deswelling

Deswelling is the process by which a material, tissue, or structure loses water or solvent and returns to a less swollen or unswollen state. It is the reverse of swelling and can occur passively through diffusion and evaporation or actively through external forces or changes in environmental conditions that favor water expulsion.

In biology and medicine, deswelling describes the resolution of tissue swelling, or edema, as excess interstitial fluid is cleared by venous return and lymphatic drainage. This process is influenced by osmotic gradients, capillary filtration rates, and therapeutic interventions such as compression therapy, elevation, and diuretics that reduce fluid buildup.

In materials science, deswelling is a common behavior of hydrogels and porous polymers that expel water in response to stimuli. Thermoresponsive polymers, for example, may deswell when the temperature rises above a critical solution temperature, causing the network to collapse and release water. Other triggers include changes in ionic strength, pH, solvent quality, or applied mechanical compression. Deswelling kinetics depend on factors such as crosslink density, water diffusivity within the network, and ambient conditions.

Measurement of deswelling often involves tracking changes in mass, volume, or dimensions to determine deswelling ratios and rate constants. Techniques include gravimetric, volumetric, and rheological analyses. Applications span drug delivery systems, tissue engineering scaffolds, soft actuators, and sensors, where controlled shrinkage or rapid deswelling can be advantageous.