Glen Mchale

Glen Mchale
The University of Edinburgh | UoE · School of Engineering

About

265
Publications
50,365
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Introduction
Glen McHale currently works in the School of Engineering at Edinburgh University and leads the Chemical Engineering discipline. Glen does research in Interfacial Science & Engineering including droplets, soft matter, materials and fluid dynamics, as part of the Research Institute for Multiscale Thermofluids.

Publications

Publications (265)
Article
Full-text available
Ice accretion on economically valuable and strategically important surfaces poses significant challenges. Current anti-/de-icing techniques often have critical issues regarding their efficiency, convenience, long-term stability, or sustainability. As an emerging ice mitigation strategy, the thin-film surface acoustic wave (SAW) has great potentials...
Article
Full-text available
Slippery liquid-infused porous surfaces (SLIPS) are an innovation that reduces droplet-solid contact line pinning and interfacial friction. Recently, it has been shown that a liquid analogue of Young's law can be deduced for the apparent contact angle of a sessile droplet on SLIPS despite there never being contact by the droplet with the underlying...
Article
Full-text available
Programmable fluidic systems on curved and flexible substrates are of increasing interest. One approach to achieving programmability is the controlled sequential wetting and dewetting on a surface using voltage actuation. In particular, liquid dielectrophoresis techniques have recently been shown to provide the ability to form a spread liquid film on...
Preprint
Superhydrophobicity has only ever been achieved by a combination of chemical hydrophobicity and surface topography due to our inability to attain complete non-wetting on the smooth surface of any known material. Here, we report extreme non-wetting of condensation-induced droplets with contact angles approaching 180° on a smooth surface using suspen...
Article
Full-text available
The empirical laws of dry friction between two solid bodies date back to the work of Amontons in 1699 and are pre-dated by the work of Leonardo da Vinci. Fundamental to those laws are the concepts of static and kinetic coefficients of friction relating the pinning and sliding friction forces along a surface to the normal load force. For liquids on...
Article
There are significant challenges in controlling uniformity of crystal inclination angles, growth orientations and film thicknesses to generate dual-mode surface acoustic waves (e.g., Rayleigh ones and shear-horizontal ones) for lab-on-a-chip applications. In this study, we demonstrate large area (up to three inches) and uniformly inclined piezoelec...
Article
Liquid-infused surfaces (LISs) are composite solid–liquid surfaces with remarkable features such as liquid repellency, self-healing, and the suppression of fouling. This review focuses on the fluid mechanics on LISs, that is, the interaction of surfaces with a flow field and the behavior of drops on such surfaces. LISs can be characterized by an ef...
Chapter
The Leidenfrost effect is a case of thin-film boiling where a drop of liquid levitates on a surface heated to temperatures significantly higher than the liquid’s boiling point. When the drop contacts this superheated surface, a thin film of vapor (typically around 100 microns) forms instantaneously between the surface and the drop. The vapor layer...
Article
We theoretically investigate the apparent contact angle of drops on liquid infused surfaces as a function of the relative size of the wetting ridge and the deposited drop. We provide an intuitive geometrical interpretation whereby the variation in the apparent contact angle is due to the rotation of the Neumann triangle at the lubricant-drop-gas co...
Article
Full-text available
Superhydrophobic coatings and slippery liquid-infused porous surfaces (SLIPS) have shown their potentials in self-cleaning, anti-icing, anti-erosion, and antibiofouling applications. Various studies have been done on controlling the droplet impact on such surfaces using passive methods such as modifying the lubricant layer thickness in SLIPS. Despi...
Preprint
Full-text available
We theoretically investigate the apparent contact angle of droplets on liquid infused surfaces as a function of the relative size of the wetting ridge and the deposited droplet. We provide an intuitive geometrical interpretation whereby the variation in the apparent contact angle is due to the rotation of the Neumann triangle. We also derive linear...
Article
Full-text available
The breakup of a slender filament of liquid driven by surface tension is a classical fluid dynamics stability problem that is important in many situations where fine droplets are required. When the filament is resting on a flat solid surface which imposes wetting conditions the subtle interplay with the fluid dynamics makes the instability pathways...
