Optical time-stretch microscopy : a new tool for ultrafast and high-throughput cell imaging

Abstract

The exponential expansion in the field of biophotonics over the past half-century has been leading to ubiquitous basic science investigations, ranging from single cell to brain networking analysis. There is also one biophotonics technology used in clinic, which is optical coherence tomography, mostly for high-speed and high-resolution endoscopy. To keep up such momentum, new biophotonics technologies should be aiming at improving either the spatial resolution or temporal resolution of optical imaging. To this end, this thesis will address a new imaging technique which has an ultra-high temporal resolution. The applications and its cost-effective implementations will also be encompassed. In the first part, I will introduce an entirely new optical imaging modality coined as optical time-stretch microscopy. This technology allows ultra-fast real-time imaging capability with an unprecedented line-scan rate (~10 million frames per second). This ultrafast microscope is renowned as the world’s fastest camera. However, this imaging system is previously not specially designed for biophotonics applications. Through the endeavors of our group, we are able to demonstrate this optical time-stretch microscopy for biomedical applications with less biomolecules absorption and higher diffraction limited resolution (<2 μm). This ultrafast imaging technique is particularly useful for high-throughput and high-accuracy cells/drugs screening applications, such as imaging flow cytometry and emulsion encapsulated drugs imaging. In the second part, two cost-effective approaches for implementing optical time-stretch confocal microscopy are discussed in details. We experimentally demonstrate that even if we employ the two cost-effective approaches simultaneously, the images share comparable image quality to that of captured by costly specialty 1μm fiber and high-speed ( >16 GHz bandwidth) digitizer. In other words, the cost is drastically reduced while we can preserve similar image quality. At the end, I will be wrapping up my thesis by concluding all my work done and forecasting the future challenges concerning the development of optical time-stretch microscopy. In particular, three different research directions are discussed.