Resolution doubling in optofluidics and sample-scanning fluorescence microscopy
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A great interest in high-throughput fluorescence microscopy for biological and medical imaging has led to the flourishing of new imaging methods where the sample is quickly scanned through the optics. Optofluidic microscopes use fluids' properties as an additional degree of freedom for optical detection and microfluidics to perform simple and low-cost object manipulation. Even though several devices have been optimized for fluorescence-based imaging, these systems can rarely resolve sub-micron details, posing a limit to the structures that can be studied. An exception is represented by systems developed for particle detection, which are capable to quantify protein expression and analyze small molecules even at nanoscale resolution. However, in this case, high resolution requires a low emitter density and it cannot be used to visualize densely packed structures such as membranes and organelles. Hence, we have developed a system for sub-diffractionlimited optofluidic scanning microscopy (OSM) that uses the optofluidics paradigm to extract the inherent super-resolution information of a confocal system. OSM uses the optofluidic flow scanning scheme and a multifocal illumination pattern to obtain resolution doubling with minimal system complexity. In addition, it does not require any mechanical part for the scanning, so that it can be readily adapted to different levels of integration from commercial microscopes to on-chip configurations. This makes our system the most viable configuration for super-resolution optofluidics, being both suitable for continuous flow scanning and compatible with on-chip configurations through the adoption of integrated optics, like custom micro-lenses or Fresnel zone plates. Finally, we demonstrate how the same concept can be adapted to digital slide scanners for super-resolution whole slide imaging.