Quantitative phase imaging for tracing the motion of waveguide trapped bead particle

Abstract

Motility of cells plays an important role to determine the cell growth, health and to monitor the gene transformation. The aim of the current study is to propose a combination of a high-contrast label-free imaging method and a computational approach (conventionally used for super-resolution) which can be used as a tool in tracing the motion of the cells and organelles. Here, we integrate quantitative phase microscopy (QPM) with waveguide-based trapping (WT) and applied multiple signal classification algorithm (MUSICAL) to analyze the motion of the trapped particle. We successfully trapped and displaced a 1µm polystyrene bead particle on a strip waveguide using a 1064 nm laser beam. While propelling the polystyrene bead particle, we recorded time-lapsed interferometric images using a partially spatially coherent (PSC) lightbased off-axis QPM system. The reconstruction of time-lapsed phase images of the trapped particle is accomplished using the Fourier transform and transport of intensity algorithm, which further used in MUSICAL for the motion trace analysis. Here, we traced the motion of a trapped bead particle with scale finer than the size of the object i.e., diffraction limit of the system. We show super-resolved motion trace even though the particle's image is itself diffraction limited in each frame. The proposed study could be useful in different biological applications such as cell monitoring, cell tracking, manipulation, and classification between healthy and unhealthy cells.