Lyotropic chromonic liquid crystals are water-based materials composed of self-assembled cylindrical aggregates. Their behavior under flow is poorly understood, and quantitatively resolving the ...optical retardance of the flowing liquid crystal has so far been limited by the imaging speed of current polarization-resolved imaging techniques. Here, we employ a single-shot quantitative polarization imaging method, termed polarized shearing interference microscopy, to quantify the spatial distribution and the dynamics of the structures emerging in nematic disodium cromoglycate solutions in a microfluidic channel. We show that pure-twist disclination loops nucleate in the bulk flow over a range of shear rates. These loops are elongated in the flow direction and exhibit a constant aspect ratio that is governed by the nonnegligible splay-bend anisotropy at the loop boundary. The size of the loops is set by the balance between nucleation forces and annihilation forces acting on the disclination. The fluctuations of the pure-twist disclination loops reflect the tumbling character of nematic disodium cromoglycate. Our study, including experiment, simulation, and scaling analysis, provides a comprehensive understanding of the structure and dynamics of pressure-driven lyotropic chromonic liquid crystals and might open new routes for using these materials to control assembly and flow of biological systems or particles in microfluidic devices.
Recovering tiny nanoscale features using a general optical imaging system is challenging because of poor signal to noise ratio. Rayleigh scattering implies that the detectable signal of an object of ...size d illuminated by light of wavelength λ is proportional to d
/λ
, which may be several orders of magnitude weaker than that of additive and multiplicative perturbations in the background. In this article, we solve this fundamental issue by introducing the regularized pseudo-phase, an observation quantity for polychromatic visible light microscopy that seems to be more sensitive than conventional intensity images for characterizing nanoscale features. We achieve a significant improvement in signal to noise ratio without making any changes to the imaging hardware. In addition, this framework not only retains the advantages of conventional denoising techniques, but also endows this new measurand (i.e., the pseudo-phase) with an explicit physical meaning analogous to optical phase. Experiments on a NIST reference material 8820 sample demonstrate that we can measure nanoscale defects, minute amounts of tilt in patterned samples, and severely noise-polluted nanostructure profiles with the pseudo-phase framework even when using a low-cost bright-field microscope.
The radial segregation phenomena of a mixture of two different size grains in a horizontal rotating drum are studied by DEM simulations. The grano-dynamics of radial segregation phenomena is examined ...as a function of the axial length and the friction between grains and not-rotating end-plates of the drum. The results indicate that, in the longer drums, the radial segregation ratio is higher and the friction on the end-plates shows little effect. Whereas in the shorter drums, the radial segregation is very slow or negligible; however, decreasing the friction on non-rotating end-plates increases the segregation ratio. If we increase the friction further (greater than the frictions between the grain-grain and the grains and the inner wall), the segregation ratio drops in the longer drums while in the shorter drums mixing is seen instead. The cause of these phenomena lies in the mechanism of diffusion in granular flows due to shearing strain by the end-plates. For more roughened end-plates, this shearing activity increases the granular temperature of the system and only the mixing can be observed instead of the segregation.
► DEM simulations of radial segregation in horizontal granular. ► Effect of roughened end-plates and drum length on radial segregation. ► In longer drums the segregation ratio is higher than for the shorter drum. ► Lower friction on non-rotating side-plates shows higher segregation. ► These phenomena are due to the diffusive collisions of particles in the active layer.
Instead of various mathematical stitching algorithms, an aspheric subaperture stitching interferometric method relying on modern computer modeling technique is presented. Based on our previously ...reported non-null annular subaperture stitching interferometry (NASSI), a simultaneous reverse optimizing reconstruction (SROR) method based on system modeling is proposed for full aperture figure error reconstruction. All the subaperture measurements are simulated simultaneously with a multi-configuration model in a ray tracing program. With the multi-configuration model, full aperture figure error would be extracted in form of Zernike polynomials from subapertures wavefront data by the SROR method. This method concurrently accomplishes subaperture retrace error and misalignment correction, requiring neither complex mathematical algorithms nor subaperture overlaps. Experiment results showing the validity of SROR method are presented.
