Fabricating a Flexible Thermoplastic 3D Printed Wrist Support Device for Injury Immobilization and Healing

Wrist sprains, fractures, and contusions are common, with an estimated incidence of 896 hand and wrist injuries per 100,000 people yearly¹. During recovery, most of these injuries require immobilizing the wrist for protecting the injury and promoting faster healing. Today, wrist braces are made using materials that are either too bulky or lack the rigidity needed to immobilize the injured area. Thus, there is a need to design and use a material for a lightweight, rigid brace that still gives the wearer the ability to do everyday tasks.

Inspired by ActivArmor^TM , a custom 3D printed support device, the goal of this research is to fabricate a wrist brace using thermoplastic polyurethane (TPU), a 3D-printable polymer. The material shows promise in that it has a smooth finish, abrasion-resistance and is simultaneously rigid and elastic. When 3D-printed thinly, the material can bend and flex, but when printed above a certain thickness, the material becomes stiff and rigid. The TPU cast is created by scanning the wearer’s forearm and hand, which is processed and refined in AutodeskⓇ Meshmixer to model and generate a cast with a vertical clamshell opening. This is then printed at a filament temperature of 225°C and 20% infill. The cast features a Voronoi pattern, a computer-generated tessellation pattern that removes the maximum amount of material from the cast body possible while still maintaining stability, for a more breathable and sustainable design. Cylindrical notches are present on both sides of the clamshell opening and connected across by O-rings to create a closing mechanism.

The lightweight, Voronoi-patterned TPU cast is flexible enough to allow the cast to be opened and put on while simultaneously being rigid enough to hold the cast’s shape and the wearer’s wrist in place once secured. Additionally, the cast’s design allows for a one-handed open/close mechanism. For this specific cast, the use of a 3D scan allows for a custom fit around the wearer’s forearm and wrist. Using a 3D print compatible material allows for cost-effective and environmentally friendly manufacturing, as the brace is removable, washable, and has the potential for long-term use.

[1] Gordon, A. M.; Malik, A. T.; Goyal, K. S. Trends of Hand Injuries Presenting to US Emergency Departments: A 10-Year National Analysis. The American Journal of Emergency Medicine 2021, 50, 466–471. https://doi.org/10.1016/j.ajem.2021.08.059.