This PDF file contains the front matter associated with SPIE Proceedings volume 7288, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Energy harvesting - the collection of otherwise unexploited energy in the local environment - is attracting increasing attention for the powering of electronic devices. While the power levels that can be reached are typically modest (microwatts to milliwatts), the key motivation is to avoid the need for battery replacement or recharging in portable or inaccessible devices. Wireless sensor networks are a particularly important application: the availability of essentially maintenance free sensor nodes, as enabled by energy harvesting, will greatly increase the feasibility of large scale networks, in the paradigm often known as pervasive sensing. Such pervasive sensing networks, used to monitor buildings, structures, outdoor environments or the human body, offer significant benefits for large scale energy efficiency, health and safety, and many other areas. Sources of energy for harvesting include light, temperature differences, and ambient motion, and a wide range of miniature energy harvesters based on these sources have been proposed or demonstrated. This paper reviews the principles and practice in miniature energy harvesters, and discusses trends, suitable applications, and possible future developments.

Insights and observations of fascinating aspects of birds, bugs and flying seeds, of inspired aerodynamic concepts, and visions of past, present and future aircraft developments are presented. The evolution of nature's flyers, will be compared with the corresponding evolution of commercial aircraft. We will explore similarities between nature's creations and man's inventions. Many critical areas requiring future significant technology based solutions remain. With the advent of UAVs and MAVs, the gap between "possible" and "actual" is again very large. Allometric scaling procedures will be used to explore size implications on limitations and performance capabilities of nature's creations. Biologically related technology development concepts including: bionics, biomimicry, neo-bionic, pseudo-mimicry, cybernetic and non-bionic approaches will be discussed and illustrated with numerous examples. Technology development strategies will be discussed along with the pros and cons for each. Future technology developments should include a synergistic coupling of "discovery driven", "product led" and "technology acceleration" strategies. The objective of this presentation is to inspire the creative nature existing within all of us. This is a summary all text version of the complete report with the same title that report includes approximately 80 figures, photos and charts and much more information.

Thin film NiTi produced by sputter deposition was used in the design of small vessel grafts intended to treat small vessel aneurysms. Thin film small vessel grafts were fabricated by "hot-target" DC sputter deposition. Both stress-strain curves and DSC curves were generated for the film used to fabricate small vessel grafts. The films used for small vessel grafts had an Af temperatures of approximately 36 degrees allowing for body activated response from a micro-catheter. Thin film small vessel grafts were tested in a pulsatile flow loop in vitro. Small vessel grafts could be compressed into and easily delivery in < 3 Fr catheters. Theoretical frictional and wall drag forces on a thin film NiTi small vessel vascular graft were calculated and the radial force exerted by thin film small vessel grafts was evaluated theoretically and experimentally. In-vivo studies in swine confirmed that thin film NiTi small vessel grafts could be deployed accurately and consistently in the swine vascular system.

A negative capacitance circuit has been designed to change the effective natural frequency of a fixed-free piezoelectric strip attached to a non piezoelectric substrate. Experiments have investigated the extent to which resonances can be shifted using a redesigned negative capacitance circuit. The design replaces the resistive element in the feedback loop with a capacitor, effectively causing the behavior of the circuit to become frequency independent. A PVDF film was mechanically excited and the voltage generated from the piezoelectric effect fed to the circuit. This paper summarizes the theoretical model and describes ongoing experimental work.

In the present work, we have successfully fabricated nanostructured LiCoO₂ fibers using electrospinning technique from a viscous solution of lithium acetate/cobalt acetate/PVP (Polyvinylpyrrolidone), XRD (X-ray diffraction) and SEM (scanning electron microscopy) were performed to investigate the phase and microstructures of the electrospinning fibers respectively. Furthermore CV (cyclic voltammetry) and charge-discharge experiments were applied to characterize the electrochemical properties of LiCoO₂ nanofibers. It is noteworthy that the nanostructured cathode offers a higher charge-discharge capacity compared with conventional powder or film cathodes, thus LiCoO₂ nanofiber cathode may become a promising candidate for the construction of microscale lithium ion batteries due to its larger surface to volume ratio.

The power supply of wireless sensor systems is an issue of growing importance since replacement of batteries is very expensive over the sensor lifetime. An energy harvesting system which generates electrical energy from flowing media without any rotating parts will be presented. The harvester consists of piezoelectric cantilevers which oscillate in a media flow and convert kinetically energy into electrical energy. A model of the harvester was developed and the influence of geometrical parameters was simulated. Important design information was achieved as result of the simulation. Several harvester systems were built up using commercially available and not optimized PZT ceramic plates. Measurements were carried out in wind and water channels. It was found that the output voltage of the harvesters increase with the streaming velocity of the media. An output power of about 0.1mW was achieved at power adjustment in air. Optimized harvesters could deliver an up to two orders higher output.

Advances in piezoelectric energy harvesting have motivated many research efforts to propose suitable electronic interfaces for power optimization. Two kinds of electronic interfaces are currently used in literature. The common one is the standard interface which includes an AC/DC rectifier followed by a filtering capacitance. Another recently emerged one is the 'synchronized switch harvesting on inductor' (SSHI) which is added to the piezoelectric element together with the standard DC technique. It has been shown that the latter has several advantages over the former; however, the effect of frequency deviation from resonance on the electrical behavior of an SSHI system is not taken into account from the original analysis. We here propose several improved estimates for both Parallel- and Series-SSHI interfaces accounting for this effect, and make comparisons between these two. It shows that both Parallel- and Series-SSHI systems exhibit significant improved bandwidth, while the electrical behavior of the Parallel-SSHI (Series-SSHI) system is similar to that of a strongly coupled electromechanical standard system operated at the short (open) circuit resonance.

An analytical method is developed to calculate the natural frequencies and the corresponding mode shapes of a zigzag structure proposed for MEMS energy harvesting from ambient vibrations. The high natural frequencies of the existing designs of MEMS vibrational energy harvesters are serious drawbacks. A zigzag design is proposed to overcome this deficit. The governing partial differential equations are solved using separation of variables for each of the lateral beams in the structure. The vibration of each beam is related to the vibration of its neighbor beams by continuity and equilibrium conditions. Finally enforcing the boundary conditions results the corresponding eigenvalue problem revealing the natural frequencies and mode shapes. The usefulness of the design is proved by the relation between the natural frequencies and number of elements, providing a method of designing a MEMS harvester with low natural frequency.

