first developed in the military at the beginning of the millennium and later for therapeutic purposes. Gait robots for stroke patients or for paraplegics already exist - for standing, walking or grasping, for example.

Power Suit for Industry

In the meantime, craft businesses, the automotive industry, logistics service providers and operators of care facilities are also interested in exoskeletons. For example, for wearable robots that take over lifting while protecting the spine of employees. Forces acting on the spine, shoulders and neck are taken over and redirected by the exoskeleton. The areas of application? Wherever physically demanding tasks are performed. For example, when several tons of spare parts, car bodies, suitcases or cement bags have to be weighed every day, or when bedridden patients have to be lifted in nursing homes. This potential has also been recognized by the German prosthesis manufacturer Ottobock. In the long term, the exoskeleton segment is seen as a larger market than prosthetics, Ottobock CEO Oliver Jakobi recently told the Frankfurter Allgemeine Zeitung. He expects sales in this segment to double as early as this year. 

Exoskeletons can be divided into two types: Passive models have neither motors nor batteries. They transfer loads to other parts of the wearer's body via springs and pulleys.

Unlike active exoskeletons, such as those made by the Augsburg-based company German Bionic. The company manufactures different power suits. These have force amplifying motors and do the lifting. For example the Cray X: a so-called Power Suit Exoskeleton designed to improve the physical performance of workers and developed specifically for use in the manufacturing industry when lifting and lowering loads on pallets or racks.

The exoskeleton helps reduce stress on the upper body and thus prevent muscle fatigue and injury. It works similarly to the hand exoskeleton of Children's Rehab Switzerland, is strapped on via leg loops and on the upper body via a vest.

Huge market

Cray X is modular, which means that the exoskeleton can be individually configured depending on the wearer's area of application and needs. It can also be equipped with various sensors and monitoring systems to monitor the wearer and their work and collect data on performance and load.

German Bionic is not the only company experimenting with exoskeletons and offering such devices. Numerous startups are dabbling in the field. According to the Indian analytics firm MarketsandMarkets the global market for exoskeletons will grow steadily and reach a value of 6.8 billion US dollars by 2025. Other market research institutes estimate sales for industrial exoskeletons at 20 billion US dollars by 2030, up from 96 million US dollars in 2016.

Health prevention and risk assessment

A laboratory study by the Fraunhofer Institute for Material Flow and Logistics found that the use of exoskeletons in manufacturing had a positive effect on productivity. Work efficiency was increased by up to 25 percent, it said. Employees were able to work faster and longer without showing signs of fatigue through the use of exoskeletons. The study was conducted in collaboration with various companies that already use exoskeletons in their production.

The researchers also found that employees had fewer musculoskeletal disorders and strains as a result of using exoskeletons. The use of exoskeletons helped reduce the risk of repetitive strain injuries during physically demanding activities.

However, there were also criticisms of the use of exoskeletons in industry. For example, it was criticized that the exoskeletons are still quite heavy and bulky, which can limit the mobility of employees. Also, some exoskeletons are still quite expensive, making them difficult to use in smaller companies. And there is a lack of long-term studies to assess the consequences in real industrial use. These include possible side effects such as muscle breakdown in active exoskeletons or the increased strain on the cardiovascular system in systems for overhead work.

Back to the Children's Rehab Switzerland. Wanda [real name known to the editors] comes into the treatment room; she is one of around 240 children and young people per year who spend several weeks or, like the 14-year-old, even months in rehab. The reason: they struggle with the consequences of spinal cord or brain injuries after strokes, for example.

Troublesome therapy

Wanda also had a stroke a year ago and could no longer move her left arm, leg and hand properly. Intensive rehabilitation has changed all that. Wanda speaks fluently again, but her hand still does not want to move as well as before.

Now she has to use the hand exoskeleton to grab small building blocks from a wooden box and place them across a partition into a second box. What is easy for other children is hard for Wanda.

She gives the command via the voice control to close her hand, suddenly the motors of the exoskeleton begin to whirr softly. Her paralyzed fingers curl, she grabs the small wooden block and places it in the opposite box.

Star Wars fantasy

Will hand exoskeletons eventually come close to the functions of real hands? Van Hedel's answer: No, the human hand is too delicate and complicated to be artificially replaced like Luke Skywalker's robotic hand. It remains a Star Wars fantasy of the Hollywood dream factory.

Nevertheless, an exoskeleton could be helpful for some children with brain damage, the research director sums up. "Commercially, this is not a huge target group," and adds: "The humanity of a society is shown precisely in how it treats its weakest. Children are our future!"

Source: Exoskeletons: As if by magic | Economy | DW | 07.04.2023