Pull-off and friction forces of micropatterned elastomers on soft substrates: the effects of pattern length scale and stiffness

Beilstein Journal of Nanotechnology

Peter van Assenbergh^1¹  Julian Langowski^2²  Marike Fokker^1³  Jan van Esch^2⁴ 

[1] Biomechanical Engineering Department, Delft University of Technology, Mekelweg 2, 2628 CD Delft, The Netherlands^1;Chemical Engineering Department, Delft University of Technology, Van der Maasweg 9, 2629 HZ Delft, The Netherlands^2;Experimental Zoology Group, Wageningen University & Research, De Elst 1, 6708 WD Wageningen, The Netherlands;Polymer Science, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, 9747 AG Groningen, The Netherlands more less^3

关键词: adhesion;    biomimetic micropatterned adhesive;    colloidal lithography;    friction;    pull-off;    soft substrate;   

DOI  :  10.3762/bjnano.10.8

学科分类：地球科学(综合)

来源: Beilstein - Institut zur Foerderung der Chemischen Wissenschaften

【 摘 要 】

The adhesiveness of biological micropatterned adhesives primarily relies on their geometry (e.g., feature size, architecture) and material properties (e.g., stiffness). Over the last few decades, researchers have been mimicking the geometry and material properties of biological micropatterned adhesives. The performance of these biomimetic micropatterned adhesives is usually tested on hard substrates. Much less is known about the effect of geometry, feature size, and material properties on the performance of micropatterned adhesives when the substrate is deformable. Here, micropatterned adhesives of two stiffness degrees (Young’s moduli of 280 and 580 kPa) were fabricated from poly(dimethylsiloxane) (PDMS) and tested on soft poly(vinyl alcohol) (PVA) substrates of two stiffness degrees (12 and 18 kPa), and on hard glass substrates as a reference. An out-of-the-cleanroom colloidal lithographic approach was successfully expanded to fabricate adhesives with two geometries, namely dimples with and without a terminal layer. Dimples without a terminal layer were fabricated on two length scales, namely with sub-microscale and microscale dimple diameters. The cross section of samples with a terminal layer showed voids with a spherical shape, separated by hourglass-shaped walls. These voids penetrate the terminal layer, resulting in an array of holes at the surface. We found that on soft substrates, generally, the size of the dimples did not affect pull-off forces. The positive effects of sub-microscale features on pull-off and friction forces, such as defect control and crack trapping, as reported in the literature for hard substrates, seem to disappear on soft substrates. The dimple geometry with a terminal layer generated significantly higher pull-off forces compared to other geometries, presumably due to interlocking of the soft substrate into the holes of the terminal layer. Pull-off from soft substrates increased with the substrate stiffness for all tested geometries. Friction forces on soft substrates were the highest for microscale dimples without a terminal layer, likely due to interlocking of the soft substrate between the dimples.

【 授权许可】

CC BY