Fabric-based muscles: hand exoskeleton supports finger movement

They have been featured extensively in the news or in rehabilitation centers: Exoskeletons are wearable medical devices that help users walk again if they suffered a spinal cord injury. Researchers now want to apply the same principle on a much smaller scale to assist finger joints. An exoskeleton glove is designed to give operators who no longer have full control over the muscles in their hands a new chance at grabbing a book or a cup.

COMPAMED-tradefair.com spoke to Klaus Richter from ITP GmbH, coordinator of the joint research project "Textiler Muskel – Entwicklung eines Handschuhs zur Unterstützung der Fingerkraft mit textilen Aktoren" (English: Fabric-based buscles – exo glove development to support finger extension and flexion with textile actuators), about the current status of the development.

Mr. Richter, some modern exoskeletons help paraplegics to walk again. Unfortunately, hand exoskeletons are still somewhat uncommon. You want to change that. Can you tell us how?

Klaus Richter: We plan to use textile actuators. This physical approach integrates silicon electrodes with electrolytes, which cause an increase in volume when a voltage is applied. In theory, the volume can be increased by up to 400 percent. Not much electrical energy is required to prompt the volume expansion. The volume expansion is subsequently translated into flexion. Thanks to the glove, the finger bends, which strengthens any remaining muscles. The project’s practical goal is to help people with limited hand mobility and muscle strength to hold a cup on their own, for example. To do this, the glove is coated in the finger section and controlled via electronic and sensor technologies. We want to position the sensors that control the movements on the wrist. They register the muscle information and later translate them into impulses that activate the fabric-based muscles in the fingers, allowing users to grab objects. Users also need to let go of the items, which takes place via another muscle impulse. In this case, the fabric-based muscles relax again, stretch, and release the object.

What will the glove look like once it has been completed?

Richter: It will look like a slim, lightweight sensor glove. We no longer need big cables and similar technology since the sensors are integrated in the delicate coating in the fingers of the glove.

Is the glove customized to the individual’s hand size?

Richter: The glove can be customized if necessary. However, our goal is to avoid using too much material, which means the fabric-based muscle components also don't have to be individually adjusted for each patient.

What is the current status of the project?

Richter: We are almost halfway through the project as the latter will continue until October 2023. We already reached our most important goal of achieving the desired functionality. The material behaves as proposed and is currently being optimized to facilitate muscle strengthening. We must now develop a power-based control process. Hopefully, we will reach the prototype stage of the project at the end of next year. It will still be a few years until the project is completed and before we have a market-ready device.