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Beam profile images (a) without lens (NL); and (b) with laser focusing lens (LF); (c) Intensities of original and focused laser beam, and the focusing efficiency of the proposed lens.
Source publication
Microfluidic systems based on fluorescence detection have been developed and applied for many biological and chemical applications. Because of the tiny amount of sample in the system; the induced fluorescence can be weak. Therefore, most microfluidic systems deploy multiple optical components or sophisticated equipment to enhance the efficiency of...
Contexts in source publication
Context 1
... order to evaluate the performance of the proposed hybrid lens for laser focusing, a laser beam profiler (BEAMAGE-CCD12, Gentec-eo Inc., Quebec, QC, Canada) is used to measure the beam properties. Figure 5a and Figure 5b show the profiles of the original laser beam and the focused laser beam after passing through the proposed hybrid lens, respectively. They show that the width of the focused laser beam (315 μm) is significantly narrower than that of the original laser beam (1,725 μm). ...
Context 2
... order to evaluate the performance of the proposed hybrid lens for laser focusing, a laser beam profiler (BEAMAGE-CCD12, Gentec-eo Inc., Quebec, QC, Canada) is used to measure the beam properties. Figure 5a and Figure 5b show the profiles of the original laser beam and the focused laser beam after passing through the proposed hybrid lens, respectively. They show that the width of the focused laser beam (315 μm) is significantly narrower than that of the original laser beam (1,725 μm). ...
Citations
... Microfluidics offers control over individual or small groups of cells within tiny channels and microfluidic structures have been used to investigate the movement of mammalian cells and various microorganisms such as fungi, algae, and bacteria [123]. Their ability to produce nanoparticles with precise control over the size distribution, shape, and high encapsulation efficiency makes them valuable for various applications [124]. ...
... Some aspects of microfluidic systems are amenable to be integrated with light; for example, the use of polydimethylsiloxane (PDMS) micropatterning can enhance the effectiveness of delivering excitation light and collecting fluorescence in microfluidic systems [123]. Similarly, modern techniques in optofluidic manipulation allow the precise handling of micro-and nano-sized objects within tiny fluid samples [126]. ...
Light is a key environmental component influencing many biological processes, particularly in prokaryotes such as archaea and bacteria. Light control techniques have revolutionized precise manipulation at molecular and cellular levels in recent years. Bacteria, with adaptability and genetic tractability, are promising candidates for light control studies. This review investigates the mechanisms underlying light activation in bacteria and discusses recent advancements focusing on light control methods and techniques for controlling bacteria. We delve into the mechanisms by which bacteria sense and transduce light signals, including engineered photoreceptors and light-sensitive actuators, and various strategies employed to modulate gene expression, protein function, and bacterial motility. Furthermore, we highlight recent developments in light-integrated methods of controlling microbial responses, such as upconversion nanoparticles and optical tweezers, which can enhance the spatial and temporal control of bacteria and open new horizons for biomedical applications.
... The chemical and physical properties of Marlotherm LH are shown in Table 1. The fluorophore nile red (C 20 H 18 N 2 O 2 , Sigma Aldrich: Bellefonte, PA, USA) was initially used in the field of microfluidic systems and biology (Zhang et al. 2018;Lin et al. 2014;Greenspan and Fowler 1985). Recent studies applied the tracer for planar droplet sizing of fuel sprays, two-color thermometry and composition measurements (Koegl et al. 2019a(Koegl et al. , 2020c(Koegl et al. , 2021(Koegl et al. , 2022a. ...
