Smart Fibres
Microencapsulation
Microencapsulated fabrics are among the latest generation of intelligent textiles. Microencapsulation involves encapsulating liquid or solid substances in tiny thin-walled natural or synthetic bubbles. Microspheres gradually release active agents by simple mechanical rubbing, which ruptures the membrane over time.
Encapsulation has allowed moisturisers, therapeutic oils, and insecticides to be incorporated into fabrics. Buzz Off is an encapsulation treatment designed to prevent mosquito bites. Originally developed for the military, Buzz Off uses microspheres containing permethrin, an all-natural insect repellent derived from the chrysanthemum plant, and is now being sold worldwide for cotton fabrics destined for holiday clothing.
Medical application of encapsulation has centred around the delivery of drug treatments through clothing, to patients. One such application involves the delivery of antimicrobial treatments to cut down the bugs causing the hospital super-infection MRSA. The potential of microencapsulation for use in sportswear, underwear and workwear was soon recognised and now it is becoming a common treatment for fashion clothing. The use of microencapsulated antibacterials was encouraged by the difficulty of eliminating bacteria from clothing. One common treatment works by blocking the cell walls of the bacteria and cause them to starve, keeping garments fresh and hygienic.
Micro-encapsulation is also used in thermo-chromic and photo-chromic fabrics, which change colour with changes in temperature or light. The fabrics themselves are not thermo or photo-chromic, but their microencapsulated colourings are. For the time being, thermo-chromic micro-encapsulation is almost entirely limited to the lingerie and swimwear sectors and industrial clothing such as protective and safety clothes.
Micro-encapsulation also offers another way of maintaining body heat. Phase-change micro-encapsulation involves encapsulating a paraffin-based phase change material (PCM) in plastic shells. In contrast to the microcapsules used in cosmetic textiles, which must be thin-walled enough to allow for the gradual release of the material within the shell, the shells used for heat retention are hard; to protect the paraffin based substance from wear and tear. The spheres are small – about 1,000 microcapsules can fit on a single pinhead. The PCM is ultra-sensitive to temperature variations: below 37° the PCM remains in its solid state; above this temperature it turns to liquid, storing surplus body heat. When it solidifies again, the PCM releases body heat stored in the plastic shells and distributes it evenly around the body. This re-heating effect can last several hours. Fabrics containing PCM microcapsules are capable of storing at least 10 times more heat than untreated products.
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