The sensor combines pyroelectric and thermoelectric effects with a nano-optical phenomenon. (Image: Thor Balkhed)

Robotics, prostheses that react to touch, and health monitoring are three fields in which scientists are working to develop electronic skin. Researchers have developed a sensor that, similar to human skin, can sense temperature variation that originates from the touch of a warm object as well as the heat from solar radiation. The sensor combines pyroelectric and thermoelectric effects with a nano-optical phenomenon.

A voltage arises in pyroelectric materials when they are heated or cooled. It is the change in temperature that gives a signal, which is rapid and strong, but that decays almost as rapidly. In thermoelectric materials, in contrast, a voltage arises when the material has one cold and one hot side. The signal here arises slowly and some time must pass before it can be measured. The heat may arise from a warm touch or from the Sun; all that is required is that one side is colder than the other.

A pyroelectric polymer was combined with a thermoelectric gel, resulting in a rapid and strong signal that lasts as long as the stimulus is present. Furthermore, the two materials interact in a way that reinforces the signal.

The sensor also uses another nano-optical entity known as plasmons, which arise when light interacts with nanoparticles of metals such as gold and silver. The incident light causes the electrons in the particles to oscillate in unison, which forms the plasmon. This phenomenon provides the nanostructures with optical properties such as high scattering and high absorption.

The sensor is also pressure-sensitive so a signal arises when the sensor is pressed with a finger, but not when it is subjected to the same pressure with a piece of plastic — it reacts to the heat of the hand.

For more information, contact Magnus Jonsson at This email address is being protected from spambots. You need JavaScript enabled to view it.; +46 11-36-34-03.