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Cephalopods, marine animals like squid, octopus, cuttlefish, or nautilus, have attracted the interest of the scientific community for many years due to their sophisticated neurophysiology, complex behavioral patterns, and stunning camouflage displays. It is thus not surprising that these animals have inspired a plethora of scientific advances in the fields of neuroscience, cell biology, and materials engineering. A part of this exciting research is reflected in the Special Issue Cephalopods: Inspired science.

Advanced thermal management technologies represent an important research frontier because such materials and systems show promise for enhancing personal physiological comfort and reducing building energy consumption. These technologies typically offer the advantages of excellent portability, user-friendly tunability, energy efficiency, and straightforward manufacturability, but they frequently suffer from critical challenges associated with poor breathability, inadequate wash stability, and difficult fabric integration. Within this broader context, our laboratory has previously developed heat-managing composite materials by drawing inspiration from the color-changing skin of the common squid. Herein, we describe the design, fabrication, and testing of breathable, washable, and fabric-integrated variants of our composite materials, which demonstrate state-of-the-art adaptive infrared properties and dynamic thermoregulatory functionalities. The combined findings directly advance the performance and applications scope of our bioinspired thermoregulatory composites and ultimately may guide the incorporation of desirable multifunctionality into other wearable technologies.

Acenes and N-heteroacenes have been synthesized and studied for over a century because of their fundamentally interesting materials properties and promise for device applications. Within this context, our laboratory has previously synthesized nitrogen-containing tetrabenzo[de,hi,op,st]pentacenes via an aza-Diels-Alder reaction-based approach, and herein, we expand our methodology to obtain substituted, expanded, functionalized, and dimeric tetrabenzoacenes. Overall, our study adds to the limited number of tetrabenzoacene derivatives reported to date and may open further opportunities for these materials in organic optoelectronics applications.

Multifunctional platforms that can dynamically modulate their color and appearance have attracted attention for applications as varied as displays, signaling, camouflage, anti-counterfeiting, sensing, biomedical imaging, energy conservation, and robotics. Within this context, the development of camouflage systems with tunable spectroscopic and fluorescent properties that span the ultraviolet, visible, and near-infrared spectral regions has remained exceedingly challenging because of frequently competing materials and device design requirements. Herein, we draw inspiration from the unique blue rings of the Hapalochlaena lunulata octopus for the development of deception and signaling systems that resolve these critical challenges. As the active material, our actuator-type systems incorporate a readily-prepared and easily-processable nonacene-like molecule with an ambient-atmosphere stability that exceeds the state-of-the-art for comparable acenes by orders of magnitude. Devices from this active material feature a powerful and unique combination of advantages, including straightforward benchtop fabrication, competitive baseline performance metrics, robustness during cycling with the capacity for autonomous self-repair, and multiple dynamic multispectral operating modes. When considered together, the described exciting discoveries point to new scientific and technological opportunities in the areas of functional organic materials, reconfigurable soft actuators, and adaptive photonic systems.

Wearable thermoregulatory technologies have attracted widespread attention because of their potential for impacting individual physiological comfort and for reducing building energy consumption. Within this context, the study of materials and systems that can merge the advantageous characteristics of both active and passive operating modes has proven particularly attractive. Accordingly, our laboratory has drawn inspiration from the appearance-changing skin of Loliginidae (inshore squids) for the introduction of a unique class of dynamic thermoregulatory composite materials with outstanding figures of merit. Herein, we demonstrate a straightforward approach for experimentally controlling and computationally predicting the adaptive infrared properties of such bioinspired composites, thereby enabling the development and validation of robust structure-function relationships for the composites. Our findings may help unlock the potential of not only the described materials but also comparable systems for applications as varied as thermoregulatory wearables, food packaging, infrared camouflage, soft robotics, and biomedical sensing.

Cephalopods (e.g., squids, octopuses, and cuttlefishes) possess remarkable dynamic camouflage abilities and therefore have emerged as powerful sources of inspiration for the engineering of dynamic optical technologies. Within this context, we have focused on the development of engineered living systems that can emulate the tunable optical characteristics of some squid skin cells. Herein, we expand our ability to controllably incorporate reflectin-based structures within mammalian cells via genetic engineering methods, and demonstrate that such structures can facilitate holotomographic and standard microscopy imaging of the cells. Moreover, we show that the reflectin-based structures within our cells can be reconfigured with a straightforward chemical stimulus, and we quantify the stimulus-induced changes observed for the structures at the single cell level. The reported findings may enable a better understanding of the color- and appearance-changing capabilities of some cephalopod skin cells and could afford opportunities for reflectins as molecular probes in the fields of cell biology and biomedical optics.

