Nano-wrinkles and actuation break up infectious biofilms on implants

Nano-wrinkles and actuation break up infectious biofilms on implants Lisa Lock Scientific Editor Robert Egan Senior Editor 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. Nano-wrinkles slow bacterial growth 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. Actuators disrupt established biofilms 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. Passing an electrical current through the spring causes it to heat and contract, squeezing the top nano-wrinkles together and popping bacteria off the surface. The insulation surrounding the spring and protruding wires keeps the heat inside the device to prevent harm when implanted. When cultured with bacteria, the dynamic actuation combined with nano-wrinkles produced near-complete disruption and removal of mature biofilms. The system combated biofilm buildup over repeated challenges and maintained its shape through 200 actuation cycles. "What makes this approach particularly exciting is that we are moving beyond passive antibacterial surfaces toward a system that can actively respond to bacterial buildup. By integrating mechanical actuation with engineered surface topography, we can physically disrupt established biofilms and potentially prevent persistent infections on medical implants," said Sungmin Nam, an assistant professor of mechanical engineering at U-M and co-corresponding author of the study. DARTS performs well in mice To test the platform in living animals, the team implanted the DARTS devices bearing bacteria (Staphylococcus aureus) beneath the skin in mice. After seven days, the researchers collected the device and a sample of surrounding tissue. The DARTS platform was actuated 20 times immediately after surgery and again on days 1, 3 and 5. The actuated DARTS platform had markedly lower bacterial contamination and better local tissue outcomes compared with all controls. The team also showed that a near-infrared laser can actuate the device wirelessly. This could make the approach more practical for clinical use, where an external light wand might one day clear bacterial buildup without surgery. "Rather than relying on passive coatings, our surface physically removes bacteria when needed. That opens a new path toward preventing implant infections," said Min. Publication details Mohammad Asadi Tokmedash et al., Dynamically Actuated Reconfigurable Topographical Surface Enables Active Control of Implant‐Associated Infections, Advanced Functional Materials (2026). DOI: 10.1002/adfm.77707 Journal information: Advanced Functional Materials Key concepts BiofoulingMechanical deformationSurface & interfacial phenomenaMicrobial multicellular systemsNanostructuresProvided by University of Michigan