The study investigates a jet impingement cooling process of a cylindrical geometry relevant for electric and electronic applications. The applied two-color detection technique enables a simultaneous determination of film temperature and film thickness. For this purpose, the heat transfer oil Marlotherm LH was doped with the temperature-sensitive fluorescence tracer nile red. The temperature determination was realized by suitable band pass filters. Preliminary spectral investigations were carried out in terms of varying dye concentration, temperature and film thickness. At high dye concentrations (up to 37.5 mg/L), reabsorption effects lead to a spectral shift toward higher wavelengths with increasing film thickness. Low dye concentrations (0.29 mg/L, 0.59 mg/L) show no film thickness dependent spectral shift. A film temperature investigation at low dye concentration showed no bias of the intensity ratio due to film thickness, i.e., no additional spectral shift toward lower wavelengths was observed. The investigations on the jet impingement setup revealed an increasing film temperature and decreasing film thickness with increasing solid temperature. The average film temperature increases with increasing solid temperature from 298 (solid temperature 298 K) to 308 K (solid temperature 398 K). At higher solid temperatures, the film temperature increases with distance to the stagnation zone. The average film thickness decreases with increasing solid temperature from 0.24 to 0.17 mm. At high solid temperatures, the film temperature increased with radial distance to the stagnation zone. This behavior is caused by the increasing temperature gradient with increasing solid temperature and decreasing viscosity with increasing film temperature.
... The chemical and physical properties of the investigated liquids are shown in Table 1. Nile red (C 20 H 18 N 2 O 2 , Sigma Aldrich: Bellefonte, PA, USA,) is a well-known fluorophore; the applications of Nile red were initially based in microfluidic systems and biology [85][86][87]. Recent studies utilized the tracer for planar droplet sizing of fuel sprays [57,59,88]. ...
This study investigates a novel two-color LIF (laser-induced fluorescence) technique for thermometry in coolants relevant for electric components. In principle, this diagnostic enables thermometry in liquid flows but also a simultaneous determination of film thickness and film temperature, which is relevant e.g. for jet impingement cooled electric components. Temperature measurements are based on a temperature sensitive intensity ratio of special tracers realized by suitable band pass filters within the respective emission spectra. For this purpose, the heat transfer fluids Fragoltherm F12, Marlotherm LH and a water glycol mixture WG20 (80 vol.% water, 20 vol.% glycol) and its individual components were doped with suitable tracers. The tracer Eosin-Y was utilized for polar coolants (water, WG20 and glycol) and nile red for non-polar solvents (Fragoltherm F12 and Marlotherm LH). The spectral LIF intensities were recorded for a wide range of temperatures (253 K – 393 K), which are relevant for cooling of electric motors, batteries and power electronics. Furthermore, absorption spectra were analyzed as well. The temperature dependent fluorescence measurements reveal different behavior for the polar and non-polar solvents. A temperature increase of the polar solvents (water, WG20, glycol) leads to a spectral shift of the emission peaks of Eosin-Y towards larger wavelengths (red-shifted), while the peaks of nile red in the non-polar solvents (Fragoltherm F12 and Marlotherm LH) show an opposite behavior and are blue-shifted. The highest average temperature sensitivity was achieved for Marlotherm LH (4.22 %/K), followed by Glycol (1.99 %/K), WG20 (1.80 %/K), water (1.62 %/K) and Fragoltherm F12 (1.12 %/K). These sensitivities are similar or even much higher than literature data of other LIF tracers, which were, however, not determined in those coolants. Consequently, the two novel proposed dyes for the studied heat transfer liquids enable a reliable temperature determination.
... In general, cylindrical lens can be used for various tasks in beam manipulation, which have been exploited in a range of sectors. [11][12][13][14][15][16][17][18][19][20] If the cylindrical lens is designed as variable focal length, more choices and more freedom can be brought into above applications. Meanwhile, the research on rotationally asymmetric zoom lenses is still limited compared with the spherical ones. ...
... A promising temperature insensitive dye for these group of fuels is Nile red, which was utilized for droplet sizing by the authors before [19,45]. Nile red was primarily applied in microfluidic systems and biology applications [51][52][53]. To avoid measurement uncertainties due to excitation of aromatic fuel components, the absorption should preferably take place in the visible wavelength range, to ensure that only the tracer molecules and not the solvent itself gets excited by the laser [44,48]. ...
