Conventional blood sugar sensors rely on enzymes — proteins that recognize glucose. But enzymes are finicky: they spoil from heat, moisture, and time, like cut flowers wilting without water.

Here, instead of enzymes, a non-living material does the job: nickel oxide, grown as tiny flowers on a sheet of graphite paper. Each "flower" is a cluster of petal-like nanowires that together create a huge surface area for meeting glucose. The larger the area, the better the sensor detects sugar.

When glucose touches the surface, it oxidizes, and the current increases. The rise in current is directly proportional to the amount of sugar: in the range from zero to ten millimoles per liter — which is exactly the physiological level in human blood. The sensor can detect even one-tenth of a millimole per liter.

Importantly, the sensor is not distracted by other substances present in blood: ascorbic acid, fructose, sucrose, and table salt. It picks out glucose specifically, like an experienced taster identifying the right ingredient in a complex dish.

Such a sensor could become the basis for durable and inexpensive devices that measure sugar without biological components.