This paper presents a finite element analysis of an interdigitated ( d₃₃ ) piezoelectric unimorph cantilever beam for harvesting vibration energy. The key feature that is analyzed is the poling behavior of the piezoelectric material. While simplified models of interdigitated piezoelectric devices assume some uniform and well-defined poling pattern, the finite element modeling shows that not to be the case. In this paper, a "percent poling factor" is developed with which to capture the real losses associated with non-uniform poling. A parametric study is carried out in which electrode patterns, piezoelectric layer dimensions and electrode dimensions are varied to see their effect on this percent poling factor. Optimal parameters are pointed out. Finally, experimental energy harvesting results for a micro-scale interdigitated beam are presented.

A novel class of two-stage piezoelectric-based electrical energy generators is presented for rotary machinery in which the input speed is relatively low, varies significantly over time, and is even reversing. This class of energy generators is highly suitable for applications such as wind mills, turbo-machinery used to harvest tidal flows, and the like. Current technology uses magnet-and-coil-based rotary generators. However, to make the generation cycle efficient, gearing or other similar mechanisms have to be used to increase the input speed to the generator. Variable speed-control mechanisms are also usually needed to achieve high mechanical to electrical energy conversion efficiency. This novel class of electrical energy generators uses a decoupled two-stage system. The harvesting environment (wind, tidal flow, etc.) directly provides input to the primary system. The low and varying input motion is then used to successively excite an array of vibrating elements (secondary system). The key advantage is that by having two decoupled systems, the low speed and highly varying input motion is converted into constant and much higher frequency mechanical vibrations, which are then harvested using piezoelectric elements. As a result, by eliminating the need for gearing and speed control mechanisms, the system complexity and cost - including those related to maintenance and service - is significantly reduced. Additionally, these novel generators can expand the application of power generation to much slower input speeds than are harvestable using current technology.

This paper discusses the basic design factors for modifying an original wing spar to a multifunctional load-bearing - energy harvester wing spar. A distributed-parameter electromechanical formulation is given for modeling of a multilayer piezoelectric power generator beam for different combinations of the electrical outputs of piezoceramic layers. In addition to the coupled vibration response and voltage response expressions for a multimorph, strength formulations are given in order to estimate the maximum load input that can be sustained by the cantilevered structure without failure for a given safety factor. Embedding piezoceramics into an original wing spar for power generation tends to reduce the maximum load that can be sustained without failure and increase the total mass due to the brittle nature and large mass densities of typical piezoelectric ceramics. Two case studies are presented for demonstration. The theoretical case study discusses modification of a rectangular wing spar to a 3-layer generator wing spar with a certain restriction on mass addition for fixed dimensions. Power generation and strength analyses are provided using the electromechanical model. The experimental case study considers a 9-layer generator beam with aluminum, piezoceramic, Kapton and epoxy layers and investigates its power generation and load-bearing performances experimentally and analytically. This structure constitutes the main body of the multifunctional self-charging structure concept proposed by the authors. The second part of this work (experiments and storage applications) employs this multi-layer generator along with the thin-film battery layers in order to charge the battery layers using the electrical outputs of the piezoceramic layers.

This paper is the second part of a two-part series investigating the development of multifunctional piezoelectric energy harvesting devices to be used in unmanned aerial vehicle and micro air vehicle applications. The proposed self-charging structures include piezoelectric layers and novel thin-film battery layers bonded to a substrate layer in order to create a multilayer, self-charging, load bearing energy harvesting device. Part 1 of this work (coupled modeling and preliminary analysis) presents a distributed parameter electromechanical model used to predict the response of the proposed selfcharging structures under harmonic base excitation. The model is compared to experimental results and found to be quite accurate. This paper investigates the fabrication and experimental evaluation of the self-charging structures. A detailed analysis of the thin-film batteries used in the self-charging structures is carried out, and their electrical and mechanical performance is evaluated. Typical charge and discharge curves are generated and analyzed. The fabrication process involved in creating self-charging structures is also outlined, including details on bonding of the layers and establishing electrical connections. A simple energy harvesting circuit is designed to allow the transfer of energy from the piezoelectric layers to the battery layers. Lastly, the energy harvesting performance of the self-charging structure is evaluated and typical charge and discharge time histories are recorded for the structure under base excitations.

Harvesting mechanical energy from ocean wave oscillations for conversion to electrical energy has long been pursued as an alternative or self-contained power source. The attraction to harvesting energy from ocean waves stems from the sheer power of the wave motion, which can easily exceed 50 kW per meter of wave front. The principal barrier to harvesting this power is the very low and varying frequency of ocean waves, which generally vary from 0.1Hz to 0.5Hz. In this paper the application of a novel class of two-stage electrical energy generators to buoyant structures is presented. The generators use the buoy's interaction with the ocean waves as a low-speed input to a primary system, which, in turn, successively excites an array of vibratory elements (secondary system) into resonance - like a musician strumming a guitar. The key advantage of the present system is that by having two decoupled systems, the low frequency and highly varying buoy motion is converted into constant and much higher frequency mechanical vibrations. Electrical energy may then be harvested from the vibrating elements of the secondary system with high efficiency using piezoelectric elements. The operating principles of the novel two-stage technique are presented, including analytical formulations describing the transfer of energy between the two systems. Also, prototypical design examples are offered, as well as an in-depth computer simulation of a prototypical heaving-based wave energy harvester which generates electrical energy from the up-and-down motion of a buoy riding on the ocean's surface.

