In this study, a portable and automatic immunoturbidimetric assay system based on multi-layered centrifugal microfluidics was developed for specific proteins identification from whole blood. With the development of society and medical technology, more and more immune system diseases have been noticed by people. Immune dysfunction in the human body can cause many immune system diseases. Therefore, the detection of specific proteins closely related to immune system diseases has been increasingly favored and paid more attention by medical and scientific researchers. However, for most automated biochemical analyzers, pretreatment and diagnosis process are separated, cannot provide a sample-to-answer solution. To solve this problem, we proposed a highly-integrated system which enables real-time sedimentation of blood cells by centrifugation and quantitative extraction of purified plasma by siphon valve. Also, it has calibration system of standard curves, as well as integrated optical detection device, leading to smaller error fluctuations. As a demonstration experiment, quantification of Immunoglobulin A (IgA) in human whole blood with our LOAD system was conducted. Calibrator sets with specified concentrations ranging from 0.6 to 6 g/L were first generated in real time on the chip. Then standard curves used for IgA quantitation were created. Our LOAD system was demonstrated to have good accuracy and high repeatability since the experimental results of IgA obtained from the LOAD system correlated very well with those from the standard automatic biochemical analyzer method. Furthermore, the LOAD system could conduct simultaneous detection of various specific proteins in the later stage.
We present a tunable experimental setup to obtain the three-dimensional refractive index distribution of microscopic biological structures. We introduce an adjustable system to change the position of the focal plane and perform stitched reconstruction. There are two main approaches for obtaining the projections of sample in optical diffraction tomography: beam scanning and rotating sample. Compared to beam scanning, the method of rotating sample allows the sample to be rotated 180° to capture uniformly distributed data, which improves the accuracy of the phase measurement and the resolution of the reconstruction result. The depth-of-field in the optical diffraction tomography setups is very small and the method of rotating sample inevitably causes the sample to deviate from the depth-of-field during the rotation, making it difficult to obtain ideal data. We divided the sample position deviation area into several ideal data acquisition areas and collected the ideal data in each area by shifting the position of the focal plane. By the combination of 180° projection method and stitched reconstruction method, we have obtained high measurement accuracy results with uniform resolution.
Optical diffraction tomography is an important method to obtain the microstructure of biological samples. We present a reconstruction process for the 3D refractive index distribution of samples in optical diffraction tomography. First, obtaining an accurate phase image by preprocessing the interference image is especially important for the reconstruction. The quality oriented method is used to perform phase unwrapping to avoid the influence of residual error. Then, the background phase is eliminated by curve fitting method, which reduces the experimental complexity and requirements. The positional deviation caused by the rotation of the sample is solved by autocorrelation algorithm. We apply a filtered back propagation algorithm based on Fourier diffraction theory to improve the accuracy of reconstruction. Finally, we have carried out experiments on samples such as photonic crystal fiber and pollen, and obtained the detailed internal structure of the samples with satisfactory results.
We developed a novel lab-on-a-chip device with the capability of rapidly antibody determination that use nano-beads as the solid carriers. The device combines a plasmon-assisted optical conveyor belt in the main microfluidic channel, which is made of gold nano-ellipses perpendicular to each other. In the presence of an external uniform electric field, the hot spots in the belt function as optical tweezers can trap and transport properly sized nano-beads with target antibody combined along a fix direction through rotating the polarization. Several branch channels intersecting the main microfluidic channel at right angles are used to transport smaller antigen modified nano-beads, which can be labeled with fluorescent dyes. When arriving at the crossings, the smaller nano-beads would be trapped by hotspots on the surface of two-dimensional ellipses arrays around the conveyor belt and can’t be transported between two ellipses due to their smaller size. So, the antibody modified nano-beads would be transported along the optical conveyor belt and encounter the trapped antigen modified ones in the ellipses arrays successively. Only those ones with specific antigen combined that stick to the antibody to be measured can be dragged by bigger nano-beads and transport with it. In light of that, we can determinate the antibody by identifying the fluorescence-labelled nano-beads at the exit of the main channel. With the capacity for parallel detection, our design offers an attractive scheme for rapid, high throughput determination of antibody in microfluidic channels, which are also ease to operate.
We developed a novel lab-on-a-chip device with the capability of rapidly pre-concentrating for Raman detection that use gold bead as the solid carrier of biomolecules. The device combines an array of patterned plasmonic surface (i.e. gold nano-ellipses), as the bead manipulation element. The purpose of gold bead manipulation is to provide sample pre-concentration in close proximity of the Raman detecting region. In the presence of an external uniform electric field, the gold ellipses create local electric field gradients (which is usually called hot spots) that capture the gold beads. The location of hot spots within a plasmonic nanostructure is polarization dependent, and inhomogeneous electric field between two adjacent nano-ellipses perpendicular to each other leads to highly unbalanced trap potential that give the chance of transferring trapped particles in a given direction through rotating the polarization. Nano-optical conveyor belts with staircase pattern of nano-ellipses were arranged with their terminus collected at detection area to gather biomolecules. With the capacity to transfer biomolecules precisely, our design offers an attractive scheme for rapid, high throughput and highly sensitive sensing of low abundance analytes.
For optical manipulation, a nano-optical conveyor belt consisting of an array of gold plasmonic non-concentric nano-rings (PNNRs) is demonstrated for the realization of trapping and unidirectional transportation of nanoparticles by polarization rotation of excitation beam. These hot spots of an asymmetric plasmonic nanostructure are polarization dependent, therefore, one can use the incident polarization state to manipulate the trapped targets. Trapped particles could be transferred between adjacent PNNRs in a given direction just by rotating the polarization of incident beam due to unbalanced potential. The angular dependent distribution of electric field around PNNR has been solved using the three- dimensional finite-difference time-domain (FDTD) technique. For optical enhanced catalytic activity, the spectral properties of dimers of Au nanorod-Au nanorod nanostructures under the excitation of 532nm photons have been investigated. With a super-resolution catalytic mapping technique, we identified the existence of "hot spot" in terms of catalytic reactivity at the gap region within the twined plasmonic nanostructure. Also, FDTD calculation has revealed an intrinsic correlation between hot electron transfer.
With the increasing demand for information, integrated silicon photonics technology has been highly valued. Among
them, silicon on insulator (SOI) has advantages of low cost, process maturity, and IC technology compatible, making
it to be one of the most competitive integrated optoelectronic platforms. However, due to its highly
polarization-dependent performance, polarization-selective devices are essential on SOI platform. In this paper, we
analyze the critical guiding condition of SOI waveguide as well as the hybrid plasmonic waveguide (HPW). Based
on the different critical guiding condition for both polarizations, we propose several polarization-selective devices on
SOI platform, including polarizer, polarization beam splitter (PBS) and polarization rotator. In this paper, an
ultracompact and broadband TE-pass polarizer based on HPW is proposed. In addition, an asymmetrical coupling
based polarization beam splitter is designed. Simulation results show that the designed devices have excellent optical
properties, and the sizes of the devices achieve a great breakthrough.
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