Study on factors enhancing photobleaching effect of fluorescent dye

With unique capability of biomedical diagnosis and chemical analysis, microfluidics has received worldwide applications in various fields. Multiple methods have been proposed to measure velocity profile of flow in microchannels, among which the laser induced fluorescence photobleaching anemometer (LIFPA) provides great performance with not only high spatial resolution but also superior temporal resolution compared with former systems. The measurement sensitivity and temporal resolution of LIFPA system is largely determined by the speed of fluorescence photobleaching effect, meaning that a half-life decay time as short as possible is required to achieve superior temporal resolution. In this paper, several experiments are done to investigate the influence over the half-life decay time by several factors, including incident laser power, dye concentration, buffer concentration and fluidic pH value. Based on the experimental results, a certain dye solution is specially designed, which demonstrates an extremely fast photobleaching effect with a half-life decay time of about 55 μs. Fluorescent dye solution with such a fast photobleaching effect is potentially applicable in the analysis of transient flows, such as the rise time of electroosmotic flow, where high temporal resolution is required.

► We experimentally studied factors enhancing photobleaching effect in microfluidics.
► Large laser power leads to shorter half-life decay time.
► Less buffer leads to faster photobleaching.
► We designed a dye solution with half-life decay time of 55 μs.