Schematic illustration of flexible and stretchable sEMG sensors designed for amputees. an sEMG sensor attached to different types of leg muscles. The red boxes show graphically implemented images and the blue box shows an image of the fabricated sEMG sensor. b The muscle parts are activated at different times depending on the walking phase. c Specific description of the electrode layer and base layer of the sEMG sensor. The yellow dotted line indicates the boundary of each side. d Microscopically photographed surfaces of P-PDMS as a function of citric acid concentration (scale bar, 1 mm). e Graph for P-PDMS breathability test (e, n = 20 samples for WVTR and n = 3 samples for thickness, data presented as mean ± standard deviation). f Graph of the stress-strain curve of the substrate layer. The calculated tensile stress is 253.85 kPa and Young’s modulus is 145.38 kPa. Credit: npj Flexible Electronics (2023). DOI: 10.1038/s41528-023-00282-z
A research team led by Professor Sang-hoon Lee from the Department of Robotics and Mechatronics Engineering at Daegu Gyeongbuk Institute of Science and Technology has successfully developed an imperceptive surface electromyography (sEMG) sensor. The sensor is crucial in allowing lower limb amputees to control robotic prosthetic legs as they wish and is expected to contribute greatly to rehabilitation and better quality of life.
With the recent increase in lifestyle diseases such as diabetes, the number of lower limb amputees is increasing rapidly. The permanent effects of lower limb amputation are not only a physical disability but also a psychological disability. To solve this problem, lower limb bionic technology has been developed in recent years to replace a lost leg with robotic prosthetics.
The most important thing in the development of robotic prosthetic legs is to stably implement the function of the lower limbs as intended by amputees, and to do this, the ability to quickly and accurately acquire biological signals from amputees is required. The most suitable method is to use non-invasive sEMG sensors; however, these sensors are difficult to use in practice.
The sensor should be located inside the silicone liner of the socket to record electromyographic signals. However, the silicone coating is very narrow, it creates a humid environment and it is impacted by the socket, which is subject to strong dynamic movements due to the weight of a robotic prosthetic leg. This makes it impossible to stably record biological signals from muscles for an extended period of time without damaging the sensor itself.
In this context, a research team led by Professor Sang-hoon Lee of DGIST developed an imperceptible sEMG sensor, a biointerface formed via a microelectromechanical system. The study is published in the journal npj Flexible Electronics.
The imperceptive sEMG sensor developed by the research team mimics a serpentine structure to provide flexibility and elasticity while ensuring breathability and grip. Therefore, the sensor can be applied to various amputated parts of the body and can be used repeatedly over an extended period of time. Additionally, combined with a wireless module, the sensor obtains real-time signals generated when amputees walk with robotic prosthetic limbs, sockets and silicone coverings.
To verify the sensor’s operation, the research team attached the sEMG imperceptive sensor to a lower limb amputee and assessed the sensor’s function by recording the amputee’s muscle signals. The results demonstrated that the sensor successfully acquired high-quality real-time muscle signals from the amputee walking in various environments (on flat ground, uphill and downhill, and on stairs) and transmitted the signals without wire to help the amputee walk, as verified from the motion analysis sensor embedded in the robotic prosthetic leg.
Furthermore, by analyzing the muscle signals generated by plantar flexion and dorsiflexion in amputees, the research team confirmed that the selective signal acquisition performance of the imperceptive sEMG sensor is better than that of other commercial sensors. In this regard, the research team expects the sensor to be applied to various wearable technologies, in addition to precise control of robotic prosthetic legs and hands based on biosignals.
Professor Lee said: “Although there are more amputees than we think in Korea and around the world, there are many restrictions on daily activities and life because prosthetic legs that can be controlled like what the user wants are not available. research, we will continue to deepen our research and ultimately develop bionic limbs capable of implementing sensory and motor functions, just like those of human limbs, to help amputees enjoy all activities of daily life .
More information:
Jaeu Park et al, Imperceptible and reusable skin surface EMG for lower limb neuro-prosthetic control and clinical evaluation, npj Flexible Electronics (2023). DOI: 10.1038/s41528-023-00282-z
Provided by Daegu Gyeongbuk Institute of Science and Technology (DGIST)
Quote: Research team develops new technology for robotic control of prosthetic legs (December 11, 2023) retrieved December 11, 2023 from
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