This PDF file contains the front matter associated with SPIE Proceedings Volume 8339, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Mammals, like humans, rely mainly on acoustic, visual and olfactory information. In addition, most also use tactile and thermal cues for object identification and spatial orientation. Most non-mammalian animals also possess a visual, acoustic and olfactory system. However, besides these systems they have developed a large variety of highly specialized sensors. For instance, pyrophilous insects use infrared organs for the detection of forest fires while boas, pythons and pit vipers sense the infrared radiation emitted by prey animals. All cartilaginous and bony fishes as well as some amphibians have a mechnaosensory lateral line. It is used for the detection of weak water motions and pressure gradients. For object detection and spatial orientation many species of nocturnal fish employ active electrolocation. This review describes certain aspects of the detection and processing of infrared, mechano- and electrosensory information. It will be shown that the study of these seemingly exotic sensory systems can lead to discoveries that are useful for the construction of technical sensors and artificial control systems.

Three types of spider sensors responding to different forms of mechanical energy are chosen to illustrate the power of evolutionary constraints to fine-tune the functional "design" of animal sensors to the particular roles they play in particular behavioral contexts. As demonstrated by the application of computational biomechanics and a fruitful cooperation between biologists and engineers there are remarkable "technical" tricks to be found by which spider tactile sensors, airflow sensors, and strain sensors are adjusted to their biologically relevant stimulus patterns. The application of such "tricks" to technical solutions of measuring problems similar to those animals have to cope with, seems both realistic and very promising.

Even though current micro-nano fabrication technology has reached integration levels where ultra-sensitive sensors can be fabricated, the sensing performance (resolution per joule) of synthetic systems are still orders of magnitude inferior to those observed in neurobiology. For example, the filiform hairs in crickets operate at fundamental limits of noise; auditory sensors in a parasitoid fly can overcome fundamental limitations to precisely localize ultra-faint acoustic signatures. Even though many of these biological marvels have served as inspiration for different types of neuromorphic sensors, the main focus these designs have been to faithfully replicate the biological functionalities, without considering the constructive role of "noise". In man-made sensors device and sensor noise are typically considered as a nuisance, where as in neurobiology "noise" has been shown to be a computational aid that enables biology to sense and operate at fundamental limits of energy efficiency and performance. In this paper, we describe some of the important noise-exploitation and adaptation principles observed in neurobiology and how they can be systematically used for designing neuromorphic sensors. Our focus will be on two types of noise-exploitation principles, namely, (a) stochastic resonance; and (b) noise-shaping, which are unified within our previously reported framework called Σ▵ learning. As a case-study, we describe the application of Σ▵ learning for the design of a miniature acoustic source localizer whose performance matches that of its biological counterpart(Ormia Ochracea).

The formation of lipid bilayers between ionic liquid droplets is presented as a new means of forming functional bimolecular networks. Ionic liquids are molten salts that have a number of interesting properties, such as the ability to be a liquid at room temperature and exceedingly low vapor pressure. Our research demonstrates that it is possible to consistently and repeatable form lipid bilayers on droplets of ionic liquid solutions. Characterization of the bilayers interfaces shows that the ionic liquids have negligible effects on the stability and electrical properties of the bilayer. It is also shown that the conductance levels in the gating events of Alamethicin peptide are affected by some ionic liquids.

Receptors known as hair cells give many animals this ability to sense a wide range of stimuli, such as sound, orientation, vibration, and flow. Previous researchers have mimicked natural hair cells by building electromechanical sensor systems that produce an electric response due to the bending of artificial hairs. Inspired by the roles of sensory hairs in fish, this work builds on previous research by investigating the flow dependent electrical response of a 'skin'-encapsulated artificial hair cell in an aqueous flow. This study presents the design, fabrication, and characterization of a flow sensor that will help close the loop between the sensing mechanisms and control strategies that aquatic organisms employ for functions such as locomotion regulation, prey capture, and particulate capture. The system is fabricated with a durable, artificial bilayer that forms at the interface between lipid-encased aqueous volumes contained in a flexible encapsulated polyurethane substrate. Flow experiments are conducted by placing the bio-inspired sensor in a flow chamber and subjecting it to pulse-like flows. Specifically, through temporal responses of the measured current and power spectral density (PSD) analysis, our results show that the amplitude and frequency of the current response are related to the flow over the hair. This preliminary study demonstrates that the encapsulated artificial hair cell flow sensor is capable of sensing changes in flow through a mechanoelectrical response and that its sensing capabilities may be altered by varying its surface morphology.

