A microfluidic fluorescence measurement system using an astigmatic diffractive microlens array

We demonstrate an opto-fluidic detection system based on an array of astigmatic diffractive microlenses integrated into a microfluidic flow focus device. Each astigmatic microlens produces a line excitation across the channel and collects fluorescence emission from the linear detection regions. The linear excitation spot results in uniform excitation across the channel and high time resolution in the direction of the flow. Collected fluorescence from each integrated microlens is relayed to a sub-region on a fast CMOS camera. By analyzing the signal from individual microlenses, we demonstrate counting and resolution of 500 nm and 1.1 μm beads at rates of up to 8,300 per second at multiple locations. In addition, a cross-correlation analysis of the signals from different microlenses yields the velocity dispersion of beads traveling through the channel at peak speeds as high as 560 mm/s. Arrays of specifically designed diffractive optics promise to increase the resolution and functionality of opto-fluidic analysis such as flow cytometry and fluorescence cross-correlation spectroscopy.