The present study deals with droplet sizing based on laser-induced fluorescence (LIF) and Mie scattering for varied polarization of the utilized laser (parallel or perpendicular). The polarization-dependent LIF/Mie ratio is studied for micrometric droplets (25–60 µm) produced with a droplet generator. The investigations were carried out with the dye Nile red dissolved in ethanol and ethanol/iso-octane mixtures. A spectral absorption and fluorescence characterization at various dye and ethanol concentrations is carried out in a cuvette in order to identify reabsorption effects. The ${{\rm{LIF}}_{||}}$ L I F | | droplet images (index $||$ | | : parallel polarization) show a more homogeneous intensity distribution in the droplets and slightly stronger morphology-dependent resonances (MDRs) in comparison to ${{\rm{LIF}}_ \bot}$ L I F ⊥ (index $\bot$ ⊥ : perpendicular polarization). The spectral LIF emissions reveal a dependence of the MDR on the ethanol admixture. The larger the ethanol content, the lower the MDR peak, which is also shifted further to the red part of the spectrum. The Mie droplet signal images are mainly characterized by two distinct glare points, one at the entrance of the laser light (reflection) and one at the exit (first-order refraction). The ${\rm{Mi}}{{\rm{e}}_ \bot}$ M i e ⊥ images show a more pronounced entrance glare point, in comparison to ${\rm{Mi}}{{\rm{e}}_{||}}$ M i e | | , where the exit glare point is more pronounced. These observations are in accordance with the theory. The calibration curve of the micro droplet signals revealed a volumetric trend of the LIF signals and a slightly higher ${{\rm{LIF}}_ \bot}$ L I F ⊥ signal and sensitivity in comparison to ${{\rm{LIF}}_{||}}$ L I F | | . The signal ${\rm{Mie}} \bot$ M i e ⊥ follows roughly a quadratic trend on average, while ${\rm{Mie}}||$ M i e | | follows a linear trend. Consequently, the calculated ${\rm{LIF}} \bot /{\rm{Mie}} \bot$ L I F ⊥ / M i e ⊥ ratio shows a linear trend, whereas the ${\rm{LIF}}||/{\rm{Mie}}||$ L I F | | / M i e | | ratio shows a quadratic trend, which confirms theoretical calculations. A numerical simulation of the Mie signal at various detection angles shows a good agreement with the experimental data at large apertures.
... However, it increases the source signal keeping a low ratio between the desired fluorescence signal and the undesired source. A highly sensitive detector is then required to capture the fluorescence emission [9]. Adding a lens with a short focal length and relatively high numerical aperture can help increase the intensity at Micro Nano Lett. ...
... The thermal reflow process, direct writing techniques, micro-moulding methods, and inkjet printing fabricate solid miniaturized lenses [12]. On the other hand, the cylindrical lens is easy to fabricate compared to other lenses such as spherical and parabolic [9,13]. It is also easier to integrate to vertical surfaces when imprinting techniques are used. ...
... Notice that the enhancement of fluorescence intensity could have been further improved if a different lens shape had been used. However, the fabrication process of the cylindrical lens is the most simple, inexpensive, and easier to integrate with the portable device [9,13]. Performing measurements at different concentrations between 20 and 300 nM, the results indicated an increase in the emission peak by around 137-149% (see the Table S1, Supporting Information). ...
