Biomimetic structuring via laser interference

Biomimetic structuring via laser interference

Mirco channels/canals with highest aspect ratio in photo resist
© Fraunhofer IWS Dresden

Mirco channels/canals with highest aspect ratio in photo resist

Grid-like pattern with 1.5 µm spatial period and 30° rotation angle
© Fraunhofer IWS Dresden

Grid-like pattern with 1.5 µm spatial period and 30° rotation angle

(1) Diatomee C. walesii, (2) imitated hierarchic structure of Diatomee C. walesii, (3) S. epidermidis initial adhesion on differently structured photoresist surfaces

(1) Diatomee C. walesii, (2) imitated hierarchic structure of Diatomee C. walesii, (3) S. epidermidis initial adhesion on differently structured photoresist surfaces

One focus of research in the IWS work group “Surface Functionalization” is on biomimetics, in which structures and functions of living organisms are imitated.

Natural surfaces normally consist of complex one- or two-dimensional structures which additionally are often hierarchically organized. Previously pursued technological approaches of design development and synthesis of those surfaces are time-consuming and cost-intensive. With Direct Laser Interference Lithography (LIL) Fraunhofer IWS offers a flexible and efficient technology to copy topographic elements and/or their functions from their natural template.

In this context the surface of diatom C. walessi was already reproduced. To achieve the artificial synthesis of its structure, at first a hexagonal sub micrometer pattern (period: 500 nm) was created via two beam interference using a thin photoresist layer, which was exposed twice. Between both exposure steps the substrate was rotated by 60°. Subsequently, a second layer of photoresist was applied to the already structured and developed film and irradiated with a line-like interference pattern (period 5 µm). This created structure possesses a high degree of geometric uniformity.

Furthermore, based on the antibacterial properties of the as well hole-like collembolan skin, the initial bacteria adhesion was examined on 1- to 2.5 dimensional micro and sub micrometer structures in photoresist. Results show that on a topography consisting of hexagonal oriented holes with a periodic distance of 500 nm the number of bacteria S. epidermis is 50 % less than on a non-structured reference. These works were realized in cooperation with Leibnitz IPF.

Both examples emphasize the potential of LIL as technology to produce bio-inspired surfaces.