Recent research has shown that a new class of mechanical sensor, assembled from biomolecules and which features an artificial cell membrane as the sensing element, can be used to mimic basic hair cell mechanotransduction in vertebrates. The work presented in this paper is motivated by the need to increase sensor performance and stability by refining the methods used to fabricate and connect lipid-encapsulated hydrogels. Inspired by superficial neuromasts found on fish, three hydrogel materials are compared for their ability to be readily shaped into neuromast-inspired geometries and enable lipid bilayer formation using self-assembly at an oil/water interface. Agarose, polyethylene glycol (PEG, 6kg/mole), and hydroxyethyl methacrylate (HEMA) gel materials are compared. The results of this initial study determined that UV-curable gel materials such as PEG and HEMA enable more accurate shaping of the gel-needed for developing a sensor that uses a gel material both for mechanical support and membrane formation-compared to agarose. However, the lower hydrophobicity of agarose and PEG materials provide a more fluid, water-like environment for membrane formation-unlike HEMA. In working toward a neuromast-inspired design, a final experiment demonstrates that a bilayer can also be formed directly between two lipid-covered PEG surfaces. These initial results suggest that candidate gel materials with a low hydrophobicity, high fluidity, and a low modulus can be used to provide membrane support.

Motivated by the lateral line system of fish, arrays of flow sensors have been proposed as a new sensing modality for underwater robots. Existing studies on such artificial lateral lines (ALLs) have been mostly focused on the localization of a fixed underwater vibrating sphere (dipole source). In this paper we examine the problem of tracking a moving dipole source using an ALL system. A nonlinear estimation problem is formulated based on an analytical model for the moving dipole-generated flow field, which is subsequently solved with the Gauss-Newton method. The effectiveness of the proposed approach is illustrated with simulation results.

We present the concept of an active multi-electrode catheter inspired by the electroreceptive system of the weakly electric fish, Gnathonemus petersii. The skin of this fish exhibits numerous electroreceptor organs which are capable of sensing a self induced electrical field. Our sensor is composed of a sending electrode and sixteen receiving electrodes. The electrical field produced by the sending electrode was measured by the receiving electrodes and objects were detected by the perturbation of the electrical field they induce. The intended application of such a sensor is in coronary diagnostics, in particular in distinguishing various types of plaques, which are major causes of heart attack. For calibration of the sensor system, finite element modeling (FEM) was performed. To validate the model, experimental measurements were carried out with two different systems. The physical system was glass tubing with metal and plastic wall insertions as targets. For the control of the experiment and for data acquisition, the software LabView designed for 17 electrodes was used. Different parameters of the electric images were analyzed for the prediction of the electrical properties and size of the inserted targets in the tube. Comparisons of the voltage modulations predicted from the FEM model and the experiments showed a good correspondence. It can be concluded that this novel biomimetic method can be further developed for detailed investigations of atherosclerotic lesions. Finally, we discuss various design strategies to optimize the output of the sensor using different simulated models to enhance target recognition.

