# 03 - Tailoring disorder in functional optical materials using a combined materials engineering and bioinspiration approach

**Source**: https://www.cs.tum.de/spp1839/projects/1st-period-2015-2018/03.html
**Parent**: https://www.cs.tum.de/spp1839/projects.html

Natural systems are able to generate structural
materials with unique functional properties. The formation of complex
three-dimensional structures in nature is of fundamental importance to
break the limits imposed by available construction elements, which are
generally composed of organic compounds, i.e. biopolymers
(polysaccharides and proteins). Structuring into ordered, and especially
into irregular or disordered systems is the key to define new roadmaps
to innovative engineering materials. Basic consideration on the
importance of disordered structures in biology can be most efficiently
demonstrated on natural optical materials. In our proposal we aim to
identify biological optical structures which will allow a distinct
photon management for broad band interaction in addition to specific
wavelength selectivity for angle-independent reflection. In nature, such
systems are realised in the complex structure of some butterfly
species.

We will first work on the so-called pepper-pot
structure with a distinct degree of disorder, frequently found in
butterflies. The pepper-pot structure will be subjected to numerical
calculations in order to find an optimised structure fulfilling the
above envisioned optical characteristics, which will require the
formation of tailor-made degree of disorder in the structures. These
identified structures are then abstracted (bioinspired engineering) and
the resulting architectures will be fabricated via direct laser
writing (DLW) using conventional acrylates. Since DLW has a lower limit
of approximately one micrometre resolution, finer structures, which
are required for the optical response, will be obtained after
infiltration of the written porous pepper-pot structure with cellulose
and chitin from solution. They will form polysaccharide membranes
covering the pores and the final active structure will be obtained in a
self-assembly process including controlled rupture. We will also
develop chemical synthesis routes to novel polysaccharide based
compounds, which can be used in DLW. This allows us to generate the
basic pepper-pot all from polysaccharides (as in natural systems).

Additionally, the self-organisation capabilities of
the polysaccharide are necessary for tailoring the degree of disorder
in such structures. Finally, a model device will be manufactured from
the results of each individual work package, where we can evaluate the
underlying optical principles and refer them to the introduced degree
of disorder. Our approach basically combines inspiration from biology
with a materials engineering approach and chemical synthetic and
physical methods for the design of novel optical structured, which gain
their function from a tailor-made degree of disorder.

## Contributors

- [Prof. Cordt Zollfrank](http://wz-sr.de/de/professuren/stoffliche-nutzung/biogene-polymere/)
- [Prof. Georg von Freymann](https://www.physik.uni-kl.de/freymann/startseite/)
- Marie-Christin Angermann
- Max Rothammer

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