Chemical and biomolecule patterning on 2D surfaces using atmospheric pressure microcavity plasma array devices

This paper presents a method for chemical and biomolecule patterning on planar (2D) surfaces using atmospheric pressure microplasmas. Spatially controlled surface modification is important for the development of emerging technologies such as microfluidic lab-on-a-chip devices, biosensors and other diagnostics tools. A non-fouling layer of poly(N-isopropylacrylamide) aldehyde (pNIPAM-ald) polymer, grafted onto heptylamine plasma polymer (HApp) modified silicon substrates, was used to achieve this goal. The non-fouling behaviour of the pNIPAM-ald coating was investigated at a temperature below its lower critical solution temperature (LCST) using human serum albumin (HSA). XPS and ToF-SIMS were used to characterise the plasma polymer coating and its subsequent modification with pNIPAM-ald before and after HSA adsorption. A 7 x 7 microcavity plasma array device (each cavity had a 250 mu m diameter and was separated by 500 mu m) was used for microplasma patterning. In a non-contact mode, helium microplasma treatment of the pNIPAM-ald coating was carried out for 60 s. The polymer coating was removed from regions directly exposed to microplasma cavities, as shown by ToF-SIMS. Microplasma treated regions were able to support the adsorption of fluorescently-labelled streptavidin whereas the rest of the coating was still non-fouling. This approach therefore resulted in spatially separated areas of immobilised protein.