Hair cell structures are one of the most common forms of sensing elements found in nature. In nearly all vertebrates hair cells are used for auditory and vestibular sensing. In humans, approximately 16,000 auditory hair cells can be found in the cochlea of the ear. Each hair cell contains a stereocilia, which is the primary structure for sound transduction. This study looks to develop and characterize an artificial hair cell that resembles the stereocilia of the human ear. Recently our research group has shown that a single artificial hair cell can be formed in an open substrate using a single aqueous droplet and a hydrogel. In this study, air was blown across the hair and analyzed using spectral analysis. The results of this study provided the foundation for our current work toward an artificial hair cell that uses two aqueous droplets. In the current study a test fixture was created in order to consistently measure various properties of the encapsulated hair cell. The response of the hair cell was measured with an impulse input at various locations on the test fixture. A frequency response function was then created using the impulse input and the output of the sensor. It was found that the vibration of the hair was only detectable if the test fixture was struck at the correct location. By changing the physical parameters of the hair sensor, such as hair length, we were able to alter the response of the sensor. It was also found that the sensitivity of the sensor was reliant on the size of the lipid bilayer.

Some species of the blue Morpho butterfly have a mysterious physical feature of strucural color, because it has both high reflectivity (>60%) and a single color in too wide angular range (> ± 40° from the normal), which are contradicting with each other in consideration of the interference phenomena. We have recently proven the principle of the mystery by extracting the physical essence, and emulating the nano-structures using nano-fabrication techniques. The essence was special combination of regular and irregular structures at nanometer scale. Such artificial structural color was found to concern wide applications, because the Morpho-color can produce a single color without pigment in wide angular range with high reflectivity. Also it makes colors impossible by pigment, and is resistant to fading due to chemical change over longtime. However, we must overcome several "death valleys" for wide industrial applications. One of the most serious problems was extremely low throughput in the fabrication process of nano-patterning by the conventional lithography. This difficulty was solved by use of the nano-imprinting technique. However, from the practical viewpoint, the enlargement of the mold area for nano-imprinting process was essential. This problem was found to be solved using the laser fabrication and electroforming processes. Nevertheless, to reproduce the clear blue contrast of the Morpho-color, a blackening treatment at the film interface was found to be necessary. The blackening processes and conditions by use of absorbing layers were then estimated and successfully applied to reproduce the clear contrast of the Morpho-blue, which has been confirmed by the optical measurement of the reflectivity.

Investigating the use of prismatic lenses with cross-sectional shapes inspired by the apposition compound eyes of some dipterans, we found through numerical simulations that the exposed surfaces of silicon solar cells should be textured as arrays of bioinspired compound lenses (BCLs) in order to improve performance. We used a raytracing algorithm to evaluate the light-coupling efficiency over a large wavelength range of the solar spectrum. Thus, the array configuration maximizing the light-coupling was determined. Results show that the light-coupling efficiency can be enhanced by at least 16% with respect to that of a silicon cell with a flat surface.

We have demonstrated the simple preparation of structurally colored composite films by stacking alternating Os and PB layers. Os has a much higher refractive index than PB, which causes the strong reflection at the interface between these two materials. Strong reflection colors were observed because of the interference between the multi-layers. Active control of the reflection peaks was achieved by swelling the PB layers. From these results, we conclude that black thin layers enhance the reflection of structural colors.

The results of a detailed investigation of light transmission behavior of a centric marine diatom species Coscinodiscus wailesii are reported. We measured 3-dimentional intensity distributions of both broadband and monochromatic light transmitted through individual valves of the diatom in air and water. Cross-sectional intensity profiles of transmitted light indicates valves of C. wailesii can concentrate light into certain regions. At a distance from the valve shorter than its diameter, light intensities close to the optical axis are relatively higher than those in the surrounds; at a longer distance, transmitted light intensities display ring-shaped profiles. The distance showing this light concentration characteristic becomes shorter as the wavelength of incoming light goes up. These results may offer insight into the understanding of biological functions of diatom frustules' intricate structures and inspire new optical biomimetic applications.

