scholarly journals Wetting transitions in droplet drying on soft materials

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Julia Gerber ◽  
Tobias Lendenmann ◽  
Hadi Eghlidi ◽  
Thomas M. Schutzius ◽  
Dimos Poulikakos
Keyword(s):  
Contact Line ◽  
Traction Force ◽  
Soft Materials ◽  
Wetting Transition ◽  
Surface Design ◽  
Complex Processes ◽  
Compliant Substrates ◽  
Rate Dependent ◽  
Liquid Removal ◽  
Droplet Drying

Abstract Droplet interactions with compliant materials are familiar, but surprisingly complex processes of importance to the manufacturing, chemical, and garment industries. Despite progress—previous research indicates that mesoscopic substrate deformations can enhance droplet drying or slow down spreading dynamics—our understanding of how the intertwined effects of transient wetting phenomena and substrate deformation affect drying remains incomplete. Here we show that above a critical receding contact line speed during drying, a previously not observed wetting transition occurs. We employ 4D confocal reference-free traction force microscopy (cTFM) to quantify the transient displacement and stress fields with the needed resolution, revealing high and asymmetric local substrate deformations leading to contact line pinning, illustrating a rate-dependent wettability on viscoelastic solids. Our study has significance for understanding the liquid removal mechanism on compliant substrates and for the associated surface design considerations. The developed methodology paves the way to study complex dynamic compliant substrate phenomena.

scholarly journals Explaining Evaporation-Triggered Wetting Transition Using Local Force Balance Model and Contact Line-Fraction

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Rama Kishore Annavarapu ◽  
Sanha Kim ◽  
Minghui Wang ◽  
A. John Hart ◽  
Hossein Sojoudi
Keyword(s):  
Contact Line ◽  
Force Balance ◽  
Balance Model ◽  
Wetting Transition

A Constitutive Model for Soft Materials Incorporating Viscoelasticity and Mullins Effect

2016 ◽  
Vol 84 (2) ◽  
Author(s):  
Tongqing Lu ◽  
Jikun Wang ◽  
Ruisen Yang ◽  
T. J. Wang
Keyword(s):  
High Strength ◽  
Soft Materials ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Mullins Effect ◽  
Butadiene Rubber ◽  
Zener Model ◽  
Rate Dependent ◽  
Effect Model ◽  
Loading And Unloading

Soft materials including elastomers and gels are widely used in applications of energy absorption, soft robotics, bioengineering, and medical instruments. For many soft materials subject to loading and unloading cycles, the stress required on reloading is often less than that on the initial loading, known as Mullins effect. Meanwhile, soft materials usually exhibit rate-dependent viscous behavior. Both effects were recently reported on a new kind of synthesized tough gel, with capability of large deformation, high strength, and extremely high toughness. In this work, we develop a coupled viscoelastic and Mullins-effect model to characterize the deformation behavior of the tough gel. We modify one of the elastic components in Zener model to be a damageable spring to incorporate the Mullins effect and model the viscous effect to behave as a Newtonian fluid. We synthesized the tough gel described in the literature (Sun et al., Nature 2012) and conducted uniaxial tensile tests and stress relaxation tests. We also investigated the two effects on three other soft materials, polyacrylate elastomer, Nitrile-Butadiene Rubber, and polyurethane. We find that our presented model is so robust that it can characterize all the four materials, with modulus ranging from a few tens of kilopascal to megapascal. The theory and experiment for all tested materials agree very well.

Modeling fracture in rate-dependent polymer networks: A quasicontinuum approach

2021 ◽  
pp. 1-22
Author(s):  
Ahmed Ghareeb ◽  
Ahmed Elbanna
Keyword(s):  
Adaptive Mesh Refinement ◽  
Polymer Networks ◽  
Viscoelastic Behavior ◽  
Adaptive Mesh ◽  
Soft Materials ◽  
Polymer Chains ◽  
Loading Rates ◽  
Viscous Forces ◽  
Rate Dependent ◽  
Bond Breakage

