Tested in mice with Staphylococcus aureus, a new dynamically actuated reconfigurable topographical surface built by University of Michigan researchers reduced bacterial burden and improved surrounding tissue responses by combining nano-wrinkles with a soft robotic actuator to break up infectious bacterial biofilms on medical implants.
Medical implants face bacterial sheets known as biofilms that resist standard treatments and cause chronic infections inside the body. A team at the University of Michigan Engineering has introduced an active defense system that moves beyond passive antimicrobial coatings. According to a study published in Advanced Functional Materials, the platform is called DARTS, which stands for dynamically actuated reconfigurable topographical surface.
How Nano-Wrinkles Puncture Bacterial Sheets
The foundation of the DARTS platform relies on a coated plastic base designed to shrink when heated in an oven at 130 degrees Celsius, or 266 degrees Fahrenheit.
Dipping a single time in each solution creates nano-wrinkles with wavelengths shorter than 400 nanometers. The sharp waves of the nano-wrinkles successfully puncture both gram-negative and gram-positive bacteria on contact, suppressing biofilm coverage. By contrast, the micro-wrinkles failed to stop bacterial growth because microbes could easily settle between the larger grooves.
Soft Robotic Actuators Clear Mature Biofilms
To enhance bacterial suppression further, the engineering team integrated a soft robotic actuator right beneath the topographical surface. The actuator features a tiny metallic spring embedded inside a small, soft silicone block equipped with protruding wires on either side and a thin silicone cushion sitting in the middle.
By running electrical current through the spring, it warms up and shortens, compressing the upper nano-wrinkles comparable to crushing a marshmallow using two digits. This mechanical squeeze pops bacteria off the surface.
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,
said Sungmin Nam, an assistant professor of mechanical engineering at U-M and co-corresponding author of the study, as reported by Phys.org.
When cultured with bacteria in laboratory settings, the combination of dynamic actuation and nano-wrinkles produced near-complete disruption and removal of mature biofilms. Insulation surrounding the internal spring and its wires keeps generated heat safely inside the device during operation. The system maintained its structural shape through 200 actuation cycles while combating repeated challenges from bacterial buildup.
Successful Testing in Living Animal Models
To evaluate how the platform performs inside a living organism, the researchers implanted DARTS devices bearing Staphylococcus aureus bacteria beneath the skin of mice. Bacterial levels dropped and tissue reactions surrounding the implant area were enhanced by the platform.
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.