This PDF file contains the front matter associated with SPIE Proceedings Volume 10162, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and Conference Committee listing.

Current drones are developed with a fixed morphology that can limit their versatility and mission capabilities. There is biological evidence that adaptive morphological changes can not only extend dynamic performances, but also provide new functionalities. In this paper, we present different drones from our recent developments where folding is used as a mean of morphological adaptation. First, we show how foldable wings can enable the transition between aerial and ground locomotion or to fly in different aerodynamic conditions, advancing the development of multi-modal drones with an extended mission envelope. Secondly, we show how foldable structures allow to transport drones easily without sacrificing payload or flight endurance. Thirdly, we present a foldable frame that makes drones to withstand collisions. However, the real potential of foldable drones is often limited by the use of conventional design strategies and rigid materials, which motivates to use smart, functional materials. Lastly, we describe a dielectric elastomer based foldable actuator, and a variable stiffness fiber using low melting point alloy for drones. The foldable actuator acts as an active compliant joint with folding functionality and mechanical robustness in drones, thanks to the compliance of dielectric elastomer, a class of smart materials. We also show re-configuration of a drone enabled by the variable stiffness fiber that can transition between rigid and soft states.

Inspired by the wave-like camber variation in the trailing edge feathers of large birds, the aerodynamic impact of similar variations in the geometry of morphing wings is investigated. The scope of this problem is reduced by exploring parametrically generated geometries derived from an existing morphing wing design, namely the Spanwise Morphing Trailing Edge (SMTE), which is actuated via conformally integrated Macro Fiber Composites (MFCs). Utilizing this design, the deformation of the trailing edge of the SMTE is parameterized as a function of the spanwise location using a sinusoidal relationship. The aerodynamic responses are then obtained using Computational Fluid Dynamics (CFD) simulations, while the efficacy of the proposed approach is explored using a Pareto-like frontier approach.

Selection of airfoil for better design of aerodynamic and aerodynamic performance is very important such as aircraft and wind turbine. Also, a number of military and civilian applications required efficient operation of airfoils in low Reynolds number, particularly for micro aerial vehicles. This work simulates a classical flow pattern (Von Karman street) that can form as fluid flows past a flapping NACA0012 airfoil, and S1223 airfoil at low Reynolds number. These two airfoils has been selected and investigated in computational analysis by using basic computational fluid dynamics and fluid-structure interaction modules. The S1223 airfoil, designed by University of Illinois at Urbana was selected for its high lift characteristics at low Reynolds number and the NACA0012 was chosen to check the lift at low Reynolds number. Velocity distributions are analyzed at different angles of attack for both airfoils. The results obtained from simulation have compared between the two airfoils. The magnitude and the frequencies of the oscillation generated by the fluid around the airfoils are computed and compared between the airfoils.

Plants have a sessile lifestyle, and, as a consequence of this primordial decision, they must efficiently use the resources available in their surroundings and exhibit a well-organized sensing system that allows them to explore the environment and react rapidly to potentially dangerous circumstances. Below ground, roots can sense a multitude of abiotic and biotic signals, enabling the appropriate responses while they grow searching nutrients and water to feed the whole plant body. Plant roots show efficient exploration capabilities, adapting themselves morphologically to the environment to explore. Interestingly, movement, evolved sensing systems and distributed control are among the most important topics of contemporary robotics. Plants, which we have recently considered as a new model in bioinspired and soft robotics, must address “problems” that are common also in animals, such as, for example, squid, cuttlefish, and, especially, octopus, which include distributed control to manage the infinite degrees of freedom of their body, high flexibility, the capability of growing and/or elongating their extremities, and distributed sensing capabilities. Starting from the study and imitation of these plant features, we developed innovative inspired robots and technologies, named PLANTOIDS, which move by growing, coordinating their artificial roots and showing efficient penetration strategies and high actuation forces. Applications for such technologies include soil monitoring and exploration for contamination or mineral deposits, as well as medical and surgical applications, like new flexible endoscopes, able to steer and grow in delicate human organs.

