Molecular Flux Dependence of Chemical Patterning by Microcontact Printing

Abstract

We address the importance of the dynamic molecular ink concentration at a polymer stamp/substrate interface during microcontact displacement or insertion printing. We demonstrate that by controlling molecular flux, we can influence both the molecular-scale order and the rate of molecular exchange of self-assembled monolayers (SAMs) on gold surfaces. Surface depletion of molecular ink at a polymer stamp/substrate interface is driven predominantly by diffusion into the stamp interior; depletion occurs briefly at the substrate by SAM formation, but diffusion of molecules into the bulk of the stamp dominates over practical experimental time scales. As contact time is increased, the interface concentration varies significantly due to diffusion, affecting the quality and coverage of printed films. Controlling interfacial concentration improves printed film reproducibility and the fractional coverage of multicomponent films can be controlled to within a few percent. We first briefly review the important aspects of molecular ink diffusion at a stamp interface and how it relates to experimental duration. We then describe two examples that illustrate control over ink transfer during experiments: the role of contact time on monolayer reproducibility and molecular order, and the fine control of fractional monolayer coverage for the displacement printing of 1-adamantanethiolate SAMs by 1-dodecanethiol.

Mechanistic Framework for the Formation of Different Sulfur Species by Electron Irradiation of n-Dodecanethiol Self-Assembled Monolayers on Au(111) and Au(100)

“…3 However, the attainable resolution with these methodologies might be limited due to the diffusion of the thiols when delivered to the surface. 9,10 On the other hand, preformed SAMs can be accurately patterned by its selective damaging with light (e.g. lasers, ultraviolet light, X-rays) or particles' beams (electrons, ions).…”

Patterning of supported gold monolayers via chemical lift-off lithography

“…4 ). The Au–alkanethiolate complexes on PDMS are expected to adopt a variety of orientations relative to the surface, similar to the variety of orientations of self-assembled alkanethiols at incomplete coverage on Au surfaces [ 47 – 48 ], further reducing our estimate of the apparent height. In all, our measured estimate of the topographic height of a Au–alkanethiol monolayer on PDMS is consistent with all previous CLL characterization attempts and with the predicted one or two atoms lifted-off per alkanethiolate molecule (vide infra).…”

Aptamer Recognition of Multiplexed Small-Molecule-Functionalized Substrates

“…These soaking steps removed unpolymerized residues on devices preventing them from being deposited on substrates, thereby decreasing nonspecific binding. 65 Finally, devices were rinsed with 50/50 deionized H 2 O/ethanol for 15 min and dried with nitrogen gas.…”

“…Each elastomeric mixture was cured at 60 °C for ∼20 h. Polymerized PDMS microfluidic devices were removed from the silicon master and soaked in fresh 95% hexane for 1.5 h three times. These soaking steps removed unpolymerized residues on devices preventing them from being deposited on substrates, thereby decreasing nonspecific binding . Finally, devices were rinsed with 50/50 deionized H 2 O/ethanol for 15 min and dried with nitrogen gas.…”