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.