Preventing Depletion of a Catalyst within a Microfluidic Network
Original Publication Date: 2002-Jan-13
Included in the Prior Art Database: 2003-Jun-20
Microfluidic networks (µFN) made from poly(dimethylsiloxane) (PDMS) are useful to perform reactions in confined volumes with consumption of only tiny amounts of reactants. This is especially important for the patterning of expensive materials like biochemicals or specialty polymers. Many chemical or biochemical reactions make use of some kind of catalyst (e.g. enzyme) or initiator (e.g. polymerization initiator) which is only present as a fraction of the amount of the other reactants. Any compound that is necessary in catalytic amounts for a reaction in µFNs may be subject to depletion during filling of the network, even if it only has little affinity towards the µFN material . The desired reaction may then only take place in a very constricted volume at the entrance of the channels (Fig. 1). Figure 1: Depletion of a catalyst in a µFN. Only in the filling pad and at the entrance of the channel the reactant solution contains the catalyst. After depletion of the catalyst the solution is not reactive anymore. Microfluidic networks can be filled with a polymerizable liquid which is then cured into a polymer by UV light, heat or some other means. This polymer then is structured according to the pattern given by the microfluidic network. If the PDMS-µFN is removed from the substrate the structured polymer may stay within the network or it may be left on the surface of the substrate. The later method called MIMIC (Micromolding in Capillaries) is known  . By releasing the polymer in the second step from the underlying substrate even freestanding polymeric microstructures can be made. The MIMIC technique can be applied for the fabrication of patterned color filters and color converter materials for the fabrication of displays.