Platelets are multifunctional cells whose primary function is to stop bleeding through stimulus-dependent activation. In addition to the hemostatic process, platelets are also involved in pathological thrombosis. Furthermore, according to recent reports, platelet activation and thrombus formation are a crucial factor in predicting the severity of COVID-19. However, due to the highly dynamic nature of platelets, traditional technologies fail to provide comprehensive information of platelets. Fortunately, the advent of optical time-stretch imaging enables the high-throughput, label-free single-cell imaging for analyzing platelets and platelet aggregates in blood. Recent studies also show that a combination of optical timestretch imaging, microfluidics, and deep learning provides a promising laboratory testing tool for examining the morphology of platelets on a large scale. This review article introduces the principles of optical time-stretch imaging and its application to the diagnosis of COVID-19-associated thrombosis.