Abstract Soft materials, such as rubber and gels, exhibit rate-dependent response where the stiffness, strength and fracture patterns depend largely on loading rates. Thus, accurate modeling of the mechanical behavior requires accounting for different sources of rate-dependence such as the intrinsic viscoelastic behavior of the polymer chains and the dynamic bond breakage and formation mechanism. In this chapter, we extend the QC approach presented in Ghareeb and Elbanna [Journal of the Mechanics and Physics of Solids, 137, 103819 (2020)] to include ratedependent behavior of polymer networks. We propose a homogenization rule for the viscous forces in the polymer chains and update the adaptive mesh refinement algorithm to account for dynamic bond breakage. Then, we use nonlinear finite element framework with predictorcorrector scheme to solve for the nodal displacements and velocities. We demonstrate the accuracy of the method by verifying it against fully discrete simulations for different examples of network structures and loading conditions. We further use the method to investigate the effects of the loading rates on the fracture characteristics of networks with different ratedependent parameters. Finally, We discuss the implications of the extended method for multiscale analysis of fracture in rate-dependent polymer networks.

scholarly journals State and Rate Dependent Contact Line Dynamics over an Aging Soft Surface

2020 ◽  
Vol 124 (18) ◽  
Author(s):  
Dongshi Guan ◽  
Elisabeth Charlaix ◽  
Penger Tong
Keyword(s):  
Contact Line ◽  
Rate Dependent ◽  
Soft Surface ◽  
Contact Line Dynamics

scholarly journals On the Effect of a Rate-Dependent Work of Adhesion in the Detachment of a Dimpled Surface

2021 ◽  
Vol 11 (7) ◽  
pp. 3107
Author(s):  
Antonio Papangelo
Keyword(s):  
Power Law ◽  
Soft Materials ◽  
Work Of Adhesion ◽  
Patterned Surfaces ◽  
Weak State ◽  
Partial Contact ◽  
Rate Dependent ◽  
Pressure Sensitive ◽  
Full Contact ◽  
Unloading Rate

Patterned surfaces have proven to be a valuable design to enhance adhesion, increasing hysteresis and the detachment stress at pull-off. To obtain high adhesive performance, soft materials are commonly, used, which easily conform to the countersurface, such as soft polymers and elastomers. Such materials are viscoelastic; i.e., they show rate-dependent properties. Here, the detachment of two half spaces is studied, one being flat and the other having a dimple in the limit of short range adhesion and a power law rate-dependent work of adhesion, as observed by several authors. Literature results have suggested that the dimpled surface would show pressure-sensitive adhesion, showing two possible adhered states, one weak, in partial contact, and one strong when full contact is achieved. By accounting for a power law rate-dependent work of adhesion, the “weak state” may be much stronger than it was in the purely elastic case, and hence the interface may be much more tough to separate. We study the pull-off detachment stress of the dimpled surface, showing that it weakly depends on the preload, but it is strongly affected by the dimensionless unloading rate. Finally, possible implications of the presented results in the detachment of soft materials from rough substrates are discussed.

scholarly journals Rheology-Informed Neural Networks (RhINNs) for forward and inverse metamodelling of complex fluids

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Mohammadamin Mahmoudabadbozchelou ◽  
Safa Jamali
Keyword(s):  
Neural Networks ◽  
Constitutive Equations ◽  
Automatic Differentiation ◽  
Complex Fluids ◽  
Shear Banding ◽  
Constitutive Models ◽  
Soft Materials ◽  
Specific Model ◽  
Model Parameters ◽  
Rate Dependent

AbstractReliable and accurate prediction of complex fluids’ response under flow is of great interest across many disciplines, from biological systems to virtually all soft materials. The challenge is to solve non-trivial time and rate dependent constitutive equations to describe these structured fluids under various flow protocols. We present Rheology-Informed Neural Networks (RhINNs) for solving systems of Ordinary Differential Equations (ODEs) adopted for complex fluids. The proposed RhINNs are employed to solve the constitutive models with multiple ODEs by benefiting from Automatic Differentiation in neural networks. In a direct solution, the RhINNs platform accurately predicts the fully resolved solution of constitutive equations for a Thixotropic-Elasto-Visco-Plastic (TEVP) complex fluid for a series of flow protocols. From a practical perspective, an exhaustive list of experiments are required to identify model parameters for a multi-variant constitutive TEVP model. RhINNs are found to learn these non-trivial model parameters for a complex material using a single flow protocol, enabling accurate modeling with limited number of experiments and at an unprecedented rate. We also show the RhINNs are not limited to a specific model and can be extended to include various models and recover complex manifestations of kinematic heterogeneities and transient shear banding of thixotropic fluids.

