New Zealand research project explores new design directions for future 3D printed prosthetics

Jan 19, 2018 | By David

As the technology progresses, 3D printed prosthetics are becoming more and more advanced and tailored to the needs of specific types of injuries and lifestyles. A team of researchers based in New Zealand have recently launched a major new project to explore some of the future design possibilities for 3D printing in prosthetics, both in the short term and the long term. Led by the New Zealand Artificial Limb Service, in collaboration with the University of Wellington, the research project also explored the potential for these new developments to be implemented into commercial manufacturing.

The project was roughly organized into four parts, each covering a different design direction that prosthetics could head in with the help of 3D printing. In the short term period, the team focused on new functional fairings and new socket designs, possible in the next 12-18 months. As for a longer period, within the next 7-10 years, multi-density foot printing and information-driven model generation were looked at as possibilities.

The functional fairings concept is geared towards finding new practical applications and uses for prosthetics beyond being just replacements for missing limbs. This could improve the lives of many amputees by transforming what is perceived as a loss into the potential for something more, opening up a space with increased creativity and practicality that only these prosthetic users could access. The team suggested a sport fairing, giving the example of a special prosthetic golf leg. This would have a special golf design as well as an area for spare balls and tees to be stored. There could also be special children’s fairings, with creative designs that appeal to their sense of fun and imagination.

As for the new socket designs, these would be adjustable according to size fluctuations at different times, hopefully making it no harder for a user to put on their prosthetic than for someone to put on a shoe. The team reached out to the Auckland Bioengineering Institute to better understand what might soon be possible for this kind of personalization, with the help of 3D printing technology. Soft tissue scanning can generate an accurate volumetric mesh of a patient’s limb, which allows technicians to visualise what areas of the stump are tolerant or sensitive, or what is hard and what is soft. This means that they would have a better representation of how the socket design should be sculpted. Experiments were carried out with ABS as well as the more advanced TPU material, with the latter being more promising in terms of material properties but coming with an inconveniently long post-processing time.

For the long term, ways to more cheaply produce multi-density foot prosthetics, which are currently prohibitively expensive, were explored. One of 3D printing’s advantages is the way that fill densities can be varied to match desired object performance. This is useful for making prosthetics that are simultaneously stronger and more flexible. To explain this, the team quotes a MIT student talking about the properties of natural structures: “Nature always uses graded materials. Bone, for example, consists of a hard, dense outer shell, and an interior of spongy material. It gives you a high strength-to-weight ratio.’’

There are a number of multi-density 3D printing systems used in other sectors, and the NZALS’ future approaches could take inspiration from these, such as Nervous Systems 3D printed midsole technology for New Balance, or Materialise’s similar system, which is used by Adidas. 3D printed TPU would be the way to go for multi-density prosthetics, and hopefully the technology will advance to make it easier to print with this material in future.

The future of information-driven model generation for prosthetics should see the implementation of the aforementioned soft tissue scanning, as well as what is known as Computational Anatomical Movement. This makes use of scanning, tracking and video analysis so that researchers can examine the force of each muscle, as well as the gait that a particular patient is taking and various other human body movement factors, in order to create a more personalized prosthetic with improved comfort and performance.

The researchers tested out the Stratasys Fortus as well as the UpBox FDM machines, finding pros and cons with each. They concluded that the best solution would be to use an online 3D printing service, which could provide more efficient printing with its specialized expertise and access to a variety of technologies. Shapeways, I.Materialise, and Objective 3D were also suggested as options.

According to NZALS chief executive Sean Gray, New Zealanders are great guinea pigs for developments in prosthesis technology, because they tend to test their limbs to the limits.”People have broken them because they have had them in a ski boot.”, he says. The work carried out by NZALS in collaboration with the University of Wellington and other institutions shows serious promise, and should soon lead to significant improvements in quality of life for amputees there and further afield.

Posted in 3D Printing Application

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