Stretchable Cephalopod‐Inspired Multimodal Camouflage Systems

Abstract

robotics. [9,10] More recently, the emergence of analogous platforms that dynamically modulate the propagation of IR radiation (i.e., heat) has facilitated exciting proof-of-principle demonstrations in areas such as energy conservation, [11,12] thermal management, [13,14] and IR camouflage. [15,16] Within this context, devices or systems that can potentially manipulate light across both the visible (400-740 nm) and IR (740 nm to 15 µm) spectral regions remain quite rare. To date, relatively few classes of these technologies have been reported, such as thermochromic phase-change materials, [17][18][19][20] electrochromic devices, [21][22][23] IR-reflecting platforms, [24,25] and reconfigurable soft machines [9] (see Table S1, Supporting Information), and they have featured drawbacks that include a limited degree of spectral modulation, impractical actuation requirements, poor stability to repeated actuation, slow response times, and/or complicated fabrication. [9,[17][18][19][20][21][22][23][24][25] Indeed, the engineering of devices and systems with tandem adaptive functionality across a broad spectral window (i.e., encompassing the visible, near-IR, short-wavelength IR, mid-wavelength IR, and long-wavelength IR) has proven challenging, in part because of the order of magnitude difference in the length scales associated with the propagation of visible and long-wavelength IR light. Consequently, there exists an impetus for the development of advanced multimodal camouflage platforms, which can present new scientific and technological opportunities across multiple fields.Some of the most prominent and impressive examples of soft, deformable systems that can reversibly and precisely change their appearance are found in nature-they are animals called coleoid cephalopods, [26][27][28][29][30][31][32] such as the Japetella heathi pelagic octopus (Figure 1A) [28] and the Taonius borealis glass squid ( Figure 1B). [29,30] These animals are capable of stunning feats of concealment, which include changing the transparency of their bodies by means of a sophisticated skin architecture that controls the transmission, absorption, and reflection of light ( Figure 1C). [26][27][28][29][30][31][32] In its most general form, the skin consists of multiple layers containing pigmented sizechanging organs called chromatophores, [33][34][35] typically narrowband-reflecting cells called iridophores, [36][37][38] and broadbandreflecting cells called leucophores [39][40][41] (Figure 1C). Although their precise arrangement and optical functionalities tend to Soft, mechanically deformable materials and systems that can, on demand, manipulate light propagation within both the visible and infrared (IR) regions of the electromagnetic spectrum are desirable for applications that include sensing, optoelectronics, robotics, energy conservation, and thermal management. However, the development of such technologies remains exceptionally difficult, with relatively few examples reported to date. Herein, this challenge is addressed by engineering ceph...

3D‐Printed Biomimetic Systems with Synergetic Color and Shape Responses Based on Oblate Cholesteric Liquid Crystal Droplets

“…[ 1–5 ] Many animals or plants found in nature can tune their body color, shape or morphology in response to environmental stimuli for camouflage, communication or reproduction. [ 6–9 ] These performances are generally accomplished by complex changes or deformations of their cells or tissues. For example, an octopus could adhere to a rock and become invisible by changing its color to that of surrounding environment via the elongation or contraction of its pigment cells.…”

Transparent Soft Actuators/Sensors and Camouflage Skins for Imperceptible Soft Robotics

“…Inspired by the camouflageable systems in Cephalopod, recent study developed a stretchable multimodal camouflage platform with multispectral region. [123] In order to do so, researchers used a trilayer system of acrylate elastomer substrate covered with wrinkled pentablock copolymer. As shown in Figure 8b, the irregular wrinkled surface of the pentablock copolymer is flattened by the equiaxial strain applied by the DEA actuating system and making the entire system to be transparent in visible to IR range.…”

“…Reproduced with permission. [123] Copyright 2020, Wiley-VCH. c) Active color shifting skin by the plasmonic spectral properties of electrodeposited gold and nanoarrays.…”

“…The wrinkled copolymer structure enables tunable transparency. Reproduced with permission [123]. Copyright 2020, Wiley-VCH.…”

Research Progress of Bionic Adaptive Camouflage Materials

“…Thus, in recent years, there has been an emerging demand on how to make camouflaged targets better adapt to the complex battlefield background. Meanwhile, bionic camouflage technology is becoming one of the vital ways to solve the focus issue (Lee et al, 2020;Xu et al, 2020). Organisms from many different phyla have evolved an impressive arsenal of light manipulation strategies that rely on the ability to generate and dynamically reconfigure hierarchically structured, complex optical material designs, often involving soft or fluid components.…”