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Chinese magnetic sensor breakthrough may help smartwatch detect submarine 500 metres deep
Compact chip containing Hall-effect sensor can pick up faint magnetic fields by generating a tiny voltage without increasing noise output
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Zhang Tongin Beijing
Picture a fisherman hauling in his nets on a calm morning at sea, when his smartwatch suddenly vibrates with an alert: “Magnetic anomaly detected – possible submarine passing 500 metres below.”
Far‑fetched as it sounds, Chinese scientists have just taken a decisive step towards making that scenario real.
A team from the Hefei Institutes of Physical Science and the Ningbo Institute of Materials Technology and Engineering, both under the Chinese Academy of Sciences (CAS), has created a Hall‑effect magnetic sensor so sensitive that it could, in theory, pick up the faint magnetic shadow of a steel‑hulled submarine from half a kilometre (1,640 feet) away – all within a chip no bigger than a grain of dust.
Their findings, published on July 17 in the journal Physical Review Letters, shatter a decades-old sensitivity-versus-noise trade-off that has kept everyday magnetic sensors from hearing the quietest signals.
Hall‑effect sensors are the unsung workhorses inside many everyday gadgets. Already built into smartwatches, smartphones, car wheel‑speed detectors and hospital scanners, they detect magnetic fields by generating a tiny voltage when a field is present. They are simple, cheap, fast and compact – perfect for wearables.
But until now, shrinking them and making them more sensitive came with a punishing side‑effect: more noise, much like cranking up a radio’s volume also amplifies the hiss.
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