3D-printed pen creates sensor to detect water pollutant

A pen typically used for 3D drawing has become a tool for creating a chemical sensor in a laboratory at the University of São Paulo. Researchers used it to produce small electrodes that help measure the concentration of boric acid, a water-soluble compound that can contaminate water if not properly disposed of.

Instead of a large 3D printer, the team loaded the pen with a plastic filament containing conductive carbon. They then combined the resulting electrodes with filter paper that draws sample droplets toward its surface. When an electrical voltage is applied, the device measures a response that varies according to the amount of the compound present in the solution.

The researchers tested the method in the laboratory, including experiments on lake water samples. It could be useful in the future for rapid preliminary screening at remote sites, before sending samples requiring confirmation to a specialized laboratory. The results do not mean that an ordinary pen alone can test drinking water, nor that a commercially ready device has been launched.