No description available.

Ionic polymer membranes are commonly used in fuel cell power generation, water electrolysis and desalinization, chlorine generation, and other niche applications. Since the early 1990s ionic polymer membranes have also shown promise as distributed electromechanical actuators and sensors. The cost of these materials is very high because of the expensive noble metals that are used as the electrodes in these applications, however. Currently, high cost of these devices has prevented them from experiencing widespread use. The goal of the current research project is to study new methods of plating metal electrodes onto ionic polymer membranes in order to reduce the cost of these materials and open the door for potential industrial, aerospace, and biomedical applications. At this time ionic polymer actuators are only made using gold or platinum as the electrode in a lengthy and labor-intensive process. The current research focuses on using less costly metals and revising the metal deposition process. Several new methods allowing for faster deposition of metals onto ionic polymer membranes are developed and evaluated including sputter-coating, electroless plating, and impregnation/reduction. Using these methods, metal electrodes have been plated onto ionic polymer membranes in processes resulting in a purely surface deposition and in processes resulting in interpenetration of the metal into the polymer. This work shows that electromechanical coupling is present with all of these processes, although results indicate that interpenetration of the electrode is important for good adhesion of the metal and good performance of the transducers. Also studied were different metals; X-ray photoelectron spectroscopy (XPS) testing shows that the use of non-noble metals as the electrodes results in oxidation of the metal and corresponding loss of performance in the actuator. Noble metals are found to not experience the oxidation problem. Further work shows that non-noble metals can be effectively employed as electrodes if alloyed with noble metals by using a co-reduction technique. Also studied is the use of protective coatings of noble metal to stabilize the non-noble metal electrodes. Using these approaches, a new plating method is developed and the stability of the electrodes made using this method is studied. These results indicate that samples made using this new process may be actauted continuously for over 150,000 cycles with very little degredation in their performance. Using this new plating method, ionic polymer membrane transducers can be made in less than five hours. Characterization of these new devices shows that they have a mass energy density of 4-20 mJ/kg in the cantilevered mode. This compares well with a baseline material, which is found to have a mass energy density of 3-12 mJ/kg. Composition and morphology of the electrodes made using the new method are investigated using scanning electron microscopy (SEM) and the density and tensile modulus are measured. The density of the new material is found to be approximately 2100 kg/m^3 as compared to about 3200 kg/m^3 for the baseline material. Also, the tensile elastic modulus of the new material is about 55 MPa, or roughly one fourth of the tensile modulus of the baseline material (about 190 MPa). These results indicate that the new materials contain much less noble metal in the electrodes than the baseline material. The sensitivity of these devices has also been quantified and compared to the baseline. Results indicate that the new materials have a sensitivity on the order of 0.1-0.3 uA/mm/s whereas similarly sized samples of the baseline material typically have sensitivities on the order of 0.2-0.8 uA/mm/s. The most important conclusion of this work is that ionic polymer membrane transducers can be made using much less noble metal in the electrode than previously believed without sacrificing the performance of these devices. / Master of Science

This thesis describes the use of an ultrasonic goal-seeking algorithm while using ionic polymer metal composite (IPMC), an electroactive polymer, as the actuator to drive a vessel towards a goal. The signal transmitting and receiving circuits as well as the goal seeking algorithm are described in detail. Two test vessels were created; one was a larger vessel that contained all necessary components for autonomy. The second was a smaller vessel that contained only the sensors and IPMC strips, and all power and signals were transmitted via an umbilical cord. To increase the propulsive efforts of the second, smaller vessel, fins were added to the IPMC strips, increasing the surface area over 700%, determined to yield a 22-fold force increase. After extensive testing, it was found that the three IPMC strips, used as oscillating fins, could not generate enough propulsion to move either vessel, with or without fins. With the addition of fins, the oscillating frequency was reduced from 0.86-Hz to 0.25-Hz. However, the goal-seeking algorithm was successful in guiding the vessel towards the target, an ultrasonic transmitter. When moved manually according to the instructions given by the algorithm, the vessel successfully reached the goal. Using assumptions based on prior experiments regarding the speed of an IPMC propelled vessel, the trial in which the goal was to the left of the axis required 18.2% more time to arrive at the goal than the trial in which the goal was to the right. This significant difference is due to the goal-seeking algorithm’s means to acquire the strongest signal. After the research had concluded and the propulsors failed to yield desired results, many factors were considered to rationalize the observations. The operating frequency was reduced, and it was found that, by the impulse-momentum theorem, that the propulsive force was reduced proportionally. The literature surveyed addressed undulatory motion, which produces constant propulsive force, not oscillatory, which yields intermittent propulsive force. These reasons among others were produced to rationalize the results and prove the cause of negative results was inherent to the actuators themselves. All rational options have been considered to yield positive results.

