microcapsule

Microcapsules are tiny particles in which a core material is enclosed by a protective shell. The core can be a liquid, solid, or gas, and the shell provides physical separation from the surrounding environment. Encapsulation can protect sensitive substances from degradation, mask taste or odor, and enable controlled or targeted release of the core material.

Shell materials come from natural polymers such as alginate, gelatin, or starch; synthetic polymers such as polyurea, polyurethane, or polylactic acid; or inorganic coatings such as silica or calcium carbonate. In many cases, multi-layer or composite shells are used to tune permeability, stability, and release behavior.

Microencapsulation is achieved by several processes, including coacervation and complex coacervation, interfacial polymerization, spray drying, spray cooling or congealing, extrusion, and phase separation. The choice of method depends on the core properties, desired capsule size, and required release profile.

Release mechanisms include diffusion through the shell, dissolution of the core, rupture of the shell, or shell degradation triggered by pH, temperature, moisture, or enzymes. These mechanisms enable sustained, delayed or site-specific delivery of the payload.

Applications span pharmaceuticals for controlled-release drugs, food and beverages for flavor and nutraceutical delivery, cosmetics for active ingredient delivery, and agriculture for encapsulated pesticides and fertilizers. Typical microcapsule sizes range from about 1 to 1000 micrometers, with ongoing research into smaller, nano-scale capsules.