University spin-out designs a tiny low-power chip to run coastal flood sensors for years

Flood sensors along a coastline have a simple job: measure the water level and tell someone when it is rising. The hard part is keeping them working. Batteries run flat, salt eats into casings and engineers have to walk sea walls and marshes to swap them. A small company spun out of the University of Wrenhaven believes it has a fix at the level of the silicon itself.

Tidemark Silicon, founded three years ago by two electronic engineers and a marine scientist, has designed a chip that combines a pressure sensor interface, a radio and a tiny processor on a single piece of silicon measuring three millimetres across. In tests, a sensor built around the chip drew an average of four microwatts, which the company says would let it run for more than ten years on a coin-sized battery while reporting every five minutes.

The key, according to co-founder Dr Lena Vasquez, is that the chip spends almost all its time asleep. A low-power timer wakes it, it takes a reading, and it only switches on the power-hungry radio if the level has changed by more than a set amount or a scheduled report is due.

Most sensors waste their battery saying nothing has happened. Ours only speaks when it has news.

Testing on the Saltings

The first wafers were manufactured at a commercial foundry abroad earlier this year. Forty prototype sensors have since been fixed to posts and sluice gates across the Saltings, the tidal marsh east of the city, in a trial with the Wrenhaven Marine Institute. Readings are relayed to a shared gateway at the ferry stop and on to the institute's servers.

Cost is the other selling point. Existing tide and river gauges in the region cost several thousand euros each to install and need a site visit at least once a year. Tidemark says its sensors could sell for under €150, small enough to clip onto a post, and would only need replacing when the casing wears out. The company has filed two patents covering the wake-up circuit and the way the radio negotiates with the gateway.

Professor Graham Okonkwo, who leads coastal monitoring at the institute, said the trial would run through the winter storm season. If the devices hold up, he wants to place one sensor every 200 metres along vulnerable stretches of the bay, rather than the handful of gauges that exist today. The company has raised €2.4 million from regional investors and the university's own fund, and is now in talks with two national flood agencies about pilot orders.