On high spatial resolution scalar measurement with LIF

Wang, G. R.; Fiedler, H. E.

doi:10.1007/s003489900083

Cited by 29 publications

(24 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…For microfluidics in bioanalytical systems, flow velocity is often in the range of 10 mm s 21 -10 mm s 21 . This can easily be measured with sufficiently high sensitivity, if we focus the laser to a cylindrical spot 46 instead of the sheet in the present work for a laser beam with power of several hundreds of milliWatts. The present work used a laser sheet for a different purpose, and thus reduced the laser intensity in the detecting probe volume.…”

Section: Discussionmentioning

confidence: 99%

“…The response time of LIFPA is determined by the fluorescence photobleaching kinetics or decay time constant, which can be several hundreds of microseconds. 46 Therefore the temporal resolution of LIFPA could be in the order of milliseconds. The decay time constant can be further reduced by enhancing photobleaching.…”

Section: Discussionmentioning

confidence: 99%

“…In contrast to conventional fluorescence based diagnostics, the present study desires a fluorescence dye with strong photobleaching property. Since photobleaching can be enhanced with the increase of dye concentration, 46 a high concentration fluorescein dye solution was used in the present study to increase photobleaching. Although fluorescein has high absorption at a wavelength of 488 nm, our test shows that UV light around 337.5-356.40 nm gives stronger photobleaching and higher sensitivity.…”

Section: Methodsmentioning

confidence: 99%

“…46 In the model, fluorescence intensity of the dye increases with fluid velocity at the measuring point due to the LIFP. Such a phenomenon is considered as a negative effect for concentration measurement based on LIF, since we assume that the fluorescence intensity depends only on dye concentration.…”

Section: Theoretical Backgroundmentioning

confidence: 99%

See 3 more Smart Citations

Laser induced fluorescence photobleaching anemometer for microfluidic devices

Wang

2005

Lab Chip

Self Cite

View full text Add to dashboard Cite

We have developed a novel, non-intrusive fluid velocity measurement method based on photobleaching of a fluorescent dye for microfluidic devices. The residence time of the fluorescent dye in a laser beam depends on the flow velocity and approximately corresponds to the decaying time of the photobleaching of the dye in the laser beam. The residence time is inversely proportional to the flow velocity. The fluorescence intensity increases with the flow velocity due to the decrease of the residence time. A calibration curve between fluorescence intensity and known flow velocity should be obtained first. The calibration relationship is then used to calculate the flow velocity directly from the measured fluorescence intensity signal. The new method can measure the velocity very quickly and is easy to use. It is demonstrated for both pressure driven flow and electroosmotic flow.

show abstract

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Theoretical Backgroundmentioning

confidence: 99%

See 2 more Smart Citations

Laser induced fluorescence photobleaching anemometer for microfluidic devices

Wang

2005

Lab Chip

Self Cite

View full text Add to dashboard Cite

show abstract

“…Photobleaching is a phenomenon that occurs when a fluorophore loses the ability to fluoresce due to photon-induced chemical degradation. [28] The average number of excitation and emission cycles that occur for a particular fluorophore before photobleaching is dependent upon the molecular structure and the local environment. Some fluorophores bleach quickly after emitting only a few photons, while others can undergo thousands or millions of cycles before being bleached.…”

Section: Fluorescence Intensity Dependence On Dye Migration Velocitymentioning

confidence: 99%

Frontal analysis in microchip CE: A simple and accurate method for determination of protein–DNA dissociation constant

