A simple and intuitive methodology for estimating red blood cell surface antigen expression variation using optical cell-detachment technique

The analysis of surface antigens on cells, especially red blood cells (RBCs), has attracted increasing attention due to the recognition of antigenic variation that can facilitate early diagnoses. This paper presents an alternative methodology to estimate the variation of surface antigen expressions using an optical cell-detachment technique to validate the binding of individual RBCs stuck on corresponding antibody-coated surfaces. The detachment tests were implemented by an optical tweezers with gradually decreasing laser powers associated with serial antibody dilutions. Then, the antigen expression variation was estimated based on the known antibody dilution folds. The B- and B3-types of RBCs were selected for the demonstration subjects. With the semi-quantitative analysis, the proposed methodology was successfully verified for evaluating the variation of the RBC surface antigen expressions. The analysis result shows good consistency with the literature’s findings.

Simultaneous Absorbance and Fluorescence Measurements Using an Inlaid Microfluidic Approach

A novel microfluidic optical cell is presented that enables simultaneous measurement of both light absorbance and fluorescence on microlitre volumes of fluid. The chip design is based on an inlaid fabrication technique using clear and opaque poly(methyl methacrylate) or PMMA to create a 20.2 mm long optical cell. The inlaid approach allows fluid interrogation with minimal interference from external light over centimeter long path lengths. The performance of the optical cell is evaluated using a stable fluorescent dye: rhodamine B. Excellent linear relationships (R2 > 0.99) are found for both absorbance and fluorescence over a 0.1–10 µM concentration range. Furthermore, the molar attenuation spectrum is accurately measured over the range 460–550 nm. The approach presented here is applicable to numerous colorimetric- or fluorescence-based assays and presents an important step in the development of multipurpose lab-on-chip sensors.

An Energy Efficient Thermally Regulated Optical Spectroscopy Cell for Lab-on-Chip Devices: Applied to Nitrate Detection

Reagent-based colorimetric analyzers often heat the fluid under analysis for improved reaction kinetics, whilst also aiming to minimize energy use per measurement. Here, a novel method of conserving heat energy on such microfluidic systems is presented. Our design reduces heat transfer to the environment by surrounding the heated optical cell on four sides with integral air pockets, thereby realizing an insulated and suspended bridge structure. Our design was simulated in COMSOL Multiphysics and verified in a polymethyl methacrylate (PMMA) device. We evaluate the effectiveness of the insulated design by comparing it to a non-insulated cell. For temperatures up to 55 °C, the average power consumption was reduced by 49.3% in the simulation and 40.2% in the experiment. The designs were then characterized with the vanadium and Griess reagent assay for nitrate at 35 °C. Nitrate concentrations from 0.25 µM to 50 µM were tested and yielded the expected linear relationship with a limit of detection of 20 nM. We show a reduction in energy consumption from 195 J to 119 J per 10 min measurement using only 4 µL of fluid. Efficient heating on-chip will have broad applicability to numerous colorimetric assays.

Complex Wavefront Shaping through a Multi-Core Fiber

Wavefront shaping through a multi-core fiber (MCF) is turning into an attractive method for endoscopic imaging and optical cell-manipulation on a chip. However, the discrete distribution and the low number of cores induce pixelated phase modulation, becoming an obstacle for delivering complex light field distributions through MCFs. We demonstrate a novel phase retrieval algorithm named Core–Gerchberg–Saxton (Core-GS) employing the captured core distribution map to retrieve tailored modulation hologram for the targeted intensity distribution at the distal far-field. Complex light fields are reconstructed through MCFs with high fidelity up to 96.2%. Closed-loop control with experimental feedback denotes the capability of the Core-GS algorithm for precise intensity manipulation of the reconstructed light field. Core-GS provides a robust way for wavefront shaping through MCFs; it facilitates the MCF becoming a vital waveguide in endoscopic and lab-on-a-chip applications.

Electrically turning periodic structures in cholesteric layer with conical–planar boundary conditions

Electro-optical cell based on the cholesteric liquid crystal is studied with unique combination of the boundary conditions: conical anchoring on the one substrate and planar anchoring on another one. Periodic structures in cholesteric layer and their transformation under applied electric field are considered by polarizing optical microscopy, the experimental findings are supported by the data of the calculations performed using the extended Frank elastic continuum approach. Such structures are the set of alternating over- and under-twisted defect lines whose azimuthal director angles differ by $$180^\circ$$ 180 ∘ . The $$U^+$$ U + and $$U^-$$ U - -defects of periodicity, which are the smooth transition between the defect lines, are observed at the edge of electrode area. The growth direction of defect lines forming a diffraction grating can be controlled by applying a voltage in the range of $$0\le \, V \le 1.3$$ 0 ≤ V ≤ 1.3 V during the process. Resulting orientation and distance between the lines don’t change under voltage. However, at $$V>1.3$$ V > 1.3 V $$U^+$$ U + -defects move along the defect lines away from the electrode edges, and, finally, the grating lines collapse at the cell’s center. These results open a way for the use of such cholesteric material in applications with periodic defect structures where a periodicity, orientation, and configuration of defects should be adjusted.

Mobile- and Hot Spot Measurement with OPC based Dust Monitor EDM264

<p>With the EDM264, GRIMM offers a [A1] solution for mobile short- and long-term measurements in outdoor areas and at production sites. For research as well as permanent areal observations on a near reference quality base.</p><p>The model EDM264 features a powerful and robust measuring cell based on optical particle counting (OPC) principle with all the advantages that users of GRIMM‘s portable aerosol spectrometers  are used to. The system is embedded in a compact weather-protection housing with all-weather sampling, heated inlet system, data logger and meteorological sensor.</p><p>With TSP, PM10, PM4, PM2.5, PM1 and PMcoarse, the EDM264  provides all fine dust fractions real-time, valid for outdoor applications and calculated with the proven GRIMM enviro-algorithm, as well as six additional dust mass fractions pm10, pm2.5, pm1, inhalable, thoracic and respirable for IAQ and workplace measurements.</p><p>This highly versatile instrument performs real-time monitoring of particle number, particle size and provides information on particle surface distribution as well as dust mass distribution. GRIMM‘s EDM264 has 31 equidistant size channels, which are PSL traceable.</p><p>A high-end data logger enables data acquisition and wireless communication via LTE, WLAN or wired via Ethernet. Backup copies of the measurement data are stored in the device directly.</p><p>The rinsing air function, which protects the laser and detector in the optical cell, further increases the reliability and long term stability of the EDM264 under different environmental and climatic conditions.</p><p>The entire sample volume flow of 1.2 L/min is analyzed by 100% in the optical cell, which assures excellent counting efficiency at low and high concentrations and complies to the ISO 21501-1standard for OPCs.</p><p>With  all  these  features,  the  EDM264 is a world-leading dust monitor for precise monitoring of particulate matter and particle number concentration. This highly reliable instrument is an indispensable tool for many users, who need to measure aerosol levels and air quality outdoors, on construction sites, or at production facilities.</p><p>Keywords — aerosol research, aerial observation, fence line monitoring, wild fire detection   </p>