A low-cost, high-yield fabrication method for producing optimized biomimetic dry adhesives

Abstract

We present a low-cost, large-scale method of fabricating biomimetic dry adhesives. This process is useful because it uses all photosensitive polymers with minimum fabrication costs or complexity to produce molds for silicone-based dry adhesives. A thick-film lift-off process is used to define molds using AZ 9260 photoresist, with a slow acting, deep UV sensitive material, PMGI, used as both an adhesion promoter for the AZ 9260 photoresist and as an undercutting material to produce mushroom-shaped fibers. The benefits to this process are ease of fabrication, wide range of potential layer thicknesses, no special surface treatment requirements to demold silicone adhesives and easy stripping of the full mold if process failure does occur. Sylgard R 184 silicone is used to cast full sheets of biomimetic dry adhesives off 4" diameter wafers, and different fiber geometries are tested for normal adhesion properties. Additionally, failure modes of the adhesive during fabrication are noted and strategies for avoiding these failures are discussed. We use this fabrication method to produce different fiber geometries with varying cap diameters and test them for normal adhesion strengths. The results indicate that the cap diameters relative to post diameters for mushroom-shaped fibers dominate the adhesion properties.

Cleaning properties of dry adhesives

“…In ref. [3], gold-coated silicon wafers were used as the substrate for the moulds while we used 4" PMMA (OPTIX) discs with a 2 mm thickness as substrates for this application. This was done in order to reduce costs and manufacturing time as well as increasing the mould's lifetime; silicon wafers are prone to cracking easily during demoulding.…”

“…Using Micro Electro-Mechanical Systems (MEMS) as well as micro and nano fabrication techniques, synthetic fibrillar biomimetic dry adhesives have been developed and successfully tested by many different groups [2][3][4][5]. Among these research groups, there has been a loss in performance of the adhesive sheets as the sample is tested [5].…”

Manufacturing of mushroom-shaped structures and its hydrophobic robustness analysis based on energy minimization approach

“…However, the fabricated inverse-trapezoidal microstructures are different from microstructures with mushroom-shaped tips. Using positive-and negative-tone photoresist materials, Sameoto et al 16 fabricated pillar arrays with mushroom-shaped tips employing photolithography and a molding process, where the unexposed negative-tone photoresist was used to generate undercut microholes. The limitation of this process is that it is necessary to precisely control the exposure dose to avoid the underneath negative-tone photoresist being exposed.…”

Durability Improvement of Synthetic Dry Adhesives by Metal Coatings

“…Dip transfer, multistep photolithography, UV-assisted CFL, and multistep template are typical examples of numerous trials. Micro-and nanopillars with a higher aspect ratio are essential to achieve reasonable adhesion, but the aforementioned fabrication methods cannot be used commercially since extremely precise equipment and a long time are required for fabrication [24,[28][29][30][31][32][33][34][35][36][37][38][39][40][41]. In contrast, polymers or elastomers such as polydimethylsiloxane (PDMS) have been widely used for SDAs due to their flexibility and ease of fabrication.…”