This thesis describes the use of an ultrasonic goal-seeking algorithm while using ionic polymer metal composite (IPMC), an electroactive polymer, as the actuator to drive a vessel towards a goal. The signal transmitting and receiving circuits as well as the goal seeking algorithm are described in detail. Two test vessels were created; one was a larger vessel that contained all necessary components for autonomy. The second was a smaller vessel that contained only the sensors and IPMC strips, and all power and signals were transmitted via an umbilical cord. To increase the propulsive efforts of the second, smaller vessel, fins were added to the IPMC strips, increasing the surface area over 700%, determined to yield a 22-fold force increase. After extensive testing, it was found that the three IPMC strips, used as oscillating fins, could not generate enough propulsion to move either vessel, with or without fins. With the addition of fins, the oscillating frequency was reduced from 0.86-Hz to 0.25-Hz. However, the goal-seeking algorithm was successful in guiding the vessel towards the target, an ultrasonic transmitter. When moved manually according to the instructions given by the algorithm, the vessel successfully reached the goal. Using assumptions based on prior experiments regarding the speed of an IPMC propelled vessel, the trial in which the goal was to the left of the axis required 18.2% more time to arrive at the goal than the trial in which the goal was to the right. This significant difference is due to the goal-seeking algorithm’s means to acquire the strongest signal. After the research had concluded and the propulsors failed to yield desired results, many factors were considered to rationalize the observations. The operating frequency was reduced, and it was found that, by the impulse-momentum theorem, that the propulsive force was reduced proportionally. The literature surveyed addressed undulatory motion, which produces constant propulsive force, not oscillatory, which yields intermittent propulsive force. These reasons among others were produced to rationalize the results and prove the cause of negative results was inherent to the actuators themselves. All rational options have been considered to yield positive results.

No description available.

Electrical motors and/or hydraulics and pneumatics cylinders are commonly used methods of actuation in mechanical systems. Over the last two decades, due to arising market needs, novel self-independent mobile systems such as mobility assistive devices have emerged with the help of new advancements in technology. The actuation criteria for these devices differ greatly from typical mechanical systems, which has made the implementation of classical actuators difficult within modern assistive devices. Among the numerous challenges, limited energy storage capabilities by mobile systems have restricted their achievable operational time. Furthermore, new expectations for device weight and volume, as well as actuator structural compliance, have added to this quandary. Electroactive polymers, a category of smart materials, have emerged as a strong contender for the use in low-cost efficient actuators. They have demonstrated great potential in soft robotic and assistive device/prosthetic applications due to their actuation potential and similar mechanical behaviour to human skeletal muscles. Dielectric Elastomers, in particular, have shown very promising properties for these types of applications. Their structures have shown large achievable deformation, while remaining light-weight, mechanically efficient, and low-cost. This thesis aims to characterize, and model the behaviour of 3MTM VHB polyacrylic dielectric elastomer, in order to establish a foundation for its implementation in a proposed novel linear actuator concept. In this thesis, a comprehensive experimental evaluation is accomplished, which resulted in the better understanding of the elastomer’s biaxial mechanical and electro-mechanically coupled behaviours. Subsequently, a constitutive biaxial mechanical model was derived in order to provide a predictive design equation for future actuator development. This model proved effective in providing a predictive tool for the biaxial mechanical tensile response of the material. Finally, a simplified prototype was devised as a proof of concept. This first iteration applied experimental findings to validate the working principles behind the proposed actuator design. The results confirmed the proof of concept, through achieved reciprocal linear motion, and provided insight into the design considerations for prototype optimization and final actuator development.

Workshop 2015 Veranstalter: Fraunhofer-Institut für Werkzeugmaschinen und Umformtechnik IWU, Dresden / Technische Universität Dresden, Technisches Design / SLUB Dresden Ort: Makerspace der SLUB Dresden