Recently, widespread attention has been directed towards scavenging energy from renewable sources such as wind. Piezoelectric materials are particularly suitable for capturing energy from motion since mechanical deflection of a piezoelectric specimen results in an electric displacement. This electricity can be stored in batteries or used to power portable devices. The present work is on the development of a device that can generate electricity from an oscillating motion using a piezoelectric Macro Fiber Composite (MFC) bimorph. Previously, bimorph vibration was created by a rotating or reciprocating part hitting the bimorph tip; whereas in the current work, base reciprocation excites the piezoelectric bimorph. The device includes a fan blade, which aligns with the direction of the wind and moves a rod in vertical direction. The microfiber composite beams (MFC) are attached to the upper end of the rod. Reciprocation of the rod acts as a harmonic excitation for the MFC bimorphs. Vibration of the MFCs produces electricity which is stored in a capacitor to be used to power electronic systems such as different types of remote sensors. Simulation and experimental results have been compared. In vibration and wind tunnel experiments, comparable amounts of energy were collected and accumulated in a capacitor.

Piezoelectric cantilever devices for energy harvesting purposes have typically been tuned by manipulating beam dimensions or by placement of a tip mass. While these techniques do lend themselves well to designing a highly tuned resonance, the design is fixed and causes each system to be unique to a specific driving frequency. In this work, we demonstrate the design of a nonlinear tuning technique via a variable external, attractive magnetic force. With this design, the resonance of the piezoelectric energy harvester is able to be tuned with the adjustment of a slider mechanism. The magnetic design uses the well of attraction principle in order to create a varying nonlinear stiffness, which shifts the resonance of the coupled piezoelectric beam. The significance of this work is the design of a piezoelectric energy harvesting system with a variable resonance frequency that can be adjusted for changes in the driving frequencies over a wide range without the replacement of any system components; thus, extending the usefulness of these vibration energy harvesting devices over a larger frequency span.

Biological molecules including phospholipids and proteins offer scientists and engineers a diverse selection of materials to develop new types of active materials and smart systems based on ion conduction. The inherent energy-coupling abilities of these components create novel kinds of transduction elements. Networks formed from droplet-interface bilayers (DIB) are a promising construct for creating cell mimics that allow for the assembly and study of these active biological molecules. The current-voltage relationship of symmetric, "lipid-in" dropletinterface bilayers are characterized using electrical impedance spectroscopy (EIS) and cyclic voltammetry (CV). "Lipid-in" diphytanoyl phosphatidylcholine (DPhPC) droplet-interface bilayers have specific resistances of nearly 10MΩ•cm2 and rupture at applied potentials greater than 300mV, indicating the "lipid-in" approach produces higher quality interfacial membranes than created using the original "lipid-out" method. The incorporation of phospholipids into the droplet interior allows for faster monolayer formation but does not inhibit the selfinsertion of transmembrane proteins into bilayer interfaces that separate adjacent droplets. Alamethicin proteins inserted into single and multi-DIB networks produce a voltage-dependent membrane conductance and current measurements on bilayers containing this type of protein exhibit a reversible, 3-4 order-of-magnitude conductance increase upon application of voltage.

A novel THz antenna structure, made of carbon nanotube arrays is suggested. Using CST MICROWAVE STUDIO (CST MWS), the capabilities of carbon nanotube terahertz (THz) antenna arrays have been simulated and this CNT antenna array has been fabricated.

The purpose of this study is improvement of a fish robot actuated by four light-weight piezocomposite actuators (LIPCAs). In the fish robot, we developed a new actuation mechanism working without any gear and thus the actuation mechanism was simple in fabrication. By using the new actuation mechanism, cross section of the fish robot became 30% smaller than that of the previous model. Performance tests of the fish robot in water were carried out to measure tail-beat angle, thrust force, swimming speed and turning radius for tail-beat frequencies from 1Hz to 5Hz. The maximum swimming speed of the fish robot was 7.7 cm/s at 3.9Hz tail-beat frequency. Turning experiment showed that swimming direction of the fish robot could be controlled with 0.41 m turning radius by controlling tail-beat angle.

This paper describes an approach to increase the flapping frequency of a previously developed flapper actuated by Lightweight Piezo- Composite Actuator (LIPCA) to mimic the flapping frequency of Allomyrina Dichotoma of which flapping frequency is typically 30Hz. To achieve this purpose, the dynamic characteristics of the LIPCA and modification of a four-bar linkage have been studied. The parametric study showed that an appropriate combination of linkage lengths can provide a better moment transmission for a given flapping angle amplification, thus the flapping frequency could be increased. A newly designed four-bar linkage system was fabricated based on the parametric study and then tested to verify the possibility. The test results showed that the optimal flapping frequency of the modified flapper was measured to be about 15 Hz, which is about 50% increases compared to that of the previous flapper. The modified flapper could also produce 3.02 gram force in vertical direction with 97 degree of flapping angle at the optimal frequency.

This paper presents an actuator placement study for a bio-inspired joint that is part of a smart-materials-based bat wing. The wing has been designed as part of the BATMAV project with the final goal of developing a biologically-inspired micro-air vehicle with foldable wings for flapping flight. The wing uses superelastic Shape Memory Alloy (SMA) joints and SMA muscle wire actuation. A kinematic model for the bat's flapping flight motion has been developed in a previous paper, while the current paper presents a study to determine attachment points for SMA actuator wires. At the center of the current analysis is the requirement to maintain compatibility with a typical SMA's strain capabilities while simultaneously ensuring the required joint angle motion to be achieved. The study yields a range of attachment parameters, which result in contraction strains of up to 2.5%, appropriate for high-cycle actuation.

This paper proposes an adaptive neural network composed of Gaussian radial functions for mapping the behavior of civil structures controlled with magnetorheological dampers. The online adaptation takes into account the limited force output of the semi-active dampers using a sliding mode controller, as their reaction forces are state dependent. The structural response and the actual forces from the dampers are used to adapt the Gaussian network by tuning the radial function widths, centers, and weights. In order to accelerate convergence of the Gaussian radial function network during extraordinary external excitations, the learning rates are also adaptive. The proposed controller is simulated using three types of earthquakes: near-field, mid-field, and far-field. Results show that the neural controller is effective for controlling a structure equipped with a magnetorheological damper, as it achieves a performance similar to the passiveon strategy while requiring as low as half the voltage input.

