Manufacturing technology
with DSP, heat-curing polymers with a free radical polymerisation process such as heat- curing thermosets, which could not be printed using light or heat-based processes, can now be printed directly.
Habibi and the team at Concordia saw an opportunity to use the cavitation phenomenon observed in the strike of a mantis shrimp’s club to create a new 3D printing process.
Habibi and the team point to thermoset polymers. These are often the common choice for handheld medical devices due to their durability and noncorrosive qualities, but also as a biocompatible material for use inside the body or for in vitro organ-on-a-chip devices, as is the case with polydimethylsiloxane (PDMS). As Habibi and his colleagues note in their published Nature Communications paper, thermoset polymers require arduous post-processing to remove toxic photopolymerisation by-products and unreacted compounds by solvents used in light-based methods; for thermal-based methods, the addition of additives to alter the viscosity of the printing material – explained as its ability to resist the forces upon it as it cures using extreme heat – as well as the use of a supportive bath to achieve the same end, can create geometric inaccuracies in the final product.
“One of the medical applications of high- intensity focused ultrasound is tumour ablation, which the FDA has approved as a method for treating prostate cancer.”
Shervin Foroughi
“An effective on-demand curing of heat-curing polymers is yet to be introduced due to the difficulty of applying very short heating and cooling rates at small, localised regions,” explains Habibi. “Sonochemistry can be a solution to print such materials due to its highly localised temperature with fast heating and cooling rates.” To delve more into the science at work: acoustic cavitation creates chemically active regions in the printing resin or resin mixture medium, in which the resin undergoes fast phase transformation from liquid to solid under sonochemical reactions. This means
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Habibi and his colleagues’ paper did highlight a few issues, including difficulty with multi- material printing using the mechanism harnessed in their research, as the build chamber needed to be refilled each time a new material was used for printing. Another difficulty was printing overhanging structures, as the printed spot needed to be supported. The researchers also noted that an alternative mechanism based on the same DSP concept along with the use of support materials can help resolve these problems, however. This is something that Habibi says they have already begun to develop.
The future of DSP Clearly, there are adaptations and refinements required to realise the lofty ambitions of Habibi and the team, but given the promise DSP holds for 3D printing, he expects the method to develop rapidly as fellow researchers contribute and collaborate to the science. “DSP introduced a completely different paradigm in 3D printing,” he says. “We expect to see more applications of DSP in engineering and medical fields, which will lead to the commercialisation of products for different industries. In addition, we expect that more and more researchers will be attracted to this new field and start to participate in the collaborating efforts to develop this area, just like in every other discipline in science.”
As for when we can expect to see DSP being used to print prosthetics directly into the body, we may be waiting a while. “We presented the concept of using DSP to print directly into the body in 2022 and we are working on the real-use case,” says Habibi. “We expect to see the results soon and to publish them in peer-reviewed journals. It is difficult to predict the future at such a level of cutting-edge technologies, but we are determined to make it happen.” In terms of what’s next for the team of researchers, we can expect to see them to continue to refine the direct sound printing process and prepare it for use in clinical practice, as well as outside of the medical industry. As Habibi explains: “Besides the medical aspect of DSP, we are working on the mechanical and acoustic aspects of this technology to mature the method as much as possible. We plan to publish out results in 2023 in two papers. We also hope that these developments make the technology ready for commercial use soon.” ●
Medical Device Developments /
www.nsmedicaldevices.com
Thierry Eidenweil/
Shutterstock.com
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