Material design by means of defect engineering: German Research Foundation approves new Collaborative Research Center at Mainz University

DFG to fund new CRC investigating options for manipulating defects in soft matter

25 May 2023

When we talk about defects, we generally think of flaws or impairments. However, as far as materials science is concerned, defects represent windows of opportunity. A new Collaborative Research Center (CRC) in the field of soft matter based at and administered by Johannes Gutenberg University Mainz (JGU) will explore these opportunities. The German Research Foundation (DFG) has approved CRC 1552 "Defects and Defect Engineering in Soft Matter" and will be providing funding of some EUR 8 million over the next four years. Also participating are the Max Planck Institute for Polymer Research and the Fraunhofer Institute for Microengineering and Microsystems IMM. The participating researchers in the fields of biology, chemistry, and physics will be taking an innovative approach with the objective of developing a novel design concept for soft matter involving defect engineering. The same basic principle was employed to develop the semiconductors that have made possible our digital world.

Defects can determine how a material functions

Soft matter is part of our everyday lives, and a vast array of different substances belongs to this class of materials – from shower gels and toothpaste through rubber and paper to yoghurt, emulsion paints, and all sorts of plastics, to name just some examples. Even plants, animals, and humans are composed to a large extent of soft matter, which primarily constitutes biological matter like blood and tissue. The term itself is just about 30 years old and was first coined by Pierre-Gilles de Gennes, who received the Nobel Prize in 1991 for his work in this field. Though the relevant substances appear to be most diverse, there are also certain things they have in common: "Soft matter is made up of building blocks that are relatively large while interacting through comparatively weak energies," explained Professor Sebastian Seiffert of JGU, the spokesperson of the new CRC.

The question is how materials of this kind, which come with a vast range of dissimilar structures and underlying frameworks that are often not coherently organized, can be configured in the same way as semiconductors that have revolutionized our way of life. "It is frequently the case that defects determine how a material functions," explained Professor Sebastian Seiffert, describing the starting point for the future research. For example, semiconductor properties in metals and metalloids are the result of defects, such as when the metalloid silicon is made into an electrically conductive semiconductor by local replacement of individual silicon atoms by substitutes. Another example is Damascus steel, which owes its characteristics to being doped with carbon and given elaborate microstructuring. However, there have not yet been many approaches to understand, evaluate, and modulate defects in soft matter. "Liquid crystals are a sole notable exception in this regard", Seiffert pointed out. Seiffert, who is Professor of Physical Chemistry of Polymers at Johannes Gutenberg University Mainz, put together an extensive review paper on defects and their manipulation in soft matter three years ago, thereby providing the outline of a new field of research.

Mainz provides an ideal research landscape

"It is thanks to the Mainz research hub that we are now able to investigate this topic in the context of a Collaborative Research Center," emphasized Seiffert. Outstanding expertise in the disciplines of chemistry, polymer science, and physics of soft matter comes together here and the researchers profit from the close and fruitful collaborations already at hand that can be readily extended. Together with Professor Kurt Kremer, Director at the Max Planck Institute for Polymer Research, Professor Friederike Schmidt of JGU's Institute of Physics, and Professor Pol Besenius of JGU's Department of Chemistry, Seiffert has defined three types of defects that they will be focusing on doping defects, connectivity defects, and topological defects. Defects of this kind determine, for example, the attributes of flexible solar cells, baby diapers, and biomembranes.

In the first four-year funding period, the researchers will aim to understand defects and to manage them to a certain extent, while later engineering of the various defects to produce functioning elements of components will be at the forefront of efforts. The final goal is to combine all three defect types in one single system. "We will be trying to tune these individual defects like musical instruments so that they play in harmony," said Seiffert, describing the project objectives.

Extending the field of polymer research

The new CRC 1552 will involve a total of 21 project managers, including ten early-career researchers. Four of these hold a junior professorship with tenure track options. The CRC thus acts as a major vehicle for the promotion of young research talents. The proportion of participating female researchers – 33 percent – is above the average.

In January 2023, the Collaborative Research Center 1551 "Polymer Concepts in Cellular Function" was launched under the aegis of Mainz University. The participating researcher's goal is to apply findings of polymer research to molecular processes to better understand what happens in body cells. "These two projects form a synergistic tandem," concluded Seiffert. They will take polymer science in new directions – into the realm of materials and the life sciences.