Biological multilayer reflectors are common in nature and some are able to reflect light across a broad range of wavelengths with a low degree of polarization over all angles of incidence. This inspired us to examine theoretically possible mechanisms that would allow stacks of biological materials to produce broadband omnidirectional reflections. Through the application of anisotropic multilayer theory, we establish that the degree of polarization of light reflected from the structure can be neutralized by birefringent layers with variations in the orientation of their optics axis and random variations in their optical thickness. The degree of polarization of reflected light decreases with the number of crystal layers and can be made arbitrarily low to produce true omnidirectional reflection. We also show that systematic variation in orientation and layer thickness can produce the same effect. This reflective structure is distinct from existing omnidirectional mirrors and can produce omnidirectional reflection even if the refractive index of the external environment is same as the low index isotropic layers.

The emerald ash borer (EAB), Agrilus planipennis, is an invasive species of beetles threatening the ash trees of North America. The species exhibits a mating behavior in which a flying male will first spot a stationary female at rest and then execute a pouncing maneuver to dive sharply onto her. The pouncing behavior appears to be cued by some visual signal from the top surface of the female's body. We have adopted bioreplication techniques to fabricate artificial visual decoys that could be used to detect, monitor, and slow the spread of EAB populations across North America. Using a negative die made of nickel and a positive die made of a hard polymer, we have stamped a polymer sheet to produce these decoys. Our bioreplication procedure is industrially scalable.

This paper presents the development of a biomimetic closed-loop flight controller that integrates gust alleviation and flight control into a single distributed system. Modern flight controllers predominantly rely on and respond to perturbations in the global states, resulting in rotation or displacement of the entire aircraft prior to the response. This bio-inspired gust alleviation system (GAS) employs active deflection of electromechanical feathers that react to changes in the airflow, i.e. the local states. The GAS design is a skeletal wing structure with a network of featherlike panels installed on the wing's surfaces, creating the airfoil profile and replacing the trailing-edge flaps. In this study, a dynamic model of the GAS-integrated wing is simulated to compute gust-induced disturbances. The system implements continuous adjustment to flap orientation to perform corrective responses to inbound gusts. MATLAB simulations, using a closed-loop LQR integrated with a 2D adaptive panel method, allow analysis of the morphing structure's aerodynamic data. Non-linear and linear dynamic models of the GAS are compared to a traditional single control surface baseline wing. The feedback loops synthesized rely on inertial changes in the global states; however, variations in number and location of feather actuation are compared. The bio-inspired system's distributed control effort allows the flight controller to interchange between the single and dual trailing edge flap profiles, thereby offering an improved efficiency to gust response in comparison to the traditional wing configuration. The introduction of aero-braking during continuous gusting flows offers a 25% reduction in x-velocity deviation; other flight parameters can be reduced in magnitude and deviation through control weighting optimization. Consequently, the GAS demonstrates enhancements to maneuverability and stability in turbulent intensive environments.

Army combat operations have placed a high premium on reconnaissance missions for Unmanned Aerial Vehicles (UAVs) and Micro Air Vehicles (MAVs) (less than 15 cm in dimension and less than 20 g in mass). One approach for accomplishing this mission is to develop a biologically inspired flapping wing insect that can maneuver into confined areas and possess hovering capabilities. Analysis of insect flight indicates that in addition to the bending excitation (flapping), simultaneous excitation of the twisting degree-of-freedom (pitching) is required to manipulate the control surface adequately. Traditionally, bimorph piezoelectric PZT (Pb(Zr_0.55Ti_0.45)O₃) actuators have been used in many applications to excite the bending degree-of-freedom. In laminated or layered structures, bend-twist coupling is governed by the existence of at least one anisotropic layer not aligned with the primary plate axes. By adding a layer of off-axis PZT segments to a PZT bimorph actuator, thereby producing a layered structure to be referred to as a functionally- modified bimorph, bend-twist coupling may be introduced to the flexural response of the layered PZT. Furthermore, by selectively charging off-axis layers in specific combinations with the bimorph, the response of the functionally-modified bimorph may be tailored yielding a biaxial actuator to actively control the flapping wing response. The present study presents an experimental investigation of both traditional bimorph and functionally-modified PZT bimorph designs intended for active bend-twist actuation of cm-scale flapping wing devices.

