Figure 1

Microfluidic chip design and validation. (a) Each chip contained two channels comprising of an array of 6 × 8 wells. The channel facilitated fluid flow in one direction through the droplet formation well and bypass channel, while droplet was formed in the well due to restricted flow at the restriction; the neck prevented droplet escape and droplet coalescence with subsequent incoming aqueous fluid. (b) Correlation between observed volume (y-axis) and preset volume (x-axis) was plotted, where observed volume was calculated by multiplying the number of occupied wells (at 0.5 increments) by the theoretical well volume (length × width × height) of each well, whereas preset volume referred to the volume set on syringe pump; error bars denoted standard deviation of mean observed volumes obtained from all replicates for each preset volume. (c) Chip occupancy (y-axis) was plotted against preset volume (x-axis), where occupied wells was the number of occupied wells and preset volume referred to the volume set on syringe pump; error bars denoted standard deviation of the observed occupied wells in all replicates for each preset volume. (d) Two aqueous color dyes were loaded consecutively on chip to illustrate the sequential loading of different screening conditions in consecutive droplet formation wells. In this experiment, the food dyes were dissolved in water, representing the aqueous phase; the oil phase contained Fluorinert® FC-40 oil (Sigma-Aldrich, USA) supplemented with 2% 008-Fluorosurfactant (Ran Biotechnologies, USA). Firstly, we loaded the chip with oil. Next, food dyes of blue and green colors were segregated by translucent oil phase and loaded consecutively on chip. Each dye formed droplets in sequential order that was identical to the loading sequence.