This paper proposes a new haptic cue device for vehicle accelerator pedal utilizing magnetorheological (MR) fluids. As a first step, an MR fluid-based haptic device is devised to be capable of rotary motion of accelerator pedal. Under consideration of spatial limitation, design parameters are optimally determined to maximize control torque using finite element analysis. The proposed haptic cue device is then manufactured and integrated with accelerator pedal. Its fielddependant torque is experimentally evaluated. Vehicle system emulating gear shifting is constructed in virtual environment and communicated with the haptic cue device. The time responses of the manufactured haptic device are then experimental evaluated. Haptic cue algorithm using the feed-forward control algorithm is formulated to achieve optimal gear shifting in driving. Control performances are experimentally evaluated via feed-forward strategy and presented in time domain.

The increased prevalence of semi-active control systems is largely due to the emergence of cost effective commercially available controllable damper technology such as Magneto-Rheological (MR) devices. Unfortunately, MR dampers are highly nonlinear, which presents an often over-looked complexity to the control system designer. The well-known Skyhook Damping control algorithm has enjoyed great success for both fully active and semi-active control problems. The Skyhook design strategy is to create a control force that emulates what a passive linear damper would create when connected to an inertial reference frame. Skyhook control is device independent since it generates a desired control force command output that must be produced by the control system. For simplicity, MR dampers are often assumed to have a linear relationship between the current input and the force output at a given relative velocity. Often this assumption is made implicitly and without knowledge of the underlying nonlinearity. In this paper, we show that the overall performance of a semi-active Skyhook control system can be improved by explicitly inverting the nonlinear relationship between input current and output force. The proposed modification will work with any semi-active control algorithm, such as Skyhook, to insure that the controller performance is at least as good as the performance without the proposed modification. This technique is demonstrated through simulation on a quarter-vehicle system.

This study provides a comprehensive analysis of the characteristics of MR mounts in squeeze mode which is the least commonly-analyzed aspect of MR fluids. The results of the study are based on a novel rheometer that is designed and fabricated for the purpose of better understanding the characteristics of MR fluids in squeeze mode. The paper describes the details of the rheometer design. It further provides the test results for MR fluids tested in squeeze mode. The tests indicate a clumping effect of the fluid when tested in repeated cycles that does not appear to have been documented previously. The paper describes, in detail, the clumping effect and provides possible reasons for this phenomenon.

The harmonic steady-state responses of an MR seat isolator, designed and fabricated at the University of Maryland for the driver/commander seat of the Expeditionary Fighting Vehicle (EFV), are measured over a temperature range from 100°C to 1000°C, and the damper behavior is characterized using a variant of the nonlinear Bingham plastic model. The effect of damper self-heating on the model parameters is investigated and the trends with temperature variation are presented. Numerical simulations are carried out to investigate seat isolation performance across a broad frequency spectrum as temperature and payload vary. Conclusions are drawn about the performance robustness to temperature variations of the semi-active skyhook control algorithm typically utilized in vibration isolation problems.

Based on the latest investigations on the formulation of new magneto-rheological fluids, it is envisioned that the use of ionic liquids as carriers of magneto-rheological fluids will open new possibilities of applications for these smart fluids due to the fact that their physical and chemical properties can be fine-tuned in a broad range. This contribution addresses one potentially important advantage of magneto-rheological fluids which use ionic liquids as novel carriers. In connection with this, magneto-rheological fluids with a low viscosity in the off-state without compromising other properties of the formulations (e. g., sedimentation of the dispersed magnetic particles, liquid state of the carriers in a broad range of temperatures) are often required for specific applications. In this regard, ionic liquids of low viscosity can be very useful in the development of such magneto-rheological fluids. Thus, this contribution reports on the magnetorheological properties of iron(II, III) oxide particles dispersed in the ionic liquid 1-ethyl-3-methylimidazolium thiocyanate (a low viscosity ionic liquid) in the temperature range from 20 °C to 80 °C. The experimental results have revealed that the apparent viscosity of the dispersion slightly changes with the temperature when a constant magnetic field is applied and its value mainly depends on the shear rate and the strength of the magnetic field. The viscosity of the dispersion remains practically unmodified with both the temperature and the magnetic field intensity as the magnetic saturation of the material is reached; in this regime the viscosity will only depend on the applied shear rate. In contrast, the yield stress values of the dispersion as well as the corresponding shear stress vs. shear rate curves have shown an inverse behavior with temperature for a constant magnetic field.

Based on the state-of-the-art about seismic damage principles and aseismic strengthening technology, analysis and design method of seismic retrofitting for earthquake damaged reinforced concrete frame using magnetorheological (MR) damper is proposed. Three levels of fortification objects are put forward and quantified or intelligent retrofitting of reinforced concrete frame using MR damper. The experiment system of a three-floor reinforced concrete frame-shear wall eccentric structure has been built based on Matlab/Simulink software environment and hardware/software resources of dSPACE. The shaking table experiment of seismic retrofitting of earthquake damaged reinforced concrete frame-shear wall structure using MR damper is implemented using rapid control prototyping (RCP) technology. The validity of passive control strategies and semi-active control strategy is verified under El Centro earthquake excitations with different peak value. The experimental results indicate that MR dampers can significantly enhance aseismic performance level of the seismic damaged reinforced concrete frame, and meet all the earthquake fortification levels. The aseismic ability of MR damper intelligent aseismic structure system of auto-reinforcement is much better than both the damaged structure and the aseismic structure reinforced by the passive damper.

The concept of power harvesting works towards developing self-powered devices that do not require replaceable power supplies. One important parameter defining the performance of a piezoelectric power harvesting system is the efficiency of the system. However, an accepted definition of the energy harvesting efficiency does not currently exist. This article will develop a new definition for the efficiency of an energy harvesting system which rather than being defined through energy conservation as the ratio of the energy fed into the system to maintain the steady state to the output power, we consider the ratio of the strain energy over each cycle to the power output. This new definition is analogous to the material loss factor. Simulations will be performed to demonstrate the validity of the efficiency and will show that the maximum efficiency occurs at the matched impedance; however, for materials with high electromechanical coupling the maximum power is generated at the near open and closed-circuit resonances with a lower efficiency.