The adaptive honeycomb structure actuated by pneumatic muscle fibers is proposed in this paper. The FE model of adaptive honeycomb structure is developed by use of ANSYS software. The elastics modulus of the developed pneumatic muscle fibers is experimentally determined and their output force is tested. The results show that the contraction ratio of the pneumatic muscle fibers with inner diameter of 2mm could reach up to 26.8% and the force could reach to a value of 27N when the applied pressure is 0.4MPa and the contraction ratio is zero. When the adaptive honeycomb has a certain load and an effective output displacement, the applied force must be greater than a certain value. The adaptive honeycomb must be consumed extra energy when the output displacement and force are produced.

Undersea distributed networked sensor systems require a miniaturization of platforms and a means of both spatial and temporal persistence. One aspect of this system is the necessity to modulate sensor depth for optimal positioning and station-keeping. Current approaches involve pneumatic bladders or electrolysis; both require mechanical subsystems and consume significant power. These are not suitable for the miniaturization of sensor platforms. Presented in this study is a novel biologically inspired method that relies on ionic motion and osmotic pressures to displace a volume of water from the ocean into and out of the proposed buoyancy engine. At a constant device volume, the displaced water will alter buoyancy leading to either sinking or floating. The engine is composed of an enclosure sided on the ocean's end by a Nafion ionomer and by a flexible membrane separating the water from a gas enclosure. Two electrodes are placed one inside the enclosure and the other attached to the engine on the outside. The semi-permeable membrane Nafion allows water motion in and out of the enclosure while blocking anions from being transferred. The two electrodes generate local concentration changes of ions upon the application of an electrical field; these changes lead to osmotic pressures and hence the transfer of water through the semi-permeable membrane. Some aquatic organisms such as pelagic crustacean perform this buoyancy control using an exchange of ions through their tissue to modulate its density relative to the ambient sea water. In this paper, the authors provide an experimental proof of concept of this buoyancy engine. The efficiency of changing the engine's buoyancy is calculated and optimized as a function of electrode surface area. For example electrodes made of a 3mm diameter Ag/AgCl proved to transfer approximately 4mm3 of water consuming 4 Joules of electrical energy. The speed of displacement is optimized as a function of the surface area of the Nafion membrane and its thickness. The 4mm3 displaced volume obtained with the Ag/AgCl electrodes required approximately 380 seconds. The thickness of the Nafion membrane is 180μm and it has an area of 133mm3.

Robots are widely used nowadays for tasks that are either impossible or hazardous for humans to perform. Search-andrescue operations are among these, especially in the hazardous environments of nuclear power, chemical and biological plants. These rescue robots are expected to operate well in cases of natural disaster, e.g earthquakes, by overcoming unpredicted obstacles, as well as rough and even slippery surfaces like those associated with oil spills and snow storms. In this paper we discuss a robot which has claws that are normally in the retractable position, and can be activated when the robot encounters slippery surfaces or wants to climb a rough terrain. This combination takes advantage of the locomotion efficiency of wheels, and at the same time uses the retractable paws as legs or even for hooking it to objects that it wants to climb. The results of our simulations have been satisfactory and our goal is to have a working prototype with further test results at the conference.

Polymer implants are interesting alternatives to the contemporary load-bearing implants made from metals. Polyetheretherketone (PEEK), a well-established biomaterial for example, is not only iso-elastic to bone but also permits investigating the surrounding soft tissues using magnetic resonance imaging or computed tomography, which is particularly important for cancer patients. The commercially available PEEK bone implants, however, require costly coatings, which restricts their usage. As an alternative to coatings, plasma activation can be applied. The present paper shows the plasma-induced preparation of nanostructures on polymer films and on injection-molded micro-cantilever arrays and the associated chemical modifications of the surface. In vitro cell experiments indicate the suitability of the activation process. In addition, we show that microstructures such as micro-grooves 1 μm deep and 20 μm wide cause cell alignment. The combination of micro-injection molding, simultaneous microstructuring using inserts/bioreplica and plasma treatments permits the preparation of polymer implants with nature-analogue, anisotropic micro- and nanostructures.

