Microencapsulation

A huge range of compounds can be encapsulated in tiny polymer spheres so they can be handled conveniently.

For example, drugs can be encapsulated so that when they are swallowed, the polymer coating breaks down slowly allowing the drug to be released over a long period.
And microspeheres containing inks can be coated onto the back of paper to make 'carbonless paper' - the spheres break when they are crushed by running a pen over them, releasing the ink.

These spheres are created by stirring together two immiscible liquids - one containing the polymer and the other containing the active component (such as the drug). The resulting emulsion is then dried until both liquids have evaporated, leaving the microspheres as a dry powder.

Unfortunately it is not possible to study the process in detail since the mixture needs to be stirred constantly to keep the two components separate. However, in the absence of gravity, the emulsion can be left to stabilise. As the evaporation proceeds it is possible to observe the droplets in detail and thus understand the physical processes involved.

With increased understanding it should be possible to improve the industrial process and thus form more regular spheres with less wastage. This in turn should allow such advances as multiple drug doses in a single pill or injection that are released over a several separate delayed periods - a goal of the World Health Organisation in treating disease in developing countries.

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