2.5D printing: "It only takes about five minutes to print an orthosis"

Customized finger orthoses that can be printed quickly: Lukas Boxberger from the Fraunhofer Institute for Machine Tools and Forming Technology IWU in Dresden focuses his research on this subject. In the future, the WEAM orthosis will support the customization of standard orthoses. In this interview, he explains the processes and materials that will turn this concept into a reality.

Mr. Boxberger, you are exploring a finger orthosis that is made using a 2.5D printing process and that might one day replace prefabricated, off-the-shelf orthoses. What makes your 2.5 D printing process so unique?

Lukas Boxberger: The term "2.5D" does not refer to the actual printing process but serves to illustrate the concept. In reality, we use a conventional 3D printer to make the orthosis. However, in this case, we only print several millimeters to build up the height of the orthosis, which means we don’t create a complex shape, but rather a strip. It is used to integrate the wires. To do this, we developed a special printer head at the Fraunhofer IWU. This process allows us to make orthoses of different sizes and devices for the finger, arm, or foot. The benefit here is that you can later mold the plastic.

How do you heat the plastic?

Boxberger: The plastic is heated via the integrated wire by using electrical current. The heat from the wire enables the plastic to reach the right temperature so you can mold it. You knead the plastic gently to shape it into the desired form.

Our printer head allows us to integrate wires into the plastic during the printing process. We can vary both the polymer and the wire depending on the required electrical function.

How warm does the plastic get?

Boxberger: The temperature our first prototypes reach is currently 60°C. However, we are working on a solution that facilitates moldability at 35 degrees Celsius and depends on the plastic you choose. The point of moldability is achieved very quickly as you only heat the finger orthosis for about 30 seconds. At this point it can be molded and becomes solid again after 30 seconds of cooling. This makes it possible to quickly readjust the orthosis during the treatment process should you need a different angel for the finger, for example. I can see this technique being used in the treatment of scoliosis as it pertains to the support corset suffers must wear. It would be a big advantage if you could make quick adjustments to the structure.

When it comes to further development, a great feature would be the option of using an orthosis on more than just one patient. For now, we haven’t factored in sterilization processes in the materials selection, though it would be interesting to take our research in this direction as well.

What is the expected service lifetime for this type of orthosis since it is being molded repeatedly?

Boxberger: We don't have any study data on this aspect yet. At this stage, we have heated and shaped our finger orthoses more than 25 times without detecting any changes in the material properties. However, further research is needed in this case to reliably establish thresholds and repeatability.

How complex is the production process of this type of orthosis using the 2.5D printing process?

Boxberger: There are two different ways of integrating the wires. The first option is to use our special printer head. The other way is to use conventional 3D printers and adapted software.

However, unlike 3D printed products, the printing time of an orthosis that’s manufactured using WEAM is much faster. It only takes about five minutes to print an orthosis.

Is the orthosis also suitable for children? Standard orthotic models often don’t have the right fit if the child is in between sizes.

Boxberger: Definitely. We also have our eye on this aspect. For example, babies have such tiny hands that it is often difficult to get a good 3D impression. These adaptable orthoses would be a great fit for them.

Will we see you and your orthosis solution at the next COMPAMED?

Boxberger: We already showcased 3D printing models at the last COMPAMED, but we did not introduce finger orthotics that are made using the WEAM technology. We will definitely highlight bone replacement materials, 3D printing processes, and sensors again. We will choose the models we will feature at the trade fair right before the event.