Bioinspired Color Change through Guided Reflection

Abstract

been pursued, which is highly desirable in potential wide spread civil and military applications. [20][21][22][23] Some tunable coloration systems, such as stimuli-responsive chromic polymers, [24] cholesteric liquid crystals, [25] photonic crystals, [26,27] microfluidic system, [28,29] and plasmonic structures have been extensively investigated. [30,31] These systems help lay the foundation for the engineering of artificial adaptive camouflage systems with the capability similar to those biological systems that can rapidly alter their colors and patterns in response to the changing background. For example, through the use of simple microfluidic networks, Whitesides and co-workers were able to demonstrate the adaptive color change of their soft robots by pumping fluids with different colors into the microfluidic networks, [28] and using the similar microfluidic approach they further demonstrated entirely soft, autonomous robots. [32] Recently, a biomimetic plasmonic chameleon has been demonstrated, which showed the ability in matching the background using three primary colors by integrating color sensors, microcontrol system, and Au/Ag core-shell nanostructures. [33] Rogers and co-workers also reported an autonomous camouflage system consisting of a thermochromic dye film, distributed Joule heating actuators, and photodetectors lately. [34] With such system they were able to demonstrate the capability of adaptively matching of the background patterns without user input and external measurement.The above mentioned approaches certainly represent the exciting development in adaptive color change. Most of them, however, require the integration of color sensing, signal processing, and active color generation components in their color-change systems, which make both the systems and their fabrication processes relatively complex. Recently, there are explorations of using metamaterials to redirect the background light for "cloaking" of targets, and the practical applications involving metamaterial systems are actively pursued. [35][36][37][38][39][40] Currently, achieving effective color change that can response fast to match background spectra over the entire visible region through a practical and compact system is still a challenging task.Different from above active color-change approaches that involve active color sensing, signal processing, and active color generation, in this work, we explored a passive color-change approach based on guiding of the reflected light from the background (Figure 1a). The use of guiding of the light for matching Color change to match background has attracted particular attentions for many civil and military applications. Different from most current efforts in adaptive color change that include active color processing and generation, in this work a new passive color-change approach without the need of color processing and generation is proposed. Such approach takes inspiration from the biological camouflage systems such as those in the midwater squid Galiteuthis, which use "leaky" fiber-l...

Hydrogel for light delivery in biomedical applications

“…The structural cross section of photophores function as leaky light guides that counterilluminate to match downwelling sunlight for camouflage [ 44 ]. Deep-sea creatures are an excellent source of inspiration for light manipulating strategies such as the leaky waveguides in Galiteuthis phyllura [ 45 ] , transparent teeth from Idiacanthus atlanticus [ 46 , 47 ], and the body of jellyfishes [ 48 , 49 ]. By studying these natural wonders, the capabilities in light guiding and manipulation can be applied to innovative materials not only in biomedical fields but others as well.…”