Fish feeding mechanics inspire a new solution for cleaner laundry wastewater.
The global microplastic crisis is no longer a distant environmental threat; these tiny pollutants are now ubiquitous, found everywhere from deep-sea trenches to human lung tissue. A primary, often overlooked culprit is the domestic washing machine, which sheds between 10 and 120 grams of synthetic fibers per person every year. While industrial wastewater plants can catch much of this, the captured fibers frequently accumulate in sewage sludge that is later spread onto agricultural fields, effectively “recycling” the plastic back into our food chain. Until now, home filtration attempts have been notoriously unreliable, plagued by rapid clogging and poor retention.
However, a breakthrough study published in npj Emerging Contaminants by Leandra Hamann and her colleagues introduces a revolutionary solution: a bio-inspired, self-cleaning filter that mimics the evolutionary perfection of fish anatomy.
B. Gill rakers and denticles form the mesh and are replicated using a glued commercial filter mesh.
C. Scombrid surface features are mimicked by ellipsoids (short gill rakers) and hooked tape (denticles and teeth) applied to the Large-11 filter element.
To solve the clogging dilemma, researchers at the University of Bonn and the Fraunhofer Institute looked toward “ram-feeders”—pelagic fish like the Atlantic mackerel, anchovy, and pilchard. These creatures swim with their mouths open, effortlessly straining tiny plankton from massive volumes of water. The secret lies in the “gill arch system,” a cone-shaped geometry within the buccal cavity. As water enters, it flows tangentially to the filter medium the gill rakers in a process known as semi-cross-flow filtration. This prevents particles from pinning against the mesh; instead, they stay in suspension, rolling along the surface until they reach the esophagus.
The research team abstracted these biological traits into a physical “Fish-Inspired Filter” (FiF). This cone-shaped device features a wide inflow mimicking a fish’s mouth and a narrow outflow mimicking the gullet. Unlike standard “dead-end” filters that force all water through a mesh until it chokes on debris, the FiF allows clean water to exit laterally as “permeate,” while the concentrated microplastics move toward a separate outlet.
“The geometry is critical,” the researchers noted. “By maintaining an ‘angle of attack’ ($\alpha$) lower than 20°, we can keep particles rolling and prevent the premature clogging that dooms traditional filters.”
B. FiF setup with a long inlet and the Large-11 filter element.
C. MP fibre observations in the Large-11 filter element at the start, before cleaning, and after cleaning.
D. MP fibre observations in the Small-11 filter element at the start, before cleaning, and after cleaning.
To ensure the design was flawless, the team utilized Computational Fluid Dynamics (CFD) and physical flow tanks. They found that an internal “swirl” inlet produced a more uniform flow and removed dead zones where fibers accumulate. In addition, automated valves create a double-cleaning effect by flushing the concentrate and inducing a brief reverse flow that detaches trapped fibers.
The results of the laboratory trials were striking. The FiF successfully retained up to 99.6% of microplastic test fibers. Perhaps more importantly for the consumer, the device delays clogging by a factor of seven compared to standard designs.
“Because we collect up to 85% of fibers in the concentrate outlet rather than on the filter mesh itself, the ‘dirt-holding capacity’ is no longer limited by the physical volume of the filter,” the study explains.
The system is also remarkably efficient, producing a concentrate volume of only about 5% of the total fluid. This minimal waste is vital for making the technology practical for home use without requiring massive post-treatment.
While the initial tests used standardized 2mm rod-shaped fibers, the researchers are already moving toward real-world scenarios. The next step involves testing the “Large-11” model—an 11° angle filter—against the irregular textile fibers, hair, detergent, and sand typical of a standard laundry load.
This isn’t just an engineering win; it is a testament to the power of biological inspiration. By looking at how mackerel have fed for millions of years, we may have finally found a way to stop the tide of microplastics from entering our environment. This technology could soon lead to washing machines that require far less maintenance while providing nearly total protection for our planet’s waterways.
SOURCE:
Hamann, L., Reuß, C., Herzog, H., Schreiber, K., Geitner, C., & Blanke, A. (2025). A self-cleaning, bio-inspired high retention filter for a major entry path of microplastics. npj Emerging Contaminants.
