These images depict how the photonic sensor translates finger movements into
color changes, as the photonic crystal reacts to the change in local humidity
caused by the approach of the finger without direct contact.
(September 23, 2015) Chemists at LMU have fabricated a novel nanosheet-based photonic crystal that changes color in response to moisture. The new material could form the basis for humidity-sensitive contactless control of interactive screens on digital devices.
LMU chemists have developed a photonic crystal from ultrathin nanosheets which are extremely sensitive to moisture. “These photonic nanostructures change color in response to variations in local humidity. This makes them ideal candidates for the development of novel user interfaces for touchless devices,” says Professor Bettina Lotsch of the Department of Chemistry at LMU and the Max Planck Institute for Solid State Research in Stuttgart. The new sensing platform is described in the journal “Advanced Materials”.
“The humidity around a fingertip is slightly higher than the overall level of moisture in the ambient air,” explains Katalin Szendrei, a member of Prof. Lotsch’s research group. “This difference can be detected by our photonic sensor, and causes it to change color – without any contact with the nearby fingertip.” It is this extreme sensitivity to local moisture that makes the nanostructure so interesting for use in “touchless”-screens. “Contactless control is a particularly attractive option for next-generation positioning interfaces such as ticket machines or cash dispensers, which are used by hundreds of customers each day. In this case, touchless navigation has obvious advantages with respect to hygiene,” says Szendrei, pointing to one potential application for the new device.