Abstract

Many nano- and microstructured surfaces found in nature can serve as an inspiration for im-proving technical applications. Although most biomimetic archetypes can be replicated with advanced techniques on a lab-scale, it remains a challenge to develop processes for large-scale fabrication techniques appropriate for commercial applications. Here, I review some recent approaches with high potential for up-scaling.

The super-hydrophobic surfaces of water ferns like Salvinia and Pistia can be mimicked with nanofur, a dense fur of nanoscale hair hot pulled from polymer surfaces. This fractal surface can be utilized as a coating for solar cells and OLEDS . It enables self-cleaning while improv-ing optical efficiency at the same time [1, 2].

The scales of the black butterfly Pachliopta aristolochiae are micro- and nanostructured and harvest sunlight over a wide spectral and angular range. We fabricated such bio-inspired ab-sorbers using a scalable, self-assembly patterning technique based on the phase separation of a binary polymers mixture. Such nano-patterned absorbers achieve a relative integrated ab-sorption increase of 90% at normal incident angle of light to as high as 200% at large incident angles [3].

White beetles of the genus Cyphochilus are well-known for their scales producing a nearly perfect whiteness in a very efficient way with an astonishing low amount of material. Inspired by this biological architecture, we developed two techniques allowing for the fabrication of ultra-thin, yet highly scattering, white polymer films. Both approaches can be utilized for vari-ous applications ranging from extremely white but ultra-thin coatings to scattering particles as potential replacements for titanium dioxide.

[1] F. Vüllers, G. Gomard, J. B. Preinfalk, E. Klampaftis, M. Worgull, B. S. Richards, H. Hölscher, M. N. Ka-valenka, Bioinspired Superhydrophobic Highly Transmissive Films for Optical Applications, Small 12, 6144–6152 (2016)

[2] F. Vüllers, B. Fritz, A. Roslizar, A. Striegel, M. Guttmann, B. S. Richards, H. Hölscher, G. Gomard, E. Klampaftis, M. Kavalenka, Self-Cleaning Disordered Microcavity Array for Photovoltaic Modules, ACS Appl. Mater. Interfaces 10, 2929 (2018)

[3] R. H. Siddique, Y. J. Donie, G. Gomard, S. Yalamanchili, T. Merdzhanova, U. Lemmer, H. Hölscher, Bio-inspired Phase Separated Disordered Nanoholes for Thin Photovoltaic Absorbers, Sci. Adv. 3, e1700232 (2017)

[4] J. Syurik, R. H. Siddique, A. Dollmann, G. Gomard, M. Schneider, M. Worgull, G. Wiegand, H. Hölscher. Bio-inspired, large scale, highly scattering films for nanoparticle-alternative white surfaces, Sci. Rep. 7, 46637 (2017).

[5] J. Syurik, G. Jacucci, O. D. Onelli, H. Hölscher, S. Vignolini. Bio-inspired Highly Scattering Networks via Polymer Phase Separation, Adv. Funct. Mater. 28, 1706901 (2018).