The external surfaces of an implanted prosthesis must be biocompatible. As the properties of a biological surface vary, often gradually but also abruptly, the implant surface should be endowed with a gradient of surface roughness and wettability for good integration with proteins and cells. We have made free-standing, flexible, fibrous, nano/micro-textured thin films of parylene-C with thickness-controlled surface morphology and hydrophobicity; furthermore, varying degrees of hydrophilicity are displayed after oxygen-plasma treatment. The bioinspired thin films are mechanically robust and have been shown to support both protein binding and cellular attachment as well as growth. By conformally covering an implant surface with patches of these thin films of varying thickness and oxygen-plasma-treatment duration, gradients of protein/cell attachment can be tailored and thus tissue integration can be managed on different parts of the implant surface.

Sea creatures are a leading source to some of the more interesting discoveries in adhesives. Because sea water naturally breaks down even the strongest conventional adhesive, an alternative is important that could be used in repairing or fabricating anything that might have regular contact with moisture such as: Repairing broken and shattered bones, developing a surgical adhesive, use in the dental work, repairing and building ships, and manufacturing plywood. Some of nature's prototypes include the common mussel, limpet, some bacteria and abalone. As we learn more about these adhesives we are also developing non adhesive fasteners, such as mimicked after studying the octopus, burdock burrs (i.e. Velcro®) and the gecko.

In this report, we demonstrate the adhesive and frictional properties of the first commercial mushroom-shaped adhesive microstructure (MSAMS), which has been inspired by the attachment devices of beetles. It was shown that MSAMS have about twice higher pull-off force compared to a smooth control made from the same material measured on smooth substrates. MSAMS retained their adhesive performance over thousands of attachment cycles and initial adhesive capability could be recovered by washing after being contaminated. In shearing, MSAMS exhibits reduced and stabilized friction in comparison with a smooth control, which demonstrated pronounced stick-slip motion, and shows zero pull-off force in a sheared state, allowing the adhesion to be switched on and off. The presence of oil in the contact zone showed adhesion enhancement on both smooth and rough substrates. All these features lead us to conclude that MSAMS may have practical potential in a variety of applications.

Since the ventral body side of snakes is in almost continuous contact with the substrate during locomotion, their skin is presumably adapted to generate propulsion (high friction) and simultaneously slide along the substrate at rather low friction. In this study, the microstructure of ventral scales is shown and its influence on frictional properties was investigated by the use of scanning electron microscopy and microtribometry. To analyze the role of the system stiffness on the frictional anisotropy, two different types of sample cushioning (hard and soft) were tested while sliding in four different directions. Frictional anisotropy for both types of sample cushioning was demonstrated, however, the anisotropy was much stronger expressed in the soft cushioned sample. This effect is explained by the stronger ability of the soft-cushioned microstructure to slip along (or resist) the micro- and nanoscale features of the substrate, if compared with the hard-cushioned one.

Sophisticated methods have been created by nature to produce structure-based colors as a way to address the need of a wide variety of organisms. This pallet of available structures presents a unique opportunity for the investigation of new photonic crystal designs. Low-temperature sol-gel biotemplating methods were used to transform a single biotemplate into a variety of inorganic oxide structures. The density of optical states was calculated for a diamond-based natural photonic crystal, as well as several structures templated from it. Calculations were experimentally probed by spontaneous emission studies using time correlated single photon counting measurements.