Quinolines and quinoline-containing macromolecules are renowned for their valuable biological activities and excellent materials properties. Herein, we validate a general strategy for the synthesis of chloro-containing quinoline, benzoquinoline and polybenzoquinoline variants via the aza-Diels-Alder reaction. The described findings could be ultimately implemented in other synthetic pathways and may open new opportunities for analogous quinoline-derived materials.

Naturally occurring and recombinant protein-based materials are frequently employed for the study of fundamental biological processes and are often leveraged for applications in areas as diverse as electronics, optics, bioengineering, medicine, and even fashion. Within this context, unique structural proteins known as reflectins have recently attracted substantial attention due to their key roles in the fascinating color-changing capabilities of cephalopods and their technological potential as biophotonic and bioelectronic materials. However, progress toward understanding reflectins has been hindered by their atypical aromatic and charged residue-enriched sequences, extreme sensitivities to subtle changes in environmental conditions, and well-known propensities for aggregation. Herein, we elucidate the structure of a reflectin variant at the molecular level, demonstrate a straightforward mechanical agitation-based methodology for controlling this variant's hierarchical assembly, and establish a direct correlation between the protein's structural characteristics and intrinsic optical properties. Altogether, our findings address multiple challenges associated with the development of reflectins as materials, furnish molecular-level insight into the mechanistic underpinnings of cephalopod skin cells' color-changing functionalities, and may inform new research directions across biochemistry, cellular biology, bioengineering, and optics.

Although many animals have evolved intrinsic transparency for the purpose of concealment, the development of dynamic, that is, controllable and reversible, transparency for living human cells and tissues has remained elusive to date. Here, by drawing inspiration from the structures and functionalities of adaptive cephalopod skin cells, we design and engineer human cells that contain reconfigurable protein-based photonic architectures and, as a result, possess tunable transparency-changing and light-scattering capabilities. Our findings may lead to the development of unique biophotonic tools for applications in materials science and bioengineering and may also facilitate an improved understanding of a wide range of biological systems.

Stem cells have attracted significant attention due to their regenerative capabilities and their potential for the treatment of disease. Consequently, significant research effort has focused on the development of protein- and polypeptide-based materials as stem cell substrates and scaffolds. Here, we explore the ability of reflectin, a cephalopod structural protein, to support the growth of murine neural stem/progenitor cells (mNSPCs). We observe that the binding, growth, and differentiation of mNSPCs on reflectin films is comparable to that on more established protein-based materials. Moreover, we find that heparin selectively inhibits the adhesion of mNSPCs on reflectin, affording spatial control of cell growth and leading to a >30-fold change in cell density on patterned substrates. The described findings highlight the potential utility of reflectin as a stem cell culture material.

Effective thermal management is critical for the operation of many modern technologies, such as electronic circuits, smart clothing, and building environment control systems. By leveraging the static infrared-reflecting design of the space blanket and drawing inspiration from the dynamic color-changing ability of squid skin, we have developed a composite material with tunable thermoregulatory properties. Our material demonstrates an on/off switching ratio of ~25 for the transmittance, regulates a heat flux of ~36 W/m2 with an estimated mechanical power input of ~3 W/m2, and features a dynamic environmental setpoint temperature window of ~8 °C. Moreover, the composite can manage one fourth of the metabolic heat flux expected for a sedentary individual and can also modulate localized changes in a wearer's body temperature by nearly 10-fold. Due to such functionality and associated figures of merit, our material may substantially reduce building energy consumption upon widespread deployment and adoption.

This roadmap outlines the role semiconductor-based materials play in understanding the complex biophysical dynamics at multiple length scales, as well as the design and implementation of next-generation electronic, optoelectronic, and mechanical devices for biointerfaces. The roadmap emphasizes the advantages of semiconductor building blocks in interfacing, monitoring, and manipulating the activity of biological components, and discusses the possibility of using active semiconductor-cell interfaces for discovering new signaling processes in the biological world.