Flexible steerable needles can follow complex curved paths inside the human body. In a previous work, we developed a multiple-part steerable needle prototype with a diameter of 1.2 mm, inspired by the ovipositor of parasitoid wasps. The needle consisted of seven nickel-titanium longitudinally aligned wires held together at the tip by a cylindrical ring with seven holes. The steerability of the needle was evaluated in a gelatin phantom and was found to be lower than that of other steerable needles in the literature. One possible cause of this limited steerability is that during motion the wires tend to separate from each other (i.e., bifurcate). Our aim here was to reduce bifurcation in order to increase the steering curvature of the needle, while keeping the diameter around 1.5 mm, and thus compatible with needles used in medical practice. To achieve that, we changed the shape of the ring from cylindrical to conical. We evaluated the steering performance in gelatin, using the conical ring in two configurations: (1) with the apex of the cone towards the needle tip, so that the wires converge, thus expected to reduce bifurcation, (2) with the apex of the cone placed towards the needle base, so that the wires diverge, thus expected to magnify bifurcation. Results showed that the diverging ring generated larger steering curvatures. We can conclude that reducing the bifurcation of the wires is not enough for increasing the steering curvature and that inducing this same phenomenon instead could actually lead to higher curvatures.

The stinging proboscis in mosquitos have diameters of only 40-100 μm which is much less than the thinnest medical needles and the mechanics of these natural stinging mechanisms have therefore attracted attention amongst developers of injection devises. The mosquito use a range of different strategies to lower the required penetration force hence allowing a thinner and less stiff proboscis structure. Earlier studies of the mosquito proboscis insertion strategies have shown how each of the single strategies reduces the required penetration force. The present paper gives an overview of the advanced set of mechanisms that allow the mosquito to penetrate human skin and also presents other biological mechanisms that facilitate skin penetration. Results from experiments in a skin mimic using biomimetic equivalents to the natural mechanisms are presented. This includes skin stretching, insertion speed and vibration. Combining slow insertion speed with skin tension and slow vibration reduces the penetration force with 40%.

For natural scientists and engineers, learning from nature has tradition and is often driven by bio-inspired processes and materials. For example, engineers have designed multifunctional materials with hierarchical structures. Lipid bilayers, the principal components of cell membranes, can form vesicles, termed liposomes. Such liposomes are usually recognized as foreign by the immune system of a patient, which makes it challenging to use liposomes as containers for targeted drug delivery. There are, however, promising non-spherical, mechano-sensitive, artificial liposomes about 100 nm in diameter, which were recently identified. These bio-inspired containers offer a wide range of applications. In particular, the targeted release at critically stenosed arteries formed as a result of atherosclerosis significantly reduces the undesired side effects such as a drop of blood pressure. It is well known that FDA-approved liposomal drugs, currently on the market, often induce adverse immune responses. Therefore, to exclude the hypersensitivity of the recently discovered mechano-sensitive liposomes, we have performed in vitro complement activation experiments and related animal studies with pigs. Recently, it has been shown that the drug-free Pad-PC-Pad liposomes surprisingly lack any complement activation. In this study, we demonstrate that nitroglycerin-loaded liposomes with relevant human therapeutic dosage exhibit low complement activation compared to the FDA-approved phospholipid drugs, including Abelcet. Furthermore, the liposomal suspensions applied are stable for a period of more than two months. Consequently, the non-spherical liposomes of nanometer size we have developed are promising containers for physically triggered, targeted drug delivery.

In the dense gel that is the intracellular matrix forming part of living cells electrochemical reactions take place provoking the interchange of ions and water with the surroundings. Systems containing conducting polymers mimic this feature of biological organs. In particular, conducting polymers are being studied as dual sensing-actuating reactive materials giving new multifunctional sensing-actuators, which allow the construction and theoretical description of artificial proprioceptive devices. Here films of polypyrrole/dodecyl benzene sulfonate (PPy-DBS) coating a platinum electrode were submitted to potential sweeps at different sweep rates in order to explore if the polymer reaction senses the working electrochemical conditions. The effective consumed electrical energy per cycle follows a fast decrease when the scan rate increases described by the addition of two exponential sensing functions. Moreover, the variation of the hysteresis from the parallel charge/potential loop with the scan rate is also described by the addition of two exponential functions. In both cases the exponential functions fitting results at low scan rates are related to reaction-driven conformational movements of the polymer chains, being closer to biochemical conformational and allosteric sensors. The second exponential functions fitting results at high scan rates are related to diffusion kinetic control, being closer to present electrochemical sensors.

