For the 80 million people around the world who are estimated to have tremors, simple daily activities, such as holding coffee cups, can be frustrating. Now, researchers have developed slim, lightweight artificial muscles that may wear out carefully to suppress these involuntary movements.
Scientists from the Max Planck Intelligent System, Tübingen University and Stuttgart University have shown that a pair of artificial muscles tied to a person’s forearm can effectively counteract back and forth movements caused by tremors.
The technology uses soft materials that can respond to electrical signals to stabilize manual movements in response to tremor rhythms, detailed in a study published on March 6 in the journal Equipment.
“We see muscles become part of a clothing that can be worn with caution so that others don’t even realize the loss of the person being subjected to tremor,” said Alona Shagan Shomron, a postdoctoral fellow in the robotics material division of Max Planck Institute.
The team’s approach addresses significant gaps in current tremor treatment. Although medication and surgical interventions, such as deep brain stimulation, can help many patients, these choices may have side effects or less effective over time. Some patients simply cannot use these treatments.
No patient test
To avoid putting experimental techniques directly on patients, the researchers developed what they call “mechanical patients” – a robotic arm that reproduces tremors recorded by actual patients. This allows them to test the working status of their artificial muscles without causing real people to adhere to early technology.
The robot group can be programmed to mimic various tremor patterns from mild to severe and different frequencies. This covers typical ranges for conditions such as Parkinson’s disease and basic tremor.
In the test, artificial muscles (technical called Peano-Hasel actuators) reduced tremor amplitudes by 76% to 94% in various intensities and frequencies.
“We show that artificial muscles based on Hasel technology are very fast enough to accommodate various tremors in the wrist,” Shagan Shomron said.
The team also created computer simulations to verify that these artificial muscles produce enough power to suppress tremors in the actual human arms, not just their mechanical models.
Another muscle
The artificial muscles used in the study are different from traditional rigid robot components. They are about 1 mm thick and weigh only 15 grams, and are made of thin polyester plates, these thin sheets and carbon-based electrodes, filled with silicone oil.
When voltage is applied, the liquid inside is displaced, causing the material to contract like natural muscles. This design allows them to respond quickly to counteract the fast, rhythmic movement of the tremor.
The softness and flexibility of these actuators make them likely more comfortable and shocking than rigid devices, a key obstacle to patients’ acceptance of wearable assistive technology.
From the laboratory to life
Current tremor treatment involves from medication to invasive surgery, but the limitations of these methods remain. Some patients will tolerate the tolerance of treatment over time, while others will have significant side effects. The team believes their technology can provide non-pharmacological, non-surgical alternatives.
“By the combination of mechanical patient and biomechanical models, we can measure any tested artificial muscle that is sufficient to suppress all tremors, even very powerful. So if we created a wearable, we can adjust it to respond to each tremor alone.
The study is still in its early stages and there are some challenges that must be faced before these artificial muscles become part of the patient’s wearable devices. The current design works in a single wrist position and the safety system of electrical components will require further development.
There is another question about how such devices will distinguish between voluntary movement and involuntary tremor – the current research cannot solve it, but this is crucial for practical applications.
Beyond the tremor
The test platform developed for this study can also accelerate research on other movement disorders. Syn Schmitt, professor of computational biophysics and biological sciences at the University of Stuttgart, emphasized the value of their approaches in early research.
“Mechanical patients allow us to test the potential of new technologies very early in the development without the need for expensive and time-consuming clinical testing of real patients,” Schmidt said. “Because clinical testing is expensive and time-consuming and difficult to fund in the early stages of technology development, there are often no further pursuit of many good ideas. Our Mechanical patients are the solution, which allows us to test potential very early in the development.”
For people with tremors, the prospect of a light, inconspicuous device using medication or surgery can stabilize both hands, representing a promising path to research, although commercial applications may last for years.
“Robot technology has great potential in healthcare applications. This successful project highlights the critical role that soft robotic systems based on flexible and deformable materials will play.
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