Quantifying nucleation in flow by video-FLIM

During a precipitation experiment in microfluidics, crystals appear in the flow. Using a molecule that turns fluorescent in the solid phase, these crystals can be counted, measured and their polymorph identified. From this collection of data, the nucleation rate, the growth rate and the polymorph branching ratio are measured. Hundreds of crystals are analysed at a rate of one per second with a transit time in the field of view of 80 ms. Principal component analysis of the ensemble of the fluorescence photons is less efficient than the analysis of individual flowing particles identified by their burst of long-lived photons in the flow. Even if burst as small as 10 photons are detected, the smallest stable crystal, the nucleus, is not detected. The storage capacity of single photons allows deep post-analysis of transient phenomena.