Novel method for determination of contact angle of highly volatile liquids

The characterization of wettability of substrates by liquid nanodrops

Wettability of a substrates is characterized by a contact angle. Applicability of the simple formula developed by Derjaguin, which relates to the contact angle and disjoining pressure to nano-scale liquid droplets is reconsidered within the framework of the theory of the first-order wetting transition of volatile liquids. It is concluded that his formula is generally correct for large droplets on an incompletely-wettable substrate. But it can not be applied to nanodroplets, in particular, on a completely-wettable substrate. An effective contact angle can be defined even for the nanaodroplet. A…

Universal deformation of soft substrates near a contact line and the direct measurement of solid surface stresses

Droplets deform soft substrates near their contact lines. Using confocal microscopy, we measure the deformation of silicone gel substrates due to glycerol and fluorinated-oil droplets for a range of droplet radii and substrate thicknesses. For all droplets, the substrate deformation takes a universal shape close to the contact line that depends on liquid composition, but is independent of droplet size and substrate thickness. This shape is determined by a balance of interfacial tensions at the contact line and provides a novel method for direct determination of the surface stresses of soft sub…

低接触角蒸发液滴三相接触线附近的流动结构

Flow Structure near Three Phase Contact Line of Low-Contact-Angle Evaporating Droplets

本文结合数学建模、microPIV和红外热成像，揭示了蒸发液滴三相接触线附近毛细流动与Marangoni流动的竞争机制，量化了两者的时空变化，为解释沉积图案和复杂液体系统分析提供理论基准。

Two-component Marangoni-contracted droplets: friction and shape

When a mixture of propylene glycol and water is deposited on a clean glass slide, it forms a droplet of a given apparent contact angle rather than spreading as one would expect on such a high-energy surface. The droplet is stabilized by a Marangoni flow due to the non-uniformity of the components' concentrations between the border and the center of the droplet, itself a result of evaporation. These self-contracting droplets have unusual properties such as absence of pinning and the ability to move under an external humidity gradient. The droplets' apparent contact angle is a function of their …

PANDA-D：无界面确定两种动态接触角

PANDA-D: Interface-free determination of two dynamic contact angles

该研究提出PANDA-D方法，无需提取界面即可确定受驱动液辊的两种动态接触角，通过联合拟合密度与质心位移，在合成液辊及Lennard-Jones液辊模拟中均实现了高精度的接触角分析，可用于自动化的分子轨迹角度分析。

Construction and calibration of a goniometer to measure contact angles and calculate the surface free energy in solids with uncertainty analysis

Here, we present the construction and calibration of a low-cost goniometer to measure contact angles by the sessile drop method. Besides, we propose a simple and fast method to calculate the uncertainty in the determination of the surface free energy (SFE) and its polar and dispersive components through the Owens-Wendt model and tested it by using two testing liquids. The goniometer performance and the SFE uncertainty were determined on two polymers: polytetrafluorethylene (PTFE) and polyoxymethylene (POM), by using water and methylene iodide. The values of contact angle measured were used to …

三维幂律梯度弹性固体的切向接触：一般理论及其在部分滑移中的应用

Tangential contacts of three-dimensional power-law graded elastic solids: A general theory and application to partial slip

本文提出三维幂律梯度弹性固体切向接触的一般理论，基于Mossakovskii-Jäger过程推导闭式解，包含非轴对称位移分量，并应用于抛物线形接触，研究材料梯度和泊松比对耗散能量密度的影响。

Modeling of multiple three phase contact lines of liquid droplets on geometrically patterned surfaces: continuum and mesoscopic analysis

By solving the Young Laplace equation of capillary hydrostatics one can accurately determine equilibrium shapes of droplets on relatively smooth solid surfaces. The solution, however of the Young Laplace equation becomes tricky when a droplet is sitting on a geometrically patterned surface and multiple, and unknown a priori, three phase contact lines have not been accounted for, since air pockets are trapped beneath the liquid droplet. In this work, we propose an augmented Young-Laplace equation, in which a unified formulation for the liquid/vapor and liquid/solid interfaces is adopted, incorp…

间隙中固着液滴的蒸发——扩散限制与相变限制状态之间的过渡

Sessile drop evaporation in a gap -- crossover between diffusion-limited and phase transition-limited regime

本文针对狭窄间隙中挥发性固着液滴的蒸发问题，建立了梯度动力学形式的介观薄膜模型，并通过与直接数值模拟和实验对比，揭示了扩散限制与相变限制蒸发状态之间的过渡机制。

Drop Impact on Hot Plates: Contact times, Lift-off and the Lamella Rupture

When a liquid drop impacts on a heated substrate, it can remain deposited, or violently boil in contact, or lift off with or without ever touching the surface. The latter is known as the Leidenfrost effect. The duration and area of the liquid--substrate contact is highly relevant for the heat transfer, as well as other effects such as corrosion. However, most experimental studies rely on side view imaging to determine contact times, and those are often mixed with the time until the drop lifts off from the substrate. Here, we develop and validate a reliable method of contact time determination …

静态接触角的通用模型

A General Model for Static Contact Angles

针对静态接触角受实际因素影响的问题，本研究扩展Young的局部热力学方法，提出统一易用模型，覆盖通用几何形貌与浸润程度，恢复经典润湿极限、解释中间状态并识别新的逆Wenzel极限状态，为稳健应用设计提供指导。

Nanofocusing, shadowing, and electron mean free path in the photoemission from aerosol droplets

Angle-resolved photoelectron spectroscopy of aerosol droplets is a promising method for the determination of electron mean free paths in liquids. It is particularly attractive for volatile liquids, such as water. Here we report the first angle-resolved photoelectron images of droplets with defined sizes, viz. of water, glycerol, and dioctyl phthalate droplets. Example simulations of water droplet photoelectron images and data for electron mean free paths for liquid water at low kinetic energy (< 3eV) are provided. We present an approach that allows one to gradually vary the conditions from sha…