Wetting phenomena are ubiquitous in nature and technology. A solid substrate exposed to the environment is almost invariably covered by a layer of fluid material. In this review, the surface forces that lead to wetting are considered, and the equilibrium surface coverage of a substrate in contact with a drop of liquid. Depending on the nature of the surface forces involved, different scenarios for wetting phase transitions are possible; recent progress allows us to relate the critical exponents directly to the nature of the surface forces which lead to the different wetting scenarios. Thermal fluctuation effects, which can be greatly enhanced for wetting of geometrically or chemically structured substrates, and are much stronger in colloidal suspensions, modify the adsorption singularities. Macroscopic descriptions and microscopic theories have been developed to understand and predict wetting behavior relevant to microfluidics and nanofluidics applications. Then the dynamics of wetting is examined. A drop, placed on a substrate which it wets, spreads out to form a film. Conversely, a nonwetted substrate previously covered by a film dewets upon an appropriate change of system parameters. The hydrodynamics of both wetting and dewetting is influenced by the presence of the three-phase contact line separating "wet" regions from those that are either dry or covered by a microscopic film only. Recent theoretical, experimental, and numerical progress in the description of moving contact line dynamics are reviewed, and its relation to the thermodynamics of wetting is explored. In addition, recent progress on rough surfaces is surveyed. The anchoring of contact lines and contact angle hysteresis are explored resulting from surface inhomogeneities. Further, new ways to mold wetting characteristics according to technological constraints are discussed, for example, the use of patterned surfaces, surfactants, or complex fluids.

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Wetting and Spreading

Although it was thought that apoptotic cells, when rapidly phagocytosed, underwent a silent death that did not trigger an immune response, in recent years a new concept of immunogenic cell death (ICD) has emerged. The immunogenic characteristics of ICD are mainly mediated by damage-associated molecular patterns (DAMPs), which include surface-exposed calreticulin (CRT), secreted ATP and released high mobility group protein B1 (HMGB1). Most DAMPs can be recognized by pattern recognition receptors (PRRs). In this Review, we discuss the role of endoplasmic reticulum (ER) stress and reactive oxygen species (ROS) in regulating the immunogenicity of dying cancer cells and the effect of therapy-resistant cancer microevolution on ICD.

Immunogenic cell death and DAMPs in cancer therapy.

The physics of moving wetting lines

Contact angle hysteresis is an important physical phenomenon. It is omnipresent in nature and also plays a crucial role in various industrial processes. Despite its relevance, there is a lack of consensus on how to incorporate a description of contact angle hysteresis into physical models. To clarify this, starting from the basic definition of contact angle hysteresis, we introduce the formalism and models for implementing contact angle hysteresis into relevant physical phenomena. Furthermore, we explain the influence of the contact angle hysteresis in physical phenomena relevant for industrial applications such as sliding drops, coffee stain phenomenon (in general evaporative self-assembly), and curtain and wire coating techniques

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Contact angle hysteresis: a review of fundamentals and applications

Polymer vesicles prepared by self-assembly techniques have attracted increasing scientific interest in recent years. This is as a result of their numerous potential applications such as tunable delivery vehicles, for the templating of biomineralization, as nanoreactors and as scaffolds for biological conjugation. Presented in this review are the recent advances in the preparation and application of ‘smart’ and functional block copolymer vesicles such as those which respond to external stimuli to afford a change in structure, morphology or controlled release event. In this Highlight, we first give an overview of the structure of polymer vesicles, followed by a summary of the methods used for their preparation. We then focus on recently developed intelligent polymer vesicles which can respond to the application of external stimuli such as a change in temperature, pH or redox to afford novel nanomaterials. The potential applications of these materials are explored with specific focus on the functionalization of various domains of the polymer vesicles. Finally, the current limitations in the preparation and application of polymer vesicles are explored as are the challenges facing the development of these nanostructures towards real-world applications.

Advances and challenges in smart and functional polymer vesicles

A combined molecular-hydrodynamic approach to wetting kinetics

A mechanism of release of calreticulin from cells during apoptosis.

The bending elasticity of a fluid membrane is characterized by its modulus and spontaneous curvature. We present a new method, advanced flicker spectroscopy of giant nonspherical vesicles, which makes it possible to simultaneously measure both parameters for the first time. Our analysis is based on the generation of a large set of reference data from Monte Carlo simulations of randomly triangulated surfaces. As an example of the potential of the procedure, we monitor thermal trajectories of vesicle shapes and discuss the elastic response of zwitterionic membranes to transmembrane pH gradients. Our technique makes it possible to easily characterize membrane curvature as a function of environmental conditions.

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Advanced Flicker Spectroscopy of Fluid Membranes

Effect of Hydroperoxides on Red Blood Cell Membrane Mechanical Properties

The phase behavior of the Triton X100/water binary mixture is investigated using rheological, optical, and X-ray synchrotron techniques. In particular, the storage shear modulus G‘ response, as a function of temperature and strain amplitude, has been related to the structural transformation into the hexagonal phase of cylindrical micelles. Results demonstrate a characteristic critical behavior at the phase transition boundary T = Tc. However, we also find that the rheological signature of the ordering phase transition crucially depends on the particular dynamical mode applied to the sample. Stress−strain variation reflects the shear-induced alignment of the principle column axis, which results in the two-dimensional melting of hexagonal order and the onset of creep flow above a threshold strain e*.

Peter G. Petrov

Papers

A combined molecular-hydrodynamic approach to wetting kinetics

A mechanism of release of calreticulin from cells during apoptosis.

Advanced Flicker Spectroscopy of Fluid Membranes

Effect of Hydroperoxides on Red Blood Cell Membrane Mechanical Properties

Rheology at the Phase Transition Boundary: 2. Hexagonal Phase of Triton X100 Surfactant Solution