reaggregation

Reaggregation is the process by which particles, molecules, or cells that have been dispersed or dissociated come back together to form larger aggregates or clusters. It is the reverse of dispersion or disaggregation and can occur in a wide range of systems, from colloidal suspensions to biological tissues.

In many materials, reaggregation is driven by attractive interparticle forces such as van der Waals interactions, electrostatic forces, depletion attractions, or hydrophobic effects. Changes in the surrounding medium—such as increased ionic strength, pH shifts, temperature changes, or the presence of destabilizing additives—can screen repulsive forces or enhance attractive ones, promoting reaggregation. Shear, time, and concentration also influence the rate and extent of aggregation, with collisions between particles enabling agglomeration.

Reaggregation appears in several contexts. In colloidal chemistry and paints, dispersed pigment or pigment-laden particles may re-cluster, affecting stability, color, and rheology. In soils, dispersed clay or silt particles can reaggregate when conditions favor attraction, influencing soil structure and porosity. In biology, dissociated cells may reaggregate into multicellular structures or spheroids through cell–cell adhesion molecules and extracellular matrix interactions, a process exploited in tissue engineering and cancer research. In polymers and nanomaterials, reaggregation can alter mechanical properties, porosity, and conductivity.

Measurement and control commonly involve dynamic light scattering, zeta potential, microscopy, and rheology to assess aggregate size and stability. Strategies to prevent unwanted reaggregation include surface modification, surfactants, charge stabilization, and careful control of pH, ionic strength, and shear conditions.