Researchers in Europe have developed a novel sensing foam that would help in knowing when store shelves need restocking.
Shelves when attached to a thin layer of the foam can inform staff when products are out of stock, allowing a store to automatically monitor supply.
Researchers at Johannes Kepler University, in Linz, Austria, said that another application of the foam is that it can give other objects and surfaces sensing abilities.
The foam is created out of flexible sheets of polyolefin, each a quarter of a millimetre thick and containing air gaps that make the material light and elastic.
The similar material is presently used to make insulation for pipes and for padding in packaging.
Siegfried Bauer and colleagues developed cheap sensors using the foam by applying strips of silver-containing paint to either side of a sheet.
The electrically conductive stripes act as capacitors, storing a small amount of electric charge. When a product is placed on top of the foam, it is compressed slightly, changing the capacitors' ability to store charge.
Every foam sensor can detect differences of at least 10 grams or more per square centimetre, not particularly sensitive, but adequate for the purpose.
A grid of many individual sensor 'cells', developed by criss-crossing silver strips, can sense a box of cereal or a can of soup by weight. And, if printed using copper, instead of silver, the sensors should only cost about one dollar per metre.
Bauer said that many companies want low-cost ways of monitoring the stock on their shelves, adding that the foam technology is already being tested in one company.
"Being out of stock in a supermarket is a big issue, since it can cost them a few per cent of their income," New Scientist quoted him, as saying.
He further said that the foam could make other types of sensor, for instance it could be built into flooring to monitor people as they move around.
ZhongYang Cheng of Auburn University said: "I think this is a very great achievement. There are many sensors [available], but the issue is cost. For a supermarket, it could certainly reduce a lot of labour."
Cheng said that the foam technology could also be used to make portable keyboards for computers or cell phones.
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