Hygroscopy

Hygroscopy is the phenomenon of attracting and holding water molecules via either absorption or adsorption from the surrounding environment, which is usually at normal or room temperature.

For example, a finely dispersed hygroscopic powder, such as a salt, may become clumpy over time due to collection of moisture from the surrounding environment.

Hygroscopy is essential for many plant and animal species' attainment of hydration, nutrition, reproduction and/or seed dispersal.

[4] He noted pea seeds, both living and dead (without germinative capacity), responded similarly to atmospheric humidity, their weight increasing or decreasing in relation to hygrometric variation.

Being hygroscopic, their microscopic particles provide an attractive surface for moisture vapour to condense and form droplets.

Deliquescence, like hygroscopy, is also characterized by a strong affinity for water and tendency to absorb moisture from the atmosphere if exposed to it.

Owing to their very high affinity for water, these substances are often used as desiccants, which is also an application for concentrated sulfuric and phosphoric acids.

The phrase "hygroscopic movement" originated in 1904's "Vorlesungen Über Pflanzenphysiologie", translated in 1907 as "Lectures on Plant Physiology" (Ludwig Jost and R.J. Harvey Gibson, Oxford, 1907).

[10] Hygromorphy is a common mechanism of seed dispersal as the movement of dead tissues respond to hygrometric variation,[11] e.g. spore release from the fertile margins of Onoclea sensibilis.

[11] The direction of the resulting force depends upon the architecture of the tissue and is capable of producing bending, twisting or coiling movements.

Typical of hygroscopic movement are plant tissues with "closely packed long (columnar) parallel thick-walled cells (that) respond by expanding longitudinally when exposed to humidity and shrinking when dried (Reyssat et al., 2009)".

[2] Graded distributions varying in density and/or cell orientation focus hygroscopic movement, frequently observed as biological actuators (a hinge function); e.g. pinecones (Pinus spp.

All rely upon a bi-layered parallel fiber hygroscopic cell physiology to control the awn's movement for dispersal and self-burial of seeds.

[35] Several hygroscopic approaches to harvest atmospheric moisture have been demonstrated and require further development to assess their potentials as a viable water source.

The most common cause of synthetic glue failure at high humidity is attributed to water lubricating the contact area, impacting bond quality.

Hygroscopic glues may allow more durable adhesive bonds by absorbing (pulling) inter-facial environmental moisture away from the glue-substrate boundary.

[14] Integrating hygroscopic movement into smart building designs and systems is frequently mentioned, e.g. self-opening windows.