Conventional filters, such as those used in wastewater treatment and other applications, are designed to allow small objects to pass through while trapping larger particles. A novel filter developed at Pennsylvania State University performs the reverse - a stabilized liquid material screens out smaller objects while allowing passage An overlay of four time-lapse images extracted from a video capturing two PTFE beads (one small and one large) falling into a liquid membrane at the same time from the same drop height. Source: Image: Tak-Sing Wong Lab, Pennsylvania State Universityof larger ones.

Unlike conventional filters, the new membrane does not separate objects by size but instead responds to an object's kinetic energy. A larger object with a higher kinetic energy will pass through while the smaller object with lower kinetic energy will be retained. The filter also wraps around the object as it passes through, allowing the membrane to completely self-heal over the top of the object passing through it.

The membrane is formed with water and a substance that stabilizes the interface between liquid and air, and has a structure similar to that of a biological cell membrane. The researchers used a simple soap film to create the initial prototype. The components could then be modified and optimized to serve unique purposes, such as enhanced mechanical robustness, antibacterial properties or odor-neutralization.

Prospective applications in sanitation and medicine are envisioned. This material could act as a surgical film to help replicate the clean environment needed to safely operate in remote areas where clean operating rooms are unavailable. The membrane filter could potentially prevent germs, dust or allergens from reaching an open wound. Selective membranes can be tailored for use in waste or odor management to inhibit gas and vapor passage while allowing solids to pass through.

The research is published in Science Advances.