A method for high-resolution imaging that we call virtual fluorescence emission difference microscopy (vFED) is presented. In vFED the analyzed samples are scanned only by a doughnut-shaped pattern ...and imaged by a detector array, which is very different from the previous FED system. By using photon reassignment, we can obtain imaging results with matched solid and hollow point spread functions, and the difference between them is used to estimate the spatial distribution of the analyzed sample. This method results in greatly simplified equipment in the configuration and enhanced imaging speed. Results show that the resolution can be enhanced by at least 27% compared with that in confocal microscopy with a point detector, or is 1.8-2-fold higher than that in wide-field microscopy. Plus, negative intensities can be avoided by using vFED during the subtraction process, leading to the elimination of the deformation in reconstructed images.
Optical anisotropy measurement is essential for material characterization and biological imaging. In order to achieve single‐shot mapping of the birefringence parameters of anisotropic samples, a ...novel polarized light imaging concept is proposed, namely quantitative polarization interference microscopy (QPIM). QPIM can be realized through designing a compact polarization‐resolved interference microscopy system that captures interferograms bearing sample's linear birefringence information. To extract the retardance and the orientation angle maps from a single‐shot measurement, a mathematical model for QPIM is further developed. The QPIM system is validated by measuring a calibrated quarter‐wave plate, whose fast‐axis orientation angle and retardance are determined with great accuracies. The single‐shot nature of QPIM further allows to measure the transient dynamics of birefringence changes in material containing anisotropic structures. This application is demonstrated by capturing transient retardance changes in a custom‐designed parallel‐aligned nematic liquid crystal‐based device.
Quantitative polarization interference microscopy (QPIM) is developed for mapping birefringence parameters in a single‐shot acquisition, which is a new advance in optical microscopy. By providing new quantitative imaging information (e.g., mapping stress and grain boundaries of 2D materials and microtubules in cells), QPIM is expected to contribute to research discoveries in material and biology in the near future.
Virtual fluorescence emission difference microscopy (vFED) has been proposed recently to enhance the lateral resolution of confocal microscopy with a detector array, implemented by scanning a ...doughnut-shaped pattern. Theoretically, the resolution can be enhanced by around 1.3-fold compared with that in confocal microscopy. For further improvement of the resolving ability of vFED, a novel method is presented utilizing fluorescence saturation for super-resolution imaging, which we called saturated virtual fluorescence emission difference microscopy (svFED). With a point detector array, matched solid and hollow point spread functions (PSF) can be obtained by photon reassignment, and the difference results between them can be used to boost the transverse resolution. Results show that the diffraction barrier can be surpassed by at least 34% compared with that in vFED and the resolution is around 2-fold higher than that in confocal microscopy.
•A novel method utilizing fluorescence saturation for super-resolution imaging based on a detector array is proposed.•The diffraction can be surpassed by at least 34% compared with that in virtual fluorescence emission difference microscopy (vFED) and the resolution is around 2-fold higher than that in confocal microscopy.•Photon reassignment is used in our method and only one saturated hollow excitation pattern is used to illuminate the sample, which shows greatly simplified configuration and high imaging speed.
A novel fluorescence emission difference method is proposed to improve the lateral resolution of SPCEM without increasing instrument complexity. We discovered the profile of transverse PSF in SPCEM ...will dramatically change from a hollow spot to a solid spot, when the axial position of sample varies within one wavelength in the vicinity of the focal plane. The subtraction of an image whose PSF is hollow spot and an image with solid PSF will greatly enhance the resolution and contrast of SPCEM images. The mechanism of the distinctive PSF is demonstrated through basic optics theories, and the improvement of lateral resolution is verified by theoretical simulations and experimental results. It is believed that our method will stand out for its pleasant resolution enhancement and its instruments' simplicity to facilitate many biological cellular observations.
We proposed a novel method to reconstruct images taken by array detected confocal microscopy without prior knowledge about its detector distribution. The proposed frequency domain phase-shifted ...confocal microscopy (FDPCM) shifts the image from each detection channel to its corresponding place by substituting the phase information in Fourier domain. Theoretical analysis shows that our method could approach the resolution nearly twofold of wide-field microscopy. Simulation and experiment results are also shown to verify the applicability and effectiveness of our method. Compared to Airyscan, our method holds the advantage of simplicity and convenience to be applied to array detectors with different structure, which makes FDPCM have great potential in the application of biomedical observation in the future.
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