Weakly electric fish use a process called 'active electrolocation' to orientate in their environment and to localize objects based on their electrical properties. To do so, the fish discharge an electric organ which emits brief electrical current pulses (electric organ discharge, EOD) and in return sense the generated electric field which builds up surrounding the animal. Caused by the electrical properties of nearby objects, fish measure characteristic signal modulations with an array of electroreceptors in their skin. The fish are able to gain important information about the geometrical properties of an object as well as its complex impedance and its distance. Thus, active electrolocation is an interesting feature to be used in biomimetic approaches. We used this sensory principle to identify different insertions in the walls of Plexiglas tubes. The insertions tested were composed of aluminum, brass and graphite in sizes between 3 and 20 mm. A carrier signal was emitted and perceived with the poles of a commercial catheter for medical diagnostics. Measurements were performed with the poles separated by 6.3 to 55.3 mm. Depending on the length of the insertion in relation to the sender-receiver distance, we observed up to three peaks in the measured electric images. The first peak was affected by the material of the insertion, while the distance between the second and third peak strongly correlated with the length of the insertion. In a second experiment we tested whether various materials could be detected by using signals of different frequency compositions. Based on their electric images we were able to discriminate between objects having different resistive properties, but not between objects of complex impedances.

The beetle Melanophila acuminata is highly dependent on forest fires. The burned wood serves as food for the larvae and the adults copulate on the burned areas to put their eggs in the freshly burned trees. To be able to detect forest fires from great distances the beetle developed a highly sensitive infrared receptor which works according to a photomechanical principle. The beetle has two pit organs, one on each lateral side, of which each houses around 70 dome shaped infrared receptors. These IR-receptors consist of a hard outer cuticular shell and an inner microfluidic core. When IR-radiation is absorbed, the pressure in the core increases due to the thermal expansion. This results in a deflection of a dendritic tip of a mechanosensitiv neuron which generates the signal. This biological principle was transferred into a new kind of un-cooled technical infrared receptor. To demonstrate the functional principle and the feasibility of this IR-sensor a macroscopic demonstrator sensor was build. It consisted of an inner fluid filled cavity (pressure chamber), an IR-transmissive window and a membrane. The deflection of the membrane due to the absorbed IR-energy was measured by a sensitive commercial capacitive sensor. In the experiments ethanol with added black ink, a mix of ethanol and glucose with additional absorber, air with additional absorber and water were used as fillings of the cavity and compared against each other. In order to get insights into the physics of the results of the experiments accompanying simulations using FEM methods and analytical calculations have been performed. The results showed that ethanol and air as fillings of the cavity caused the largest deflection of the membrane. Furthermore it turned out that the thermal expansion of the sensor housing material has an important influence. The comparison of the measured deflection with calculated deflections showed a good concordance.

Primary feathers allow birds to fly; however, morphology and material properties of theses feathers vary in different bird species. We therefore analysed both morphology and material properties of primary feathers in two raptor species, the peregrine falcon (Falco peregrinus) which is the fastest vertical flyer known, and the kestrel (Falco tinnunculus), using scanning electron microscopy (SEM) and nanoindentation. The program AutoCAD was used for the computation of the moments of inertia. The reduced E-modulus of the cortex of the rachis of the first, fifth, and tenth primary were measured at proximal (10% of total rachis length), central (50%) and distal (75%) cross-sections. In all cross sections the kestrel showed higher E-moduli than the peregrine falcon (values varied between 6.7 and 9.1 GPa). In the primaries, values increased from proximal to central but decreased distally. Looking at the hardness, the kestrel had higher values than the peregrine falcon yet again. The main differences occurred in the first primary. Values ranged between 0.17 and 0.4 GPa. SEM studies revealed that the tenth primary was more stable in the peregrine falcon, featuring more hamuli than the kestrel at all analysed positions and longer hamuli at the distal positions. The higher moments of inertia found in the peregrine falcon caused a much higher bending stiffness in this species. Values were 4.4 to 9.1 times larger in the peregrine falcon than in the kestrel. Because the given structures are responsible for the stability of the feather face it seems that the feathers of F. peregrinus are more robust than those of F. tinnunculus. Even when considering the higher body mass of the peregrine falcon compared to the kestrel (3.4 times), the determined stability of the feather compensates for this problem.