Bingham Plastic
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A viscoplastic material that behaves as a rigid body at low stresses but flows as a viscous fluid at high stress. A common example is toothpaste, which will not be extruded until a certain pressure is applied to the tube. It then is pushed out as a solid plug.
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Boundary Layer
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A boundary layer is that layer of fluid in the immediate vicinity of a bounding surface. The boundary layer effect occurs at the field region in which all changes occur in the flow pattern. The boundary layer distorts surrounding nonviscous flow.
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Colloid
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A type of chemical mixture where one substance is dispersed evenly throughout another. The particles of the dispersed substance are only suspended in the mixture, unlike a solution, where they are completely dissolved within. This occurs because the particles in a colloid are larger than in a solution - small enough to be dispersed evenly and maintain a homogenous appearance, but large enough to scatter light and not dissolve.
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Condensation
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The change of the physical state of aggregation (or simply state) of matter from gaseous phase into liquid phase.
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Electropermanent Magnet
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A type of magnet which consists of both an electromagnet and a dual material permanent magnet, in which the magnetic field produced by the electromagnet is used to change the magnetisation of the permanent magnet. Allows creating controllable permanent magnets where the magnetic effect can be maintained without requiring a continuous supply of electrical energy.
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In the case of a ferromagnetic liquid.
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Electrophoretic Deposition
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A term for a broad range of industrial processes which includes electrocoating, cathodic electrodeposition, and electrophoretic coating, or electrophoretic painting. A characteristic feature of this process is that colloidal particles suspended in a liquid medium migrate under the influence of an electric field (electrophoresis) and are deposited onto an electrode.
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Electrostatic Deposition
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Liquid sprayed onto a substrate using electrostatic force. Used to apply a surface coating.
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Faraday Wave
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(or Faraday Ripples) Nonlinear standing waves that appear on liquids enclosed by a vibrating receptacle. When the vibration frequency exceeds a critical value, the flat hydrostatic surface becomes unstable. The waves can take the form of stripes, close-packed hexagons, or even squares or quasiperiodic patterns.
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Filter (physical)
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A device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. Filters are often used to remove harmful substances from air or water, for example to remove air pollution, to make water drinkable, to prepare coffee. In domestic food and drink preparation where bulk solids are removed from liquids, this is often called a strainer.
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For example, accumulating a viscous liquid on a filter.
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Fluid Spray
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When a liquid is dispersed as a stream of droplets (atomisation), it is called a spray. Spray nozzles are used to achieve two primary functions: increase liquid surface area to enhance evaporation, or distribute a liquid over an area.
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Funnel
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A funnel is a pipe with a wide, often conical mouth and a narrow stem. It is used to channel liquid or fine-grained substances into containers with a small opening. Without a funnel, much spillage would occur.
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Gel
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A gel is a solid, jelly-like material that can have properties ranging from soft and weak to hard and tough. Gels are defined as a substantially dilute crosslinked system, which exhibits no flow when in the steady-state. By weight, gels are mostly liquid, yet they behave like solids due to a three-dimensional crosslinked network within the liquid. It is the crosslinks within the fluid that give a gel its structure (hardness) and contribute to stickiness (tack).
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Gravitation
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A natural phenomenon by which objects with mass attract one another. In everyday life, gravitation is most commonly thought of as the agency which lends weight to objects with mass.
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Hydrogel
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(also called aquagel) is a network of polymer chains that are hydrophilic, sometimes found as a colloidal gel in which water is the dispersion medium. Hydrogels are highly absorbent (they can contain over 99.9% water) natural or synthetic polymers. Hydrogels also possess a degree of flexibility very similar to natural tissue, due to their significant water content.
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Some hydrogels have the ability to sense changes of pH, temperature, or the concentration of metabolite and release their load as result of such a change.
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Magnetic Field
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A vector field which surrounds magnets and electric currents, and is detected by the force it exerts on moving electric charges and on magnetic materials. When placed in a magnetic field, magnetic dipoles tend to align their axes parallel to the magnetic field. Magnetic fields also have their own energy with an energy density proportional to the square of the field intensity.
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For example, in the case of a ferromagnetic liquid.
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Magnetism
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One of the phenomena by which materials exert attractive or repulsive forces on other materials. Some well-known materials that exhibit easily detectable magnetic properties (called magnets) are nickel, iron, cobalt, and their alloys; however, all materials are influenced to greater or lesser degree by the presence of a magnetic field.
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Melting
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A process that results in the phase change of a substance from a solid to a liquid. The internal energy of a solid substance is increased (typically by the absorbtion of heat) to a specific temperature (called the melting point) at which it changes to the liquid phase.
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Metal Organic Framework
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(or MOF). A class of cordination polymers consisting of metal ions or clusters coordinated to organic ligands to form 1, 2 or 3-dimensional structures with the special feature that they are often porous. MOFs are of interest for the storage of gases such as hydrogen and carbon dioxide. Other possible applications of MOFs are in gas purification, gas separation, catalysis, as sensors and as supercapacitors.
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Microfluidic Pump
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Devices that can control and manipulate small fluid volumes. Typically this term refers to pumps with functional dimensions in the micrometer range.
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Nucleation
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The extremely localised budding of a distinct thermodynamic phase. Some examples of phases that may form via nucleation in liquids are gaseous bubbles, crystals or glassy regions. Creation of liquid droplets in saturated vapor is also characterized by nucleation. Most nucleation processes are physical, rather than chemical, but a few exceptions do exist (e.g. electrochemical nucleation).
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Ostwald Ripening
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An observed phenomenon in solid solutions or liquid sols that describes the change of an inhomogeneous structure over time, i.e., small crystals or sol particles dissolve, and redeposit onto larger crystals or sol particles. Occurs because larger particles are more energetically favored than smaller particles. This stems from the fact that molecules on the surface of a particle are energetically less stable than the ones in the interior. Ostwald ripening is also observed in liquid-liquid systems, causing diffusion of monomers (i.e. individual molecules or atoms) from smaller droplets to larger droplets due to greater solubility of the single monomer molecules in the larger monomer droplets.
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Physisorption
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(or physical adsorption) A type of adsorption in which the adsorbate adheres to the surface only through Van der Waals (weak intermolecular) interactions, which are also responsible for the non-ideal behaviour of real gases.
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Roller
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A cylindrical device that rotates around its principle axis, typically to perform useful work, such as the compression of sheet metal between a pair of rollers.
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Sol
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A colloidal suspension of solid particles (1-500 nanometres in size) in a liquid. Examples include blood, pigmented ink, and paint.
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Spin Coating
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A procedure used to apply uniform thin films to flat substrates. In short, an excess amount of a solution is placed on the substrate, which is then rotated at high speed in order to spread the fluid by centrifugal force.
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Spray
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When a liquid is dispersed as a stream of droplets (atomisation), it is called a spray. Spray nozzles are used to achieve two primary functions: increase liquid surface area to enhance evaporation, or distribute a liquid over an area.
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Wetting
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The ability of a liquid to maintain contact with a solid surface, resulting from intermolecular interactions when the two are brought together. The degree of wetting is determined by a force balance between adhesive and cohesive forces. Adhesive forces between a liquid and solid cause a liquid drop to spread across the surface. Cohesive forces within the liquid cause the drop to ball up and avoid contact with the surface.
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