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An ouzo droplet is a multicomponent liquid comprising ethanol, water, and anise oil, each possessing distinct thermophysical properties, volatility, and mutual miscibility. Evaporation leads to the complex physicochemical process of coupled mass and heat transfer, spontaneous emulsification, and liquid–liquid phase separation, known as the ouzo effect. An acoustically levitated ouzo droplet undergoes five characteristic stages of evaporation based on temporal temperature variation. Such levitated droplet shows a significantly longer lifespan upon evaporation because of the thermal isolation in air, as well as a drastic initial cooling. Sessile droplets, on the other hand, have heat transferred from the surroundings via the substrate to replenish latent heat of vaporization. A conductive substrate thus helps the droplet to stay close to the ambience and a shorter lifespan. A rudimentary theoretical model based on dimensional analysis is developed and shows consistency with measurements. [ABSTRACT FROM AUTHOR]

A levitated glycerol droplet supported by an acoustic standing wave, when subject to modulated field at frequency on the order of 150 Hz, behaves as a solid plate and exhibits flexural bending resonance rather than the conventional equatorial star-shape oscillations. Three oscillation modes are observed: seesaw, saddleback, and monkey saddle with the increasing energy levels. The finite element analysis generates droplet shapes consistent with the experimental observation and yields apparent plate flexural rigidity in terms of surface tension and aspect ratio of plate thickness to diameter. High viscosity leads to the plate-like behavior of the droplet. [ABSTRACT FROM AUTHOR]

An array of gold nano-pillars is fabricated on silicon, before chemical vapor deposited graphene is transferred to the substrate. Intrinsic intersurface attraction pulls the monolayer into intimate contact conforming to the substrate geometry, but the pillars support an array of circular blisters. A simple delamination mechanics model is constructed to extract the materials and interface properties. The graphene-gold interfacial adhesion energy is found to be γ = 450 ± 100 mJ m-2 by measuring the blister dimension. Should the ratio of pillar height to inter-pillar separation falls short of (γ/Eh)1/4 with graphene elastic modulus, E and thickness, h, the blisters stay isolated; otherwise, adjacent blisters coalesce. Critical design guidelines are set for graphene devices. [ABSTRACT FROM AUTHOR]

A nano-cheese-cutter is fabricated to directly measure the adhesion between two freestanding nano-fibers. A single electrospun fiber is attached to the free end of an atomic force microscope cantilever, while a similar fiber is similarly prepared on a mica substrate in an orthogonal direction. External load is applied to deform the two fibers into complementary V-shapes, and the force measurement allows the elastic modulus to be determined. At a critical tensile load, 'pull-off' occurs when the adhering fibers spontaneously detach from each other, yielding the interfacial adhesion energy. Loading-unloading cycles are performed to investigate repeated adhesion-detachment and surface degradation. [ABSTRACT FROM AUTHOR]

A prestressed rectangular film clamped at both ends delaminates from a rigid punch. Based on a thermodynamic energy balance, the delamination mechanics is derived to relate the simultaneous external tensile force applied to the punch, punch displacement, and contact area. Effects of the coupled tensile residual membrane stress and adhesion energy at the punch-film interface are investigated. A “pinch off” (stable shrinking of the contact area to a line) is predicted, contrasting the nonzero “pull-off” radius in a clamped circular film. The model is useful in understanding the behavior of various adhesion-delamination phenomena, especially in one dimensional capacitive microelectromechanical systems radio frequency switches, microstructure network, and nanostructures. [ABSTRACT FROM AUTHOR]

The theory of two-dimensional linear quaternion-valued differential equations (QDEs) was recently established {see the work of Kou and Xia [Stud. Appl. Math. 141(1), 3–45 (2018)]}. They observed some profound differences between QDEs and ordinary differential equations. Also, an algorithm to evaluate the fundamental matrix by employing the eigenvalues and eigenvectors was presented in the work of Kou and Xia [Stud. Appl. Math. 141(1), 3–45 (2018)]. However, the fundamental matrix can be constructed providing that the eigenvalues are simple. If the linear system has multiple eigenvalues, how to construct the fundamental matrix? In particular, if the number of independent eigenvectors might be less than the dimension of the system, that is, the numbers of the eigenvectors are not enough to construct a fundamental matrix, how to find the "missing solutions"? The main purpose of this paper is to answer this question. [ABSTRACT FROM AUTHOR]

We report a technique to characterize adhesion of monolayered/multilayered graphene sheets on silicon wafer. Nanoparticles trapped at graphene-silicon interface act as point wedges to support axisymmetric blisters. Local adhesion strength is found by measuring the particle height and blister radius using a scanning electron microscope. Adhesion energy of the typical graphene-silicon interface is measured to be 151±28 mJ/m2. The proposed method and our measurements provide insights in fabrication and reliability of microelectromechanical/nanoelectromechanical systems. [ABSTRACT FROM AUTHOR]

Fingering of an inviscid liquid droplet upon impact on a super-hydrophobic surface is revisited. Generation of coronal fingers is investigated here using a transverse rim instability analysis based on the toroidal curvature of rim, instead of the linear front assumption in the classical Rayleigh-Plateau (R-P) model. The governing equations are formulated from the first principles and solved numerically. For a droplet with a known volume and impact velocity, the model predicts the number of spires upon impact, k. Here k is found to be the largest wave number with a positive growth rate on the droplet rim and is shown to be in the order of (Weber)3/5. The theoretical model is consistent with our water droplet experiments for 60 < We < 160, superseding the R-P prediction. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented in response to the article "Adhesion-delamination mechanics of a presented rectangular film adhered onto a rigid substrate."

Uptake of cytotoxic drugs by typical tumor cells is limited by the dense dendritic network of oligosaccharide mucin chains that forms a mechanical barrier. Atomic force microscopy is used to directly measure the force needed to pierce the mucin layer to reach the cell surface. Measurements are analyzed by de Gennes' steric reputation theory. Multidrug resistant ovarian tumor cells shows significantly larger penetration load compared to the wide type. A pool of pancreatic, lung, colorectal, and breast cells are also characterized. The chemotherapeutic agent, benzyl-α-GalNac, for inhibiting glycosylation is shown to be effective in reducing the mechanical barrier. [ABSTRACT FROM AUTHOR]