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Tiny Polymer Stent Could Treat Pediatric Urethral Strictures

By HospiMedica International staff writers
Posted on 20 Aug 2019
A novel manufacturing technique can be used to fabricate stent-like microstructures with shape memory properties that are 40 times smaller than current stents.

Developed by researchers at the Swiss Federal Institute of Technology (ETH; Zurich, Switzerland), Politecnico di Milano (Italy), and Kantonnspital Aarau (Switzerland), the manufacturing process uses three-dimensional (3D) printed sacrificial high-resolution micro-molds that are produced by direct laser writing. The printed templates are then infused with polymers and set using ultraviolet (UV) light. The structure is then dissolved in a solvent bath, leading to a 3D printed microstructure that has shape memory properties.

Image: A 4D microstent just 50 micrometers wide and half a millimeter long could be used to help children with urinary tract defects (Photo courtesy of ETH Zurich).
Image: A 4D microstent just 50 micrometers wide and half a millimeter long could be used to help children with urinary tract defects (Photo courtesy of ETH Zurich).

The method was used to manufacture 3D stents with minimum features of 5 µm, which is 40 times smaller than those reported to date. The polymer provides the stent's shape-memory properties, which the researchers refer to as a fourth dimension (4D); even if the 3D construct is deformed, it remembers its original shape and returns to it when warm. The method can also be used to indirectly 3D and 4D soft microrobots constructed of gelatin helices filled with magnetic nanoparticles. The study describing the new manufacturing process was published on July 5, 2019, in Advanced Materials Technologies.

“We've printed the world's smallest stent with features that are 40 times smaller than any produced to date. Before human studies can be conducted to show whether they are suitable for helping children with congenital urinary tract defects, the stents must first be tested in animal models,” said lead author Carmela De Marco, PhD, of the ETH multi-scale robotics laboratory. “But the stents are still a long way from finding real-world application; however, the initial findings are promising. We firmly believe that our results can open the door to the development of new tools for minimally invasive surgery.”

Approximately one in every thousand children develops a urethral stricture, including in fetuses. If a stent could be inserted to widen the constriction while the fetus is still in the womb, life-threatening levels of urine that accumulate in the bladder could be avoided. But while stents are regularly used to treat blocked coronary vessels, the urinary tract in fetuses is much narrower in comparison.

Related Links:
Swiss Federal Institute of Technology
Politecnico di Milano
Kantonnspital Aarau


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