Where does wetting collide?

In surface science wetting is the degree to which a liquid spreads across a solid instead of beading up, fixed by the balance of the solid–vapour, solid–liquid, and liquid–vapour interfacial energies and read off as the contact angle where the three phases meet. Young's An essay on the cohesion of fluids set out the force balance at that contact line that still carries his name, a low angle meaning good wetting and a high angle poor wetting. The referent is the equilibrium spreading of a liquid on a surface, a thermodynamic construct measured by contact angle, and it is the parent of the soldering meaning while being wholly unrelated to the childhood condition that shares the word.[1]

Unit

The contact angle a liquid makes against a solid surface

Recovery means

Not applicable

Measured by

Quantified by the equilibrium contact angle, spreading coefficient, and surface-energy terms of Young's balance

In soldering, wetting is the spreading of molten solder over a metal surface and its reaction with it to form a continuous, low-angle fillet bonded by an intermetallic layer, the condition for a sound joint rather than a solder ball sitting on top of the pad. Humpston and Jacobson's Principles of soldering treats this as the same interfacial-energy spreading as general wetting, with the added feature that the molten alloy chemically reacts with the base metal as it wets. The referent is the solderability of a surface, measured by wetting force and time on a wetting balance and by the dihedral angle of the fillet; it is the surface-science construct applied to molten metal, and shares nothing but the word with bedwetting.[2]

Unit

The wetting force and contact angle of molten solder on a base metal

Recovery means

Not applicable

Measured by

Assessed on a wetting-balance meniscograph by wetting force and time to wet, and by the spread area and fillet angle of the solidified joint

In pediatric urology, bedwetting (nocturnal enuresis) is involuntary urination during sleep in a child old enough to be expected to stay dry, understood as a mismatch among nighttime urine production, bladder capacity, and arousal from sleep rather than a behavioural fault. Nevéus's Nocturnal enuresis—theoretic background and practical guidelines sets out these mechanisms and the stepwise approach to treatment. The referent is a clinical condition of urinary continence, tracked by wet-night frequency and response to therapy, and it collides with the physics of spreading liquids only through the everyday verb 'to wet'.[3]

Unit

The frequency of involuntary wet nights in a child past the expected dry age

Recovery means

Many children outgrow it spontaneously; enuresis alarms and desmopressin raise the chance of sustained dry nights

Measured by

Tracked by wet-night counts, voiding and drinking diaries, and response to alarm or pharmacological treatment