Research over the past few decades has shown that the ear exhibits an important, nonlinear amplification called the “cochlear amplification.” It is responsible for boosting faint sounds and improving frequency sensitivity, which allows the ear to process a larger range of sound intensities (from about 20 micro-Pa to 20 Pa). In contrast, typical microphones, accelerometers, and other dynamic sensors are designed to operate linearly in the sensor’s quasi-static response region. Instead, the cochlea operates in the resonance region, where weak inputs are significantly amplified. The goal of our research is to develop unique, piezoelectric-based MEMS sensors that mimic the function of hair cells in the mammalian cochlea. Inspired by the geometry of the hair cells, a set of artificial hair cells (AHCs) are designed based on piezoelectric cantilever beams.

Developing piezoelectric, MEMS AHC arrays capable of mimicking the cochlea’s behavior is the main scope of this work. The design consists of a substrate material and two layers of Lead Zirconate Titanate (PZT) deposition that represents artificial hair cells. Abaqus finite element software is used to model the AHC arrays. Fundamental frequencies of the AHCs and also frequency response function due to a base excitation of the array are obtained by linear perturbation frequency analysis and steady-state linear dynamic analysis, respectively. As a proof of concept, a series of dynamic tests are conducted on larger scale single AHCs and an array of four AHCs to measure the response of the sensors to an external stimulus.

We present a new method to observe living organisms by a common scanning electron microscope (SEM) including a field emission SEM. A simple surface modification to extracellular substances by electron beams or plasmas can equip some multicellular organisms with a thin extra layer, coined the “ NanoSuit(R)”, and hence can keep them alive under the high vacuum (10^-3-10^-7 Pa) conditions. The “NanoSuit(R)” acts as a flexible ‘Nano-spacesuit’ barrier to the passage of gases and liquids and thus protects the organism. Using this method, it was found that the surface fine structure of living organisms is very different from that of traditionally treated samples, and the active movements of living animals are also observed in an SEM. We next invented the coating method by the “biomimetic NanoSuit” based on artificial substance for the organism which lack the natural extracellular substances. After observation of living organisms by an SEM, despite the high vacuum it is possible to rear many of them subsequently in normal culture conditions. In addition to this method, it is now available to observe human tissues using new surface shield enhancer NanoSuit(R). Those new “ NanoSuit(R)” methods will be useful for numerous applications, particularly in the life sciences.

Our body is hierarchically organized down to individual cells. Cutting-edge clinical imaging facilities reach a spatial resolution of a fraction of a millimeter, living cells invisible. A decade ago, post-mortem X-ray imaging by means of synchrotron radiation enabled the identification of Os-stained ganglion and unstained Purkinje cells. Very recently, even sub-cellular structures, such as nucleolus and the dendritic tree of Purkinje cells, were extracted by means of phase-contrast single-distance synchrotron radiation-based hard X-ray tomography. At the same time, conventional absorption-contrast, laboratory-based micro computed tomography was successfully applied to visualize brain components including individual Purkinje cells within a cerebellum specimen. Thus, the goal of isotropic-cellular-resolution visualization of soft tissues within a laboratory environment without application of any dedicated contrast agent was achieved. In this communication, we are discussing (1) to which extend the quality gain of the laboratory-based absorption-contrast tomography can be driven with respect to optical microscopy of stained tissue sections and (2) what value such a technique would add. As a proof of principle, four histological sections were affine-registered to corresponding three-dimensional (3D) tomography dataset. We are discussing a semi-automatic landmark-based 2D-3D registration framework and compare registration results based on mean square difference (MSD) metrics.

In recent years, robots have emerged as relevant means for studying individual and social behavior, providing highly customizable and controllable instruments for a wide number of behavioral investigations. As zebrafish is gaining momentum among laboratory animals, several robotics-based paradigms have been proposed to study its complex behavior. However, previous studies have failed to report attraction toward robotic stimuli, comparable with live conspecifics. Here, we investigate this aspect in a within-subject experiment by testing zebrafish and comparing the attraction toward a live conspecific and a 3D-printed replica in binary-choice preference tests. We find that zebrafish have an analogous appraisal for live and robotic stimuli in preference experiments.