Orientador: Assis Vicente Benedetti / Resumo: Os revestimentos de poliuretano (PU) foram preparados a partir de óleos vegetais (crambe e mamona) e modificados pela incorporação de inibidores de corrosão (tanino condensado). A reação foi monitorada caracterizando os produtos intermediários (poliéster e pré-polímero). O poliéster foi caracterizado pela solubilidade em metanol, índice de acidez, grupos hidroxila e espectroscopia no infravermelho por transformada de Fourier com refletância total atenuada (FTIR), e o pré-polímero foi caracterizado por teor de sólido, teor de solvente, isocianato livre (NCO) e FTIR. Os revestimentos de PU foram caracterizados por FTIR e absorção de água. Esses revestimentos foram aplicados sobre as ligas de alumínio com extensômetro. O processo de cura foi conduzido em temperatura ambiente (~25 oC). A espessura dos revestimentos foi determinada por microscopia eletrônica de varredura (SEM) e a adesão foi avaliada pela Norma ASTM D3359. Após a caracterização química e morfológica dos revestimentos foi realizado o estudo eletroquímico. A resistência à corrosão e o processo de degradação do filme (longevidade da ação do revestimento), foram estudadas por medidas de potencial em circuito aberto (EOCP) e espectroscopia de impedância eletroquímica (EIS) em solução aquosa 0,6 mol L-1 NaCl com o tempo de imersão. Foram empregadas técnicas eletroquímicas localizadas como espectroscopia de impedância eletroquímica local (LEIS) em solução aquosa 0,005 mol L-1 NaCl e as técnicas de varredura com eletrodo ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Polyurethane (PU) coatings were prepared from vegetable oils (crambe and castor) and modified by the incorporation of corrosion inhibitors (condensed tannins). The reaction was monitored by characterizing the intermediate products (polyester and prepolymer). Polyester was characterized by solubility in methanol, acidity index, hydroxyl groups and attenuated total reflectance Fourier transform infrared spectroscopy (FTIR), and the prepolymer was characterized by solid content, solvent content, free-isocyanate (NCO) groups and FTIR. PU coatings were characterized by FTIR and water uptake. These coatings were applied on aluminum alloys with an extensometer. The curing process was carried out at room temperature (~25 oC). The thickness of the coatings was determined by scanning electron microscopy (SEM) and the adhesion was assessed using the ASTM D3359 standard. After the chemical and morphological characterization of the coatings, the electrochemical study was carried out. The corrosion resistance and the film degradation process (longevity of the coating action) were studied by open circuit potential measurements (EOCP) and electrochemical impedance spectroscopy (EIS) in 0.6 mol L-1 NaCl aqueous solution with the immersion time. Localized electrochemical techniques were also used, such as local electrochemical impedance spectroscopy (LEIS) in 0.005 mol L-1 NaCl aqueous solution and scanning techniques with vibrating electrode (SVET) and with ion-selective electrode (SIET), in ... (Complete abstract click electronic access below) / Doutor

This thesis presents the design and development of two switching amplifiers used to drive the so-called smart material actuators. Different from conventional circuits, a smart material actuator is ordinarily a highly capacitive load. Its capacitance is non-linear and its strain is hysteretic with respect to its electrical control signal. This actuator's reactive load property usually causes a large portion of reactive power circulating between the power amplifier and the driven actuator, thus reduces the circuit efficiency in a linear power amplifier scenario. In this thesis, a switching amplifier design based on the PWM technique is proposed to develop a highly efficient power amplifier, and peak current mode control is proposed to reduce the actuator's hysteretic behavior. Since the low frequency current loop gain tends to be low due to the circuit's capacitive load, average current mode control is further proposed to boost the low frequency current loop gain and improve the amplifier's low frequency performance. Both of the circuits have been verified by prototype design and their experimental measurement results are given. / Master of Science

Origami is making an impact in engineering as solutions to problems are being found by applying origami principles (eg. flat-foldability) and using specific crease patterns as inspiration. This thesis presents an in-depth analysis of a particular origami fold -- the waterbomb base -- to facilitate its use in future engineering problems. The watebomb base is of interest due to its familiarity to the origami community, simple topology (can be made by folding a single sheet of paper four times), scalability, generalizability, and interesting kinetic behavior. It can behave as a nonlinear spring as well as a one- or two-way bistable mechanism. This thesis presents models of the kinetic behavior of the traditional waterbomb base as well as some non-traditional variants to be used as tools in future development of waterbomb-base-inspired mechanisms. In all cases considered here, developability as well as rotational symmetry in both the geometry and motion of the mechanisms are assumed. The thesis provides an introduction to origami and reviews some of the ways in which it has been studied and applied in engineering fields. The waterbomb base is also presented as a specific origami fold with practical application potential. Models for the behavior of the traditional waterbomb base are introduced and its potential usefulness as a testbed for actuation methods is discussed. Models are developed for its kinematic and bistable behavior, including the forces needed to transition between stable states. These models are validated by comparison to physical prototype testing and finite element analysis. The thesis introduces the generalized waterbomb base (WB) and generalized split-fold waterbomb base (SFWB). The WB maintains the pattern of alternating mountain and valley folds around the vertex but in this generalized case any even number of folds greater than or equal to 6 is allowed. An SFWB is created by splitting each fold of a WB into two “half folds”, effectively doubling the number of folds and links but halving the deflection at each fold. The same models that were developed for the traditional waterbomb base are developed for the WB and the SFWB and a few potential applications are discussed.