Determination of volume, shape and refractive index of individual blood platelets

An unambiguous derivation of the effective refractive index of biological suspensions and an extension to dense tissue such as blood

The van de Hulst formula provides an expression for the effective refractive index or effective propagation constant of a suspension of particles of arbitrary shape, size and refractive index in an optically homogeneous medium. However, its validity for biological matter, which often consists of very dense suspensions of cells, is unclear because existing derivations of the formula or similar results rely on far-field scattering and/or on the suspension in question being dilute. We present a derivation of the van de Hulst formula valid for suspensions of large, tenuous scatterers -- the type b…

Scattering oblique plane microscopy for in-vivo blood cell imaging

Oblique plane microscopy (OPM) enables high speed, volumetric fluorescence imaging through a single-objective geometry. While these advantages have positioned OPM as a valuable tool to probe biological questions in animal models, its potential for in vivo human imaging is largely unexplored due to its typical use with exogenous fluorescent dyes. Here we introduce a scattering-contrast oblique plane microscope (sOPM) and demonstrate label-free imaging of blood cells flowing through human capillaries in vivo. The sOPM illuminates a capillary bed in the ventral tongue with an oblique light sheet,…

折射率高达2.7的TiO₂溶胶-凝胶涂层锐钛矿-金红石转变研究

Investigation of the anatase-to-rutile transition for TiO$_2$ sol-gel coatings with refractive index up to 2.7

本文研究了溶胶-凝胶TiO₂涂层在不同退火条件下锐钛矿向金红石的转变，制备出折射率高达2.7、光学损耗低至0.5%的薄膜，并揭示了片晶形成机制及其对光学损耗的影响。

Holographic intravital microscopy for 2-D and 3-D imaging intact circulating blood cells in microcapillaries of live mice

Intravital microscopy is an essential tool that reveals behaviours of live cells under conditions close to natural physiological states. So far, although various approaches for imaging cells in vivo have been proposed, most require the use of labelling and also provide only qualitative imaging information. Holographic imaging approach based on measuring the refractive index distributions of cells, however, circumvent these problems and offer quantitative and label-free imaging capability. Here, we demonstrate in vivo two- and three-dimensional holographic imaging of circulating blood cells in …

Total 3D imaging of phase objects using defocusing microscopy: application to red blood cells

We present Defocusing Microscopy (DM), a bright-field optical microscopy technique able to perform total 3D imaging of transparent objects. By total 3D imaging we mean the determination of the actual shapes of the upper and lower surfaces of a phase object. We propose a new methodology using DM and apply it to red blood cells subject to different osmolality conditions: hypotonic, isotonic and hypertonic solutions. For each situation the shape of the upper and lower cell surface-membranes (lipid bilayer/cytoskeleton) are completely recovered, displaying the deformation of RBCs surfaces due to a…

Optical diffraction tomography using a digital micromirror device for stable measurements of 4-D refractive index tomography of cells

Optical diffraction tomography (ODT) is an interferometric microscopy technique capable of measuring 3-D refractive index (RI) distribution of transparent samples. Multiple 2-D holograms of a sample illuminated with various angles are measured, from which 3-D RI map of the sample is reconstructed via the diffraction theory. ODT has been proved as a powerful tool for the study of biological cells, due to its non-invasiveness, label-free and quantitative imaging capability. Recently, our group has demonstrated that a digital micromirror device (DMD) can be exploited for fast and precise control …