Visual, non-invasive monitoring of body temperature of patients without using a thermometer may become a reality soon, thanks to the work carried out by a team of scientists led by John Philip, head of the smart materials section at the Indira Gandhi Centre for Atomic Research (IGCAR), Kalpakkam, near Chennai. The concept is based on ferrofluid emulsion contained in a thin film that changes colour with rise in temperature within a narrow range — 30-40° C. The study was published in the journal Optical Materials. The emulsion has iron oxide nanoparticles containing oil droplets dispersed in water. “Till now ferrofluid was used as a magnetic stimuli-responsive material. We now found that in the presence of a temperature-sensitive polymer — poly(N-isopropylacrylamide), also known as PNIPAM) — the ferrofluid emulsion can be used as a thermally tunable grating to produce different colours,” says Dr. Philip.

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