The Hong Kong Polytechnic University (PolyU) yesterday announced the development of a robotic arm to facilitate self-help and upper-limb mobile rehabilitation for stroke patients. The robotic arm, called “mobile exo-neuro-musculo-skeleton”, is the first-of-its-kind integration of exo-skeleton, soft robot and exo-nerve stimulation technologies.

Developed by Dr Hu Xiao-ling and her research team in the Department of Biomedical Engineering (BME) of PolyU, the “mobile exo-neuro-musculo-skeleton” features a lightweight design (up to 300g for wearable upper limb components, which are fit for different functional training needs), low power demand (12V rechargeable battery supply for 4-hour continuous use), and can be used with sportswear.

Dr Hu said that the development of the novel device was inspired by the feedback of many stroke patients who were discharged from hospital and faced problems in having regular and intensive rehabilitation training crucial for limb recovery.

The robotic arm integrates exo-skeleton and soft robot structural designs – the two technologies commonly adopted in existing upper-limb rehabilitation training devices for stroke patients as well as the PolyU-patented exo-nerve stimulation technology.

The working principle of both exo-skeleton and soft robot designs is to provide external mechanical forces driven by voluntary muscle signals to assist the patient’s desired joint movement. Conventional exo-skeleton structure is mainly constructed by orthotic materials such as metal and plastic, simulating external bones of the patient. Although it is compact in size, it is heavy and uncomfortable to wear.

Soft robot, made of air-filled or liquid-filled pipes to simulate one’s external muscles, is light in weight but very bulky in size. Both types of structures demand high electrical power for driving motors or pumps, thus it is not convenient for patients to use them outside hospitals or rehabilitation centres.

Combining the advantages of both structural designs, the robotic arm is compact and lightweight, rapid in response and demands minimal power supply, making it suitable for both outdoor and indoor environments.

An initial trial of the robotic arm on 10 stroke patients indicated better muscle coordination, wrist and finger functions, and lower muscle spasticity of all after they have completed 20 two-hour training sessions. Further clinical trials will be carried out in collaboration with hospitals and clinics.

Dr Hu and her research team anticipated that the robotic arm can be commercialised in two years.