et al. 2007

View full text Add to dashboard Cite

Equilibrium constants, such as the dissociation constant (K d ), are a key measurement of noncovalent interactions that are of importance to the proper functioning of molecules in living systems. Frontal analysis (FA) is a simple and accurate capillary electrophoresis (CE) method for the determination of K d . Microchip CE coupled with laser-induced fluorescence (LIF) detection was used to determine K d of protein-DNA interactions using the FA method. A model system of immunoglobulin E (IgE) and the IgE-binding aptamer was selected to demonstrate the capability of FA in microchip CE. Because the fluorescence emission was dependent on the dye migration velocity, the velocity of the free aptamer was adjusted to be the same as that of the aptamer-IgE complex by setting up individual separation voltage configurations for the free and bound aptamers. The ratio of the free and bound aptamers in the equilibrium mixture was directly measured from the heights of their plateaus detected at 1.0 cm from the intersection of the microchip, and no internal standard was needed. The K d of the IgE-aptamer pair was determined as 6 ± 2 nM which is consistent with the reported results (8 nM).

show abstract

On large structures and turbulent mixing in confined mixing layers under forcing

Wang

2005

AIChE Journal

Self Cite

View full text Add to dashboard Cite

IntroductionFluid mixing is of surpassing interest in science and engineering applications. [1][2][3][4] In many cases, we need fast mixing, such as in combustion, 5 acoustic noise reduction, 6 and protein folding in biotechnology. 7 Traditionally, agitated tank and static mixer, 8,9 jet, and mixing layer 10,11 are often used to enhance mixing. Other mixing augmentation methods include chaotic mixing at relatively low Reynolds number flows 12,13 and an oscillatory flow mixer consisting of tubes fitted with equally spaced orifice plate baffles. 14 Recently, Wang 15,16 introduced a novel extremely fast mixing process in a confined three-dimensional mixing layer in a pipe (that is, the inlet of the pipe is a mixing layer), where the initial two streams can be mixed, at least on the large scale, within one pipe diameter downstream of the splitterplate. The rapid mixing can also be obtained at relatively small Reynolds number flow in this confined configuration, where the Reynolds number is 400 based on the mean velocity and pipe diameter and the original flow is laminar without forcing. For this relatively small Reynolds number flow, the scalar power spectrum can display Ϫ5/3 Oboukhov-Corrsin spectrum in the near field under strong forcing. This could have a substantial impact in technologies that require fast mixing, both in laminar and turbulent flows. Such an interesting flow could also be a new candidate for homogeneous turbulence Nygaard and Glezer,28 Wiltse and Glezer, 29 and many others. An important common conclusion from these works is that the spreading rate, which is one of the most important fundamental parameters and is often used as a mixing criterion in the mixing layer (see, for example, Cantwell 30 and Dimotakis 31 ), can be enhanced through the active forcing.Unfortunately the effect of conventional initial periodic forcing in mixing layers for mixing enhancement is limited by the saturation phenomenon arising from the nonlinear effect. 24,25 For instance, Fiedler and Mensing 27 observed the saturation when the forcing amplitude was sufficiently high, that is, the intensity of the maximum periodic transverse velocity constituents and saturation Strouhal number became constant and independent of forcing amplitude when the forcing amplitude was Ͼ6.5%. They obtained the same mean spreading rate for both strong and weak forcing, that is, twice the neutral value and independent of forcing amplitude. Weisbrot and Wygnanski 32 also investigated strong forcing and reported no distinguishing difference in the spreading rate from that of Fiedler et al. 33 and Oster and Wygnanski. 25 On the foundation of the above-mentioned observations and that of others, Browand and Ho 34 proposed a quasi-universal spreading rate of the forced and unforced mixing layers.In the confined mixing layer, however, Wang 15,16 surprisingly found that the aforementioned saturation limitation of the spreading rate of the shear layer could be overcome when the flow was forced under a specific narrow-frequency band. Thus, the mixing ca...

show abstract

On high spatial resolution scalar measurement with LIF

Cited by 29 publications

References 0 publications

Laser induced fluorescence photobleaching anemometer for microfluidic devices

Laser induced fluorescence photobleaching anemometer for microfluidic devices

Frontal analysis in microchip CE: A simple and accurate method for determination of protein–DNA dissociation constant

On large structures and turbulent mixing in confined mixing layers under forcing

Contact Info

Product

Resources

About