This PDF file contains the front matter associated with SPIE Proceedings Volume 11374, including the Title Page, Copyright information, and Table of Contents.

There is great interest to develop materials with properties that resemble those of biological systems. While supramolecular chemistry offers an exciting opportunity to grow materials with nanoscale precision, the ability to transform molecular design into functional devices with enhanced functionality and utility at the macroscale remains a challenge. The talk will present strategies that use self-assembly and the interplay between protein order and disorder to develop functional materials with properties such as hierarchical organization, the capacity to grow, or tuneable mechanical properties.

Inorganic, non-metallic materials exhibit interesting passive and active mechanical properties, when structured hierarchically down to the nanometer scale by biotemplating. While nature does provide a great wealth of structural templates, tailoring biotemplated materials' architectures on defined hierarchical levels is a desirable goal. We combine biotemplating techniques, developed earlier with two novel approaches to create tailored templates, namely the utilization of microbial phototaxis, and rheotaxis. The generally uncommon ductilities of biotemplated, hierarchically and anisotropically structured silica materials were determined and traced via a stick-slip model of parallel rods. Further, we observed passive moisture-driven bilayer actuation in silica structures derived from actuating biological templates, illustrating one of the attainable novel properties. With regard to the creation of tailored templates by phototaxis, the directions, velocities and patterns of movement of a selection of microbe species were found to depend on illumination brightness, wavelength, direction, and also the culturing conditions. Further, rheotactical structuring of first promising tailored templates was achieved in custom-built planar and cylindrical flow cells.

Cephalopods possess unrivaled camouflage and signaling abilities that are enabled by their sophisticated skin architecture, wherein multiple layers contain chromatophore pigment cells (which act like color filters, and are part of larger chromatophore organs) and different types of reflective cells called iridocytes (which act like biological Bragg stacks) and leucophores (which act like broadband Lambertian diffusers). The optical functionality of these cells (and thus cephalopod skin) is enabled by subcellular structures, which are partially composed of a class of unusual structural proteins known as reflectins. Herein, we highlight studies that investigate reflectins’ structure-function relationships, particularly within the context of stimuli-induced color changing devices and systems. Specifically, we will discuss the how the self-assembly of these proteins enables the manipulation of their light reflecting properties. In addition, we will discuss the multi-faceted properties of this unique class of proteins (e.g. proton conductivity), challenges in working with them, and the future potential of these proteins. Overall, our findings hold relevance for the development of protein-based optoelectronic technologies.

Among the natural creatures that have structural colors, the Morpho butterfly is one of the most remarkable species because its blue color displays both a high reflectivity from interference and a low angular dependence. The origin of this unique coloration is thought to be a specific three-dimensional nanostructure with order and disorder that prevents the rainbow color. More importantly, the artificial Morpho-color has been successfully realized in spite of the lack of vertical randomness. Thus, we have recently studied the optical role of in-plane randomness using a numerical simulation, and revealed that the three-dimensional randomness can be replaced by a two-dimensional randomness. However, the details of the simulation methodology and its validity were not explicitly discussed. In this paper, we report the three-dimensional simulation method for analyzing the optical properties of non-periodic structures such as the Morpho butterfly. Moreover, the effect of light incoherence on the Morpho-coloration is evidently shown.

Zebrafish is extensively used in behavioral, pharmacological, and neurological studies due to a number of method- ological and practical advantages, including genetic and neurobiological homologies with humans and a fully se- quenced genome. Critical to a biologically-based understanding of zebrafish behavior is the ability to reconstruct their complex behavioral repertoire in three-dimensions. Toward this aim, several efforts have been made to score their ethogram in three-dimensions, but most of these studies are constrained by a single-view imaging. A promising line of approach to extract refined information about the mechanosensory and perceptual systems of zebrafish is point cloud reconstruction. Here, we provide an initial review of the state of knowledge in zebrafish tracking and we propose a potential methodology that can capture the dynamic three-dimensional geometry of fish swimming. We utilize a stereo vision camera, calibrated with a pinhole camera model with refraction cor- rection to allow for multi-medium imaging. The corrected pinhole camera model accounts for refraction through multiple mediums and allows for more accurate point cloud reconstruction from two cameras. From the point cloud data, we could recreate the three-dimensional geometric model of the fish and analyze its swimming be- havior in three dimensions. The extracted dynamic fish geometry should allow for an improved understanding of mechanosensation and perception, which are critical to elucidate how zebrafish process visual cues and perceive flow structures.

