# 05- Tailoring disorder in functional optical materials using a combined materials engineering and bioinspiration approach
**Source**: https://www.cs.tum.de/spp1839/projects/2nd-period-2018-2021/05.html
**Parent**: https://www.cs.tum.de/spp1839/projects.html
The intricate photonic
structures found in the scales of white beetles are a paradigm for
tailored disorder in nature: the scattering strength has been optimized
with respect to the low available refractive index contrast, the weight
of the structure, its volume as well as its stability. These properties
are static, however. Nature also excels in systems, which adjust their
shape or other properties depending on external stimuli like humidity or
temperature. We want to use this self-actuation in this project, to
derive artificial photonic materials, which change their properties
under external stimuli. We start with our cellulose-based photoresist
and extend it to the poly-saccharide chitin. We fabricate strong
scattering structures from these materials via three-dimensional
laserlithography. A model developed by us will be used as a blueprint,
which follows the construction principle of the white beetle’s
scales. Embedding swellable materials into the structures (e.g.
cellulose spheres), critical dimensions can be tuned in dependence of
humidity. This allows us to switch the material from a nearly
transparent state (collapsed material, strong optical crowding) to a
highly scattering state (open structure). Our approach might open the
way to bio-based materials, whose optical properties can be controlled
by external stimuli.
## Contributors
Prof. Cordt Zollfrank
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Maximilian Rothammer
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Prof. Georg von Freymann
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Dominic Meiers
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Marie-Christin Heep
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## References
- Enabling direct laser writing of
cellulose-based submicron architectures, M. Rothammer, M.C. Heep, G. von
Freymann, and C. Zollfrank, Cellulose 25, 10, 6031-6039. (2018)
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