Stroke patients can be greatly helped by intensive, repeated and long-term rehabilitation training, which is used to enhance their physical mobility. Yet access to outpatient rehab services can be limited — not to mention the fact that stroke patients may find it difficult to travel from their homes to outpatient clinics.
In Hong Kong, which in recent years has seen about 25,000 new incidences of stroke annually, a research team at The Hong Kong Polytechnic University (PolyU) has addressed this problem by developing a robotic arm to facilitate self-help and upper-limb mobile rehabilitation. The lightweight device — a first-of-its-kind integration of exoskeleton, soft robot and exo-nerve stimulation technologies — enables patients to engage in intensive self-help rehabilitation exercise anywhere.
The "mobile exo-neuro-musculo-skeleton" features low power demand, which is served by a 12-volt rechargeable battery supply for four-hour continuous use. Wearable upper limb components, which can be fitted for different functional training needs, weigh up to 300 grams.
"We are confident that with our mobile exo-neuro-musculo-skeleton, stroke patients can conduct rehabilitation training anytime and anywhere, turning the training into part of their daily activities,” said Dr. Hu Xiao-ling, who developed the device along with her research team in the biomedical engineering department of the university.
Both exoskeleton and soft robotic technologies can be used to assist a patient’s desired joint movement. Either type of device provides external mechanical forces driven by voluntary muscle signals. Yet both designs have their shortcomings: conventional exoskeleton structure is constructed with orthotic materials such as metal and plastic, which simulate external bones. Although this makes for a compact device, it is heavy and uncomfortable to wear. By contrast, the air- or liquid-filled pipes used to simulate external muscles in a soft robot structure are lightweight but bulky in size. Both types require high electrical power for driving motors or pumps, which tends to limit their use to hospitals and rehab centers.
The new robotic arm combines the best of both worlds: It is lightweight and compact, offers a quick response and demands minimal power supply. Its external mechanical force design also has been integrated with PolyU’s patented Neuro-Muscular Electrical Stimulation (NMES) technology, which is used to trigger on-demand muscle contraction responses. The incorporation of NMES has been shown to make the external mechanical force component 40% more effective for stroke rehab.
The robotic arm consists of components for wrist/hand, elbow and fingers; these can be worn separately or together for different functional training needs. Sportswear features such as washable fabric, ultraviolet protection and good ventilation also make the robotic arm a comfortable wear. A mobile app can also be connected to the device in order to record real-time training data for better monitoring of the rehabilitation progress by both healthcare practitioners and patients. It can even serve as a social network platform for stroke patients to communicate online with each other for mutual support.
The team anticipates possible commercialization of the robotic arm in two years.