Protein- and peptide-based proton-conducting biomaterials have been touted as particularly promising for bioelectronics applications because of their advantageous chemical and physical characteristics, typically excellent biocompatibilities, and readily understood electrical properties. Within this context, our laboratory has previously discovered and systematically investigated bulk proton conduction for a unique family of cephalopod structural proteins called reflectins. Herein, we leverage a combination of experimental and computational methodologies to investigate the bulk electrical properties of hierarchically nanostructured films self-assembled from a previously reported truncated reflectin variant. Our findings indicate that the truncated reflectin variant exhibits protonic conductivities and associated figures of merit on par with those reported for both full-length reflectins and other proteinaceous proton-conducting materials. The combined studies enhance current understanding of reflectins' functional properties within the framework of bioengineering and bioelectronics applications and may ultimately facilitate the development of other protein- and peptide-based conductive biomaterials. [ABSTRACT FROM AUTHOR]

Cephalopods possess remarkable camouflage capabilities, which are enabled by their complex skin structure and sophisticated nervous system. Such unique characteristics have in turn inspired the design of novel functional materials and devices. Within this context, recent studies have focused on investigating the self-assembly, optical, and electrical properties of reflectin, a protein that plays a key role in cephalopod structural coloration. Herein, we report the discovery that reflectin constitutes an effective material for the growth of human neural stem/progenitor cells. Our findings may hold relevance both for understanding cephalopod embryogenesis and for developing improved protein-based bioelectronic devices.

Perylene-3,4,9,10-tetracarboxylic diimides (PTCDIs) are a well-known class of organic materials. Recently, these molecules have been incorporated within DNA as base surrogates, finding ready applications as probes of DNA structure and function. However, the assembly dynamics and kinetics of PTCDI DNA base surrogates have received little attention to date. Herein, we employ constant temperature molecular dynamics simulations to gain an improved understanding of the assembly of PTCDI dimers and trimers. We also use replica-exchange molecular dynamics simulations to elucidate the energetic landscape dictating the formation of stacked PTCDI structures. Our studies provide insight into the equilibrium configurations of multimeric PTCDIs and hold implications for the construction of DNA-inspired systems from perylene-derived organic semiconductor building blocks.

We report on lighting panels based on ruthenium(II) tris-bipyridine complexes that can be sourced directly from a standard US outlet. With the aid of the ionic liquid 1-butyl-3-methylimidazolium, the conductivity of the light emitting layer was enhanced to achieve device operation at a 60 Hz frequency. Lighting panels were prepared using a cascaded architecture of several electroluminescent devices. This architecture sustains high input voltages, provides fault tolerance, and facilitates the fabrication of large area solid-state lighting panels. Scalability of the drive voltage, radiant flux, and external quantum efficiency is demonstrated for panels with up to N=36 devices. Direct outlet operation is achieved for panels with N=16, 24, and 36 devices. © 2006 American Institute of Physics.

The temporal evolution of the current, radiance and efficiency of electroluminescent devices with various electrodes was discussed. It was observed that the performance of the organic electroluminescent devices was dominated by the process of charge injection. Different top electrodes were found to inject holes with different efficiency. It was found that, under forward bias the device characteristics were independent of the electrodes used.

The fabrication and operation of 'plug and play' organic light emitting devices that could be sourced directly from a standard US outlet, namely 110-120 V rms and 60 Hz are demonstrated. This work demonstrates a technique for developing large area solid-state lighting panels that are cost effective and fault tolerant, which supports the implementation of organic electroluminescent devices for general lighting purposes.

The use of silicon chips with 16 DNA-modified electrodes (DME chips) utilizing DNA-mediated charge transport for multiplexed detection of DNA and DNA-binding protein targets is described. The results have shown how DME chips have facilitated sensitive and selective detection of DNA and DNA-binding protein targets in a robust and internally standardized multiplexed format.

A rapid and sensitive electrochemical assay is used for the electrochemical detection of nanomolar TATA-binding protein (TBP) binding to DNA in the presence of other proteins. This method is based on an interruption of DNA-mediated electrochemistry associated with protein binding and hence can be applied in detecting other proteins that perturb the DNA base stack.