A team of researchers from the Adolphe Merkle Institute (AMI), together with international collaborators, has developed a novel method for creating ultrathin membranes inspired by cell membranes. This discovery could have significant applications in fields ranging from implantable artificial electric organs to water desalination.

The new technique uses the interface between two liquids that do not mix to form and stabilize these membranes. By carefully controlling the conditions under which two solutions interact with the opposing sides of these membranes, the researchers created an ultrathin polymeric layer that is just 35 nanometers thick (much thinner than a human hair), but can cover areas larger than 10 square centimeters without defects. «This approach takes advantage of favorable interactions to stabilize ultrathin self-assembled structures that are at least one thousand-fold larger than was previously possible,» Assistant Prof. Alessandro Ianiro, a former group leader at the AMI Biophysics lab, explained.

Membranes inspired by electric rays
The method employs block copolymers (BCPs), highly tunable (modifiable) polymers consisting of two or more distinct segments, to form a bilayer at the interface of the two phases. The resulting membranes exhibit remarkable mechanical properties and self-healing capabilities, making them robust and durable in various applications.

These artificial membranes replicate the selective ion transport functions of natural cell membranes. By incorporating a peptide (that is, a small chain of proteins), these membranes become capable of generating electric power from different salt solutions. This functionality is inspired by the electric organs of rays and other electric fish, which use similar principles to generate power.

Many industrial applications
This development, reported in the journal Nature, could have significant applications:

• Energy storage: These membranes could enable the development of large-scale devices to efficiently store electrical energy.
• Water desalination: They could serve as highly selective barriers that separate ions from salt water to obtain fresh drinking water.
• Medical treatments such as dialysis: Thanks to their ability to selectively filter ions, these membranes could make dialysis a more efficient and less invasive procedure for patients.
• Implantable energy sources: They could open the way to the engineering of implantable devices in the human body that would be continuously recharged thanks to the body’s own metabolic energy.

Hope for the future
As AMI Chair of Biophysics Prof. Michael Mayer stressed, «This advancement takes our previous aspirations to develop fish-inspired artificial electric organs a significant step closer to biocompatible power sources. Ultimately our goal is that these human-made systems will closely mimic – and interact with – the complex functions of biological organisms.»

Future iterations of these membranes, possibly incorporating more efficient ion channels, could achieve performance levels comparable to the electric organ of biological systems like the electric ray. The scalability of these membranes also suggests that they could be not only made to cover larger areas to increase the transport rate across them, but also stacked to create larger systems for use in separation processes or power generation and storage.

This research was led by the AMI Biophysics group in collaboration with the Sustainable Functional Polymers group of Nico Bruns at the Technical University of Darmstadt, a Theory and Computer Simulation group at the University of Paris-Saclay, the Bio- and Nano-Instrumentation lab at EPFL, and finally the Polymer Chemistry and Soft Matter Physics groups at AMI.

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Adolphe Merkle Institute:
The Adolphe Merkle Institute (AMI) at the University of Fribourg is an independent center focused on nanoscience research and education, particularly in soft nanomaterials. Established in 2008, AMI is unique within Switzerland’s research landscape, combining fundamental and applied research in a multidisciplinary environment. Collaborating with industry partners, AMI aims to drive innovation and enhance industrial competitiveness. The institute’s 100 researchers are organized into four main and two junior research groups specializing in areas like bionanomaterials, polymer chemistry, soft matter physics, biophysics, smart energy materials, and mechanoresponsive materials.