Programmable droplet-based microfluidic serial dilutor.

• A microfluidic device is developed to perform serial dilution of compounds in solution in a series of droplets. • A micromixer and a droplet generator are combined by integrated microvalves. • Automated serial dilutions of rhodamine B isothiocyanate-dextran are demonstrated with various dilution factors. A programmable droplet-based microfluidic serial dilutor platform is presented, which is capable of generating a series of droplets with the scalable stepwise concentration gradient of a sample. Sequential dilution of a target molecule was automatically performed in sub-nanoliter scale droplets by synchronizing a microfluidic peristaltic mixer and a valve-assisted droplet generator. The volume of droplets dispensed from the mixer was controlled by microvalve operation, which enabled to tune the dilution with various dilution factors. After evaluation of the mixer efficiency and calibration of the droplet size at different valve operating conditions, serial dilutions of rhodamine B isothiocyanate-dextran was demonstrated, in an automated manner, at three different dilution factors. Specifically, the effect of the rhodamine B isothiocyanate-dextran concentration and temperature on variations of the fluorescent intensity was quantified. This programmable microfluidic droplet serial dilutor will open new avenues, an analytical tool, to evaluate complex chemical and biochemical reactions, especially when limited sample volume is available, for example, at the early stage of drug discovery and biochemical process developing. [ABSTRACT FROM AUTHOR]