Are smart materials the future of assistive medical ware?

Wearable assistive materials (WAM) is a project at UCL which began with the initial intention to make a significant difference to individuals who experience difficulty walking. Ultimately, the project’s aim was to create a device that would give someone the ability to walk without any visible assistance. Their approach was the development of a wearable exoskeleton that could act as a muscle in such a way that it could potentially aid the whole walking cycle — providing support, control and assistance to a given user enabling them to walk unaided. To this end, the researchers have been working towards the development of a material with the capability of delivering these requirements. The final result was a a so-called architectured material — i.e., a combination of two or more materials — in the form of a fabric, based on a combination of vanadium pentoxide (V205) fibres, medieval chain-mail, nano-porous gels, and microcontroller electronics.

A variety of smart materials were explored before the researchers decided to work within the field of architectured materials in the development of their wearable assistive material. A solid block of material has a set of well-defined physical properties, such as its density or compressive strength. However, creating a different structure with the same material can introduce different properties. For example, it may have the same compressive strength as the block form but be more lightweight, and could hypothetically have better thermal properties. These types of materials have become increasingly common recently due to advances in 3D printing.

The use of 3D printing to achieve complex structures enabled the researchers to generate a ‘chain-mail’-like pattern in the material. As a fabric, chain mail is very flexible, but it’s also mechanical. The ability to control the shape and flexibility of the fabric as a function of the geometry of the linkages within this chain structure is an area that shows much promise. This particular part of the research is therefore of high interest, and is the focus of Mark Ransley, a PhD student at UCL, whose specialism lies in this area of the research. He explains, “I take the actuators—little strips that bend in the presence of a voltage—and consider structures that they could be embedded in to produce a far more interesting range of behaviours.”

Figure 1: Prototype section of the architectured chain-mail structure developed by researchers at UCL.

Using the concept of chain-mail, all the linkages are exchanged with actuators that are also types of motors, responsible for moving or controlling a mechanism. As a result, they create a dynamically controllable material with a greater movement parameter than a single actuator on its own. The ability to control the material is not only helpful when it comes to generating a stiffening and shape-morphing material, but also demonstrates the high adaptability of the material.

The main component of the developed material was key to its success: V205, the chemical actuator, is able to flex when it is subject to an electrostatic potential while also exhibiting great strength – ten times the strength of a skeletal muscle. This makes it ideally suited to use as supportive ware. The chain-mail structure, along with the actuator, provides the stiffness required to support a skeleton and—due to its architectured structure—it is also able to bend in desired directions, making it ideal for wear by an individual needing varying support.

Assistive walking is just one of the applications such a material could enable — other joints could also potentially benefit. Ankles, elbows, knees, and wrists are all possible candidatess, as controlled bending of these joints when injured is necessary. The assistance provided could also be made variable when desired. For example, if the user would benefit from carrying out an activity unaided, the parameters of the material could be changed so that they are encouraged to perform particular tasks independently. Conditions such as limb fractures would benefit from a variably flexible material, too — absolutely fixed support is vital during the early process of healing, but associated muscles would benefit greatly if they were rehabilitated while the fracture is healing. However, this is usually not possible because the muscles are still weak when support is removed. A supportive, self-morphing material would avoid this by enabling rehabilitation for the muscles during healing.

So far, a few prototype patches have been 3D printed, and have demonstrated a promising starting point for further development. When asked about when the potential for commercialisation, Mark claims “it will take another 5-10 years for us to finalise the material and make it suitable for actual medical use”. The researchers are currently investigated methods by which to improve the general strength of the material (e.g., by trying different architectures), as well as working to make the dimensions of the material suitable to be physically worn. Although the project will not produce a final, fully working prototype for a walking support system, it will determine the stiffness and strength that the developed material can deliver and whether or not the the material can be further developed with the help of medical experts.

“By the end of my PhD, we hope to have developed the theory behind a light, thin, and energy efficient smart material, and to have produced a prototype patch” says Mark about the current research. “This highly ambitious and interdisciplinary project requires modelling and simulation across a number of scales, from the electronics and their effect on the solid-state V2O5 actuators to the shape changing chain-mail linkage and the morphing of the structure as a whole.”

Given that the project will span a number of years before reaching a point of implementation, it can be concluded that—despite the current gap in the market for smart materials to act as assistive-ware—it is unlikely to happen for a long time. However, it seems clear that such a technology would benefit users that require this kind of support. As such, if the project were to expand further, the process of commercialisation could potentially be faster.