Moving shot, an affordable and high-throughput setup for direct imaging of fast-moving microdroplets

Droplet microfluidics have a great potential in chemical and biomedical applications, due to their high throughput, versatility, and massive parallelism. To enhance their throughput, many devices based on the droplet microfluidics are using a flow-through configuration, in which the droplets are generated, transported, and analyzed in a continuous stream with a high velocity. Direct imaging of moving droplets is often necessary to characterize the spatiotemporal dynamics of the chemical reaction and physical process in the droplets. However, due to the motion blur caused by the movement of the droplets during exposure, an expensive high-speed camera is required for clear imaging, which is cost prohibitive in many applications. In this paper, we are presenting ‘Moving shot’ to demonstrate direct imaging of fast-moving droplets in microfluidic channels at an affordable cost. A microfluidic device is translated at the same velocity but in the opposite direction of moving droplets in it, so that the droplets are stationary with respect to the objective lens. With this approach, we can image fluorescent droplets moving at 0.34 cm s⁻¹ with an exposure time up to 2 s without motion blur. We strongly believe that the proposed technique can enable cost-effective and high-throughput imaging of fast-moving droplets in a microfluidic channel.