Synergism of Dewetting and Self-Wrinkling To Create Two-Dimensional Ordered Arrays of Functional Microspheres

Abstract

Here we report a simple, novel, yet robust nonlithographic method for the controlled fabrication of two-dimensional (2-D) ordered arrays of polyethylene glycol (PEG) microspheres. It is based on the synergistic combination of two bottom-up processes enabling periodic structure formation for the first time: dewetting and the mechanical wrinkle formation. The deterministic dewetting results from the hydrophilic polymer PEG on an incompatible polystyrene (PS) film bound to a polydimethylsiloxane (PDMS) substrate, which is directed both by a wrinkled template and by the template-directed in-situ self-wrinkling PS/PDMS substrate. Two strategies have been introduced to achieve synergism to enhance the 2-D ordering, i.e., employing 2-D in-situ self-wrinkling substrates and boundary conditions. As a result, we achieve highly ordered 2-D arrays of PEG microspheres with desired self-organized microstructures, such as the array location (e.g., selectively on the crest/in the valley of the wrinkles), diameter, spacing of the microspheres, and array direction. Additionally, the coordination of PEG with HAuCl4 is utilized to fabricate 2-D ordered arrays of functional PEG-HAuCl4 composite microspheres, which are further converted into different Au nanoparticle arrays. This simple versatile combined strategy could be extended to fabricate highly ordered 2-D arrays of other functional materials and achieve desirable properties and functionalities.

Pressure tunable adhesion of rough elastomers

“…Past research has focused on utilizing silicon wafers coated with a hydrophobic coating. Han et al concurrently utilized wrinkling and dewetting mechanics to precisely pattern an elastomeric substrate 47 and Song et al utilized poly(dimethyl siloxane) as a substrate and a liquid crystalline polymer as the film. 48 In the present work, we explore the use of polymer (polystyrene) thin film dewetting on an elastic substrate (poly(dimethyl siloxane)) to create patterned surfaces with the intent of altering the substrate adhesion to develop a pressure tunable adhesive (PTA).…”

“…1(b)), defects in the film, or contaminants such as dust on the substrate that serve as nucleation sites for dewetting. 44,47 The standard distribution in asperity height increases with increasing film thickness, most likely due to fingering instabilities. Fingering instabilities as seen for the t = 97 nm and t = 169 nm films in images (ix), (xvi), and (xvii) of Fig.…”

Mechanically Switchable Wetting Petal Effect in Self-Patterned Nanocolumnar Films on Poly(dimethylsiloxane)

“…Particularly, in elastomeric surfaces of PDMS, self-generated wrinkling processes are known to induce reversible wetting, although the phenomenon is hardly controllable due to the randomness in the generation of surface structures [24] and the dependence of water adhesion on the hysteresis contact angle [25]. Nonetheless, the fabrication of mechanically switchable wetting devices relying on anisotropically structured PDMS has been attempted with different success using complex processes such as ink transfer printing [26] and 3D printing [27], laser [28][29][30], bending by magnetic induction [31], wave-like nanofibers on pre-stretched substrates [32,33], incorporation of templates [34,35], nanostructures [36,37], metallic [38][39][40] and oxide [12,41] coatings, the selective surface functionalization through plasma treatments [42] or the deposition of superhydrophobic layers [24,43,44]. In general, these procedures lack robustness and require relatively sophisticated engineering steps to ensure straightforward functionality and full reversibility upon actuation.…”

Engineering Surface Patterning of Colloidal Rings through Plateau–Rayleigh Instability

“…[8] TheP-R instability can occur for awetting liquid column on aflat substrate,leading to the generation of surface pattern. [9] Generally,t his process can be well controlled when the substrate is large and immobile.Inprinciple, if the P-R instability can occur in aw ell-controlled way on Brownian colloidal particles,itwill provide anew approach to surface patterning of colloidal particles,r esulting in new patchy particles.Despite this intriguing perspective,however, this has not been explored before.P articularly,i ti sk nown that P-R instability is induced by small perturbations to the uniform surface profile,but such perturbations are ubiquitous for aB rownian particle.…”