Impact of Beads and Drops on a Repellent Solid Surface: A Unified Description

Arora, Srishti; Fromental, Jean-Marc; Mora, Serge; Phou, Ty; Ramos, Laurence; Ligoure, Christian

doi:10.1103/physrevlett.120.148003

Cited by 23 publications

(36 citation statements)

References 27 publications

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“…The radius of the dishes, R, and the height, h, are between 36 mm and 150 mm and between 8 mm and 40 mm respectively. The shear modulus of the gel is measured by indentation of a non-adhesive rigid sphere (diameter 6 mm at the surface of control samples fully covered with pure water in order to remove capillary forces [14][15][16]. For the experiments reported here, it lies between 10 and 160 Pa, a low value compared to modulus of ordinary rubber-like materials (µ ∼ 1 MPa), but comparable with the modulus of tissues (as liver or brain).…”

Section: Methodsmentioning

confidence: 96%

The shape of hanging elastic cylinders

et al. 2019

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Deformations of heavy elastic cylinders with their axis in the direction of earth's gravity field are investigated. The specimens, made of polyacrylamide hydrogels, are attached from their top circular cross section to a rigid plate. An equilibrium configuration results from the interplay between gravity that tends to deform the cylinders downwards under their own weight, and elasticity that resists these distortions. The corresponding steady state exhibits fascinating shapes which are measured with lab-based micro-tomography. For any given initial radius to height ratio, the deformed cylinders are no longer axially symmetric beyond a critical value of a control parameter that depends on the volume force, the height and the elastic modulus: self-similar wrinkling hierarchies develop, and dimples appear at the bottom surface of the shallowest samples. We show that these patterns are the consequences of elastic instabilities.

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Section: Methodsmentioning

confidence: 96%

The shape of hanging elastic cylinders

et al. 2019

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“…Next, we measure the deformation behaviour of the hydrogel spheres and introduce an energy decomposition similar to that used in (Zhao et al 2015b) to estimate the portions of the impact kinetic energy invested in each of sphere deformation and crater formation. Moreover, using this energy decomposition we show that the maximum deformation data can be collapsed by means of the introduction of an (elastocapillary) Mach number, in a manner similar to that done for hydrogel spheres impacting on a solid substrate (Tanaka, Yamazaki & Okumura 2003;Tanaka 2005;Arora et al 2018). Finally, we investigate the conditions under which the spheres rebound, and analyse them in terms of the spreading and impact time scales.…”

Section: Introductionmentioning

confidence: 94%

“…They showed that the spreading dynamics can be rationalized from a balance between inertia and bulk elasticity, E k = E e , where E k is the kinetic energy just before impact and E e is the elastic energy stored in the sphere at its maximum deformation, namely at the point where the kinetic energy can be assumed to be zero. Starting from the analysis described in Arora et al (2018), the stored bulk elastic energy is expressed as a function of the maximum deformation…”

Section: Impactor Deformation: Maximum Spreading Diametermentioning

confidence: 99%

“…The reason is neglecting the effect of surface tension for the small values of the Young's modulus. To incorporate surface tension we again follow Arora et al (2018) and add a surface energy term E c to the balance, which in the large-deformation limit may be approximated as the product of the surface tension coefficient γ and the sum of the upper and lower surface areas of the pancake-shaped deformed sphere, i.e. E c ≈ (πD 2 0 γ λ 2 m )/2.…”

Section: Impactor Deformation: Maximum Spreading Diametermentioning

confidence: 99%

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Hydrogel sphere impact cratering, spreading and bouncing on granular media

Meer

2021

J. Fluid Mech.

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The impact of a hydrogel sphere onto a granular target results in both the deformation of the sphere and the formation of a prominent topographic feature known as an impact crater on the granular surface. We investigate the crater formation and scaling, together with the spreading diameter and post-impact dynamics of spheres by performing a series of experiments, varying the Young's modulus $Y$ and impact speed $U_{0}$ of the hydrogel spheres, and the packing fraction and grain size of the granular target. We determine how the crater diameter and depth depend on $Y$ and show the data to be consistent with those from earlier experiments using droplets and hard spheres. Most specifically, we find that the crater diameter data are consistent with a power law, where the power exponent changes more sharply when $Y$ becomes less than 200 Pa. Next, we introduce an estimate for the portion of the impact kinetic energy that is stored as elastic energy during impact, and thus correct the energy that remains available for crater formation. Subsequently, we determine the deformation of the hydrogel spheres and find that the normalized spreading diameter data are well collapsed introducing an equivalent velocity from an energy balance of the initial kinetic energy against surface and elastic energy. Finally, we observe that under certain intermediate values for the Young's modulus and impact velocities, the particles rebound from the impact crater. We determine the phase diagram and explain our findings from a comparison of the elastocapillary spreading time and the impact duration.

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“…Upon impact with the surface, the soft hydrogel sphere significantly deforms, as shown in the image sequence of figure 1c. We quantify this deformation using stretch λ and strain ε [32][33][34] (supplemental figure 6(a,b)).…”

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confidence: 99%

Droplet lift-off from hydrophobic surfaces from impact with soft-hydrogel spheres

Rabbi¹,

Kiyama²,

Allen³

et al. 2021

Preprint

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Droplet impacts on superhydrophobic surfaces may result in complete bouncing, with the absence of contact hysteresis and viscous dissipation leading the droplet to fully rebound off the surface. This rebound usually happens in the retraction phase, when the droplet retracts back after reaching a maximum spread diameter. Here, we present experimental evidence of a novel bouncing phenomenon where a sessile droplet on a hydrophobic surface bounces off the surface in its spreading phase when a soft deformable hydrogel sphere axisymmetrically impacts the droplet. We term this as 'Lift-Off' and propose a simple force balance based on the deformation characteristics of the hydrogel sphere to explain the out-of-plane jump of the droplet during spreading. We observe three different impact regimes, and propose their dependency on a modified elastic 'Mach' number (Ma*) with (Ma*)=0.2 corresponding to the onset of lift-off. We also report on the unique acoustic signatures of lift-off cases, associated with the capture of air-bubbles through the air-borne retracting droplet rim. Concerning the novel lift-off results, this work may have potential applications for drainage and surface cleaning, non-stick surface coating, industrial mixing and plant disease spreading.

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Impact of Beads and Drops on a Repellent Solid Surface: A Unified Description

Cited by 23 publications

References 27 publications

The shape of hanging elastic cylinders

The shape of hanging elastic cylinders

Hydrogel sphere impact cratering, spreading and bouncing on granular media

Droplet lift-off from hydrophobic surfaces from impact with soft-hydrogel spheres

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