The present work generates steady-state traveling waves in fin-like continuous structures with the help of Macro-Fiber Composite (MFC) piezoelectric actuators. To produce traveling waves, two MFCs simultaneously excite a clamped-free beam at a common frequency with a preset phase difference. Previous research has shown that optimal traveling waves are developed in structures when the common frequency lies halfway between two adjacent resonant frequencies and the phase difference between the two inputs is 90°. These traveling waves closely replicate the undulatory patterns that propel aquatic animals but at a low amplitude linear regime. The present work studies the generation of underwater traveling waves and investigates the range of propulsive forces generated through such mechanism. The ability of continuous structures to produce thrust using undulations is the first step towards mimicking the bio-kinematics and biomechanics of aquatic animals.

Biologically-inspired robots are emerging as promising research tools in laboratory experiments to study animal behavior. Zebrafish are attaining an important role as model organisms for the study of emotional responses, including fear and anxiety. Here, we attempt at characterizing zebrafish response to fear-evoking stimuli using a live predator and a biologically-inspired 3D printed replica of the predator, actuated by an ad-hoc robotic platform. Fish motion tracking and information theoretic tools are integrated to quantify the interaction between zebrafish and the stimuli.

Pitcher plants have liquid-infused structured surfaces to slip and digest insects, which have oily surfaces on their body, inside of their pods. By mimicking the slipping mechanism of pitcher plant pods, the omniphobic slippery surface has been created by infusing liquid lubricants into porous materials. We have reported honeycomb-patterned porous films can be prepared by casting polymer solution under humid conditions. By using condensed water droplets onto the surface of cast solutions of polymers as templates, uniformly sized pores were formed on the polymer films after evaporation of solvent and template water droplets. By peeling the top layer of honeycomb films with adhesive tape, the pincushion-like surface structure can be created. This pincushion surface has high water repellency due to their high surface porosity and hydrophobic nature. By infusing lubricants into the pincushion film, omniphobic slippery surfaces can be prepared. When fluorinated lubricants infuse into fluorinated pincushion film, they slip both oil and water droplets with inclined the film only a few angle. Furthermore, the motion of sliding liquids can be controlled by stretching of the film or surface patterning. In the presentation, we will show the biomimetic liquid repellent surfaces based on self-organized honeycomb films. Moreover, other applications of honeycomb films for stretchable electrodes for epidermal sensing and on-demand separation systems.

As its name suggests the glasswing butterfly (Greta oto) features transparent wings with remarkable low reflectance even for large view angles [1]. This omnidirectional anti-reflection behavior is caused by small nanopillars covering the transparent region of its wings. In difference to other anti-reflection coatings found in nature (moth eye, hawk moth wing, cicada wing) these pillars are not periodically arranged and feature a random height and width distribution. We analyze the specular and diffuse reflection of the surface and explain the concept of transparency by randomness. Such anti-reflective surfaces can be adapted to improve the light collection in solar cells or for efficient anti-reflection displays. The hierarchical structures found in the scales of the black butterfly (Pachliopta aristolochia), consisting of disordered nano-holes assemblies surrounded by micrometer-spaced triangular ridges, are crucial for controlling light absorption and therefore the butterflies colors and thermoregulation properties. We studied numerically the light harvesting performance of these hierarchical structures. Based on these observations, efficient nano-patterned thin absorbers can be designed for photovoltaics applications. We show that using a lateral phase separation process enables to fabricate disordered nano-holes assemblies with tunable density and size distribution in a resist layer and onto large surfaces. [1] Siddique, R. H., G. Gomard and H. Hölscher. “The role of random nanostructures for the omnidirectional anti-reflection properties of the glasswing butterfly”, Nature Communications, Vol. 6, 6909 (2015)

Many spiders exhibit vivid colors that are not produced by pigments, but rather by optical interference, diffraction, and scattering — structural colors. Traditionally, structural color research in nature focused on birds, butterflies and beetles. But the long evolutionary history and extreme diversity of spiders provide fruitful new territory. The repeated evolution of blue in large, nearly blind tarantulas and the diversification of sexual display colors in tiny peacock spiders provide two striking examples. Here, we show how tarantula blue is produced using specialized hairs with complex hierarchical structure that greatly reduces iridescence — which has been a key obstacle to the production of synthetic structural colorants without the shimmering effects. On the other hand, the strikingly iridescent scales of the rainbow peacock spider (Maratus robinsoni) can produce every color of the rainbow, and may hold the secrets for future optical device miniaturization. We used an interdisciplinary biomimetic approach to investigate both questions by including techniques such as: morphological characterization (SEM/TEM), phylogenetic analysis, spectrophotometry, optical simulation, and rapid prototyping by 3D nano-printing. Particularly with the rapid prototyping capability, we can create engineering models to test biological hypotheses in a controlled manner that may not be feasible with the living systems. Hence, biomimicry is not only taking what we learned from natural systems to practical human applications, but it is also providing insightful feedbacks and ideas to deepen our understanding of the biological system subject matter during the process.