Personal electronic devices such as mobile/cell phones, radios and wireless sensors traditionally depend on energy storage technologies, such as batteries, for operation. By harvesting energy from the local environment, these devices can achieve greater run-times without the need for battery recharging or replacement. Harvesting energy could also achieve a reduction in the weight and volume of the personal devices - as batteries often make up more than half the weight/volume of these devices. Motion energy harvesting is one such approach where energy from mechanical motion can be converted into electrical energy. This can be achieved through the use of flexible piezoelectric transducer materials such as polyvinylidene fluoride (PVDF). A problem with these transducer materials it that their behaviour is non-linear due to operating and environmental conditions. Hence, for this reason researchers have found it has been difficult to measure the harvesting performance i.e. mechanical-to-electrical conversion efficiency. At CSIRO we are currently evaluating the performance of flexible transducers for use as motion energy harvesters. Preliminary results suggest an overall energy harvesting conversion efficiency of 0.65% for a flexible transducer material.

Over the last decade, wireless computing and mobile devices have decreased in size and power requirements. These devices traditionally have power requirements that necessitate the need for batteries as a power source. As the power requirements reduce, alternative means of power become available. One of these is the use of thermal energy. The use of thermal energy requires a high temperature source and a lower temperature sink. Energy is extracted as heat flows from the hot side to the cold side. The magnitude of the heat source is not as critical as the magnitude of the temperature difference between the source and sink. One source of temperature difference is that between a body of water and a solar heated object. A device has been designed and tested to capture thermoelectric energy where one side of the device is immersed in water. The other side is exposed to solar radiation. Typically, during the day this is warmer than the water. However, at night this situation is reversed. This paper discusses the design and manufacture of an innovative thermal energy capturing device. This device was used to capture energy across an air water boundary. Theoretical estimations of power available from measured temperature differences are compared with the results of the designed device.

A novel class of piezoelectric-based event sensing and energy-harvesting power sources is presented for gunfired munitions. The power sources are designed to harvest energy from firing acceleration and vibratory motions during the flight. The piezoelectric element may be used to measure setback acceleration level, indicate the barrel exit time and impact time and force levels for fuzing purposes. The developed power sources have the added advantage of providing safety, since the fuzing electronics are powered only after the munitions have exited the barrel. The developed piezoelectric-based energy harvesting power sources produce enough electrical energy for applications such as fuzing. The power sources are designed to withstand firing accelerations in excess of 120,000 G. In certain applications such as fuzing, the developed power sources have the potential of completely eliminating the need for chemical batteries. The design of a number of prototypes, including their packaging for high G hardening, and the results of laboratory, air-gun and firing tests are presented.

In this paper, we present experimental investigations using energy harvesting and wireless energy transmission to operate embedded structural health monitoring sensor nodes. The goal of this study is to develop sensing systems that can be permanently embedded within a host structure without the need for an on-board power source. With this approach the required energy will be harvested from the ambient environment, or periodically delivered by a RF energy source to supplement conventional harvesting approaches. This approach combines several transducer types to harvest energy from multiple sources, providing a more robust solution that does not rely on a single energy source. Both piezoelectric and thermoelectric transducers are considered as energy harvesters to extract the ambient energy commonly available on civil structures such as bridges. Methods of increasing the efficiency, energy storage medium, target applications and the integrated use of energy harvesting sources with wireless energy transmission will be discussed.

A significant portion of railroad infrastructure exists in areas that are relatively remote. Railroad crossings in these areas are typically only marked with reflective signage and do not have warning light systems or crossbars due to the cost of electrical infrastructure. Distributed sensor networks used for railroad track health monitoring applications would be useful in these areas, but the same limitation regarding electrical infrastructure exists. This motivates the search for a long-term, low-maintenance power supply solution for remote railroad deployment. This paper describes the development of a mechanical device for harvesting mechanical power from passing railcar traffic that can be used to supply electrical power to warning light systems at crossings and to remote networks of sensors via rechargeable batteries. The device is mounted to and spans two rail ties such that it directly harnesses the vertical displacement of the rail and attached ties and translates the linear motion into rotational motion. The rotational motion is amplified and mechanically rectified to rotate a PMDC generator that charges a system of batteries. A prototype was built and tested in a laboratory setting for verifying functionality of the design. Results indicate power production capabilities on the order of 10 W per device in its current form. This is sufficient for illuminating high-efficiency LED lights at a railroad crossing or for powering track-health sensor networks.

Aeroelastic vibration of structures represents a novel energy harvesting opportunity that may offer significant advantages over traditional wind power devices in many applications. Such a system could complement existing alternative energy sources by allowing for distributed power generation and placement in urban areas. The device configuration of a simple two degree aeroelastic system suitable for piezoelectric power harvesting is presented. The mechanical, electromechanical, and aerodynamic equations of motion governing the dynamics and electrical output of the system as a function of incident wind speed are derived. The response and current output of one design for a bench top scale harvester are simulated and presented. Finally, a strategy for expanding the operating envelope of the power harvester is proposed and discussed.

This paper presents recent analytical results pertaining to the optimization of power flow from vibratory energy harvesting systems, using principles from optimal feedback control and network theory. Historically, much of the research concerning such technologies has presumed that the vibratory energy source, from which power is to be extracted, oscillates harmonically at a known frequency. In this case, the optimization of power extraction from such sources by a resonant energy harvester can readily be accomplished through the use of classical impedance matching techniques. However, in many applications, vibratory power sources exhibit dynamic behavior more appropriately characterized by a stochastic process. In some cases, the power spectrum of this process may exhibit a rather wide band. In such circumstances, impedance matching techniques cannot be used to optimize power flow from the harvester, because the dynamic impedance they prescribe is always anticausal. This paper presents several theoretical concepts, intended for broad application in the energy harvesting area, which can be used to optimize power extracted from broadband sources. It is shown that in the broadband case, an optimal causal impedance still exists which maximizes power generation, but in order to derive it, the dissipation in the electrical system, as well as the mechanical system, must be taken into account in the system model. Levels of power generation with this controller are compared to those of the anticausal optimal performance, as well as to control design techniques that match the anticausal impedance at the resonant frequency. It is demonstrated that such causal matching techniques can be significantly sub-optimal in broadband applications, especially when electronic conversion is relatively efficient.