Self-replication is the de facto hallmark of life and has thus far eluded efforts to mimic it in physical engineered systems. According to the John von Neumann self-replication model, there are four major components – (i) a physical instantiation of a program of instructions to build the self-replicator (DNA), (ii) a mechanism for copying those instructions (DNA polymerase), (iii) a controller to interpret those instructions into a set of physical procedures (proteins), and (iv) a means to physically construct the self-replicator (ribosomes). The first and latter two parts constitute a universal Turing machine and universal constructing machine respectively. It is these three parts, in particular, with which we are concerned. The most important constraint is in physical closure which requires a: (i) minimum materials inventory; (ii) minimal set of chemical processes; (iii) minimum set of component part types; (iv) minimal set of manufacturing methods; (v) minimal assembly requirements. This aids in the requirements for energy and information closure. We have identified (i) a minimal list of functional materials (demandite) to build the self-replicator; (ii) a single electrochemical process to extract the metals supplemented with a small set of mineral pre-processing methods; (iii) a set of two fundamental components that are key – the electric motor (which may be configured into any kinematic machine, i.e. universal constructor) and vacuum tube (active component of Turing-complete neural electronics, i.e. universal computer); (iv) a set of additive manufacturing techniques to 3D print all parts including electric motors and vacuum tubes.

Among all aquatic species, mantas and rays swim by oscillating their pectoral fins; this motion is similar to other fishes in term of efficiency, but it gives better agility in turning with respect to fishes moving their caudal fin. The fin motion is featured by a travelling wave going opposite to the forward motion, producing a force thanks to momentum conservation. Another contribution to the generation of thrust is given by the generation of a vortex in correspondence of the leading edge of the fin, which pulls the fish forward thanks to the lower pressure in its centre. In literature these contributions have been highlighted, but it remains to understand which one of these two mechanisms is prevailing according to different conditions of swimming, how they affect each other and what is the influence of the two on energetical efficiency. The object of this activity is to investigate how thrust generation is influenced by geometrical characteristics of the fin, such as size, geometry and flexibility and by parameters of motion, such as speed, amplitude and frequency of fin oscillation and velocity of the travelling wave. A CFD model of the fish has been implemented in OpenFOAM, not only confirming that both upstroke and downstroke contribute positively to the forward movement according to the momentum conservation principle, but also highlighting the formation of a leading-edge vortex enhancing thrust generation. The description of how thrust generation is linked to motion parameters is simulated also coupling the CFD with a multibody to simulate the whole motion in its complexity.

Invasive alien species threaten natural ecosystems worldwide, prey on native species, and deplete their food sources. Mosquitofish is one of the most invasive freshwater fish worldwide and its negative impacts on the native fauna are alarming. Despite the urgency of contrasting the mosquitofish invasion, we have access to very few methods to combat them. Even when successful, these methods can be excessively labor-intensive or dangerous to native species. Robotic predators may constitute a promising tool in combating mosquitofish. Our group has recently proposed the use of a robotic predator that can perform targeted attacks against mosquitofish. The robotic predator consists of three operational parts: a two-dimensional robotic platform, a magnetically connected replica of a native mosquitofish predator, and an in-house developed live tracking software. The robotic replica was programmed to swim along a predetermined trajectory and randomly target mosquitofish in real time through a dedicated tracking software. Building on available experimental results, we put forward a comprehensive mathematical toolbox based on symbolic dynamics, recurrence quantification, and information theory to detail the behavioral interaction between the robotic predator and mosquitofish.

