Cell-inspired synthetic fibers reveal a reversible route to self-protecting smart materials

Researchers at the University of Bayreuth have created a synthetic fiber system modeled after the cellular cytoskeleton, which can self-protect through controlled bundling. This breakthrough, detailed in the journal Advanced Materials, opens up possibilities for smart, alterable materials that respond to specific stimuli. Inspired by how living cells maintain delicate structures using weak intermolecular interactions and hierarchical organization, the synthetic polymer system replicates this biological mechanism.

The key is a zinc-containing planar molecule linked to a temperature-responsive polymer that spontaneously assembles into nanofibers in water. These nanofibers can bundle together into micrometer-sized structures when heated above 32°C, a process that can also be triggered by changes in salt concentration or solvent composition.

Reversing the stimulus causes the bundles to dissociate again, demonstrating the reversible nature of the process. Crucially, the bundled fibers remain stable, protecting the individual nanofibers from rapid disassembly or chemical attack. This selectivity is similar to how cells compartmentalize different regions within their environment.

The researchers demonstrate this by irradiating the zinc complex with UV light, causing it to heat up and maintain the bundles in their protected state as long as the light source is active. Once the light is removed, the bundles dissociate and the building blocks disintegrate under acidic conditions, mimicking the energy-dependent maintenance seen in acid-resistant bacteria.

The hierarchical bundling not only enhances the stability of the fibers but also allows for a visible change when heated, forming a hydrogel at concentrations 200 times lower than those needed in conventional polymer systems. Cooling reverses the process, returning the gel to a liquid state. This reversible gelation could be particularly useful for 3D printing, where the material could serve as a recyclable, switchable printing resin.

Additionally, the light-responsive properties of the zinc-containing building block offer potential applications in sensing and optoelectronics, as well as in the development of more robust and intelligent materials in nanotechnology and biotechnology.