Seventy percent of the Earth's surface is covered by water and all living things are dependent upon this resource. As such there are many applications for monitoring environmental data in and around aquatic environments. Wireless sensor networks are poised to revolutionise this process as the reduction in size and power consumption of electronics are opening up many new possibilities for these networks. Aquatic sensor nodes are usually battery powered, so as sensor networks increase in number and size, replacement of depleted batteries becomes time consuming, wasteful and in some cases unfeasible. Additionally, a battery that is large enough to last the life of a sensor node would dominate the overall size of the node, and thus would not be very attractive or practical. As a result, there is a clear need to explore novel alternatives to power sensor nodes/networks, as existing battery technology hinders the widespread deployment of these networks. By harvesting energy from their local environment, sensor networks can achieve much greater run-times, years not months, with potentially lower cost and weight. A potential renewable energy source in aquatic environments exists via the temperature gradient present between the water layer and ambient air. A body of water will be either a few degrees warmer or colder than the air directly above it dependant on its latitude, time of year and time of day. By incorporating a thermal energy harvesting device into the sensor node deployment which promotes the flow of heat energy across the thermal gradient, a portion of the energy flow can be converted into useable power for the sensor node. To further increase this temperature difference during the day the top section can be heated to temperatures above the ambient air temperature by absorbing the incoming sunlight. As an initial exploration into the potential of this novel power source we have developed a model of the process. By inputting environmental data, the model calculates the power which can be extracted by a thermal energy harvesting device. Initial outputs show a possibility of up to 10W/m2 of power available from measured sites assuming a thermal energy harvester operating with Carnot efficiency.

There are a number of approaches to power harvesting that are under-exploited in many applications germane to sensing and communication. Power can usually be obtained from numerous sources - such as solar, thermal, vibrational, and electromagnetic energy - using a variety of transduction methods. However, in general a power harvesting system and its associated electronics interface are designed only to exploit a single energy source. This research presents the development of innovative ways of gathering power and addressing the design issues in providing a unified energy source from disparate power harvesting approaches, specifically alternating and direct current methods. These power sources are integrated into a single source to be utilized for sensing and communication. Several circuit designs are offered to improve the combined energy harvesting performance over that of the individual harvesters. The transient dynamics of charging a storage capacitor are presented for the individual and combined power sources. Complications arising from backwards electromechanical and mutual coupling are discussed.

The authors proposed a sandwich structure that consists of a shape memory alloy (SMA) honeycomb core and carbon fiber reinforced plastic (CFRP) skins as a lightweight geometric-variable structure. This method has the better ability to bend skins with high in-plane stiffness, because the SMA honeycomb core generates a recovery-shear-force and applies the force uniformly to the skins. Hence, although this sandwich beam is really lightweight and has a moderate specific bending stiffness, the beam can be bent by raising the temperature. The honeycomb core was made of thin Ti-Ni SMA foils, and skins were thin unidirectional CFRP laminates. Pre-shear-strain was applied to the SMA honeycomb core, and the both ends of the two skins were fixed. When the beam was heated, it was bent upward taking the form of a sigmoid curve. Furthermore, it was verified that the beam was able to generate the sufficient actuation force. Then, when the specimen was cooled down to the room temperature, the specimen returned to the straight beam again. Hence the twoway actuation is possible by heating and cooling. Also the mechanism of this bending deformation could be clarified by a numerical simulation using the finite element method.

A method is described for solving an inverse design problem to find the unassembled, stress-free component shapes of a structure thatis integrally actuated with shape memory alloy (SMA) actuators. Morphing and multifunctional structures are of interest in the aerospace industry becasue of the potential for improving structural and aerodynamic performance across multiple operating conditions. The focus of this work is on structures that are morphed with SMA flexural actuators. For the case where the geometry is known for unassembled components, assembly can be simulated to find the assembled shapes of the morphing structure. In the usual design case, however, only the desired shapes as assembled are known in multiple actuation states, and the corresponding unassembled shapes must be determined by an iterative solution process. An iterative finite element analysis approach to this problem is reported here. First an initial guess for the unassembled shapes is made and assembly is simulated with the finite element method. The resulting shapes are found for both SMA phases and compared with the desired shapes. A gradient-based optimization method is employed to update the initial geometry and iteration continues until the desired shapes are achieved. A simplified method of modeling the SMA material behavior is used for computational efficiently. It is found that this approach provides a practical way to solve the inverse design problem for structures that are integrally actuated with SMA material.

Smart precast concrete frame connection based on unbonded shape memory alloy (SMAPCFC) was proposed as a possible seismic resistance measure for reinforced concrete frame buildings. To investigate the restoring force characteristics of SMA wire, cyclic tensile tests on superelastic NiTi SMA wires with three diameters were carried out. The effects of the different loading conditions, namely: cyclic loading-unloading number, strain amplitude, loading frequency and ambient temperature, on the mechanical behavior described by some fundamental quantities, such as energy dissipation per cycle, secant stiffness, equivalent damping, residual strain, were examined. The temperature changes of the SMA wires due to the latent heat under different loading conditions were also discussed.

Short Bowel Syndrome (SBS) is medical condition characterized by insufficient small intestine length, leading to improper nutrient absorption and significant mortality rates. The complications of current treatment methods have encouraged the development of a novel treatment method based on mechanotransduction, the process through which mechanical tensile loading induces longitudinal growth of intestine. Animal based studies with simple extension devices have demonstrated the potential of the treatment to grow healthy bowel, but an implantable device suitable for clinical use remains undeveloped. This paper presents the development of an instrumented fully implantable bowel extender based upon a shape memory alloy driven linear ratchet that can be controlled and monitored remotely. The overall bowel extender system is described with respect to specifications for pig experimental tests. The functionality of the mechanical and electrical subsystems of the device are detailed and experimentally validated on the bench top, in segments of living bowel tissue removed from a pig, and in cadaveric pigs. Mechanical loading characteristics and safe load limits on bowel tissue are identified. Results from these experiments establish the readiness of the device to be tested in living pigs, enabling studies to move one step closer to clinical studies.

