Particle trapping and binding in optical potential wells provide a versatile platform for various biomedical applications. However, implementation systems to study multi-particle contact interactions ...in an optical lattice remain rare. By configuring an optofluidic lattice, we demonstrate the precise control of particle interactions and functions such as controlling aggregation and multi-hopping. The mean residence time of a single particle is found considerably reduced from 7 s, as predicted by Kramer's theory, to 0.6 s, owing to the mechanical interactions among aggregated particles. The optofluidic lattice also enables single-bacteria-level screening of biological binding agents such as antibodies through particle-enabled bacteria hopping. The binding efficiency of antibodies could be determined directly, selectively, quantitatively and efficiently. This work enriches the fundamental mechanisms of particle kinetics and offers new possibilities for probing and utilising unprecedented biomolecule interactions at single-bacteria level.
Cell refractive index is a key biophysical parameter, which has been extensively studied. It is correlated with other cell biophysical properties including mechanical, electrical and optical ...properties, and not only represents the intracellular mass and concentration of a cell, but also provides important insight for various biological models. Measurement techniques developed earlier only measure the effective refractive index of a cell or a cell suspension, providing only limited information on cell refractive index and hence hindering its in-depth analysis and correlation. Recently, the emergence of microfluidic, photonic and imaging technologies has enabled the manipulation of a single cell and the 3D refractive index of a single cell down to sub-micron resolution, providing powerful tools to study cells based on refractive index. In this review, we provide an overview of cell refractive index models and measurement techniques including microfluidic chip-based techniques for the last 50 years, present the applications and significance of cell refractive index in cell biology, hematology, and pathology, and discuss future research trends in the field, including 3D imaging methods, integration with microfluidics and potential applications in new and breakthrough research areas.
Cell refractive index is an important biophysical parameter, which provides new biological and biomedical insight for disease diagnosis and cell biology.
Quantum key distribution (QKD) is a quantum communication technology that promises unconditional communication security. High-performance and cost-effective QKD systems are essential for the ...establishment of quantum communication networks1–3. By integrating all the optical components (except the laser source) on a silicon photonic chip, we have realized a stable, miniaturized and low-cost system for continuous-variable QKD (CV-QKD) that is compatible with the existing fibre optical communication infrastructure4. Here, the integrated silicon photonic chip is demonstrated for CV-QKD. It implements the widely studied Gaussian-modulated coherent state protocol that encodes continuous distributed information on the quadrature of laser light5,6. Our proof-of-principle chip-based CV-QKD system is capable of producing a secret key rate of 0.14 kbps (under collective attack) over a simulated distance of 100 km in fibre, offering new possibilities for low-cost, scalable and portable quantum networks.
An optofluidic chip is demonstrated in experiments for high-resolution and multi-range particle separation through the optically-induced microscopic vibration effect, where nanoparticles are trapped ...in loosely overdamped optical potential wells created with combined optical and fluidic constraints. It is the first demonstration of separating single nanoparticles with diameters ranging from 60 to 100 nm with a resolution of 10 nm. Nanoparticles vibrate with an amplitude of 3-7 μm in the loosely overdamped potential wells in the microchannel. The proposed optofluidic device is capable of high-resolution particle separation at both nanoscale and microscale without reconfiguring the device. The separation of bacteria from other larger cells is accomplished using the same chip and operation conditions. The unique trapping mechanism and the superb performance in high-resolution and multi-range particle separation of the proposed optofluidic chip promise great potential for a diverse range of biomedical applications.
•Light focusing in optofluidic waveguides is used as the detection signal for chemical reaction monitoring.•The optimized operating conditions of r and Pe are obtained for better sensitivity.•The ...method has broad applications in microreactors, chemical synthesis, and quantification of biomolecular interactions.