Design for Environment (DfE or ecodesign) aims at developing products with an enhanced environmental performance, without compromising functionality and other key requirements (such as cost and quality). Common DfE guidelines for product design include: reduction of material diversity, extension of useful life (e.g., by enabling repair and upgrade), avoidance of toxic materials and nonrenewable resources, use of recycled components, and ease of disassembly and recyclability after the end of useful life. DfE requires the integration of environmental considerations into the traditional design processes, supporting decisions that could enhance the environmental profile of the product. Biologicallyinspired- design (BID) teams identify and isolate the core principles of relevance for systems, products, and processes from the bioworld for consideration and possible incorporation during each of the design stages. Synergies and potential trade-offs existing between DfE and BID must be considered when integrating the two methodologies into Biologically Inspired Design for Environment for the design of products and systems.

Inspired by the mechanisms of some insects which are capable of climbing and moving freely on various vertical rough surfaces with their claws and accessory components, we presented a new design of a flexible spiny structure called DNspine (a spine with double needles) featuring two anchoring points to enhance the mobility of wall-climbing robots (WCR). Each flexible spine consists of two separate suspension systems so that the near subspines in the flexible spiny structure will not interface with each other. The two-anchoring point design increases the contact area of spiny array to achieve a better attachment for WCRs. The single DNspine and its array were fabricated via fast prototyping. A customized setup using displacement-control method was carried out to characterize the contact performance of the single DNspine as well as its DNspine array. Their adhesion forces were measured on a sandpaper surface. The results show that both the DNspine and the DNspine array are able to increase the spine adhesion significantly compared with a single flexible spine and its array with only one anchoring point on rough surfaces.

The use of soft, compliant actuators has recently gained research attention as a potential approach to improve human-robot interaction compatibility. Fluidic artificial muscles, or McKibben actuators, are a popular class of soft actuator due to their low cost and high force-to-weight ratio. However, traditional McKibben actuators face efficiency problems, as in most actuation schemes, the actuator is sized for the largest possible load, resulting in energy loss when operating at lower force regimes. To address this issue, our group has developed a bio-inspired actuation strategy called variable recruitment. In variable recruitment, actuators are placed within a bundle and can be sequentially activated depending on the required load. This strategy mimics the hierarchical architecture of mammalian muscle tissue and improves system efficiency and bandwidth while allowing for variable stiffness properties. Previous variable recruitment models and controllers assume that the force output of each actuator is independent and that these forces sum to provide the total bundle force. However, our recent work has shown that there is significant interaction between actuators within a bundle, particularly at lower recruitment states. This is because at these states, inactive or partially activated actuators resist bundle motion and reduce total force production. In this paper, we study these resistive effects at low recruitment states by considering two different variable recruitment configurations: a fixed-end configuration (with resistive forces) and a tendon configuration (designed with tendons to eliminate resistive forces). We then assess the tradeoffs between the two configurations. We found that while using the tendon configuration eliminates resistive forces, if we consider both configurations with the same overall system length, the tendon configuration has less overall system free strain because its FAMs have to be shorter than those of the fixed-end configuration. However, despite this difference in free strain, our results still show that the tendon configuration can have higher maximum load capacity and efficiency than the fixed-end configuration and that the specific application and system requirements will dictate the proper configuration choice.

Many flying organisms operate nearby to, and transit over, water as part of their natural cycle, yet currently man made aerial systems are fragile in this same environment as they rely almost exclusively on satellite navigation. In this study we developed a visual navigation technique that allows aerial systems to navigate above water surface environments, extending previous work on bio-inspired navigation over land. We demonstrate through flight experiments that limited knowledge of the local environment and visually identifiable information from the the maritime surface is sufficient to achieve accurate inertial frame ground track control over substantial distances under real world wind and water conditions.