Inspired by the multilayer structure of the cuticle of some gold beetles whose shell exhibits broadband reflection in the visible wavelength range, we numerically analyzed irregularly chirped dielectric mutilayers. The analysis was performed using a dedicated genetic algorithm which searches for the multilayer configurations that maximizes the reflection bandwidth. We found that the genetic algorithm leads to irregularly chirped structures which significantly outperform the regularly chirped ones proposed and analyzed in literature.

The conspicuous blue of Morpho butterfly is a single color in too wide angular range (< ± 40° from the normal), which contradicts the optical interference effect originating its high reflectivity. After proven the principle of the mystery by emulating the specific nanostructures of their scales, we found the reproduced Morpho-color to serve wide applications, because it can produce a brilliant single color in wide angular range with high reflectivity without chemical pigment, which is resistant to fading caused by chemical change for long time. We have then developed various technologies for practical applications of the specific color, such as mass-production processes, control and simulation of their optical properties. One of the remaining key issues is to produce the substrate-free color materials, because all processes have long been accompanied with the thick substrate designed with a specific nanostructure, which has limited the variety of applications. We have recently developed a simple process to mass-fabricate the color powders that are substrate-free color material. The method was quite simple, because the colored thin-film part was peeled-off by immersion of the imprinted mass-productive color-material into hot water. However, this process was limited to produce powders, because the detached thin-film part was broken into small pieces during process. Thus, we developed a new process to produce a continuous colored thin-film without break, which can be realized only by immersion into hot water. The fabricated colored thin-film was flexible, having endurance against stress and strain, and found to maintain the original optical properties of Morpho-color under the bent condition. This process will extend effectively the applications of the Morpho-color, which enables the coloring without limit of solid substrate.

Inspired by biological multicontrollability, we have devised the concept of multicontrollable metasurfaces. Comprising electrically small elements called MetaAtoms, a metasurface could be either homogeneous or graded on the wavelength scale for operation in the terahertz regime. The MetaAtoms would comprise diverse pixels each of which is made of magnetically controlled, thermally controlled, electrically controlled, or optically controlled material. Stacks of parallel multicontrollable metasurfaces would function as multicontrollable metamaterials.

This project uses biologically inspired chemotactic movements to navigate a robot towards the source of a chemical spill. These movements are inspired by organisms like the bacterium Escherichia coli (E. coli) and the silkworm moth Bombyx mori that react to stimulants in an observable way. For these organisms, stimulants might include food sources or pheromones that signal mating readiness, and others. E. coli for example use the intracellular signaling pathway to process the temporal change in the chemical concentration to determine if the E. coli should run (move forward) or tumble (spin in place). In our project, we introduced a robotic controller mediator that is responsible for processing information that exists in the environment. The robotic controller that was developed uses a finite state machine to decide which specific control algorithms to use such as waypoint navigation, plume tracking, or plume recovery algorithms at various environment readings. The controller has been simulated as well as tested on a small-scale robot that imitates E. Coli chemotaxis in order to locate the source of a chemical cloud. The robotic controller utilizes the Robot Operating System (ROS) to separate different parts of this project into interdependent modules that communicate with each other. This robotic controller can be adapted to other situations with various plume configurations and be made compatible with different sensors. By making the robotic controller general, chemotaxis algorithms can be tested on different environments with minimal customization to the backend code. The overall goal of this project is to use the robotic controller as an effective way to select the most appropriate algorithm to find the source of a chemical leak in various environments.

A new type of tissue, based on the combination of tobacco cells and multi-walled carbon nanotubes exhibited good mechanical stability even after more than 2 years of room temperature storage. The original intermediate value of electrical conductivity in coplanar configuration, decreased strongly after high electric field stress before the storage period. In the visible wavelength range optical transmission values between 0.1% and 1% have been measured for the more than 100 μm thick sample. The bio/nano-composite in the low-conductivity state revealed to be a sensitive photoreceiver in the visible wavelength range, when illuminated with white LED light. A notable decrease of the low-frequency current noise amplitude with LED illumination has been observed.