Multifunctional wax valves for liquid handling and incubation on a microfluidic CD

Recently, several biological assays have become available on the centrifugal microfluidic platform. Despite many innovative solutions developed for on-disc fluid handling for these assays, certain challenges, including liquid incubation and simplification of a multi-step assay on a plastic device, still need to be further addressed. Incubating fluids that require downstream processing, which we call midstream incubation, can often be difficult on the microfluidic disc platform due to surface tension changes induced by varying temperatures, thus causing operating instability. We describe here strategies for liquid reagent storage, release, incubation, and transfer, all of which utilize a single combination of actuation methods-wax valving and heat actuation by halogen lamp-on a centrifugal microfluidic device made using pristine materials. The strategies that we use to perform these steps, termed multifunctional wax valves, enable manipulation of a microlitre range fluid volume without the need for complex fabrication steps or hardware. This technology's reliability and ease of use will hopefully allow for more powerful fluidics-based diagnostic tools to be created.