Hawkmoth wings consist of veins and membrane elements that undergo large deformations while moving through the air. The intention of this paper is to create an Euler-Bernoulli beam that can model the complex structure of a hawkmoth forewing. The beam undergoes bending and torsion, and its modal analysis and deformation data are validated against those of the wing structure created based on the finite-element method and a biological wing. A multibody dynamics approach is employed to model the deformation of the beam wing when it oscillates at the frequency of an actual hawkmoth.

The ceramic dental crowns subjected to occlusal contact forces are often idealized as flat multilayers that are deformed by Hertzian contact loading. These multilayer structures consist of a crown-like ceramic layer on the top, an adhesive layer in the middle and the dentin-like substrate. This study examines the crack growth in the bio-inspired dental multilayers and the fracture toughness for the materials used in the functionally graded materials. A layered structure is fabricated by the sequential depositing of nanocomposite materials with filler fraction and type that changes from the side near the soft composite foundation to the side near the hard ceramic top layer to mimic the dentin–enamel junction in natural teeth. The critical load to failure in these bio-inspired structures are shown to be ~30% greater than those in the conventional layered structures with commercially available dental adhesive materials. The effects of FGM layer thickness and architecture on the contact-induced deformation of bio-inspired dental multilayers are investigated. The combined effects of creep in the adhesive and substrate layers and creep-assisted slow crack growth in the ceramic layer are also studied. The fracture toughness of the polymer-ceramic composites that are relevant to the bio-inspired functionally graded multilayers are measured. The critical loads to failure at various clinically relevant loading rates are shown to be well predicted by a creep-assisted slow crack growth model, which integrates the actual mechanical properties that are obtained from nanoindentation experiments and creep tests and the stress predicted by finite element method and Prony series model. The implications of the results are then discussed for the design of robust dental multilayers.

We develop bimaterial composites with enhanced impact resistance by mimicking a unique hierarchical geometry inherent in nacre. Three-dimensional models of the nacre-like composites are developed using pattern-generating algorithms, and the corresponding experiment specimens are fabricated by means of an FDM-based 3D printer. Under drop weight impact tests, it is found that the impact resistance of the nacre-like composite is significantly improved compared with a monolithic stiff specimen. The performance enhancement is also verified through numerical simulation with the use of a commercial finite element code. Mimicking the natural hierarchical architecture can render a guideline toward the development of high-performance material systems.

In a bioinspired approach, we are mimicking various types of naturally occurring materials to fabricate hybrid antibacterial and biocompatible thin films for a range of applications. In this work we will present a new process for generating the Chitin and Chitosan functionality using MLD. As precursors for this MLD process we are using the sugar-type molecules N-acetyl-D-mannosamine or N-acetyl-D-glucosamine and coupling them with the surface using thionyl chloride vapors. ATR-FTIR, X-ray photoelectron spectroscopy (XPS) and Solid-state NMR (ssNMR) analysis were used to characterize chitin-type MLD films grown at different temperatures from 70 to 125 ᵒC.

Many bio-structures, such as the paddlefish rostrum, owe their remarkable resistance to permanent deformation to an optimized arrangement of hard and soft materials. This study utilizes the unique characteristics seen in biological systems to determine the optimized composition of hard and soft materials to develop an enhanced damping mechanism for dynamic load resistance. This work develops novel 3D printed prototypes inspired by the material composition of the paddlefish rostrum. The design-test-build cycle of the prototypes will consist of numerical analyses to inform the experimental boundary conditions and multi-material configuration. In biological systems, the boundary conditions determine an optimized material configuration. This study consists of quasi-static flexure experiments under different load and displacement boundary conditions to determine the optimized configuration for the given boundary condition. This investigation compares the prototypes' deformation, load transfer distribution, shear capacity, and the optimized material configuration per specific load and displacement boundary conditions against other samples with single material properties. When compared to isotropic materials currently in use, bio-inspired, multi-material structures demonstrate an enhanced stress to deformation performance . The study also determined the best material layup for the 3D printed prototype for each of the load and displacement boundary conditions.

