microscopy (2)

NEMS Photothermal Microscopy...


Topics: Microscopy, Nanotechnology, NEMS, Physics, Research

Single-molecule microscopy has become an indispensable tool for biochemical analysis. The capability of characterizing distinct properties of individual molecules without averaging has provided us with a different perspective for the existing scientific issues and phenomena. Recently, super-resolution fluorescence microscopy techniques have overcome the optical diffraction limit by the localization of molecule positions. However, the labeling process can potentially modify the intermolecular dynamics. Based on the highly sensitive nanomechanical photothermal microscopy reported previously, we propose optimizations on this label-free microscopy technique toward localization microscopy. A localization precision of 3 Å is achieved with gold nanoparticles, and the detection of polarization-dependent absorption is demonstrated, which opens the door for further improvement with polarization modulation imaging.


FIG. 2. (a) Schematic of the measurement setup. BE: beam expander. M: mirror. WP: waveplate. LP: linear polarizer. BS: beam splitter. PD: photodetector/power meter. DM: dichroic mirror. ID: iris diaphragm. CCD: charge-coupled device camera. APD: avalanche photodiode detector. (b) The transduction scheme of the trampoline resonator. (c) SEM image of the trampoline resonator.

J. Appl. Phys. 128, 134501 (2020); https://doi.org/10.1063/5.0014905

Nanoelectromechanical photothermal polarization microscopy with 3 Å localization precision, Miao-Hsuan Chien and Silvan Schmid, Journal of Applied Physics

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Holographic Microscopy...


FIG. 1. (a) Schematic of an inline digital holographic microscope. In a typical setup, a collimated laser (light red) illuminates a sample, which scatters light (dark red wavefronts). The transmitted and scattered light passes through an objective and tube lens, which focuses the light onto a digital camera. (b) A hologram of a polystyrene particle obtained from an inline holographic microscope.

Topics: Holography, Optical Physics, Microscopy, Modern Physics

In the past few years, the venerable field of holographic microscopy has been revitalized by computational data analysis. It is now possible to fit a generative (forward) model of scattering directly to experimentally obtained holograms of complex microscopic objects. This approach enables precision measurements: it allows the motion of colloidal particles and biological organisms to be tracked with nanometer-scale precision and their optical properties to be inferred particle by particle. In this Perspective, we discuss how the model-based inference approach to holographic microscopy has opened up new applications. We also discuss how it must evolve to meet the needs of emerging applications that demand lower systematic uncertainties and higher precision. In this context, we present some new results on how modeling the optical train of the microscope can enable better measurements of the positions of spherical and nonspherical colloidal particles. Finally, we discuss how machine learning might play a role in future advances. Though we do not exhaustively catalog all the developments in this field, we show a few examples and some new results that spotlight open questions and opportunities.


Precise measurements in digital holographic microscopy by modeling the optical train, Ronald Alexander, Brian Leahy, Vinothan N. Manoharan, Journal of Applied Physics

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