Review of super-hydrophobic materials research

We reviewed the research on super-hydrophobic materials. Firstly, we introduced the basic principles of super-hydrophobic materials, including the Young equation, Wenzel model, and Cassie model. Then, we summarized the main preparation methods and research results of super-hydrophobic materials, such as the template method, soft etching method, electrospinning method, and sol-gel method. Among them, the electrospinning method that has developed in recent years is a new technology for preparing micro/nanofibers. Finally, the applications of super-hydrophobic materials in the field of coatings, fabric and filter material, anti-fogging, and antibacterial were introduced, and the problems existing in the preparation of super-hydrophobic materials were pointed out, such as unavailable industrialized production, high cost, and poor durability of the materials. Therefore, it is necessary to make a further study on the application of the materials in the selection, preparation, and post-treatment.

Wetting under Electromagnetic Resonance Irradiation

The influence of the resonance electromagnetic irradiation on the wetting of a solid surface by liquid has been discussed. A simple model of a fluid consisting of two-level atoms, for which changes in their interaction due to a resonance irradiation can be found in the framework of the quantum-mechanical perturbation theory is considered, and the corresponding functional for the grand thermodynamic potential is found. The density functional method is used to calculate the surface tension at the liquid–vapor, solid–liquid, and solid–vapor interfaces, and the Young equation is applied to determine the wetting angle. It is shown that the resonance irradiation can significantly increase the latter parameter.

Numerical simulation of cell squeezing through a micropore by the immersed boundary method

The deformability of cells has been used as a biomarker to detect circulating tumor cells from patient blood sample using microfluidic devices with microscale pores. Successful separations of circulating tumor cells from a blood sample require careful design of the micropore size and applied pressure. This paper presented a parametric study of cell squeezing through micropores with different size and pressure. Different membrane compressibility modulus was used to characterize the deformability of varying cancer cells. Nucleus effect was also considered. It shows that the cell translocation time through the micropore increases with cell membrane compressibility modulus and nucleus stiffness. Particularly, it increases exponentially as the micropore diameter or pressure decreases. The simulation results such as the cell squeezing shape and translocation time agree well with experimental observations. The simulation results suggest that special care should be taken in applying Laplace–Young equation to microfluidic design due to the nonuniform stress distribution and membrane bending resistance.

Generalized Young Equation of Cylindrical Droplets Between Two Parallel Cylinders

Wetting phenomenon of a solid by a liquid is of critical importance for our daily lives and many industrial applications. In this study, we thermodynamically derive a generalized Young equation of cylindrical droplets between two homogeneous and smooth parallel cylinders including the influences of the line tension. The derivation is based on the concepts of Gibbs’s dividing surface and Rusanov’s dividing line in practice.

Maximal liquid bridges between horizontal cylinders

We investigate two-dimensional liquid bridges trapped between pairs of identical horizontal cylinders. The cylinders support forces owing to surface tension and hydrostatic pressure that balance the weight of the liquid. The shape of the liquid bridge is determined by analytically solving the nonlinear Laplace–Young equation. Parameters that maximize the trapping capacity (defined as the cross-sectional area of the liquid bridge) are then determined. The results show that these parameters can be approximated with simple relationships when the radius of the cylinders is small compared with the capillary length. For such small cylinders, liquid bridges with the largest cross-sectional area occur when the centre-to-centre distance between the cylinders is approximately twice the capillary length. The maximum trapping capacity for a pair of cylinders at a given separation is linearly related to the separation when it is small compared with the capillary length. The meniscus slope angle of the largest liquid bridge produced in this regime is also a linear function of the separation. We additionally derive approximate solutions for the profile of a liquid bridge, using the linearized Laplace–Young equation. These solutions analytically verify the above-mentioned relationships obtained for the maximization of the trapping capacity.