Come to think of it – Smart, cheap tags for plant pots

Delta and Delft Integraal often write about innovative ideas that offer big promises for the future. But what has happened to such ideas a couple years on? What for instance has happened to the inexpensive Rfid tags that could measure how much water is in a plant pot?

Delta, 25-01-2007

Professor Gerard Meijer and guest researcher dr. Max Hilhorst have invented a cheap alternative for expensive moisture meters in pot plants.

Many people come across Rfid tags every day. They’re used in library books and supermarkets, as identification or to set off alarms when products are being stolen. A guest researcher at TU Delft, dr. Max Hilhorst, has found a remarkably unusual way of using these tags to measure how much water is left in a plant pot.

Four years ago he won several grants for this invention, which he developed together with professor Gerard Meijer (Electrical Engineering, Mathematics and Computer Science). Their wireless tags have no batteries and use an electrical impedance circuit. “This circuit applies a RF signal to the tag’s electrodes, which enables it to measure the capacity and moisture between the electrodes in the plant pot”, Hilhorst explains. “The tag sends this information to the receiver, so the gardener will know whether the plants need water or not.” The researchers joined Wim Stenfert Kroese in setting up a company called SensorTagSolutions, for further developing the technology. “The last three years we’ve perfected the technique, and thanks to research at TU Delft, TNO and TU Eindhoven, the system is ready for commercialisation.” At the moment gardeners use expensive sensors replete with impractical cables that take up lots of space.

The coming months will be a very exciting time for SensorTagSolutions. This fall a pilot project starts involving ten gardeners in the Netherlands who will test the tags. “We’re very curious what they’ll think of it. We’ll also conduct user-centred research”, says Hilhorst, who expects to put the tags on the market this fall.

In order to make the tags commercially successful and competitive, however, SensorTagSolutions still has some tough nuts to crack; for instance, they must make tags that cost no more than 0.10 euro cents. “A gardener sells his pot plants at auctions for 0.50 cents, so the tags must be very cheap.” Hilhorst is currently in talks with companies to produce the tags for a low price.

He is also looking into new possibilities for his tags: “I can’t tell you exactly what they are, but we could use these tags to measure a number of things. It could set off an alarm when a baby has a wet diaper for instance. Or in a hospital it could detect the pattern of someone‘s heartbeat. The tag could tell when the pattern changes. It’s fascinating how many possibilities there are with these small tags.”


Hoe gaat Delft om met water en hoe houden we droge voeten, waren vragen die waterorganisaties afgelopen zaterdag beantwoordden op de eerste Delftse Waterdag. Door je in een megaballon over het water te bewegen, is niet de meest voor de hand liggende manier. Maar wel leuk.

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