Materials science, testing tech and creative minds

One of the most eye-catching exhibits at Interplas 2021 was a curious, vermiform exoskeleton on the Tinius Olsen booth. Rob Coker spoke to Martin Wheeler, Director Sales and Business Development, and Professor Matt Dickenson of UCLAN, to learn more.

Wheeler: When I heard what Matt was doing, I lit up because it gelled with Tinius Olsen and what we do. We love materials and materials testing. We love breaking, bending, twisting and seeing how they perform. We love helping youngsters to become interested in materials – that’s exactly what we're about. Matt’s work is about helping children with muscular illnesses, so the technology he's developed and the fact that he's trying to apply it in a way that would be affordable was just so appealing.

Dickenson: I’m dyslexic, so my school experience was not the best. But through public engagement we can inspire children to believe in what they can do. For example, I was involved in a project called Primary Engineer, and the idea is that engineers will go into schools and talk about problem solving. They then pose a problem to the pupils who draw out plans and put rudimentary prototypes together. These would end up on my desk and I'd review which could be made possible. One year I had an entry from a girl called Christina who asked: ‘Why is there not a special jacket or shirt that children could wear that could help them be mobile?’. At the time, and from my perspective, I thought she meant an exoskeleton, of which there are millions – but not for children. Children will grow out of an exoskeleton quickly and that, from a manufacturer's perspective, would be expensive, so we wanted to introduce a technology that could empower families.

We started to look at 3D printing with fused deposition modelling (FDM), but there were many questions that needed answers and trying to do that alone would have taken a lot longer. What I predicted to take around 15 years has been achieved in just two due to the partnership with Tinius Olsen. We've done some professional pilot studies and I've been able to connect with international contacts. As an academic, progress can be restrictive, but with an industry partner, it's all forward thinking. Now, when I meet with the academic group, the conversations are all about what can be achieved rather than what can’t. That type of encouragement and support has been like a slingshot into a whole new perspective.

Standing on the Interplas booth today with a functioning exoskeleton is a bit overwhelming because of how far we have come – and we have no intentions of slowing down.

Wheeler: We produce the equipment used to test and analyse the materials – that is, all the tools you need to see how that material would perform. The research, which is more focused in industry, is important because it places you on much more solid ground regarding what you're trying to achieve. Research should be used as a tool to develop things further, and it is still important to run these tests, but what's more important is that we keep going.

Dickenson: I'm not chasing the money. I'm chasing a technology that will empower those who have little money. This is not likely to make any money, but it's going to help those who need help. This version is what we’ve nicknamed ‘Generation 1.5’. The larger version has linear actuators attached. We noticed that by using actuators to power it required a lot of energy, so we knew we had to go back to the drawing board. This smaller system is more passive, but what we'd realised quickly, and without actually compromising the design, is that with something like this you can lean into it, much like you would with a crutch. It’s orthotic, supportive. When we use a crutch, we lean and that vector travels down the crutch, minimising stress on the leg. It’s the same principle with Generation 1.5 except this thing will wrap around the body, so, rather than using a linear actuator, we're trying to mimic muscular contraction.

Most exoskeletons will try to drive the joint through the use of huge, multiple bearings. So, if we mimic that point of contraction, we have a new type of actuation method, we just need to make it a little more sensitive. What started off with the intention of helping children is now generating interest from other sectors – construction, for example. There are so many potential applications as it encourages you to move more correctly. This design would be constructed onto your body in such a way so that you would be unable to lift a heavy box incorrectly, for example.

At first, we thought about making this from aluminium, but the pricing would have been astronomical, so we looked to polylactic acid (PLA) and what we soon realised, through a lot of finite element analysis (FEA), was that it could support adult bodies, not just children’s bodies. With the healthy ageing strategy, this exoskeleton could reduce the cost of healthcare and the risk of arthritis and other musculoskeletal ailments. Without 3D printing and these new polymers, we would be back to aluminium. The mechanics of copper-active PLA has so much going for it, and this is where the testing comes in.

We've been printing horizontally, which enables us to understand the material’s behaviour in different states. We wanted to establish the performance of this material so we're looking at internal meshing, which allows us to print the external circumference in antimicrobial PLA and the internal in a nylon mesh. To get to that position, we've had to test parts to make sure that when we make that next step we’ll be starting on solid ground.

Wheeler: That's an ASTM D 638 profile tensile test specimen – or ‘dog bone’. Standard PLA’s failure rate is round 45 mega pascals. In its strong components, this increases to around 55 mega pascals. In some states it outperforms some metals for what we're doing. It’s phenomenal. It's everything that we hoped for and more.

It’s all to do with understanding the material. The more you understand, the easier it will be to put on a human. Testing on children is not easily achieved, and the ethics behind testing on humans is something else completely. That's why Matt has been performing as much testing as possible and looking at healthy adults with the aim of being able to get to a comfortable position where we are reliably supporting the body.

Dickenson: When I read Christina's idea, I thought there's no way she came up with this ‘off-the-cuff’; there's too much detail, she had perspective, and she knew exactly what this should do. Her original drawing was basically a snake on someone's back, but I could see where she was going and it pushed me down a rabbit hole. I'm a firm believer in not stealing people’s ideas so I still contact Christina and her mother. It's really gone way past anything she drew but it is still important to acknowledge where these ideas come from.

The Tinius Olsen model 50ST testing system with its Horizon software underpins my testing with its tensile and flexural test capability. As a piece of kit, I use it to push materials and structures to their limits and beyond, understanding exactly how they will perform.

Martin’s colleague Shawn Byrd has also been very helpful. He encouraged me to join ASTM International to contribute with my experience and to tap into the many minds developing standards around exoskeleton technology. There is well over 100 members in the ASTM F48 committee coming from all areas of industry. People from all over the world sharing ideas to progress good standards around this technology, on a personal level, has been very thought provoking.