Essential Tremor is a debilitating disorder that in the US alone is estimated to affect up to ten million people. Unfortunately current treatments (i.e. drug therapy and surgical procedures), are limited in effectiveness and often pose a risk of adverse side-effects. In response to this problem, this paper describes an active cancellation device based on a hand-held Shape Memory Alloy (SMA) actuated stabilization platform. The assistive device is designed to hold and stabilize various objects (e.g. eating utensils, tools, pointing implements, etc.) by sensing the user's tremor and moving the object in an opposite direction using SMA actuators configured in biologically inspired antagonistic pairs. To aid in the design, performance prediction and control of the device, a device model is described that accounts for the device kinematics, SMA thermo-mechanics, and the heat transfer resulting from electrical heating and convective cooling. The system of differential equations in this device model coupled with the controller gain can be utilized to design the operation given a frequency range and power requirement. To demonstrate this, a prototype was built and experimentally tested under external disturbances in the range of 1-5 Hz, resulting in amplitude reduction of up to 80%. The extent of cancellation measured for both single-frequencies and actual human tremor disturbances demonstrate the promise of this approach as a broadly used assistive device for the multitudes afflicted by tremor.

Research efforts have shown that helicopter rotor blade morphing is an effective means to improve flight performance. Previous example of rotor blade morphing include using smart-materials for trailing deflection and rotor blade twist and tip twist, the development of a comfortable airfoil using compliant mechanisms, the use of a Gurney flap for air-flow deflection and centrifugal force actuated device to increase the span of the blade. In this paper we explore the use of a bistable mechanism for rotor morphing, specifically, blade chord extension using a bistable arc. Increasing the chord of the rotor blade is expected to generate more lift-load and improve helicopter performance. Bistable or "snap through" mechanisms have multiple stable equilibrium states and are a novel way to achieve large actuation output stroke. Bistable mechanisms do not require energy input to maintain a stable equilibrium state as both states do not require locking. In this work, we introduce a methodology for the design of bistable arcs for chord morphing using the finite element analysis and pseudo-rigid body model, to study the effect of different arc types, applied loads and rigidity on arc performance.

Magnetorheological (MR) fluid has been increasingly researched and applied in vibration isolation devices. To date, the suspension system of several high performance vehicles has been equipped with MR fluid based dampers and research is ongoing to develop MR fluid based mounts for engine and powertrain isolation. MR fluid based devices have received attention due to the MR fluid's capability to change its properties in the presence of a magnetic field. This characteristic places MR mounts in the class of semiactive isolators making them a desirable substitution for the passive hydraulic mounts. In this research, an analytical model of a mixed-mode MR mount was constructed. The magnetorheological mount employs flow (valve) mode and squeeze mode. Each mode is powered by an independent electromagnet, so one mode does not affect the operation of the other. The analytical model was used to predict the performance of the MR mount with different sets of parameters. Furthermore, in order to produce the actual prototype, the analytical model was used to identify the optimal geometry of the mount. The experimental phase of this research was carried by fabricating and testing the actual MR mount. The manufactured mount was tested to evaluate the effectiveness of each mode individually and in combination. The experimental results were also used to validate the ability of the analytical model in predicting the response of the MR mount. Based on the observed response of the mount a suitable controller can be designed for it. However, the control scheme is not addressed in this study.

The goal of this study is to develop a new model to describe the behavior of shear yield stress of magnetorheological greases/gels (MRGs) under the combined effects of applied magnetic field and temperature. MRGs are a class of field-responsive materials which consist of micron-size ferrous particles suspended in a grease/gel-like material. The main advantage of a MRG over a MR fluid is that in a MRG, ferrous particles do not settle. However, the rheological properties of grease carrier materials are very sensitive to temperature. Therefore, the temperature effect on the yield stress of MRGs may be one of the main concerns in developing these materials. In this study, the steady-shear magneto-rheological response of MRGs subject to various temperatures is investigated. All experimental data are obtained for magnetic fields ranging from 0.14T to 0.53T and temperatures ranging from 10°C to 70°C. It is observed that temperature has a pronounced effect on the field induced yield stress of MRGs. A new yield stress model for MRGs which is a function of magnetic field and temperature is proposed based on the Herschel-Bulkley constitutive equation and the Arrhenius relationship. Excellent agreement between the model predictions and experimental data is obtained.

The vibration control of microelectromechanical structures is an interesting and challenging research area that is extensively applicable in micro-mass measurement, micro-sensors and micro-mirror control. An active vibration control technique based on positive position feedback method is constructed in this paper. This method is used to control the vibration of microcantilevers through actuation of a piezoelectric layer that covers one side of the microcantilever. The modified version of positive position feedback used in this paper, employs a second order compensator for vibration suppression, and a first order compensator provides damping. Since the positive position feedback control is based on strain sensing approach, it is extensively applied to piezoelectrically controlled microcantilevers. Similar to conventional positive position feedback, stability conditions are global and independent of the dynamical characteristics of the open-loop system. Root locus diagrams are used to find proper compensator frequency and damping of the closed loop system. A numerical simulation is performed to evaluate the performance of the modified positive position feedback for both steady-state and transient dynamic control. The results indicate that the proposed method is more effective in controlling both steady-state and transient dynamics than conventional positive position feedback.

A novel active squeeze film journal air bearing actuated by high power piezoelectric transducers is presented. The proposed bearing uses in-air squeeze film levitation to suspend the rotating spindle without contact. Unlike conventional journal bearings, the presented bearing journal is formed by multiple independently vibrating surfaces driven individually by piezoelectric transducers. Langevin type piezoelectric transducers with a special radiation surface are developed. Detailed design procedures to develop the ultrasonic transducers are presented. A complete spindle-bearing system is constructed to test the proposed squeeze film bearing. Load carrying forces are measured at different vibration amplitude and compared with the calculated results. The proposed squeeze film journal bearing is operated in ultrasonic frequency range. The achieved load capacity is about 50N, which is five times of the load capacity achieved by the previous squeeze film bearings reported in the literatures.

