Micro Bioprinters for Vocal Folds: Soft Robot Precisely Applies Hydrogel

An interdisciplinary team from biomechanics and ENT surgery presents in Device (October 29) a soft, miniaturized 3D-printing robot that applies hydrogels directly at the surgical site on the vocal folds. The goal is to prevent fibrotic scarring after the removal of cysts or tumors, which can limit the vibratory capacity of the vocal folds. In clinical practice, hydrogels are injected for this purpose, but pinpoint dosing and placement are difficult within the narrow field of view constrained by a laryngoscope frame.

The researchers’ approach combines a 2.7-mm print-head module with a flexible continuum manipulator. The design is inspired by trunk geometries: a slender “trunk” guides the nozzle, actuated via tensile, tendon-like Bowden cables that terminate in a compact control module mountable on the operating microscope.

“Our device is designed not only for accuracy and print quality but also for surgeon usability,” says first author and biomedical engineer Swen Groen of McGill University. “Its compact and flexible design integrates into standardized surgical workflows and enables manual real-time control in a constrained work environment.”

“At first I thought it wasn’t feasible—it seemed an impossible challenge to build a flexible robot smaller than 3 mm,” says senior author Luc Mongeau, a biomedical engineer at McGill University.

Technically, the print head extrudes a hyaluronic-acid-based hydrogel in tracks about 1.2 mm wide. Trajectories can be programmed for repeatable, precise movements within a working space of roughly 20 mm. In feasibility studies, the team drew defined shapes on planar substrates and then reconstructed defects in vocal-fold geometry on laryngology training models, from postoperative cavities to complete replacement forms.

“Part of what makes this device so impressive is that it behaves predictably even though it’s basically a garden hose—and if you’ve ever seen a garden hose, you know it goes wild as soon as you run water through it,” says co-author Audrey Sedal, a biomedical engineer at McGill University.

“We’re trying to translate this to the clinic,” says Mongeau. “The next step is to test these hydrogels in animal studies, and hopefully that will lead to human clinical trials to evaluate the bioprinter’s and the hydrogel’s accuracy, usability, and clinical outcomes.”

At present, control is fully manual; prospectively, the team is working on a hybrid mode that combines autonomous and hand-guided control. Next steps include preclinical animal studies to assess printing accuracy, usability, and clinical endpoints before transitioning to initial human studies. For the 3D-printing community, the approach marks a pragmatic path to deploying bioprinting as an intraoperative technique in tight anatomical spaces.

“Our device is designed not only for accuracy and printing quality but also for surgeon usability,” says first author and biomedical engineer Swen Groen of McGill University. “Its compact and flexible design integrates with standard surgical workflows and provides real-time manual control in a restricted work environment.”

“I thought this would not be feasible at first—it seemed like an impossible challenge to make a flexible robot less than 3 mm in size,” says senior author Luc Mongeau, a biomedical engineer at McGill University.

“Part of what makes this device so impressive is that it behaves predictably, even though it’s essentially a garden hose—and if you’ve ever seen a garden hose, you know that when you start running water through it, it goes crazy,” says coauthor Audrey Sedal, a biomedical engineer at McGill University.

“We’re trying to translate this into the clinic,” says Mongeau. “The next step is testing these hydrogels in animals, and hopefully that will lead us to clinical trials in humans to test the accuracy, usability, and clinical outcomes of the bioprinter and hydrogel.”