Uniform surface patterning: a three-beam holographic approach

With the increased risk of antibiotic-resistant pathogens, the development of point-of-care devices for their detection is essential. Surface patterns alongside surface functionalization are often employed to create an environment conducive to bacteria adhesion. We proposed surface relief patterns that are designed to have a dual role. Optically, they provide a diffracted light signal, and they also are expected to control the adhesion of the bacteria to the surface. The strength of the diffracted signal is expected to provide a quantitative measure of the number of bacterial cells attached to the patterned surface. In this article, we described the first step in the development and characterization of such surfaces. A three-beam holographic setup for patterning of a photopolymer surface was built. The optical system allows for the creation of surface relief cross-gratings (SRCGs) with unit cell sizes ranging from 8×8 μm2 (125 lines/mm) to 1×1 μm2 (1000 lines/mm). The surfaces are analyzed via atomic force microscopy, fast Fourier transform, and diffraction efficiency measurements. The SRCG relief amplitude dependence on recording parameters and photopolymer composition is investigated, and the results demonstrate a strong dependence of the SRCG height, area roughness, and diffraction efficiency on the SRCG feature period of the recorded structures. The largest surface relief amplitude achieved is 1.4 μm at an 8-μm period. Control over surface roughness by optical patterning was experimentally confirmed.