Pencil Lines Can Turn a Piece of Paper Into a Simple Sensor

By Jamie Condliffe on at

The graphite that slips from the point of your pencil onto a page may be of more use than simply writing and drawing. A team of researchers has shown that simple pencil lines can be used as an accurate sensor to measure the deformation of objects.

The team, from the University of Science and Technology Beijing, has been investigating how plain pencil shapes drawn on common paper can be used measure by how much objects are bent. The graphite deposited by a pencil can conduct electricity — albeit badly — and its already high electrical resistance changes subtly when the object it's laid on changes shape.

By drawing a pencil rectangle on a piece of paper and accurately measuring those changes the researchers have shown that they can accurately measure the angle at which a piece of paper is bent, reports New Scientist. They also glued it to a human finger to detect the articulation of a digit, into a book to measure how far it was opened, and to a ruler to measure the bending of the simple beam. All worked well. Perhaps most impressive, though, is the fact that the measurements acquired by the paper sensors are almost as accurate as commercially available sensors. The results are published in Advanced Functional Materials.

There are clear applications for such a simple sensor that can be made over and over again for virtually nothing. In the first instance they could be used by hobbyists at home or in schools to introduce the concept of sensing to students. But further down the line the researchers reckon that graphite could be used to create ad-hoc sensors for robotics and wearable technologies, that can be used for a short while, removed, and easily reinstated at little to no cost. Not bad for a humble pencil. [Advanced Functional Materials via New Scientist]

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