The splint must then be cryogenically milled -- or frozen and grinded - microns at a time until it's a perfect fit.
While the process of creating customized splints may seem arduous, it takes only a day. And, up to 200 splints can be printed at a time, according to Hollister.
The splints must be biocompatible with a patient's immune system and able to resist external compression from surrounding tissue in the body, allow for flexibility, radial expansion or growth, and must last two to four years.
To date, the splints have met all the criteria as successful medical implants, and even begin deteriorating as planned after just six months. Once absorbed by surrounding tissue, the biomaterial is simply excreted from the body, Hollister said.
Hollister, Morrison and other researchers believe 4D biomaterials will some day go far beyond helping only babies with respiratory issues; they are already exploring their use on adults to correct skeletal applications, such as facial reconstruction or rebuilding ears with biomedical scaffolds that hold tissue in place.
University of Michigan The before and after. On top are images of three babies on ventillators who received 4D printed stints to open their airways. Below are photos of those babies after they were taken off the ventillators and went home.
What is needed to advance 4D printing are more academic and industrial partnerships that could enable the development of new materials and methods for creating implants.
"Being able to print a much broader range of soft materials for these types of reconstructions is important," Hollister said.
The researchers believe, however, that the 4D biomedical printing field will explode as new uses evolve.
"I think in the next five years, we will see an explosion of clinicians coming to table with new ideas for the use of this," Morrison said.
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