Adaptive camouflage sheet spells out “UoI” in response to light stimulus.
Cephalopods, including octopus, squid and cuttlefish, have impressive natural camouflage capabilities that let them change their appearance in real time in response to surrounding environments—with a level of autonomous sensing and adaptation that has thus far eluded artificial camouflage systems. Now, an international team of researchers has reportedly developed a bio-inspired, adaptive optoelectronic system that successfully mimics this appearance modification, and that doesn’t require user input (Proc. Natl. Acad. Sci. USA, doi: 10.1073/pnas.1410494111).
The new system is a multilayer structure, with each layer replicating the functions of different cellular mechanisms in cephalopod skin. The top layer, inspired by pigment-containing chromatophores of cephalopods, consists of thermosensitive leucodye embedded in a photosensitive transparent polymer. The dye appears black at low temperatures and clear at temperatures above 47 degrees Celsius. Under that is a silver reflective surface that provides a white backdrop for other colors, just as leucophores do in cephalopods.
An ultrathin silicon diode, the next layer, serves as an actuator and heats the dye to affect its color, mimicking the muscles in the cephalopod that control the color of chromatophores. Finally, a layer of distributed, multiplexed photodetectors senses incoming light and provides guidance to the diodes, as opsins in skin are hypothesized to do. All of these layers are built on a flexible silicon substrate that can be bent and stretched around solid objects.
Laid out in an array of 16 by 16 unit cells, the device spontaneously creates black-and-white patterns in response to changing illumination in just 1-2 seconds. Although the present incarnation is quite basic, lead researcher John A. Rogers believes that these results provide principles and architecture that could be easily improved and integrated with scalable electronics for numerous military, consumer and industrial applications. Further research will include using electric-field or current-induced switching rather than heating diodes.