Liquid membrane from Penn State filters material by responding to its kinetic energy, rather than particle size, creating a unique self‑healing barrier.


  • Self‑healing
  • Reduced cost


  • Wastewater treatment
  • Medical technologies

UN Sustainable Development Goals Addressed

  • Goal 6: Clean Water & Sanitation

  • Goal 9: Industry Innovation & Infrastructure

The Challenge

Particle filters are usually made of a fine mesh that captures larger particles while allowing smaller particles to pass through. In many applications, like wastewater treatment, the smaller particles still need to be captured at some point. Processes to get rid of these fine particles can dramatically increase the time and cost of wastewater treatment. In addition, if the filter is damaged in any way, it severely compromises the integrity of the design. Self-healing barriers are useful for a variety of applications, including medicine, where medical devices such as surgical tools could pass through while contaminants stay out.

Innovation Details

The liquid membrane is made of water and a material that stabilizes the liquid and air interface, and has a structure similar to a cell membrane. When a particle is trying to pass through, the membrane filters it out by sensing its kinetic energy rather than its size. A larger particle has more kinetic energy, so it can pass. A smaller particle has less kinetic energy so it is captured by the membrane. Unlike typical filters, larger particles can pass without smaller particles sneaking through. Additionally, the membrane wraps around the particle as it passes through, similar to the cellular process of phagocytosis, allowing the membrane to self-heal. The membrane can be designed to keep certain particles and gases from passing through.

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Biomimicry Story

Many kinds of small molecules can diffuse across the cell’s outer membrane, or travel through special embedded channels. Taking in larger materials, however, requires a different strategy. Phagocytosis allows cells to transport nutrients and other larger materials into the cell. During this process, a cell engulfs whole particles by wrapping them in its own membrane before processing them internally.