What do frozen pizzas, scratch and sniff cards, and Aspirin have in common? They are just a few of the many products that rely on microencapsulation technology. Simply put, microencapsulation is the process in which a core substance is coated by a shell. The core contains tiny particles of a liquid, gas, or solid active ingredient which is surrounded by a shell. This shell is typically composed of organic polymers and acts as a shield for the active ingredient against the environment and other external forces. These capsules are truly tiny, ranging in size from one micron (1/1000 of a millimeter) to a few millimeters.
There isn’t just one method of microencapsulation. Each application of this technology depends on the physical and chemical properties of the active ingredient as well as the purpose for microencapsulation. Depending on the technique used, the active ingredient can be released in one of six ways: mechanical rupture, dissolution, melting, biodegradation, ablation (slow erosion), or diffusion. For example, the capsules of a scratch and sniff card are released by mechanical rupture of the shells. Scratching breaks the coating of the capsules and releases the perfumed core. Aspirin utilizes diffusion for a controlled release that prevents the negative side effects of a direct dose with high initial concentrations.
Microencapsulation is a developing field and is currently undergoing a period of rapid growth. It is important to understand the science behind this process as more and more everyday household items use controlled release technology.