scholarly journals Time-controlled Multichannel Dynamic Traction Imaging of Biaxially Stretched Adherent Cells

2020 ◽  
Author(s):  
Aron N. Horvath ◽  
Andreas A. Ziegler ◽  
Stephan Gerhard ◽  
Claude N. Holenstein ◽  
Benjamin Beyeler ◽  
...  
Keyword(s):  
Single Cells ◽  
Traction Force ◽  
Beam Splitting ◽  
Force Microscopy ◽  
Computational Overhead ◽  
Rate Dependent ◽  
Induced Motion ◽  
Microscopy Method ◽  
Resolution Imaging ◽  
Potential Impact

AbstractHere, a dynamic traction force microscopy method is described which enables sub-second temporal resolution imaging of transient subcellular events secondary to extrinsic stretch of adherent single cells. The system employs a novel tracking approach with minimal computational overhead to compensate substrate-based stretch-induced motion/drift of stretched single cells in real time, allowing capture of biophysical phenomena on multiple channels by fluorescent multichannel imaging on a single camera, thus avoiding the need for beam splitting with associated loss of light. The potential impact of the technique is demonstrated by characterizing transient subcellular forces and corresponding nuclear deformations in equibiaxial stretching experiments, uncovering a high frequency strain-rate dependent response in the transfer of substrate strains to the nucleus.

scholarly journals Determination by Relaxation Tests of the Mechanical Properties of Soft Polyacrylamide Gels Made for Mechanobiology Studies

2021 ◽  
Author(s):  
Daniel Pérez-Calixto ◽  
Samuel Amat-Shapiro ◽  
Diego Zamarrón-Hernández ◽  
Genaro Vázquez-Victorio ◽  
Pierre-Henri Puech ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Materials Science ◽  
Chemical Properties ◽  
Soft Materials ◽  
Maxwell Model ◽  
Biological Tissues ◽  
Elastic Stiffness ◽  
Critical Signal ◽  
Compliant Substrates

Following the general aim of recapitulating the native mechanical properties of tissues and organs in vitro, the field of materials science and engineering has benefited from recent progress in developing compliant substrates with similar physical and chemical properties. In particular, in the field of mechanobiology, soft hydrogels can now reproduce the precise range of stiffnesses of healthy and pathological tissues to study the mechanisms behind cell response to mechanics. However, it was shown that biological tissues are not only elastic but also relax at different timescales. Cells can indeed perceive and actually need this dissipation because it is a critical signal integrated with other signals to define adhesion, spreading and even more complicated functions. The mechanical definition of hydrogels used in mechanobiology is however commonly limited to the elastic stiffness (Young’s modulus) and this value is known to depend greatly on the measurement conditions that are rarely reported. Here, we report that a simple relaxation test performed under well defined conditions can provide all the necessary information to characterize soft materials mechanically, by fitting the dissipation behavior with a generalized Maxwell model (GMM). The method was validated using soft polyacrylamide hydrogels and proved to be very useful to unveil precise mechanical properties of gels that cells can sense and offer a set of characteristic values that can be compared with what is typically reported from microindentation tests.

Asymptotic theory of fluid entrainment in dip coating

2018 ◽  
Vol 844 ◽  
pp. 1026-1037 ◽  
Author(s):  
Jian Qin ◽  
Peng Gao
Keyword(s):  
Contact Line ◽  
Analytical Formula ◽  
Dip Coating ◽  
Wetting Transition ◽  
Contact Lines ◽  
Moving Contact ◽  
Moving Contact Lines ◽  
Two Fluid ◽  
Large Speed ◽  
Line Movement

When a contact line moves with a sufficiently large speed, liquid or gas films can be entrained on a solid depending on the direction of contact-line movement. In this work, the contact-line dynamics in the situation of a generic two-fluid system is investigated. We demonstrate that the hydrodynamics of a contact line, no matter whether advancing or receding, can formally reduce to that of a receding one with small interfacial slopes. Since the latter can be well treated under the classical lubrication approximation, this analogy allows us to derive an asymptotic solution of the interfacial profiles for arbitrary values of contact angle and viscosity ratio. For the dip-coating geometry, we obtain, with no adjustable parameters, an analytical formula for the critical speed of wetting transition, which in particular predicts the onset of both liquid and gas entrainment. Moreover, the present analysis also builds a novel connection between the Cox–Voinov law and classical lubrication theory for moving contact lines.

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