□ A research team led by Professor Sang-hoon Lee at the Department of Robotics and Mechatronics Engineering, Daegu Gyeongbuk Institute of Science and Technology (DGIST; President Young Kuk) has successfully developed an imperceptive surface electromyography (sEMG) sensor. The sensor developed by the research team is a crucial device that allows lower limb amputees to control robotic prosthetic legs as they want, and is expected to contribute greatly to rehabilitation and a better quality of life in the future by allowing the control of robotic prosthetic legs as intended by the amputees.
□ With the recent rise in lifestyle diseases, such as diabetes, there is a rapidly growing number of additional lower limb amputees. The permanent disability of lower limb amputation is not only accompanied by physical disability, but by psychological disability as well due to the loss of a part of the body. To tackle this problem, bionic lower limb technology has been developed in recent years to replace a lost leg with robotic prosthetics.
□ The most important thing in developing robotic prosthetic legs is to stably implement the lower limb function as intended by amputees, and in order to do so, the ability to rapidly and accurately acquire the amputees’ biological signals is required. The most suitable method is to use a non-invasive sEMG sensors; however, it remains difficult to use such sensors in practice. The sensor must be located inside the silicone liner of the socket to record electromyographic signals. However, the silicone liner is very narrow, humid, and impacted by the socket, which is subject to strong dynamic movements due to the weight of a robotic prosthetic leg, makes it impossible to stably record muscles’ biological signals for a prolonged period of time without damaging the sensor itself.
□ In this context, a research team led by Professor Sang-hoon Lee at DGIST developed an imperceptive sEMG sensor, a biointerface formed through the microelectromechanical system. The imperceptive sEMG sensor developed by the research team mimics the serpentine structure to provide flexibility and elasticity while achieving breathability and adhesion. Hence, the sensor can be applied to various amputated parts of the body for amputees and can be used repeatedly over an extended period of time. Furthermore, combined with a wireless module, the sensor obtains real-time signals generated when amputees walk with robotic prosthetic limbs, sockets, and silicone liners.
□ To verify the sensor’s function, the research team attached the imperceptive sEMG sensor to a lower limb amputee and evaluated 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 of the amputee walking in various environments (on flat ground, up and down slopes, and on stairs) and transmitted the signals wirelessly to assist the amputee in walking, as verified from the motion analysis sensor embedded in the robotic prosthetic leg.
□ Furthermore, by analyzing muscle signals generated from 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 across various wearable technologies, in addition to precise control of robotic prosthetic legs and hands based on bio-signals.
□ Professor Sang-hoon Lee at DGIST stated that "although there are more amputees than we think in Korea and around the world, there are many restrictions on daily activities and living because prosthetic legs that can be controlled as the wearer intends are not available. Based on the results of this research, we will continue to further research and ultimately develop bionic limbs which can implement sensory and motor functions, just like that of human limbs, to help amputees enjoy all activities of daily living."
□ Meanwhile, this research was jointly conducted by the plastic surgery team at Seoul Asan Medical Center, Hugo Dynamics, and DGIST with grants in the project Localization and Development of Smart Electronically Controlled Lower Limb Products and Core Parts Applicable to Bilateral Lower Limb Amputees by the Inter-Ministry Electronic Medical Device Development Project Group. The results were published on October 25 in “npj Flexible Electronics” (JCR IF 14.6, top 2% in the field), one of the top journals in the field of materials science and interdisciplinary research.
- corresponding author e-mail address : [email protected]
 Serpentine structure: Snake-like, winding structure.
 Prosthetic limb: Artificially made arms and legs. It refers to prosthetic hands and prosthetic feet.