Control of the colloidal deposition of cellulose nanocrystal films

Promovendus/a: Alican Gençer

Promotor(en): Prof. dr. ir. Wim Thielemans

Colors! Life is more beautiful with them. Nature is full of shades of colors which stem from minerals, plants, and animals and so on. Most of these owe their color to the periodical structure they possess. Interference of visible light by interaction with these structures leads to a specific type of coloration so-called iridescence. Pollia condensate, a cellulose-based plant is a good example of such brilliant iridescence.

Taking this idea of color formation in nature further, our research at Kulak focuses on the control of the assembly of cellulose nanocrystals to produce optically active materials. Cellulose nanocrystals, solid particles with dimensions in the order of a one billionth of a meter, could be obtained via a chemical process including use of a strong acid. We study the drying of tiny water droplets loaded with these particles to obtain optically active materials. Thus, we have to understand how this deposition occurs and what the controlling factors are.

This process is similar to what happens when you spill a coffee drop on your desk. What remains of this coffee-droplet is a ring-shaped deposit which is due to the flow of particles within the drop toward the edge during drying.

Mastering this flow behavior is crucial for the control of the deposition of cellulose nanocrystal films as well. In our research, we have achieved uniform deposition of the cellulose nanocrystals films by manipulating the internal flow of drying droplets. We could thus make iridescent films with a uniform thickness to obtain iridescent materials inspired by nature.