Abstract With the increasing importance of portable sensing devices, one keeps seeking possible optimization to detect the lower concentration of target molecules with reduced reagents. Here presents a method to enhance fluorescence detection through a miniature cylindrical lens integrated into an engineered PDMS cuvette with a high refractive index embedded TiO2 nanoparticles. 3D printing technique was used to develop the moulds where the custom cuvette is produced utilizing the imprinting method. LED transmitter and blue laser diode were used as the excitation light sources to verify the light and materials interactions. In all the experiments, the fluorescence detection system was set at 90° alignments without any filters. First, the square‐shaped cuvette resulted in more fluorescence detection compared to the circular one. Hence, different fluorophore holders with square shapes were designed to investigate the efficiency of the integrated lens and the TiO2 nanoparticles inclusions. Overall, the customized cuvette with integrated lens and nanoparticles demonstrated the most significant signal enhancement that reached the lower detection limit as 10 nM/L in 1 μL detection volume. This structural and material‐modified cuvette can significantly enhance fluorescent detection at a sub‐microliter scale, allowing further device miniaturization, especially for micro and nano fluidic devices using optical detection.
... A promising temperature insensitive dye for these group of fuels is Nile red, which was utilized for droplet sizing by the authors before [19,45]. Nile red was primarily applied in microfluidic systems and biology applications [51][52][53]. To avoid measurement uncertainties due to excitation of aromatic fuel components, the absorption should preferably take place in the visible wavelength range, to ensure that only the tracer molecules and not the solvent itself gets excited by the laser [44,48]. ...
The present study deals with the solvent-dependent morphology-dependent resonances (MDR) in the laser-induced fluorescence (LIF) signal of monodisperse gasoline droplets (30 µm–60 µm) generated with a droplet generator. To investigate the influence of an ethanol addition to gasoline and the respective LIF signal of the dye nile red dissolved in these fuel blends, a reference gasoline fuel is blended with various ethanol concentrations from E0 (gasoline) to E100 (pure ethanol). A spectral fluorescence characterization of the investigated fuel mixtures at various concentrations is carried out in a micro cell in order to identify the dye and ethanol concentration influence of the respective fuel mixtures. The absorption and emission spectra of the fuel mixtures show a Stokes shift with increasing ethanol concentration towards larger wavelengths. The coefficient of variation (COV) of the fluorescence signals of spherical droplets was utilized to characterize the MDR effects within the droplet LIF images. The investigations revealed an increase of MDR contribution in terms of the COV of LIF signals with larger droplet diameters. For small droplets, no monotonic trend was found for contribution of MDR in the LIF signal as a function of the ethanol concentration. For larger droplets (e.g., 50 µm–60 µm), a lower contribution of MDR in LIF signals was observed with increasing ethanol content. For E80 and most of the studied ethanol blends, the normalized integrated COV values exhibited maxima at certain droplet sizes (40 µm, 47.5 µm, and 55 µm), which indicate the presence of distinct MDR effects.
... (2020) and mainly pyrromethene and its derivatives (e.g., 597-8C9, 597-C8) are applied, but the fluorescence strongly depends on temperature so that this dye is mainly used for thermometry (Depredurand et al. 2008(Depredurand et al. , 2010Palmer et al. 2018). The tracer Nile red (C 20 H 18 N 2 O 2 ) is one promising tracer, which is commonly used in microfluidic and in biology applications (Zhang et al. 2018;Lin et al. 2014;Greenspan and Fowler 1985). It is also soluble in realworld fuels (Durst et al. 2018). ...
A novel planar droplet sizing (PDS) technique based on laser-induced fluorescence (LIF) and Mie-scattering is utilized for the characterization of the spray structure under gasoline direct-injection spark-ignition (DISI) conditions. Fuel effects on the spray structure and cyclic variations are studied for a gasoline surrogate fuel (Toliso, consisting of 65 vol.% isooctane and 35 vol.% toluene) and the gasoline-ethanol blend E20 (20 vol.% ethanol admixture). Sauter mean diameter (SMD) results are compared with those from phase-Doppler anemometry (PDA) measurements showing good agreement especially at early points in time (up to 1.2 ms after start of injection). The liquid spray propagation and SMD are very similar for both fuels indicating similar atomization behavior. Both investigated fuels show comparable cyclic variations of the spray shape. A larger width and slightly larger droplet sizes are observed for the E20 spray when stronger evaporation occurs (at 2 ms). At these later points in time, the PDS-measured droplet sizes differ from the PDA-results. Here the limitation of the PDS-technique becomes obvious as a partial evaporation of the droplets may lead to large systematic errors. A numerical simulation of single droplets is provided for clarification of issues of droplet evaporation in PDS.
