Independently Controlling Protein Dot Size and Spacing in Particle Lithography

Particle lithography is a relatively simple, inexpensive technique used to pattern inorganics, metals, polymers, and biological molecules on the micro- and nanometer scales. Previously, we used particle lithography to create hexagonal patterns of protein dots in a protein resistant background of methoxy-poly­(ethylene glycol)-silane (mPEG-sil). In this work, we describe a simple heating procedure to overcome a potential limitation of particle lithography: the simultaneous change in feature size and center-to-center spacing as the diameter of the spheres used in the lithographic mask is changed. Uniform heating was used to make single-diameter protein patterns with dot sizes of approximately 2–4 or 2–8 μm, depending on the diameter of the spheres used in the lithographic mask, while differential heating was used to make a continuous gradient of dot sizes of approximately 1–9 μm on a single surface. We demonstrate the applicability of these substrates by observing the differences in neutrophil spreading on patterned and unpatterned protein coated surfaces.