Microcapsules that respond to light
A chemical process known as encapsulation creates small capsules by coating tiny particles or droplets of one substance in another. Many products that we use daily incorporate microcapsules, including foods, perfumes, drugs, dyes, pesticides and herbicides. Microcapsules help to stabilise and extend the life of their contents, and they allow for controlled release, among other advantages. EU-funded scientists of the PHOTOCAP (Preparation and characterization of photo-responsive microcapsules based on azobenzene derivatives, for controlled delivery of active agents under visible light) initiative have developed a novel microcapsule that can be moderated by light. They did this by first creating and characterising substances that change their molecular arrangement in response to light. Then, they used these substances to synthesise 15 different types of microcapsules filled with perfume. The researchers used various techniques to characterise these new microcapsules, including microscopy, 3D modelling and a panel of human testers. Results showed that the microcapsules were smaller after exposure to 3 hours of light compared to before irradiation. However, they subsequently recovered to almost their original size after 15 hours in the dark. The microcapsules also released their contents only after light exposure and over an extended period. This was demonstrated by the human panel, which could detect the perfume for up to 7 hours, compared to 3 hours for regular perfume. Modelling revealed that the microcapsules were less dense before light exposure than after due to the chemical rearrangement that takes place in response to light. Light-sensitive microcapsules like these could be used in household goods, medicine, electronics, textiles and the chemical industry. They could lead to more sustainable production methods, more effective healthcare products (such as sunscreens) and cheaper goods.
Keywords
Microcapsules, light-sensitive, perfumes, PHOTOCAP
