Wide band Fresnel super-resolution applied to capillary breakup of viscoelastic fluids

Fiscina, Jorge E.; Fromholz, Pierre; Sattler, Rainer; Wagner, Christian

doi:10.1007/s00348-013-1611-6

Cited by 3 publications

(9 citation statements)

References 15 publications

(24 reference statements)

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“…At these small concentrations the viscosity of the suspensions can be considered to remain equal to the viscosity of the suspending fluid and the change in thinning dynamics can unambiguously be attributed to the presence of single beads in the thread. High-speed imaging in combination with a "super resolution technique" [19] are used to characterize the break-up dynamics (fig. 1).…”

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confidence: 99%

“…Light that passes through the center of the filament is not diffracted and produces a bright line in the middle of the filament, while the light that interacts with the boundaries of the filament gets diffracted so they appear dark. In principle, the intensity profile of the diffracted light can be evaluated to achieve spatial resolutions below 100 nm [19]. The filament is filmed by a 10 bit high-speed camera (X-Stream XS-5, IDT, Tallahassee, USA) at up to 8.2 kHz frame rate depending on the spatial resolution.…”

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confidence: 99%

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Single particles accelerate final stages of capillary break-up

Lindner

Fiscina

Wagner

2015

EPL

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-Droplet formation of suspensions is present in many industrial and technological processes such as coating and food engineering. Whilst the finite time singularity of the minimum neck diameter in capillary break-up of simple liquids can be described by well known self-similarity solutions, the pinching of nonBrownian suspension depends in a complex way on the particle dynamics in the thinning thread. Here we focus on the very dilute regime where the filament contains only isolated beads to identify the physical mechanisms leading to the pronounced acceleration of the filament thinning observed. This accelerated regime is characterized by an asymmetric shape of the filament with an enhanced curvature that depends on the size and the spatial distribution of the particles within the capillary thread.Droplets are present in our daily life and their formation has been investigated scientifically since many decades or even centuries. Yet, the physical mechanisms of capillary break-up of even simple fluids has been only understood within the last 20 years [1,3]. The final stages of break up are governed by self similar laws that depend only on the fluid parameters such as surface tension, viscosity and density [2]. The situation is less clear for complex fluids such as polymer solutions [4][5][6][7] or suspensions [8][9][10][11]. Suspensions can be found in many industrial applications, such as painting, food processing or cosmetics and a better understanding of the capillary break up process will be important for a better control of e.g. the dosage.Non-Brownian suspensions have recently attracted interest as their detachment dynamics are function of the individual and collective particle dynamics in the thread and cannot be described using an effective fluid approach only. Several distinct regimes have been identified during suspension detachment [12][13][14][15] and in particular, an acceleration of the detachment compared to the interstitial fluid has been observed during the very late stages of droplet detachment [16]. Numerical simulations [17] have confirmed these experimental findings and have also indicated the exitance of an accelerated regime where the thinning rate is faster than the thinning rate of the pure solvent. While this acceleration has been experimentally quantified as a function of the number of particles in the thread [16] the exact thinning dynamics in the accelerated regime were so far outside the experimental resolution. Here we present measurements on dilute suspensions where only very few particles or even no particles at all are present in the thinning capillary bridge. At these small concentrations the viscosity of the suspensions can be considered to remain equal to the viscosity of the suspending fluid and the change in thinning dynamics can unambiguously be attributed to the presence of single beads in the thread. High speed imaging in combination with a "super resolution technique" [18] are used to characterize the break up dynamics (Fig. 1).A capillary bridge of sufficient ...

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confidence: 99%

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confidence: 99%

Single particles accelerate final stages of capillary break-up

Lindner

Fiscina

Wagner

2015

EPL

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“…The bottom rod motion was the superposition of two harmonic oscillations: a fundamental vibration with the frequency and amplitude A determined by the power amplifier, and a subdominant oscillation of frequency ω and amplitude a. In all the cases considered, ω and aω 2 A 2 , and thus the rod vibration could be regarded as quasi-periodic within the time interval analyzed. The shaker exhibited lateral resonances for a number of frequencies within the range (900 Hz-10 kHz).…”

Section: Methodsmentioning

confidence: 99%

“…, where Z is the instantaneous vertical position of the bottom rod end in the image. This position is approximately given by the function Z(t ) − Z(0) = A sin(2π t )+a 2πω), where the last term has been introduced to take into account the effect of the low-frequency (ω ) subdominant (aω 2 A 2 ) oscillation produced by the shaker. Therefore,…”

Section: Methodsmentioning

confidence: 99%

“…However, scaling down a fluid configuration inevitably entails the increase of the experimental spatial and temporal resolutions. Fortunately, the combination of high-speed imaging [1] and super-resolution detection techniques [2][3][4] allows one to measure precisely the fast evolution of tiny free surfaces. This type of experimental procedure opens the door to the study of diverse interfacial phenomena which have been analyzed only qualitatively so far.…”

Section: Introductionmentioning

confidence: 99%

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An experimental technique to produce micrometer waves on a cylindrical sub-millimeter free surface

Vega

Montanero

Ferrera

et al. 2014

Meas. Sci. Technol.

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We propose and validate an experimental method to analyze the propagation of micrometer surface waves over a liquid column held between two rods, 100 μm in radius. One of the rods vibrates at frequencies of the order of several kHz, while the other remains still. Surface waves, very few microns in amplitude, travel from the oscillating rod to the opposite end. They are almost damped by viscous stresses before reaching that end. We use a super-resolution image processing technique to measure the spatial decay of those waves down to the submicrometer scale. The results are validated from comparison with the numerical solution of the full Navier–Stokes equations.

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