UV- and Visible-Light Photopatterning of Molecular Gradients Using the Thiol–yne Click Reaction

The rational design of chemical coatings is used to control
surface
interactions with small molecules, biomolecules, nanoparticles, and
liquids as well as optical and other properties. Specifically, micropatterned
surface coatings have been used in a wide variety of applications,
including biosensing, cell growth assays, multiplexed biomolecule
interaction arrays, and responsive surfaces. Here, a maskless photopatterning
process is studied, using the photocatalyzed thiol–yne “click”
reaction to create both binary and gradient patterns on thiolated
surfaces. Nearly defect-free patterns are produced by first coating
glass surfaces with mercapto­propyl­silatrane, a silanizing
agent that forms smoother self-assembled monolayers than the commonly
used 3-mercapto­propyl­trimethoxy­silane. Photopatterning
is then performed using UV (365 nm) or visible (405 nm) light to graft
molecules onto the surface in tunable concentrations based on the
local exposure. The technique is demonstrated for multiple types of
molecular grafts, including fluorescent dyes, poly­(ethylene glycol),
and biotin, the latter allowing subsequent deposition of biomolecules
via biotin–avidin binding. Patterning is demonstrated in water
and dimethylformamide, and the process is repeated to combine molecules
soluble in different phases. The combination of arbitrary gradient
formation, broad applicability, a low defect rate, and fast prototyping
thanks to the maskless nature of the process creates a particularly
powerful technique for molecular surface patterning that could be
used for a wide variety of micropatterned applications.