This paper studies the light focusing phenomenon in optofluidic waveguides and uses it to monitor chemical reactions. Firstly, the relationship between the light focusing pattern and its contributing factors is investigated experimentally. Next, a characterization experiment is conducted to validate the use of light focusing pattern as an indicator of diffusion properties. The sensitivity and the limit-of-detection (LOD) are measured to be 1.54 μm/(μm2/s) and 3.93 × 10−12 m2/s in the over-mixed region, respectively. Then, the sucrose hydrolysis reaction is monitored using the proposed optofluidic method as a demonstration. The initial hydrolysis rate of this reaction is measured to be 19.62 μM/min, which agrees reasonably well with the reported value. Lastly, this method is extended to determine the diffusion coefficient of binary solutions. The diffusion coefficients of ethylene glycol and glycerol in water are measured to be 5.56 ± 0.12 × 10-10 and 7.01 ± 0.20 × 10-10 m2/s, respectively. This study demonstrates a new method for potential integrated biochemical sensing and paves the way for a broad range of sensing applications in microreactors, chemical synthesis, and quantification of biomolecular interactions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Bacteriophages are considered as attractive indicators for determining drinking water quality since its concentration is strongly correlated with virus concentrations in water samples. Previously, ...bacteriophage detection was based on a plague assay that required a complicated labelling technique and a time-consuming culture assay. Here, for the first time, a label-free bacteriophage detection is reported by using droplet optofluidic imaging, which uses host-cell-containing microdroplets as reaction carriers for bacteriophage infection due to a higher contact ratio. The optofluidic imaging is based on the effective refractive index changes in the microdroplet correlated with the growth rate of the infected host cells, which is highly sensitive, i.e. can detect one E. coli cell. The droplet optofluidic system is not only used in drinking water quality monitoring, but also has high potential applications for pathogenic bacteria detection in clinical diagnosis and food industry.
This paper reports an optofluidic lens with low spherical and low field curvature aberrations through the desired refractive index profile by precisely controlling the mixing between ethylene glycol ...and deionized water in an optofluidic chip. The experimental results demonstrate that the spherical aberration is reduced to 19.5 μm and the full width at half maximum of the focal point is 7.8 μm with a wide divergence angle of 35 degrees. In addition, the optofluidic lens can focus light at different off-axis positions on the focal plane with Δx' < 6.8 μm and at opposite transverse positions with |Δy - Δy'| < 5.7 μm. This is the first demonstration of a special optofluidic lens that significantly reduces both the spherical and field curvature aberrations, which enhances the focusing power and facilitates multiple light source illumination using a single lens. It is anticipated to have high potential for applications such as on-chip light manipulation, sample illumination and multiplexed detection.
The original version of this Article omitted the author Kuan Wang, who is from the 'College of Biomedical Engineering, Taipei Medical University, Taipei 11031, Taiwan' and 'Nanyang Environment & ...Water Research Institute, Nanyang Technological University, Singapore 637141, Singapore.'Also, the author S.H. Lim was incorrectly given as L.S. Hoi and A. Larsson was incorrectly given as A. Larson.The "Author contributions" was amended to reflect the authorship changes. It previously read 'Y.Z.S., C.-W.Q., and A.Q.L. jointly conceived the idea. Y.Z.S., S.X., Y.Z., J.B.Z., W.S., J.H.W., T.N.C., Z.C.Y., Y.L.H., B.L., P.H.Y., D.P.T., and C.-W.Q. performed the numerical simulations and theoretical analysis. Y.Z.S., S.X., and L.K.C. did the fabrication and experiments of particle hopping, biomolecule binding and flow cytometry. A.L. and L.S.H. did the SPR experiments. S.X., Y.Z.S., Y.Z., C.-W.Q., Y.-Y.C., L.K.C., T.H.Z., and A.Q.L. prepared the manuscript. S.X., Y.Z., C.-W.Q., and A.Q.L. supervised and coordinated all the work. All authors commented on the manuscript.' The correct version states 'B.L., K. W., P.H.Y.' instead of 'B.L., P.H.Y.' and 'S.H.L.' in place of 'L.S.H.'This has been corrected in both the PDF and HTML versions of the Article.
In this paper, for the first time, an on-chip optofluidic imaging system is innovated to measure the biophysical signatures of single waterborne bacteria, including both their refractive indices and ...morphologies (size and shape), based on immersion refractometry. The key features of the proposed optofluidic imaging platform include (1) multiple sites for single-bacterium trapping, which enable parallel measurements to achieve higher throughput, and (2) a chaotic micromixer, which enables efficient refractive index variation of the surrounding medium. In the experiments, the distinctive refractive index of Echerichia coli, Shigella flexneri and Vibrio cholera are measured with a high precision of 5 × 10(-3) RIU. The developed optofluidic imaging system has high potential not only for building up a database of biophysical signatures of waterborne bacteria, but also for developing single-bacterium detection in treated water that is in real-time, label-free and low cost.
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