Results 1 - 10 of 6523
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[en] A comparative study between the standard Washburn macroscale method for determination of the capillary wetting rate in a nonwoven textile fibre mesh and the polarization optical video-microscopy-based microscale method for investigation of the wetting process in single fibres is reported. The study was performed with profiled polyester fibres associated with superior wicking performance. Both methods resulted in very similar values of the wetting rate, which confirms that for textile materials based on such type of fibres the microstructure of a single fibre dictates liquid transport properties on the micro- as well as on the macroscale. Consequently, for such materials the microscale method is fully competitive with the standard macroscopic approaches. (paper)
[en] In the past two decades or so, there has been a renaissance of optical microscopy research and development. Much work has been done in an effort to improve the resolution and sensitivity of microscopes, while at the same time to introduce new imaging modalities, and make existing imaging systems more efficient and more accessible. In this review, we look at two particular aspects of this renaissance: computational imaging techniques and compact imaging platforms. In many cases, these aspects go hand-in-hand because the use of computational techniques can simplify the demands placed on optical hardware in obtaining a desired imaging performance. In the first main section, we cover lens-based computational imaging, in particular, light-field microscopy, structured illumination, synthetic aperture, Fourier ptychography, and compressive imaging. In the second main section, we review lensfree holographic on-chip imaging, including how images are reconstructed, phase recovery techniques, and integration with smart substrates for more advanced imaging tasks. In the third main section we describe how these and other microscopy modalities have been implemented in compact and field-portable devices, often based around smartphones. Finally, we conclude with some comments about opportunities and demand for better results, and where we believe the field is heading. (review)
[en] We describe a unique and convenient approach to multimodal hyperspectral optical microscopy, herein achieved by coupling a portable and transferable hyperspectral imager to various optical microscopes. The experimental and data analysis schemes involved in recording spectrally and spatially resolved fluorescence, dark field, and optical absorption micrographs are illustrated through prototypical measurements targeting selected model systems. Namely, hyperspectral fluorescence micrographs of isolated fluorescent beads are employed to ensure spectral calibration of our detector and to gauge the attainable spatial resolution of our measurements; the recorded images are diffraction-limited. Moreover, spatially over-sampled absorption spectroscopy of a single lipid (18:1 Liss Rhod PE) layer reveals that optical densities on the order of 10-3 may be resolved by spatially averaging the recorded optical signatures. We also briefly illustrate two applications of our setup in the general areas of plasmonics and cell biology. Most notably, we deploy hyperspectral optical absorption microscopy to identify and image algal pigments within a single live Tisochrysis lutea cell. Overall, this work paves the way for multimodal multidimensional spectral imaging measurements spanning the realms of several scientific disciples.
[en] We investigated the interactions between selected organic tanning agents and type I fibrillar collagen as a model fibrillar substrate to enable the fast direct evaluation and validation of interpretations of tanning activity. Type I fibrillar collagen (1%) as gel was used as substrate of tanning and tannic acid, resorcinol- and melamine-formaldehyde and their combination at three concentrations as crosslinking agents (tannins). To evaluate the stability of collagen during tanning, the crosslinked gels at 2.8, 4.5 and 9.0 pHs were freeze-dried as discs which were characterized by FTIR, shrinkage temperature, enzymatic degradation and optical microscopy, and the results were validated by statistical analyses. The best stability was given by combinations between resorcinol- and melamine-formaldehyde at isoelectric pH
[en] The micro-cellular foaming of two Low-density Polyethylene (LDPE) composites as the temperature increased from 140 °C to 160 °C was investigated through visualization technology with the XTL-550E OM (optical Microscopy), with which, in situ observations during heating were carried out. The results demonstrated that the relationships of N-t and D-t followed the Boltzmann and Logistic functions with higher correction coefficients beyond 0.97 through non-linear fitting. Also, the three stages (Less-foamed, Fine-foamed and Over-foamed) were obtained by the first and second derivatives of the fitting curve: (1) the first stage was the less-foamed with the rate and driving force for the cell formation as well as the growth increase with temperature; (2) the second stage was the fine-foamed with competitive interaction between the formation rate and the growth rate; (3) the third stage was the over-foamed with the formation rate and driving force at an almost zero value. Moreover, the demarcation points of the three stages by the derivatives were almost consistent with the results through the fitting equation (t 0.5 and t max) and experimentation. By contrast, certain differences existed for the three stages in the two LDPE composites. These were attributed to the heterogeneous nucleation and strengthening towards the LDPE matrix of the nano-Montmorillonite (nano-OMMT). (paper)
[en] Since its invention in 1930, Zernike phase contrast has been a pillar in optical microscopy and more recently in x-ray microscopy, in particular for low-absorption-contrast biological specimens. We experimentally demonstrate that hard-x-ray Zernike microscopy now reaches a lateral resolution below 30 nm while strongly enhancing the contrast, thus opening many new research opportunities in biomedicine and materials science.
[en] We present a low-cost overlay alignment metrology solution for nanoimprint lithography that uses optical microscopy, displacement-sensing algorithms, and specially-designed imprint molds that include shallow alignment marks that are visible to the optical system but do not pattern the wafer. This innovation reduces measurement distances to near zero, the optimal distance for displacement-sensing algorithms, and allows for alignment marks to occupy the same piece of wafer real estate without interfering in any way, thus saving silicon area. Additionally, the method we present does not require the comparison of alignment marks between the wafer and the mold, thus removing process variations as a variable. We fabricate the shallow-mark molds, show that the shallow alignment marks indeed do not leave a mark on the wafer, and, implementing our nDSE (nanoscale displacement sensing and estimation) techniques, we demonstrate nanoscale alignment to a precision of 35 nm, 1-σ. Given sufficient engineering refinement, we would fully anticipate achieving alignment errors down to the 1 nm range using these methods.
[en] We report a theoretical analysis and experimental study of the possibility of producing a novel type of interferometric near-field aperture probe for near-field optical microscopy systems using a fibre Fabry - Perot microcavity with a nanometre-scale aperture made in one of its output mirrors. The probe ensures a spatial resolution no worse than λ/14. (fibre optics)