Design of a low-cost mechanical 3D-Printed hand orthosis for grasping assistance in activities of daily living

The ability to grasp objects has a significant impact on the independence of individuals following a stroke, a spinal cord injury, or for those who are living with amyotrophic lateral sclerosis. In most cases, physical rehabilitation is not sufficient to regain the hand function necessary for day-to-day life. Hand orthoses capable of providing grasping assistance in activities of daily living are therefore crucial to a more independent lifestyle. However, most available options struggle to offer an acceptable balance between cost, size, weight and functionality, resulting in limited use in practice. This article presents a low-cost, 3D-printed hand orthosis that relies solely on mechanical elements to aid in finger flexion. An underactuated, flexible design for the fingers with nylon strips as spring blades was used to achieve a design that costs only 27% of the price of comparable commercially available options, as well as being very lightweight and easily customizable. It was also demonstrated that rigid thumb supports allowed the orthosis to be used in the majority of daily grasping tasks. Finally, the use of the proposed mechanism was shown to be able to provide up to 4 N of flexion assistance to the finger when using a medium wrap grip.