To develop the i-limbskin from silicone rubber, creating a protective glove without compromising the functionality of the prosthesis.
Paragon Rapid Technologies worked with Touch Bionics of Edinburgh with the development of their i-LIMB Hand. This is a first-to-market prosthetic device with five individually powered digits. The replacement hand looks and acts like a real human hand and represents a generational advance in bionics and patient care.
Touch Bionics is a leading developer of advanced upper-limb prostheses (ULP). The i-LIMB Hand was the world’s first commercially available multi-articulating bionic hand and was developed using leading-edge mechanical engineering techniques and is manufactured using high-strength plastics. The result was a next-generation prosthetic device that is lightweight, robust and highly appealing to both patients and healthcare professionals.
After developing the mechanical element of the i-LIMB Hand through the use of rapid prototyping techniques, Touch Bionics discussed with Paragon Rapid Technologies the feasibility of utilising similar processes to produce the i-SKIN, a thin layer of semi-transparent material to accurately wrap to every contour of the hand. The challenge was to find materials that can move and flex in the same way that human skin does.
The team at Paragon have extensive experience in producing silicone components from rigid epoxy compression tools, but the geometry of the glove would make a rigid tool impractical, so various rubbers were considered as an alternative for tooling. A range of tests and samples were carried out to identify the most suitable materials for both tooling and also for the production gloves.
Paragon was provided with a complete CAD model of the i-LIMB Skin and from that, were able to produce a fully finished stereolithography model. This master pattern was then used for the production of a polyurethane rubber tool with a rigid resin core. Initial samples were supplied in a soft silicone rubber with high elasticity, fulfilling test and marketing requirements. After implementing minor design changes the process was repeated, producing another SL master pattern and a polyurethane tool. However, this time the core was CNC machined from Aluminium, to give better definition, accuracy and stability.
The subsequent silicone mouldings have been fitted to i-LIMB to fulfil the ongoing production requirements.
Some patients, mainly military personnel, particularly love the robotic nature of the uncovered i-LIMB Hand and prefer not to wear it with a cosmesis glove. However, because of the need to provide a grip surface and to protect the hand from dust and water, the glove is necessary, so the semi-transparent material and mechanical robotic styling give the i-LIMB a very futuristic and technical look.
Touch Bionics has achieved major breakthroughs in the aesthetic appearance of its prosthetic products. The Touch Bionics products are the first prosthetic hands to imitate the true movement and lifelike accuracy of a human hand and represent a step-change in the world of upper-limb prosthetics.