Mehak Sharma

Quantitative Phase Imaging (QPI) is increasingly recognized as a potent, label-free technique for visualizing cells and tissues. This method seeks to quantify the optical phase delay introduced by variations in the refractive index, thereby facilitating non-invasive imaging of transparent structures. 1–3 Consequently, it enables the 2D, 3D, and 4D long-term imaging of cellular structures. In this study, 4D imaging will be realized through multiplane imaging, akin to the approach delineated by Descloux et al.1 Darkfield microscopy is an illumination technique that enhances contrast by omitting un-scattered light from the resultant image. Traditional darkfield microscopy necessitates a high numerical aperture (NA) condenser, which restricts the objective's NA to around 1. However, by strategically placing a mask in the Fourier plane of the microscope, darkfield images can be obtained using standard brightfield illumination. This project aims to validate the system initially on standard samples (e.g., gratings) to evaluate its phase imaging capabilities, before transitioning to biologically pertinent applications such as temperature measurements. The refractive index, particularly in liquid samples, is sensitive to temperature changes, generally decreasing as temperature increases due to liquid expansion. This characteristic is instrumental in determining temperature elevations induced by nanoparticles in photothermal therapy.