Leakiness

Leakiness refers to the tendency of a system to allow unintended passage of substances through barriers or interfaces. The term is used across disciplines to indicate how easily fluids, gases, or information can escape or leak from a controlled boundary. Measurement and consequences vary by context, but common elements include a defined boundary, driving force (pressure, concentration, voltage), and a reported leakage rate or leakage current.

In engineering and physical contexts, leakiness is quantified as a leakage rate, such as liters per minute, or grams per second, under a specified pressure difference. It applies to seals, tanks, piping, containers, and microfluidic devices. In electronics, leakiness often means leakage current: undesired current that flows through an insulating layer or junction when a voltage is applied, contributing to power loss and potential failure.

In biology and medicine, leakiness describes permeability of barriers such as epithelia and endothelium. Increased leakiness or permeability can indicate inflammation or damage, and is measured using tracer molecules or imaging techniques.

In materials science and environmental engineering, porous materials and membranes exhibit leakiness determined by pore size, connectivity, and pressure gradients; it affects filtration, gas separation, and containment. Theoretical models relate leakiness to permeability and tortuosity.

Reducing leakiness involves improving sealing, choosing materials with lower permeability, refining fabrication, and applying coatings; conversely, controlled leakiness is desirable for selective transport in membranes or sensors.