Graphic abstract
... Consequently, this dye is suitable for the investigations in the present study. In addition, the tracer nile red is commonly used in microfluidic systems and in biology applications [29][30][31]. ...
In this work, the possibility of using planar droplet sizing (PDS) based on laser-induced fluorescence (LIF) and Mie scattering was investigated within the framework of measuring the droplet Sauter mean diameter (SMD) of direct-injection spark-ignition (DISI) spray systems. For this purpose, LIF and Mie signals of monodisperse fuel droplets produced by a droplet generator were studied at engine relevant diameters (20–50 µm). The surrogate gasoline fuel Toliso (consisting of 65 vol. % isooctane, 35 vol. % toluene) and the biofuel blend E20 (consisting of 80 vol. % Toliso, 20 vol. % ethanol) were used and which were doped with the fluorescence dye “nile red”. The effects of ethanol admixture, dye concentration, laser power, and temperature variation on the LIF/Mie ratio were studied simultaneously at both macroscopic and microscopic scale. The deduced calibration curves of the LIF and Mie signals of both fuels showed volumetric and surface dependent behaviors, respectively, in accordance with the assumptions in the literature. The existence of glare points and morphology-dependent resonances (MDRs) lead to slightly higher LIF and Mie exponents of E20 in comparison to Toliso. In principle, these calibration curves enable the determination of the SMD from LIF/Mie ratio images of transient fuel sprays.
... However, due to its temperature sensitivity, it is not applicable for LIF/Mie droplet sizing but is commonly used for thermometry [33,34]. The tracer nile red (C 20 H 18 N 2 O 2 ), which is mainly used in microfluidic systems and in biology applications [35][36][37], is another dye that can also be dissolved in real-world fuels [32]. However, its fluorescence characteristics have no yet been quantified for varying conditions, which is the topic of the present study. ...
Suitable fluorescence tracers (“dyes”) are needed for the planar measurement of droplet sizes by using a combination of Laser-Induced Fluorescence (LIF) and Mie scattering. Currently, no suitable tracers are characterized for application in planar droplet sizing in gasoline and kerosene fuels as well as biofuel blends. A promising tracer is nile red, which belongs to the group of fluorophores. For its utilization for droplet size measurements, preliminary characterization of the fluorescence of the respective fuel tracer mixtures are mandatory. For this purpose, the fluorescence and absorption behaviour of nile red dissolved in the surrogate fuels Toliso and Jet A-1 as well as in biofuel blends was investigated. The fluorescence signal for nile red dissolved in the two base fuels Toliso and Jet A-1 showed a linear behaviour as a function of the dye concentrations. The temperature effect on spectral absorption and emission of nile red was investigated in a specially designed test cell. An ethanol admixture to Toliso leads to a spectral shift towards higher wavelengths. The absorption and emission bands are shifted towards lower wavelengths with increasing temperature for all fuels. Both absorption and fluorescence decrease with higher temperature for all fuels, except for E20, which showed an increased fluorescence signal with increasing temperature. Jet A-1 and its blends with Hydroprocessed Esters and Fatty Acids (HEFA) and Farnesane did not exhibit explicit variations in spectral absorption or emission, but these blends showed a more distinct temperature dependence compared to the Toliso-ethanol-blends. The effect of photo-dissociation of the LIF signal of the fuel tracer mixtures was studied and all fuel mixtures besides Toliso showed a more or less distinct decay in the fluorescence signal with time. In summary all investigated fuel-tracer mixtures are suitable for LIF/Mie ratio droplet sizing in combination with nile red at moderate temperatures and low evaporation cooling rates.