Article
Full-text available
In this paper, we explore the acoustofluidic performance of zinc oxide (ZnO) thin-film surface acoustic wave (SAW) devices fabricated on flexible and bendable thin aluminum (Al) foils/sheets with thicknesses from 50 to 1500 μm. Directional transport of fluids along these flexible/bendable surfaces offers potential applications for the next generati...
Article
Full-text available
Overcoming friction between moving components is important for reducing energy losses and component wear. Hydrodynamic lubrication via thin-film boiling provides an opportunity for reduced friction energy and mass transport. A common example of such lubrication is the Leidenfrost effect, where a liquid droplet levitates on a cushion of its own vapo...
Article
Ice accretion often poses serious operational and safety challenges in a wide range of industries, such as aircraft, wind turbines, power transmission cables, oil field exploration and production, as well as marine transport. Great efforts have been expended to research and develop viable solutions for ice prevention. Effective ice protection techn...
Article
Full-text available
Contact-line pinning and dynamic friction are fundamental forces that oppose the motion of droplets on solid surfaces. Everyday experience suggests that if a solid surface offers low contact-line pinning, it will also impart a relatively low dynamic friction to a moving droplet. Examples of such surfaces are superhydrophobic, slippery porous liquid...
Article
Different acoustic wave modes are required for effective implementation of biosensing and liquid actuation functions in an acoustic wave-based lab-on-a-chip. For efficient sensing in liquids, shear waves (either a thickness shear bulk wave or shear-horizontal surface acoustic wave) can achieve a high sensitivity, without significant loss of acousti...
Article
Full-text available
Soil wettability is important for understanding a wide range of earth system processes, from agricultural productivity to debris flows and sediment fan formation. However, there is limited research considering how soil–water interactions, where the soil grains are naturally hydrophobic, might change in the presence of oil from natural hydrocarbon l...
Article
Full-text available
Bubbles attached to surfaces are ubiquitous in nature and in industry. However, bubbles are problematic in important technologies, including causing damage to the operation of microfluidic devices and being parasitic during heat transfer processes, so considerable efforts have been made to develop mechanical and electrical methods to remove bubbles...
Article
Full-text available
The current paradigm of self-propelled motion of liquid droplets on surfaces with chemical or topographical wetting gradients is always mono-directional. In contrast, here, we demonstrate bidirectional droplet motion, which we realize using liquid infused surfaces with topographical gradients. The deposited droplet can move either toward the denser...
Article
Full-text available
Sessile droplet evaporation underpins a wide range of applications from inkjet printing to coating. However, drying times can be variable and contact-line pinning often leads to undesirable effects, such as ring stain formation. Here, we show voltage programmable control of contact angles during evaporation on two pinning-free surfaces. We use an e...
Article
Full-text available
The transport of small amounts of liquids on solid surfaces is fundamental for microfluidics applications. Technologies allowing control of droplets of liquid on flat surfaces generally involve the generation of a wettability contrast. This approach is however limited by the resistance to motion caused by the direct contact between the droplet and...
Article
Full-text available
Minimizing droplet impact contact time is critical for applications such as self-cleaning, antierosion or anti-icing. Recent studies have used the texturing of surfaces to split droplets during impact or inducing asymmetric spreading, but these require specifically designed substrates that cannot be easily reconfigured. A key challenge is to realiz...
Article
The Leidenfrost effect allows droplets to be transported on a virtually frictionless layer of vapor above a superheated substrate. The substrates are normally topographically structured using subtractive techniques to produce saw-tooth, herringbone and other patterns and bulk heated, leading to significant challenges in energy consumption and contr...
Article
Full-text available
Drop morphology can be manipulated by designing localised solid/liquid interactions to create a favourable interfacial energy equilibrium. A topographical surface with hierarchical roughness can be harnessed to generate complex drop morphologies, enhance uni-axial and anisotropic spreading, in a designable fashion. Here, we propose using an active...
Article
Full-text available
The problem of contact line pinning on surfaces is pervasive and contributes to problems from ring stains to ice formation. Here we provide a single conceptual framework for interfacial strategies encompassing five strategies for modifying the solid-liquid interface to remove pinning and increase droplet mobility. Three biomimetic strategies are in...