In this paper the damping capability of piezoelectric shunting is analysed for bladings. Beside the broadly used inductance-resistance networks, negative capacitance techniques are considered. For the validation of the theoretic results, a test rig with a model of a bladed disk with eight blades has been manufactured and equipped with two collocated piezoceramics at each blade. One of the piezoceramics is used as an actuator for an engine order excitation. The second piezoceramics is used for shunt damping. The experimental results of the test rig are compared with numerical results. Therefore, the structure and the piezoceramics are modeled in a finite element program. The modal excitation forces of the piezoelectric actuators are derived for all modes of the structure by a static analysis with a specific voltage applied to the piezoceramics. In addition, using the modal displacement field of the static analysis the modal excitation forces can be calculated. Furthermore, the number of degrees of freedom of the system is reduced by a modal reduction technique. The electrical behavior of the piezoceramics connected to each blade is modeled by one degree of freedom and coupled with the mechanical system described above. The different damping concepts are compared with respect of their effectiveness.

Piezoelectric shunt damping is new technique to damp mechanical vibrations of structures. Because of the piezoelectric effect, vibration energy is converted into electrical energy. In the attached network some part of the energy is dissipated. Switching shunts offer the possibility to adapt to varying excitation frequencies. In this paper, the damping performance of different switching techniques are calculated considering all important network parameters and non-idealities in the switching boards. Measurements on a clamped beam are performed to validate the results, and the switching techniques are applied to a squealing disc brake. It is shown that due to the piezoelectric shunt damping the sound pressure level can be reduced considerably.

Periodic arrays of hybrid shunted piezoelectric actuators are used to suppress vibrations in an aluminum plate. Commonly, piezoelectric shunted networks are used for individual mode control, through tuned, resonant RLC circuits, and for broad-band vibration attenuation, through negative impedance converters (NIC). Periodically placed resonant shunts allow broadband reduction resulting from the attenuation of propagating waves in frequency bands which are defined by the spatial periodicity of the array and by the shunting parameters considered on the circuit. Such attenuation typically occurs at high frequencies, while NICs are effective in reducing the vibration amplitudes of the first modes of the structure. The combination of an array resonant shunts and NICs on a two-dimensional (2D) panel allows combining the advantages of the two concepts, which provide broadband attenuation in the high frequency regimes and the reduction of the amplitudes of the low frequency modes. Numerical results are presented to illustrate the proposed approach, and frequency response measurements on a cantilever aluminum plate demonstrate that an attenuation region of about 1000Hz is achieved with a maximum 8 dB vibration reduction.

Piezoelectric bimorph elements are commonly used in a wide area of applications, among them various actuator applications in textile machines, applications in sensing like medical tissue identification, or the use in energy harvesting systems. Especially the last field may create a mass market for piezoelectric elements. Due to their easy use and low resonance frequency, bimorphs seem to fit energy harvesting demands quite well. To get the best possible power output, the element has to be designed as good as possible to fit the environmental excitation characteristics as excitation frequency and amplitude. Due to the need of a good understanding of the resulting system, a model based approach is desirable for the design of the used bimorphs. This is the case not only in Energy Harvesting systems but in most of the mentioned applications.

In this paper, we consider a linear piezoelectric structure which employs a fast-switched, capacitively shunted subsystem to yield a tunable vibration absorber or energy harvester. The dynamics of the system is modeled as a hybrid system, where the switching law is considered as a control input and the ambient vibration is regarded as an external disturbance. It is shown that under mild assumptions of existence and uniqueness of the solution of this hybrid system, averaging theory can be applied, provided that the original system dynamics is periodic. The resulting averaged system is controlled by the duty cycle of a driven pulse-width modulated signal. The response of the averaged system approximates the performance of the original fast-switched linear piezoelectric system. It is analytically shown that the averaging approximation can be used to predict the electromechanically coupled system modal response as a function of the duty cycle of the input switching signal. This prediction is experimentally validated for the system consisting of a piezoelectric bimorph connected to an electromagnetic exciter. Experimental results show that the analytical predictions are observed in practice over a fixed "effective range" of switching frequencies. The same experiments show that the response of the switched system is insensitive to an increase in switching frequency above the effective frequency range.

Integrating a piezoelectric circuitry, which consists of a piezoelectric transducer connected with electrical circuitry elements, to a mechanical structure can alter the dynamic behavior of the structural system. From a system dynamics standpoint, these circuitry elements are analogous to the mass, damping, and stiffness elements in the mechanical regime. Using op amp circuits we can synthesize circuitry elements with interesting characteristics such as tunable or negative elements. In this research, we demonstrate that the negative resistance element can reduce the overall system damping, thereby changing the dynamic response of mechanical structures. In particular, it will be shown that not only the response amplitude can be amplified; the response pattern in the mistuned periodic structure can be altered significantly upon the change of local structural properties. Such phenomena are analyzed systematically, and the potential advantage for structural damage detection is highlighted.

As known, the electrical induced strain of conventional piezoceramic materials is limited by 0.12 % (2 kV/mm), which often requires strain transformation designs, like levers, in order to meet application needs. High fabrication accuracy and low tolerances are crucial points in mechanical manufacturing causing high device costs. Therefore, we developed a piezoelectric composite actuator with inherent stress - strain transformation. Basically, piezoceramic sheets are laminated with spring steel of a certain curvature, which can be realised by a comparatively simple fabrication technique. The working diagram of these composite bow actuators showed a high level of performance adaptable to a wide range of applications. The authors established the value chain covering the piezoceramic formulation, the processing technology and the design in view of optimum system performance. The paper presents an overview of the design principles, simulation and various aspect of fabrication technology including lamination, sintering and polarization. The new devices are useable in different sectors, for example in automotive industry as solid state transducer or as the active part in injectors. Moreover, the composite bow actuators may find application in microsystems technology, micro optics and micro fluidics as well as vibration dampers. The composite bow actuators can be used as single component transducer, as well as multi-bow actuator in series or parallel combination on demand.