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In this report the design, fabrication, and testing of inkjet‐printed electrochromic pixels (ECPs) incorporating the biochrome, xanthommatin (Xa) as programmable display units is described. As a redox sensitive chromophore, Xa is present in some species as a physiological indicator with red (reduced) or yellow (oxidized) colors associated with different behavioral or developmental stages. These features have been recently leveraged in some materials applications, illustrating a bio‐inspired design solution to color‐changing sensors and displays. This paper describes an extension of these applications to print individually addressable ECPs that can be processed in a mild annealing step to introduce localized conductivity on initially nonconductive substrates. When formulated together with a poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) carrier ink, an addition of 0.19 wt% Xa is enough to generate dynamic ECPs which can be batch printed as lateral electrodes on any substrate to serve as both conductors and display units across electrically isolated boundaries. Application of low potentials triggers reversible color changes that span the red/yellow color space and can cycle for days. These results represent an important step towards the incorporation of alternative active materials like Xa to manufacture and scale low‐power, color‐changing pixels and patterns.

Nature is full of exemplary species that have evolved personalized sensors and actuating systems that interface with and adapt to the world around them. Among them, cephalopods are unique. They employ fast-sensing systems that trigger structural changes to impart color changes through biochemical and optoelectronic controls. These changes occur using specialized optical organs that receive and respond to signals (light, temperature, fragrances, sound, and textures) in their environments. We describe features that enable these functions, highlight engineered systems that mimic them, and discuss strategies to consider for future cephalopod-inspired sensor technologies.

xanthommatin (Xa)-based pigment granules and protein-based structural elements in the dermal chromatophore organs of squid Doryteuthis pealeii that produce a patchy iridescence of blue, green, yellow, and red colors within the same chromatocyte. [5] These observations point to a synergistic relationship between biochromes like Xa and supramolecular nanostructures that have yet to be explored in regulating tunable structural colors.In synthetic systems, the addition of biological pigments with or within artificial photonic assemblies has already shown exciting potential in regulating color hue and color purity of materials, warranting their further exploration for consumer applications such as coatings, cosmetics, apparel, and display design. [6][7][8][9] One example is the application of high refractive index melanin-based pigments incorporated into photonic assemblies to improve the color purity of a heterogeneous population of nanostructures. For example, Zhang et al. demonstrated this concept by mixing melanin-containing cuttlefish ink particles (diameter of 110 nm) with spherical polystyrene nanoparticles (diameters of 200-280 nm) to produce noniridescent amorphous photonic crystals. [6] Xiao et al. separately synthesized photonic films using melanin-inspired nanoparticles (diameter ≈ 100 nm) to produce a diverse array of colors that were governed by the thickness of the coatings. [7] Inspired by all of the advancements made using these melanin-based [6][7][8][9][10] and even non-melanin (e.g., pterin) [3] photonic structures, we asked whether other nonblack pigments that have a similarly high refractive index, such as Xa (yellow/red), can be used to design artificial photonic materials with tunable coloration.As a natural biochrome, Xa is found in pigment granules located within dermal chromatophore organs of cephalopods [5,11] and in the eyes, skin, and eggs of arthropods (e.g., dragonflies, butterflies, silkworms, and spiders). [12] Xa has a high reported refractive index range with a broad absorption profile. [13] Specifically, the real-portion of the RI for squidextracted xanthommatin was reported to be 1.92, 1.95, 1.88, and 1.73 in acidified-methanol, methanol, 50/50 methanol/water, and 0.2 m NaOH, respectively. [13] To evaluate how the absorptive profile of these yellow/red pigments change when incorporated into nanostructures, we prepared bidispersed colloidal assemblies using Xa tethered to 100 nm polystyrene (PS) spheres (PS100-XA) that were blended into variable suspensions of monodispersed PS nanoparticles (200-300 nm in diameter).The biological chromophore xanthommatin (Xa) contributes to the yellow, red, and brown colors and hues in cephalopods and arthropods. In many cases, Xa is also present as part of or coupled to supramolecular nanostructures, whose function has yet to be fully explored. To investigate how such structural elements impact the perceived color of these natural chromophores, amorphous photonic assemblies containing Xa chemically coupled to 100 nm polystyrene nanoparticles (PS10...