To address the global water scarcity issue especially in arid and semi-arid regions, efficient water collecting surfaces with fast capturing and easy drainage are essential. This concern is drastically increasing and therefore scientists and engineers are challenged with urgently developing viable solutions for this global problem. Among many other options, nanoscale membranes seem to be quite attractive and very promising options to solve the global water problem due to their low energy cost and simple operational processes to produce clean and fresh water. In this work, polyacrylonitrile (PAN) and poly (methyl methacrylate) (PMMA) with various proportions of titanium dioxide (TiO₂) nanoparticles and aluminum (Al) microparticles were electrospun into superhydrophobic nanocomposite fibers using electrospinning technique followed by stabilization and carbonization steps to remove all non-carbonaceous materials from the fibers and used for harvesting fog from the atmosphere. The fiber morphology, surface hydrophobicity, and fog harvesting capacity of the nanocomposite fibers were investigated. Test results reveal that the carbonized nanocomposite fibers mats exhibit superhydrophobic characteristics with a water contact angle of 155° and an efficient fog harvesting capacity of 621 mg/cm²/hr. Besides, water can be efficiently collected from the atmospheric fog and filtered using nano-membranes without using any large infrastructure. The produced water can be used for drinking, agriculture, gardening, medical, industrial, and other purposes.

In this study, we focus on a peristaltic motion that is locomotive pattern of earthworms. Inspired from the peristaltic motion, mobile robots moving in narrow space are able to be constructed. To realize effective motion of the peristaltic mobile robot, motion patterns are generated based on the dynamical model and the particle swarm optimization algorithm, one of the meta-heuristic optimization. The optimized results are investigated by comparing to simple periodic patterns through numerical simulations and experiments.

One field in which nature outperforms current technology is fish swimming, because its efficiency, manoeuvrability and noise are far better than those of typical ship propellers. These advantages are not only due to the streamlined shape and the low-drag skin, but also and above all to the propulsion mechanism, which makes thrust generation possible with small energy dissipation in vortices. Nowadays the interest in autonomous underwater vehicles is in constant increase following the emerging needs of underwater mining and fish farming. Batoid fishes produce thrust with their pectoral fins, they essentially produce a wave travelling in the direction opposite to their motion, pushing water backwards and gaining thrust as a consequence of momentum conservation. The motion of the fin has been studied and reproduced with a series of articulated mechanisms. In this work the optimization of the mechanism’s geometry is described and the experimental results on the reconstructed fin are presented. Moreover, a bioinspired robot mimicking cownose ray locomotion has been designed and built. In this paper the functioning of this robot is shown.

Roots are extraordinary diggers because they penetrate the soil adding new material on their tip without moving the already grown part, preventing friction from dissipating too much energy and minimising inertial forces during motion. A robot exploiting this principle can assist operations of search and rescue digging in mud or snow to find people in danger. In this work a soft pneumatic robot inspired to roots’ growth is presented. The body of the robot consists of a cylindric plastic membrane folded inside out; one extremity is kept fixed to the base, whereas the other one is folded inside itself. When air is blown from the base, the body of the robot is inflated, and its tip is everted increasing its length. Inside the tip a head is mounted, where the mechanism controlling the direction of growth is placed. On the external surface of the membrane some hooks are mounted, and tensioned wires connects them longitudinally while they are folded before being everted. These wires are cut when they pass next to the head allowing the robot to unfold; since series of hooks are distributed radially on the body of the robot, the direction of growth is controlled by selecting which wires are to be cut. On the head of the robot can be mounted an infrared sensor or a video-camera needed for the specific application.