FRAUNHOFER DEVELOPS HUMAN-MACHINE INTERFACE THAT STOPS MUSCLE TREMORS

A compact controller on a belt or under a jacket, a couple of discreet textile electrodes on the arms and legs, and electrodes three centimeters long and barely a millimeter thin in the muscle are all it will take to help people with tremor disorders in the future. Whenever muscle tremors start, the system sends electrical stimuli to the muscles; these stimuli are registered by the nervous system. The nervous system then stops sending interfering signals to the muscles, which settle down again. That is the basic idea behind the technology that scientists from Fraunhofer IBMT have been working on together with project partners by developing, manufacturing, integrating and experimentally testing a set of intramuscular and external electrodes and associated controllers.

The scientists have already made some concrete achievements. “We have managed to reduce muscle tremors significantly in trials with patients,” explains Andreas Schneider-Ickert, project manager for active implants and innovation manager.

The system is part of the EU-funded joint project “EXTEND.” A total of nine project partners from five different countries are working together to develop a versatile platform of distributed neural interfaces. The technology will be able to help people with neuromuscular disorders, such as tremors, or symptoms of paralysis. Even people with spinal cord injuries could benefit from this.

Implants for the human-machine interface
A key element of EXTEND is the implants, which are made from biocompatible platinum-iridium and silicone and are injected into the muscle through a catheter. Just three centimeters long and barely a millimeter in diameter, the tiny implant has an electrode at each end that functions as either a sensor or an actuator. External electrodes sewn into a textile ribbon supply the module with energy. This sends pulsed alternating current through the muscle tissue to the implant.

Once it has been implanted and started, the sensors register the first signs of muscle tremors and pass the information on to the external components. The controller evaluates the data and sends signals through the textile electrodes to stimulate the muscle. This closes a control circuit of intelligently networked sensor and actuator components that counteracts the tremor.

The stimulus signal is not strong enough to trigger a muscle contraction directly. It is the nervous system that plays the decisive role here. This registers the stimulation in the muscle tissue and responds by stopping the commands that trigger the muscle tremor. At least that is the theory — the finer details of the relationship between tremors and signals from the nervous system are yet to be researched.

Since tremors often occur in both arms and both legs, implants can be injected and external textile electrodes placed in all the affected muscle groups. This creates a distributed sensor network. The controllers can keep track of all the implanted and external electrodes at the same time and control them in coordination with each other. All this happens in real time, with the person experiencing no delay at all.