Structural Transformation by Electrodeposition on Patterned Substrates (STEPS): A New Versatile Nanofabrication Method

Abstract

Arrays of high-aspect-ratio (HAR) nano- and microstructures are of great interest for designing surfaces for applications in optics, bio-nano interfaces, microelectromechanical systems, and microfluidics, but the difficulty of systematically and conveniently varying the geometries of these structures significantly limits their design and optimization for a specific function. This paper demonstrates a low-cost, high-throughput benchtop method that enables a HAR array to be reshaped with nanoscale precision by electrodeposition of conductive polymers. The method-named STEPS (structural transformation by electrodeposition on patterned substrates)-makes it possible to create patterns with proportionally increasing size of original features, to convert isolated HAR features into a closed-cell substrate with a continuous HAR wall, and to transform a simple parent two-dimensional HAR array into new three-dimensional patterned structures with tapered, tilted, anisotropic, or overhanging geometries by controlling the deposition conditions. We demonstrate the fabrication of substrates with continuous or discrete gradients of nanostructure features, as well as libraries of various patterns, starting from a single master structure. By providing exemplary applications in plasmonics, bacterial patterning, and formation of mechanically reinforced structures, we show that STEPS enables a wide range of studies of the effect of substrate topography on surface properties leading to optimization of the structures for a specific application. This research identifies solution-based deposition of conductive polymers as a new tool in nanofabrication and allows access to 3D architectures that were previously difficult to fabricate.

Bacterial flagella explore microscale hummocks and hollows to increase adhesion

“…Growth and adhesion assays were carried out in static culture using M63 salts plus 0.5% (wt/vol) casamino acids and 0.2% (wt/vol) glucose (M63+). HEX substrates were cast in PDMS from a Bosch-etched silicon master, and feature sizes were varied using polypyrrole electrodeposition onto epoxynegative replicas of the silicon master, followed by PDMS casting (44). Biovolume was quantified using image analysis of confocal z stacks.…”

Nano and Microscale Topographies for the Prevention of Bacterial Surface Fouling

“…Many groups have fabricated engineered surface topography, using numerous fabrication techniques (soft lithography and double casting molding techniques, microcontact printing, electron beam lithography, nanoimprint lithography, photolithography, electrodeposition methods, etc.) [37][38][39][40][41][42][43][44][45][46][47] on a wide range of substrates, ranging from various polymeric materials (silicone, polystyrene, polyurethane, and epoxy resins) to metals and metal oxides (silicon, titanium, aluminum, silica, and gold) [21,40,45,[47][48][49][50][51][52][53][54][55]. Furthermore, engineered topography can be considered as part of a multi-faceted strategy to prevent biofouling, and could be combined with other methods such as surface chemical treatments, addition of antibiotics/bacteriostatic agents, etc.…”

Engineering of Micro‐ and Nanostructured Surfaces with Anisotropic Geometries and Properties

“…These anisotropic arrays have found applications in unidirectional wetting, [ 24 , 192 ] anisotropic adhesion, [ 195 ] chemical and biological sensing, and actuation. [ 194 ] Kim et al demonstrated several approaches to make bent polymer nanohairs for applications in unidirectional wetting and dry adhesives. [ 195 ] First, they fabricated a silicon master template using lithography and dry etching (DRIE) as shown in Figure 27 a.…”