On the development of substrate coatings for microfluidics devices: target-enhanced resolution

摘要

This study focuses on the development of highly wicking coated substrates for microfluidic devices with enhanced resolutioncompared to current filter paper-based devices. Four highly absorbing pigments, fumed silica (FM), modifiedcalcium carbonate (MCC), natural diatomite (ND) and flux-calcined diatomite (FCD), as well as three binders, styrene-acrylate (SA) latex, polyvinyl alcohol (PVOH) and carboxymethyl cellulose (CMC), were used to form coatingstructures with different wicking properties. Studies include characterisation of the pigment particles and thin layerwicking (TLW) experiments, in which wicking height of liquid in coatings is measured as a function of time. Theresults show that the choice of coating pigment and binder as well as the binder amount has a significant effect onwicking characteristics of a coating. The introduction of diatomite pigments into blends with MCC improved thewicking capabilities of the coating, especially in the case of ND. Latex was found to inhibit wicking of liquid the least,followed by PVOH and CMC. Increased binder amounts reduce wicking due to reduced pore connectivity andbinder-filled pores. It was found that the wicking resistance of pigment alone is too high for rapid analysis over longdistances in thick coatings. On the other hand, these coating structures could be utilised as high resolution analysispoints incorporated into a wicking channel matrix created, say, on a filter paper or placed at junctions of microfluidicchannels derived from controlled hydrophobic/oleophobic printing or designed shrinkage fracture geometries.