Reconfigurable microfluidic dilution for high-throughput quantitative assays

Abstract

This paper reports a reconfigurable microfluidic dilution device for high-throughput quantitative assays, which can easily produce discrete logarithmic/binary concentration profiles ranging from 1 to 100-fold dilution in parallel from a fixed sample volume (e.g., 10 μL) without any assistance of continuous fluidic pump or robotic automation. The integrated dilution generation chip consists of switchable distribution and collection channels, metering reservoirs, reaction chambers, and pressure-activatable Laplace valves. Following the sequential loading of a sample, a diluent, and a detection reagent into the individual metering chambers, the top microfluidic layer can be reconfigured to collect the metered chemicals into the reaction chambers in parallel, where detection will be conducted. To facilitate mixing and reaction in the micro-chambers, two acoustic microstreaming actuation mechanisms have been investigated for easy integratability and accessibility. Furthermore, the microfluidic dilution generator has been characterized by both colorimetric and fluorescent means. A further demonstration of the generic usage of the quantitative dilution chip has utilized a commonly available bicinchoninic acid (BCA) assay to analyse protein concentrations of human tissue extracts. In brief, the microfluidic dilution generator offers a high-throughput high-efficiency quantitative analytical alternative to the conventional quantitative assay platforms, by simple manipulation of a minute amount of chemicals in a compact microfluidic device with a minimal equipment requirement, which can serve as a facile tool for biochemical and biological analyses in regular laboratories, point-of-care and low-resource environments.

A passive microfluidic system based on step emulsification allows the generation of libraries of nanoliter-sized droplets from microliter droplets of varying and known concentrations of a sample

“…In order to measure the exact ratio of dilution and assess the quality of the gradient, we employed a procedure similar to those presented before. [34][35][36] We carried out tests using a 50 μM solution of rhodamine 110 in water with an addition of methanol (0.1% w/w) as a sample. For the diluent, we used pure water.…”

Piezoelectric-driven droplet impact printing with an interchangeable microfluidic cartridge

“…Total volume of 1.8 ll of the BSA solution is consumed for the entire droplet array, at least an order of magnitude less than that of the conventional microtiter plates (on the order of 100 ll) 35 and the microfluidic approaches (on the order of 10 ll). 36 Fig . 7 summarizes the quantitative colorimetric readouts of the printed droplet array with a concentration gradient of BSA built inside, in which the concentration profiles range from 16 lg/ml to 2000 lg/ml.…”

Novel modular pressure and flow rate balanced microfluidic serial dilution networks on printed circuit boards: Designs, Simulations and Fabrication

“…Almost every quantitative chemical and biological assay relies heavily upon accurate and prompt serial dilution. Its usefulness lies in the fact that with a suitable sample preparation procedure, a wide variety of known scaled concentration samples can be generated using a suitable diluent [1]. For example, widely known quantitative assays, such as real time polymerase chain reaction (q-PCR) or antigen assays, e.g.…”