Microneedle sensor checks fish freshness in under two minutes

Scientists in Australia have created a small handheld device that can instantly tell whether a piece of fish is still fresh. The new sensor, developed by researchers at Deakin University and Monash University, uses an array of tiny microneedles to measure a key chemical that rises as fish spoils.

When a fish dies, its DNA and other molecules begin to break down, producing a compound called hypoxanthine. The more hypoxanthine present, the longer the fish has been dead — making it a reliable indicator of freshness.

The new sensor contains a 4×4 grid of microneedles coated with gold nanoparticles and an enzyme that reacts specifically with hypoxanthine. When the array is pressed into the fish, the reaction creates a measurable electrical signal. The device reads that signal and converts it into a freshness score.

Researchers tested the device on salmon left at room temperature for up to two days. The sensor could detect extremely low levels of hypoxanthine — amounts typically associated with very fresh fish — and delivered results in about 100 seconds. Its accuracy matched that of commercial lab-based test kits, but without requiring any sample preparation or equipment.

Spoiled seafood is a major source of food poisoning, and traditional freshness checks often rely on smell, texture, or time stamps — all of which can be unreliable. This new microneedle sensor provides a fast, objective, and simple way to verify freshness. The team says it could eventually be used by restaurants, grocery stores, or food processors to quickly screen fish before it reaches customers.