Drop impact and wettability: From hydrophilic to superhydrophobic surfaces

Antonini, Carlo; Amirfazli, Alidad; Marengo, Marco

doi:10.1063/1.4757122

Cited by 304 publications

(192 citation statements)

References 43 publications

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“…The experimental stain area resulting from a single-drop impact was determined by the pixel density found via a purpose-built in-house program. The theoretically predicted stain area resulting from a single-drop impact is found from the spread factor [35][36][37] …”

Section: Resultsmentioning

confidence: 99%

Prediction of blood back spatter from a gunshot in bloodstain pattern analysis

et al. 2016

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A theoretical model for predicting and interpreting blood-spatter patterns resulting from a gunshot wound is proposed. The physical process generating a backward spatter of blood is linked to the Rayleigh-Taylor instability of blood accelerated toward the surrounding air, allowing the determination of the initial distribution of drop sizes and velocities. Then the motion of many drops in air is considered with governing equations accounting for gravity and air drag. Based on these equations, a numerical solution is obtained. It predicts the atomization process, the trajectories of the back-spatter drops of blood from the wound to the ground, the impact angle, and the impact Weber number on the ground, as well as the distribution and location of bloodstains and their shape and sizes. A parametric study is undertaken to predict patterns of backward blood spatter under realistic conditions corresponding to the experiments conducted in the present work. The results of the model are compared to the experimental data on back spatter generated by a gunshot impacting a blood-impregnated sponge. A theoretical model for predicting and interpreting blood-spatter patterns resulting from a gunshot wound is proposed. The physical process generating a backward spatter of blood is linked to the Rayleigh-Taylor instability of blood accelerated toward the surrounding air, allowing the determination of the initial distribution of drop sizes and velocities. Then the motion of many drops in air is considered with governing equations accounting for gravity and air drag. Based on these equations, a numerical solution is obtained. It predicts the atomization process, the trajectories of the back-spatter drops of blood from the wound to the ground, the impact angle, and the impact Weber number on the ground, as well as the distribution and location of bloodstains and their shape and sizes. A parametric study is undertaken to predict patterns of backward blood spatter under realistic conditions corresponding to the experiments conducted in the present work. The results of the model are compared to the experimental data on back spatter generated by a gunshot impacting a blood-impregnated sponge.

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Section: Resultsmentioning

confidence: 99%

Prediction of blood back spatter from a gunshot in bloodstain pattern analysis

et al. 2016

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“…Also, in this simulation, the effects of inertia and the wettability for nanoscale droplet spreading cannot be distinguished as shown in the previous experiment. 20 A more detailed study for the effect of inertia and the wettability is the future work.…”

Section: B Influence Of Impact Velocity On Nanodroplet Spreadingmentioning

confidence: 99%

Early stage of nanodroplet impact on solid wall

et al. 2016

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In this study, we investigated nanodroplet spreading at the early stage after the impact using molecular dynamics simulations by changing the magnitude of the intermolecular force between the liquid and wall molecules. We showed that the droplet deformation after the impact greatly depends on the intermolecular force. The temporal evolution of the spreading diameters was measured by the cylindrical control volume for several molecular layers in the vicinity of the wall. At the early stage of the nanodroplet impact, the normalized spreading radius of the droplet is proportional to the square root of the normalized time,t. This result is understood by the geometrical consideration presented by Rioboo et al.["Time evolution of liquid drop impact onto solid, dry surfaces," Exp. Fluids 33, 112-124 (2002)]. In addition, we found that as the intermolecular force between the liquid and wall becomes stronger, the normalized spreading diameter of the first molecular layer on the wall remains less dependent on the impact velocity. Furthermore, the time evolution of the droplet spreading changes from √t to logt with time. C 2016 AIP Publishing LLC.

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“…To measure the contact angle, the drop profile in the vicinity of the contact line is extracted and fitted with a circle; the contact angle is computed from the slope of the tangent to the circle. 49,50 The durability protocol consists of nine tests, and for each test, five cycles are performed. For each test, five identical fresh samples are used, and these five surfaces are tested throughout the five successive cycles.…”

Section: Durability Test Protocolsmentioning

confidence: 99%

Assessing durability of superhydrophobic surfaces

Malavasi

Bernagozzi

Antonini

et al. 2015

Surface Innovations

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Superhydrophobic surfaces (SHS) show remarkable water repellency properties, and their use may have a tremendousimpact for a plethora of applications, where liquid water accumulation needs to be controlled or minimised. However, the durability of SHS in operational conditions is a severe issue that currently represents a bottleneck for the technology transfer from laboratory to industrial applications. In the present work, we try to fill in the gap caused by the absence of a standard for evaluation for SHS durability, by developing a protocol for testing surface durability.The proposed protocol includes nine tests as follows: water immersion, acidic environment, alkaline environment, ionic solution, mechanical erosion, ultraviolet exposure, resistance to heating, alcohol immersion and hydrocarbon immersion. The protocol can serve to give an indication of surface robustness in a variety of potentially harmful environments, by providing a global figure of merit and ranking for different SHS and thereby allowing for identifying those surfaces fulfilling requirements for a specific application. To illustrate the protocol, we tested a SHS developed in-house by grafting of lauric acid molecules on an aluminum substrate. This article contains supporting information that is available online.

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Drop impact and wettability: From hydrophilic to superhydrophobic surfaces

Cited by 304 publications

References 43 publications

Prediction of blood back spatter from a gunshot in bloodstain pattern analysis

Prediction of blood back spatter from a gunshot in bloodstain pattern analysis

Early stage of nanodroplet impact on solid wall

Assessing durability of superhydrophobic surfaces

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