Tiny particles that look like flowers can do two things at once: heat up and tell you how hot they are. This isn't science fiction: it's the result of working with nanoparticles made of cobalt ferrite, a magnetic material that responds to magnetic fields. Usually, heating and temperature measurement require separate tools, but here everything is combined in a single particle.
How does it work? The particles are placed in an alternating magnetic field, and their magnetization starts to oscillate. The nature of these oscillations depends on temperature: the hotter the particle, the slower it 'flips' in the magnetic field, like honey thickening as you stir it. The researchers noticed that the shape of the magnetization loop can reveal the particle's temperature precisely. Meanwhile, the particles also heat up under infrared light, and this heating can be tracked via the change in magnetic response.
Importantly, this method works even after the particles are coated with a protective shell or placed in various liquids. This means they can be used in living tissues without worrying that the signal will be lost. In the future, such particles could help doctors precisely control heating during tumor treatment without damaging healthy cells.
Cobalt ferrite nanoflowers heat up under infrared light, which we can't see but feel as warmth from the sun or a campfire.
A similar principle of self-regulating heating appears in science fiction, where medical nanorobots maintain the body's temperature from within.