Drops and bubbles

Liquid droplets and gas bubbles are bounded by curved interfaces whose shapes and motion are governed largely by surface tension.

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Surface tension: The energy cost per unit area of a fluid interface, arising from molecular interactions. It drives interfaces to shrink and gives drops and bubbles their characteristic shapes.
Curvature: A measure of how rapidly a curve or surface changes direction in space. Interface curvature helps set the pressure jump across drops and bubbles.
Inkjet printing: A printing method that ejects controlled droplets of ink onto a substrate. Precisely timed breakup turns a liquid jet into individual printed drops.
Liquid jet: A continuous stream of liquid moving through a surrounding fluid or vacuum. A jet is an extended liquid body that may later break into droplets.
Young–Laplace equation: An equation relating pressure difference across a curved interface to surface tension and curvature. It quantifies the pressure excess inside a curved drop or bubble.
Laplace pressure: The pressure difference across a curved interface caused by surface tension. Small-radius drops and bubbles sustain larger pressure differences.
Spray drying: A process that rapidly dries liquid droplets in a heated gas to produce powders. Droplet size and evaporation govern the resulting particles.
Cavitation: The formation and collapse of vapor-filled cavities in a liquid when local pressure falls sufficiently. Cavitation bubbles arise from pressure-driven vapor formation, unlike ordinary gas bubbles.
Contact angle: The angle at which a liquid–gas interface meets a solid surface, measured through the liquid. Wetting determines whether a drop spreads or beads on a surface.
Capillary length: The length scale at which gravity and surface tension have comparable effects on a fluid interface. It separates nearly spherical small drops from gravity-distorted larger ones.