Microencapsulation may be defined as the process of surrounding or enveloping one substance within another substance on a very small scale, yielding capsules ranging from less than one micron to several hundred microns in size. The product obtained by this process is called as micro particles, microcapsules, microspheres which differentiate in morphology and internal structure.

When the particle size is below 1µm are known as nanoparticles, nanocapsules, nanospheres respectively and particles having diameter between 3 - 800µm are known as micro particles or microcapsules or microspheres. Particles larger than 1000µm are known as macroparticles.

Microcapsules may be spherically shaped, with a continuous wall surrounding the core, while others are asymmetrically and variably shaped, with a quantity of smaller droplets of core material embedded throughout the microcapsule. All three states of matter (solids, liquids, and gases) may be microencapsulated. This allows liquid and gas phase materials to be handled more easily as solids, and can afford some measure of protection to those handling hazardous materials.

Micro particles or microcapsules consist of two components namely core material and coat or shell material. The substance that is encapsulated may be called the core material, the active ingredient or agent, fill, payload, nucleus, or internal phase. The material encapsulating the core is referred to as the coating, membrane, shell, or wall material. Microcapsules may have one wall or multiple shells arranged in strata of varying thicknesses around the core.

Different types of materials like active pharmaceutical ingredients, proteins, peptides, volatile oils, food materials, pigments, dyes, monomers, catalysts, pesticides etc. can be encapsulated with different types of coat or shell materials like ethylcellulose, hydroxyl propyl methyl cellulose, sodium carboxy methyl cellulose, sodium alginate, PLGA, gelatine, polyesters, chitosans etc.

Techniques to Manufacture Microcapsules

There are various techniques are available for the encapsulation of core materials. Broadly the methods are divided into three types.

Chemical ProcessPhysico-chemical ProcessPgysico-mechanical Process
Interfacial polymerizationCoacervation and phase separationPan Coating
In situ polymerizationSol-gel encapsulationAir Suspension Coating
Matrix Polymerization Supercritical CO2 assisted microencapsulationCentrifugal Extrusion

Vibration Nozzle

Spray Drying and congealing

Fluid Bed Coating

Solvent evaporation

Microencapsulation processes and their applicabilities

Microencapsulation processNature of the core materialApproximate particle size (um)
Air SuspensionSolids35-5000*
Coacervation and phase separationSolids and Liquids2-5000*
Multiorifice centrifugationSolids and Liquids1-5000*
Pan coatingSolids600-5000*
Spray drying and congealingSolids and Liquids600
Solvent evaporationSolids and Liquids5-5000*

*The 5000µm size is not a particle size limitation. The Methods are also applicable for macrocoating

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