Article
The stability of liquid films on surfaces is critically important in microscale patterning and the semiconductor industry. If the film is sufficiently thin, it may spontaneously dewet from the surface. The timescale and rate of dewetting depend on the film repellency of the surface and the properties of the liquid. Therefore, control over the repel...
Preprint
Full-text available
We demonstrate spontaneous bidirectional motion of droplets on liquid infused surfaces in the presence of a topographical gradient, in which the droplets can move either toward the denser or the sparser solid fraction area. Our analytical theory explains the origin of this bidirectional motion. Furthermore, using both lattice Boltzmann simulations...
Article
Full-text available
The ability to actuate liquids remains a fundamental challenge in smart microsystems, such as those for soft robotics, where devices often need to conform to either natural or three-dimensional solid shapes, in various orientations. Here we propose a hierarchical nanotexturing of piezoelectric films as active microfluidic actuators, exploiting a un...
Article
Full-text available
Integration of microfluidics and biosensing functionalities on a single device holds promise in continuous health monitoring and disease diagnosis for point-of-care applications. However, the required functions of fluid handling and biomolecular sensing usually arise from different actuation mechanisms. In this work, we demonstrate that a single ac...
Article
Full-text available
The spontaneous dewetting of a liquid film from a solid surface occurs in many important processes, such as printing and microscale patterning. Experience suggests that dewetting occurs faster on surfaces of higher film repellency. Here, we show how, unexpectedly, a surrounding viscous phase can switch the overall dewetting speed so that films retr...
Article
Full-text available
Often wetting is considered from the perspective of a single surface of a rigid substrate and its topographical properties such as roughness or texture. However, many substrates, such as membranes and meshes, have two useful surfaces. Such flexible substrates also offer the potential to be formed into structures with either a double-sided surface (...
Preprint
While electric fields have been widely studied for drop shaping and digital microfluidics, a unified electromagnetic approach inclusive of magnetic fields is by far less known. Here using the electromagnetic stress tensor, we derive the stress acting on a droplet and test the results experimentally by measuring the shape of a paramagnetic drop in a...
Preprint
Full-text available
The transport of small quantities of liquid on a solid surface is inhibited by the resistance to motion caused by the contact between the liquid and the solid. To overcome such resistance, motion can be externally driven through gradients in electric fields, but these all inconveniently involve the input of external energy. Alternatively, gradients...
Article
A significant limitation for droplet mobility on solid surfaces is to overcome the inherent pinning of the droplet’s contact line that occurs due to chemical/physical heterogeneities. A recent innovation is to use surface texture or porosity to create a stabilised lubricant surface. Droplets on such Slippery Liquid Infused Porous Surfaces/Lubricant...
Article
The prospect of thermal energy harvesting in extreme environments, such as in space or at microscales, offers unique opportunities and challenges for the development of alternate energy conversion technologies. At microscales mechanical friction presents a challenge in the form of energy losses and wear, while presence of high temperature differenc...
Article
A fundamental limitation to the ability to transport sessile droplets is frictional forces arising from surface adhesion. This can be overcome by using the Leidenfrost effect on a heated substrate to levitate the droplet on a cushion of vapor. By structuring the surface under the droplet, the flow of vapor below the droplet can be controlled and th...
Article
Full-text available
A fundamental limitation of liquids on many surfaces is their contact line pinning. This limitation can be overcome by infusing a non-volatile and immiscible liquid or lubricant into texture or roughness created in or applied onto the solid substrate so that the liquid of interest no longer directly contacts the underlying surface. Such slippery li...
Article
Contact-line pinning is a fundamental limitation to the motion of contact lines of liquids on solid surfaces. When a sessile droplet evaporates, contact-line pinning typically results in either a stick-slip evaporation mode, where the contact line pins and de-pins from the surface in an uncontrolled manner or a constant contact area mode with a pin...
Poster
The Leidenfrost phenomenon, first discovered in 1756, describes a metastable state of a droplet on a substrate heated significantly above the boiling point of the liquid [1]. The droplet is levitated by an instantaneously generated vapour layer (100 µm to 200 µm) caused by the initial contact of the droplet with the substrate. The levitation yields...
