Mimicking electric eels and cell membranes to generate energy

Cell membranes play a crucial role in regulating the movement of substances in and out of cells. These membranes are made up of a thin layer of fat molecules that block most substances, while proteins act like gates that allow specific molecules to pass through. Inspired by this efficient design, NCCR Bio-Inspired Materials researchers have created artificial membranes that hold promise for applications such as energy generation and separation methods.

“The big innovation of this work is that we made bio-inspired fluid membranes in such a way that they’re stable,” says NCCR PI and study co-senior author Michael Mayer, professor of biophysics at the Adolphe Merkle Institute in Fribourg. “These membranes mimic biological membranes in many ways,” he adds, highlighting their potential for applications in bioengineering and energy conversion.

“The project originated from discussions between myself and NCCR Associate PI Nico Bruns during a winter school, where we brainstormed ideas for an NCCR Bio-Inspired Materials collaborative grant that encouraged interdisciplinary research efforts,” he says. Mayer highlights the diverse expertise within the team, which besides Bruns included Alessandro Ianiro, a physical chemist who led the project from the start, NCCR PIs Ullrich Steiner, who contributed knowledge in self-assembly, and Christoph Weder, who specializes in synthesizing block copolymers — large molecules made up of two or more different types of polymers linked together.

Researchers have recently made progress in creating stable, self-assembled membranes using block copolymers by taking advantage of the boundary between two water-based solutions that do not mix. While this system helps in the assembly process, it isn’t enough by itself. To overcome this limitation, the team developed a two-step method that uses an organic solvent to help form and stabilize the block copolymer layers. This approach helped to create large membranes that can be used for practical applications such as separating drugs and generating energy.

With a thickness of about 30 nanometers and a size of about 10 cm², these membranes are larger than those produced by other methods, and they can last for several hours before breaking. The membranes act as effective barriers against charged molecules and show self-healing properties after damage, the researchers found.

To increase the functionality of the membranes, the team incorporated a molecule that transports potassium ions into the membrane’s hydrophobic core, which enabled it to shuttle the ions across a concentration gradient — much like biological membranes do. This integration not only helps transport ions efficiently, but it also generates a transmembrane potential, which is key for obtaining energy from ion gradients — akin to the way sodium-potassium pumps in neurons allow the cells to fire.

The researchers also aimed to mimic the energy-generating mechanisms found in electric eels by creating membranes that convert ion gradients into electricity. They reported their findings in Nature.

Ianiro, who started this project while he was a postdoc with Mayer, notes that it not only addresses energy problems but also has potential applications in desalination and the separation of therapeutic molecules. “The membranes that we developed are a general platform to which we can add selective transporters.” However, he adds, “we still need to improve their mechanical stability and integrate more efficient ion channels.”

By overcoming the challenges of stability and scalability, Ianiro says, these membranes could revolutionize how we harness natural processes for real-world applications.

Reference: Sproncken, C. C. M.; Liu, P.; Monney, J.; Fall, W. S.; Pierucci, C.; Scholten, P. B. V.; Van Bueren, B.; Penedo, M.; Fantner, G. E.; Wensink, H. H.; Steiner, U.; Weder, C.; Bruns, N.; Mayer, M.; Ianiro, A. Large-Area, Self-Healing Block Copolymer Membranes for Energy Conversion. Nature 2024, 630 (8018), 866–871. https://doi.org/10.1038/s41586-024-07481-2.