Tiny Diamond Compass Peers Inside Batteries express
Ordinary magnetic sensors lose sensitivity as they shrink. But scientists turned a tiny diamond into a light-based compass. Unlike jewelry diamonds, what matters here isn't purity but artificially created defects — these are what turn the crystal into a compass. Under a laser beam, these defects start glowing, but a magnetic field sharply quenches the glow. That's how the diamond reveals the field's direction and strength.
The secret to its clarity lies in a fiber-optic bundle of many glass threads. One thread carries the beam to the diamond, while others collect the returning light, eliminating interference. This entire optical setup, along with the diamond, fits inside a 6-mm tip — thinner than a pencil.
The sensor is so sensitive it picks up fields millions of times weaker than Earth's, and it needs no bulky shielding. They brought it close to a working lithium-ion battery and, through spectroscopic measurements, mapped the internal currents.
This technology will be useful for checking microchips, implants, and even studying living tissues.
These sensors are already being tested to record nerve impulses: they sense the ultra-weak magnetic fields that neurons create.
This device is like a tricorder from Star Trek — a portable scanner that sees the internal structure of objects.