Carbon Fibre Prosthetic Exoskeleton

In 2016 Paul had no idea about carbon fibre. Unfortunately, his world changed dramatically when his wife Jane was diagnosed with a very serious bone cancer in her right hip and pelvis. The surgeons said that the only option was to operate - chemotherapy and radiation don’t work. It was only when they explained that this operation is NOT like a hip replacement - it is TOTAL REMOVAL of the hip and the pelvis and nothing is put back in. Paul’s wife would need to use a wheelchair or two crutches for the rest of her life.

After the operation, Paul set about trying to buy something to help his wife stand or walk, but there was absolutely nothing on the market. He spoke to the R&D departments of major prosthetic and orthotic manufacturers - nothing was even in plan or on the drawing board. He even commissioned a professional company to make a device for her - that was a complete and very expensive failure.

As Covid arrived, Paul thought that he would have a go - as the saying goes ‘How hard can it be ?’ - well he was to quickly find out that reproducing the human hip joint is very difficult and probably explained why nobody had done it before. Undeterred he set out on a quest to make something - even if it just helped Jane stand up for longer periods.

The first, three attempts were, looking back now, disastrous, but they seemed like a good idea at the time. Slowly, the ideas and concepts formed and it became clear that carbon fibre and composites would need to play a major role in the structure.

It was now time to learn about composites. The Easy Composites web site was soon found and Easy Composites' YouTube videos became a serious source of education and ideas.

To gain the skills necessary for this project, Paul then taught himself Photogrammetry, 3D Scanning, Computer Aided Design, Surface Modelling, 3D Printing in both plastic and metal, and of course working with carbon fibre to name but a few. Paul had his wife 3D scanned and then produced a life size model CNC carved from solid foam.

Using EL2 Epoxy laminating resin and carbon fibre cloth laid over the life size model, intricate 3D shapes could be made. There was no point making accurate moulds to work from as he didn’t know what shapes would work ( if any !). Instead he used R210 unperforated release film over the model and then finished off with PP180 peel ply. This allowed for rapid prototyping at minimal cost.

Part of the design needed some parts to be very stiff and other parts to be flexible. Using the EF80 flexible epoxy resin provided the flexible parts. One part however needed to be in just one piece, some areas had to very stiff and other areas very flexible. Paul found that using the EL2 laminating resin and transitioning to the EF80 whilst the epoxy was still wet gave him what he needed. The two different epoxy resins played very happily together with the stiffness of the carbon fibre being varied across the part based upon the ratio of the two epoxy resins at that site. By using Kevlar cloth at some of the very flexible areas it created a very strong hinge in the middle of the part.

Some custom designed silicon rubber parts were also required and both the AS40 Addition Cure silicone rubber and the CS25 Condensation Cure silicone rubber were used along with the black liquid silicone pigment to colour them.

In addition, very strong complex parts were required and these were made quite simply using plastic barriers and EL2 laminating resin mixed with finely chopped carbon fibre offcuts mixed into a paste. Not very pretty but works really well.

Recently, Paul attended an open day at Easy Composites on using the XC110 Out of Autoclave Prepreg and has now started to create the latest versions using the XC110 and finishing with the XCR coating resin to get a good smooth surface finish.

In tandem, Paul was working with Alphatech design, who are a small design and engineering company based in Devon, to create a bespoke world first external human hip joint. This joint is key to the success of the exoskeleton and has been manufactured using 3D aluminium printing.

After three long years, over 4000 hours and many failures, Paul has created a world first of a kind total bodyweight offloading exoskeleton. Not only can his wife stand for extended periods of time ( hours ) but can also walk for over a mile with just one crutch and just recently has learnt to walk using no crutches. This is an outcome that far exceeds his original dreams.

He has now set up a company, Xothotics Ltd, and has applied for a number of patents on the system.

Paul and Jane were recently featured on both the BBC and ITV news as well as some of the national and international newspapers. As a result of the media interest this new type of exoskeleton is now being reviewed by medical professionals to see who else might benefit from its development and what other conditions it may be able to help.