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Surface Characteristics of Ionic Liquid-Modified Multiwalled Carbon Nanotube-Based Styrene-Butadiene Rubber Nanocomposites: Contact Angle Studies
Published in A. K. Haghi, K. M. Praveen, Sabu Thomas, Engineered Carbon Nanotubes and Nanofibrous Materials, 2019
Jiji Abraham, Kalarikkal Nandakumar, C. George Soney, Thomas Sabu
The contact angle is measured as the tangent angle formed between a liquid drop and its supporting surface. The techniques for measuring contact angle have been reviewed in detail by Neumann and Good. According to Thomas Young, when a droplet of a liquid is formed on a flat solid surface, the balance on the three-phase interface is expressed by following equation () (γlv)cosθ=(γsv)−(γsl)
Interfaces and the Concept of Surface Tension
Published in Andrew Terhemen Tyowua, Liquid Marbles, 2018
To reiterate, surface tension causes fluids to minimize their surface area by taking a spherical geometry when in minute amount. This often leads to the formation of drops (or droplets), bubbles, or cavities. Drops are spheres of a liquid in equilibrium with their vapor. A bubble is either a region in which air and vapor are trapped by a thin film or a cavity full of vapor in a liquid. Ordinary bubbles have two surfaces (i.e. inner and outer), while cavities have only one surface. Drops and bubbles are stable (i.e. at equilibrium) because the tendency to decrease their surface area is balanced by the rise in internal pressure. The internal pressure, Pi, which tends to expand them, is usually greater than the outer (or external atmospheric) pressure, Po, which tends to contract them. Consider a relatively stable one-surface air bubble, Figure 1.1a, of radius r in a liquid of surface tension γla. A small change (increment) in the radius, from r to r+dr, will be accompanied by a change in the surface area dα.
Innovations in Noninvasive Instrumentation and Measurements
Published in Robert B. Northrop, Non-Invasive Instrumentation and Measurement in Medical Diagnosis, 2017
With modern DNA sequencing machines, only a drop is needed to obtain enough nuclear material to characterize pathogen DNA if the pathogens in the blood or their nuclear material are present in sufficiently high densities. If not, one strategy is to repeat the test several times to beat the odds, or take a larger, IV sample, concentrate it, and run the DNA test. Physiologically important ions in the blood can be measured by micro-ion-selective electrodes without harming the sample. Note that the volume of a drop is variable, depending on the fluid parameters of the liquid (viscosity, density, dissolved solids, surface tension, etc.). A “drop” is now defined by pharmacists as exactly 0.05 mL = 50 μL or 20 drops/mL; a drop is abbreviated gtt, plural: gtts (from Latin: gutta).
Thermal damages in spray drying: Particle size-dependent protein denaturation using phycocyanin as model substrate
Published in Drying Technology, 2023
Nora Alina Ruprecht, Reinhard Kohlus
The particle size is primarily determined by the size of the formed drops during atomization. The drop size is determined by liquid properties, including viscosity and surface tension, as well as atomizer properties, such as its geometry and parameters that can be adjusted during the process. The adjustable for disk atomization is the rotational speed, while for two-fluid nozzles it is the ratio of atomizing gas to feed. The drop size for pressure nozzles is determined by the pressure, which is dependent on the feed mass flow rate and the borehole diameter.[41] There are studies which varied atomization parameters to achieve different drop sizes to investigate the effect on volatile retention.[24,42–44] A direct transfer to protein retention is not possible.
Instantaneous Heat Transfer Coefficient of Droplets Impinged on Heated Surfaces
Published in Heat Transfer Engineering, 2023
Bikash Pattanayak, Sarath S. Lal, Hardik B. Kothadia
It is observed that when a liquid droplet is sufficiently small and surface tension dominates over gravity, the drop forms a spherical cap shape. Then evaporation starts from the edge. In cases of low-volume droplets at low surface superheat, single-phase evaporation with axial conduction is dominant [31]. In the case of higher surface superheat, when the liquid in contact with the surface reaches the saturation temperature, the onset of nucleate boiling occurs [13]. In both cases subsequently, the height of the droplet decreases, and the droplet evaporates. This shows the temperature gradient between the droplet and substrate impacts the surface tension and increases the wettability of the substrate. In order to study the behavior of fluid on substrates, both the metallic substrates are placed on a contact angle meter and sessile test fluid at different temperatures is placed on it. The relative uncertainty of the contact angle meter is
Dynamic behaviours and drying processes of water droplets impacting on superhydrophilic surfaces
Published in Surface Engineering, 2021
Yan Zhu, Jialiu Liu, Yongmao Hu, De-Quan Yang, Edward Sacher
Although much work has been done on the dynamical contact behaviour [31–35], much of it was related to surface superhydrophobicity; little work has so far been carried out on surface superhydrophilicity. Recently, Yamaguchi et al. [31] studied the dynamic contact performance of impacting droplets on hydrophilic/superhydrophobic surfaces. Jiang et al., [32] studied the directional transport of water droplets on super-hydrophilic curved tracks, which is important for applications such as microchannels in microfluidics, and water collection systems. In general, in the absence of splashing, a water droplet on a dry surface spreads over the surface until it reaches a maximum radius, the radius depending on the type of interaction between the water droplet and the surface. The stronger the hydrophilic interaction, the larger the radius. To characterize the surface wettability and to investigate the physical chemistry of drop-surface interactions, two approaches are commonly used: a static approach, using sessile drops, and a dynamic approach, by means of drop impact studies.