Biofilms are widely seen as a problem that needs to be eradicated because of the hazards they pose to humans and materials. But these communities of algae, fungi and bacteria possess interesting properties from a scientific and technical standpoint. A team of researchers from the Technical University of Munich (TUM) has discovered biofilms could be used as ‘construction workers’ to create structural templates for new materials that possess the properties of natural materials. This was only previously possible to a limited extent.
Whether it’s wood, bone, mother of pearl or teeth, over millions of years these materials have been optimized through evolution according to the principle of adapted stability with maintaining the lowest possible weight.
Nature has provided blueprints for many technical developments, from airplane wings and zippers to surface sealants using a lotus effect. But reverse engineering replicas can’t reproduce the structural complexity of the original item in nature.
"In nature, we find many materials with properties that artificial materials are unable to replicate in the exact same fashion," said Professor Cordt Zollfrank, who performs research on basic principles for the development of new materials together with his team at the Chair of Biogenic Polymers at the TUM Campus Straubing for Biotechnology and Sustainability.
As the interface between technology and biology, bionics uses methods and systems that are found in nature, to provide solutions to technical problems. When limited to using natural shapes, like templates for development in designing airplane wings or ship hulls, the problems remained manageable.
But imitating the material properties of natural construction materials is completely different. This is because they are normally found in the inner structures, where fibers are linked to each other over several orders of magnitude and across various levels.
"Usually, the main sources of mechanical material properties such as elasticity, strength and toughness are found at the smallest level of these hierarchies, especially at the nanometer scale," explained Dr. Daniel Van Opdenbosch, a team leader at Zollfrank's chair and one of the authors of the article.
Opdenbosch talked about the main problem when trying to translate them into technical solutions. But when the microorganisms themselves or their secretions create the material, the technically sophisticated and complex networks are already fully formed.
The researchers at TUM present a series of procedures from the field of biology that utilizes light, heat, specially prepared substrates and other stimuli in order to guide them in the direction of microorganism movements along very specific paths.
"These biological findings for controlling microbes via targeted stimuli will shape the future of material research," said Professor Cordt Zollfrank.
This is because the researchers make it possible to create tailor-made templates for new materials with natural structures from microbes themselves or their secretions.
"With our article, we want to show the direction this journey will take us in the field of biologically inspired material science," said Zollfrank.
Opdenbosch and his group are already successfully utilizing some of the methods in Straubing. Part of a Reinhart Koselleck project of the German Research Foundation (DGF), the researchers are taking advantage of the special properties of red algae, whose direction of movement depends on exposure to light, which secretes chains from sugar molecules.
Through projecting light patterns, which change over time, into the growing medium of the algae, the researchers use them to create long, fine polymer threads that serve as custom templates for the manufacture of functional ceramics.
With the assistance of the algae, any number of templates can be created for a wide array of applications, ranging from battery electrodes to new screen and display technologies to applications in medicine, like replacement bone and tissue. But the ability to grow complex microstructures, like entire components and other hierarchically structured materials, is currently still way in the future. However, it could soon become a palpable reality thanks to this basic research.
The paper on this technology was published in Advanced Materials.