This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: A nano-wrinkled surface combined with a tiny soft actuator can break up infection-causing bacterial sheets, called biofilms, that form on medical implants, according to a University of Michigan Engineering study published in Advanced Functional Materials. When implanted in mice, the platform—called DARTS (dynamically actuated reconfigurable topographical surface)—reduced bacterial burden and improved the surrounding tissue response.
"This work brings us a step closer to translating our basic biointerface research toward medical use in humans," said Jouha Min, an assistant professor of chemical engineering at U-M and co-corresponding author of the study. In humans, the platform could be adapted for medical devices like joint replacements, pacemakers and catheters, which are prone to biofilm surface growth that can lead to hard-to-treat antibiotic-resistant infections. "After years of studying how surface topographies shape cell-material interactions in the lab, we're now building those principles into an implant that actively controls those interactions in the body," said Min.
The research team built the antibacterial surface with a bottom-up nanofabrication process, stacking layers on top of one another. A prestretched, flexible plastic film forms the base. Next, the plastic is repeatedly dipped in alternating solutions with a positive or negative electrical charge, adhering layers as opposite charges attract.
The coated plastic is placed in an oven at 130°C (266°F), causing the prestretched plastic base to shrink back to its original size, much like a Shrinky Dink. The number of coatings drives the size of the wrinkles. A single coating in each solution creates nano-wrinkles, with wavelengths shorter than 400 nanometers.
Dipping the plastic 20 times creates micro-wrinkles with wavelengths of about 2 microns (2,000 nanometers). The sharp waves of the nano-wrinkles broke apart both gram-negative and gram-positive bacteria, suppressing biofilm coverage. The micro-wrinkles failed to suppress bacterial growth as bacteria could settle between the larger grooves.
To further enhance bacterial suppression, the researchers integrated a soft robotic actuator into the nano-wrinkled surface. The actuator consists of a tiny metallic spring embedded in a small, soft silicone block with wires extending outward. The actuator sits at the bottom of the device, and the nano-wrinkled surface is on top, with a thin silicone cushion in the middle.
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