Poster
Electrowetting is used in many technological applications such as lab-on-chip and display technologies. Its efficacy is limited by contact angle hysteresis and contact angle saturation. The classical model of electrowetting, derived from the energy-minimization approach, lacks a full explanation of these issues. We use magnetic fields to control th...
Article
Full-text available
A fundamental challenge for surface acoustic wave (SAW) temperature sensors is the detection of small temperature changes on non-planar, often curved, surfaces. In this work, we present a new design methodology for SAW devices based on flexible substrate and bimorph material/structures, which can maximize the temperature coefficient of frequency (T...
Article
Full-text available
Surface elastic instabilities, such as wrinkling and creasing, can enable a convenient strategy to impart reversible patterned topography to a surface. Here the classic system of a stiff layer on a soft substrate is focused, which famously produces parallel harmonic wrinkles at modest uniaxial compression that period-double repeatedly at higher com...
Article
Full-text available
In article number 1704228, John Simeon Biggins, Ben Bin Xu, and co-workers report the formation of versatile wrinkle patterns on an elastic bilayer. The image shows guided formation of the surface instability on a micro-patterned thin elastic surface under high compression. The harmonic hierarchy was caused by the in-plane distribution of strain en...
Article
2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Surface elastic instabilities, such as wrinkling and creasing, can enable a convenient strategy to impart reversible patterned topography to a surface. Here the classic system of a stiff layer on a soft substrate is focused, which famously produces parallel harmonic wrinkles at modest uniaxial compre...
Article
Much of the inspiration for the creation of superhydrophobic surfaces has come from nature, from plant such as the Sacred Lotus (Nulembo nucifera), where the micro-scale papillae epidermal cells on the surfaces of the leaves are covered with nano-scale epicuticular wax crystalloids. The combination of the surface roughness and the hydrophobic wax c...
Article
Liquid dielectrophoresis is a bulk force acting on dipoles within a dielectric liquid inside a non-uniform electric field. When the driving electrodes are interdigitated, bulk liquid dielectrophoresis is converted to an interface-localised form capable of modifying the energy balance at an interface. When the interface is a solid-liquid one, the we...
Article
Full-text available
The last two decades have witnessed an explosion of interest in the field of droplet-based microfluidics for their multifarious applications. Despite rapid innovations in strategies to generate small-scale liquid transport on these devices, the speed of motion is usually slow, the transport distance is limited, and the flow direction is not well co...
Article
Full-text available
Even with the recent extensive study into superhydrophobic surfaces, the fabrication of such surfaces on the inside walls of a pipe remains challenging. In this work we report a convenient bi-layered pipe design using a thin superhydrophobic metallic mesh formed into a tube, supported inside another pipe. A flow system was constructed to test the f...
Article
Full-text available
The authors acknowledge support from the Innovative electronic Manufacturing Research Centre (IeMRC) through the EPSRC funded flagship project SMART MICROSYSTEMS (FS/01/02/10), Knowledge Transfer Partnership No KTP010548, EPSRC project EP/L026899/1, EP/F063865/1; EP/F06294X/1, EP/P018998/1, the Royal Society-Research Grant (RG090609) and Newton Mob...
Article
Recently, piezoelectric thin films including zinc oxide (ZnO) and aluminium nitride (AlN) have found a broad range of lab-on-chip applications such as biosensing, particle/cell concentrating, sorting/patterning, pumping, mixing, nebulisation and jetting. Integrated acoustic wave sensing/microfluidic devices have been fabricated by depositing these...
Article
We demonstrate the continuous translational invariance of the energy of a capillary surface in contact with reconfigurable solid boundaries. We present a theoretical approach to find the energy-invariant equilibria of spherical capillary surfaces in contact with solid boundaries of arbitrary shape and examine the implications of dynamic frictional...
Article
We demonstrate the transport and positioning of water droplets on macro-patterned lubricant impregnated surfaces. The macro-patterning produces menisci features in the impregnating liquid layer which interact with a droplet via a capillary mechanism similar to the Cheerios effect. These interactions control the droplet motion and positioning on an...