Fabrication of Multiscale Surface-Chemical Gradients by Means of Photocatalytic Lithography

Abstract

We describe a new method for the fabrication of surface-chemical gradients. A film of titanium dioxide is brought into close proximity to a uniformly monolayer-covered surface and exposed to UV light to produce oxygen radicals. The use of a gradated grayscale mask between the UV source and the TiO2 allows the production of surface-chemical gradients via oxidation of the monolayer. The technique is demonstrated on gold surfaces bearing alkanethiol SAMs. Oxidation and subsequent replacement of the oxidized thiols has been used to produce surface-chemical gradients with lengths on the submillimeter to centimeter scales. The oxidation, removal, and replacement of the thiols during the process have been demonstrated by means of XPS. This oxidative process may be applied to other surface chemistries. Similarly, other shapes and slopes of gradients may be produced, depending on the photomask employed.

Gradient biomaterials and their influences on cell migration

“…The substrate is firstly covered with a self-assembled monolayer (SAM), which usually is thiol or silane, and then the organic layer is degraded by UV irradiation. Blondiaux et al [53] developed a technique that combined a gradually changed greyscale mask with titanium dioxide (TiO 2 ) remote photocatalytic lithography. The TiO 2 layer is placed under the photomask, and the region affected by the UV irradiation produced radicals, which diffuse vertically and thus locally degrade the organic SAM on the gold surface underneath.…”

Use of Gel‐Assembly to Fabricate Multi‐Component Molecular Gradient Layers and the Investigation of Structure and Electron Transport Therein

“…Methods so far available for the fabrication of thiol-SAMsbased two-component molecular gradient layers are as follows: cross-diffusion through a polysaccharide matrix, [13] diffusion in electrochemical potential, [14] STM-based replacement lithography, [15] controlled two-step immersion, [16] micro-contact printing [17] and by the effect of electron or soft X-ray [18] or ultraviolet radiation [19] on exchange reaction. Our method is based on a gel-assisted exchange reaction ( Figure 1) of a preformed SAM with potential molecular substituents which are capable to build SAMs on the same substrate, for example Au used herein.…”

Heat Transfer in Directional Water Transport Fabrics

“…The concept of directional fluid transport, which is also called "one-way liquid transport" or "fluid diode" is a phenomenon widely found in daily life. Examples can be found in one-dimensional (1D) materials, such as spider silk and its inspired designs for water-harvesting [9][10][11][12][13][14][15][16][17], two-dimensional (2D) solid surfaces which are fabricated typically by forming a chemical gradient [18][19][20][21][22][23], or chemically homogeneous but surface roughness variation [24][25][26][27][28] using various approaches, and three-dimensional (3D) porous materials such as textile fabrics [1,[5][6][7][29][30][31][32][33], cellulosic paper substrate [34], and electrospun nanofibrous membranes [3,7]. The 3D porous materials with directional water transport property are prepared either by forming a hydrophobicity-to-hydrophilicity gradient or two zones with opposite wettability across thickness.…”