Bioinspired monolithic polymer microsphere arrays as generically anti-adhesive surfaces

Abstract

Bioinspired surface topographies showing generic anti-adhesive behaviour by minimization of the real contact area not only with rigid, but also with soft and compliant counterpart surfaces recently attracted increasing attention. In the present study, we show that such generic anti-adhesive surfaces, which moreover demonstrate anti-fouling behaviour, can be produced on a large scale by a simple double replication of monolayers of microspheres with diameters of a few 10 μm. Thus, we obtained mechanically stable monolithic arrays of microspheres tightly connected to a support of the same material. Adhesion of these microsphere arrays to sticky and compliant counterpart surfaces was one order of magnitude weaker than that of flat control samples of the same material. The generation of nanorod arrays with nanorod diameters of a few 100 nm as the second hierarchical structure level on monolithic microsphere arrays did not significantly affect the adhesion force. The experimental data on anti-adhesive behaviour were modelled using a modified Johnson-Kendall-Roberts theoretical approach that also provided general design criteria for topographic adhesion minimization to sticky counterpart surfaces.

Nanoporous Monolithic Microsphere Arrays Have Anti-Adhesive Properties Independent of Humidity

“…The surface topography of microsphere arrays with r s values of a few 10 µm is generically anti-adhesive for soft tacky PDMS [4]. Using tacky and compliant PDMS-half-spheres as probes, at RH = 42.6% topography-induced reduction of F Ad / F L was found on NMMA-12.5/22.5 [23].…”

“…PDMS primary molds were prepared following the procedures described in reference [4]. In brief, aqueous suspensions of PS microspheres (Polybead Microspheres, Polysciences Inc., Warrington, PA, USA) with r s = 12.5 µm (2.91 × 10 6 microspheres/mL) and r s = 22.5 µm (4.99 × 10 5 microspheres/mL) were deposited onto rectangular pieces of (100) Si wafers with edge lengths of ~1 cm by applying a multistep spin coating program.…”

“…Only if the feature size of the roughness of the sample surface is increased to a few 10 µm, elastic counterpart surfaces lose their ability to form conformal contact to the sample surface. Then, the real contact area is reduced, and the sample surface is anti-adhesive even towards sticky and compliant counterpart surfaces [4]. Artificial surfaces typically exhibiting a combination of self-cleaning behavior, superhydrophobicity and anti-adhesive properties have predominantly been designed by mimicking hierarchically structured plant surfaces, such as the surface of the lotus leaf [5,6,7,8,9,10,11].…”

“…Artificial surfaces typically exhibiting a combination of self-cleaning behavior, superhydrophobicity and anti-adhesive properties have predominantly been designed by mimicking hierarchically structured plant surfaces, such as the surface of the lotus leaf [5,6,7,8,9,10,11]. Arrays of microspheres with radii r s of the order of a few 10 µm, such as monolithic arrays of solid polystyrene (PS) microspheres [4], are a suitable material platform to realize the first hierarchical structure level characterized by roughness with feature sizes of a few 10 µm. Various methods have been employed to introduce further hierarchical structure levels.…”

The Influence of Surface Topography and Surface Chemistry on the Anti-Adhesive Performance of Nanoporous Monoliths

“…Preparation of NMMAs. PDMS secondary molds were prepared as described elsewhere 20. Solutions containing 200 mg PS-b-P2VP per 1.2 mL THF (99,9 %, Sigma Aldrich) were heated to 40° C for 1 h, kept at room temperature for 24 h to remove air bubbles and then deposited onto the PDMS molds.…”