Ionic polymer transducers are a class of electroactive polymer materials that exhibit coupling between the electrical, chemical, and mechanical domains. With the ability for use as both sensors and actuators, these compliant, light weight, low voltage materials have the potential to benefit diverse application areas. Since the transduction properties of these materials were recently discovered, full understanding of their dynamic characteristics has not yet been achieved. This research has the goal of better understanding the actuation response of ionic polymers. A specific emphasis has been placed on investigating the observed nonlinear behavior because the existing proposed models do not account for these characteristics. Employing the Volterra representation, harmonic ratio analysis, and multisine excitations, characterization results for cantilever samples showed that the nonlinearity is dynamic and input-dependent, dominant at low frequencies, and that its influence varies depending on the solvent. It was determined that lower viscosity solvents trigger the nonlinear mechanisms at higher frequencies. Additionally, the primary components of the harmonic distortion appear to result from quadratic and cubic nonlinearities. Using knowledge gained from the characterization study, the utility of different candidate system structures was explored to model these nonlinear response characteristics. The ideal structure for modeling the current-controlled voltage and tip velocity was shown to consist of an underlying linear system with a dynamic input nonlinearity. The input nonlinearity is composed of a parallel connection of linear and nonlinear terms, where each nonlinear element has the form of a Hammerstein system. This system structure was validated against data from measured time and frequency responses. As a potential application, and consequently further validation of the chosen model structure, a square-plate polymer actuator was considered. In this study, the plate was clamped at the four corners where a uniform input was applied, measuring the center-point displacement. Characterization and modeling were performed on this system, with results similar to the cantilever sample. Applying output feedback control, in the form of proportional-integral compensation, showed that accurate tracking performance could be achieved in the presence of nonlinear distortions. Special attention was extended here to the potential application in deformable mirror systems. / Ph. D.

Ionic polymer transducers (IPT) are a class of electroactive polymer devices that exhibit electromechanical coupling through charge transport in ionomeric membranes that contain a charge mobilizing diluent and are interfaced with conducting electrodes. Applications of these active materials have been broadly developed in the field of actuators and sensors. Advances in fundamental understanding of IPT performance mechanisms and tuning of the device components has primarily focused on transducers constructed with the commercial ionomer Nafion® due to its overall stability, high ionic conductivity, and availability. The much smaller number of studies conducted with non-perfluorosulfonated ionomers concentrated on changes in chemical composition to address processability, price, ionic conductivity, and hydrated modulus of the final IPT. Also, nearly all ionic polymer transducers operated with water as the diluent until the recent successful development of IPTs with ionic liquids. The objective of this research is to increase the understanding of electromechanical transduction in ionic polymer transducers through the synthesis and characterization of novel branched ionomers. Controlled branching is achieved in sulfonated polysulfones (sBPS) through employment of an oligomeric A₂ + B₃ step-growth polymerization. Structure – property relationships are established for a series of linear and branched sulfonated polysulfones to resolve the effects of polymer topology and charge content on ionomer properties such as hydrated modulus and ionic conductivity. Furthermore, the variation of these parameters is investigated in the presence of ionic liquids as a function of ionic liquid uptake using two methods for introduction of the diluent. One of those methods, based on casting of IPT components in the presence of the ionic liquid, was applied to the Direct Application Process to produce a controlled set of IPT electrodes and transducers to investigate percolation effects of RuO₂ on the device's electrical properties and actuation characteristics. Equivalent circuit modeling of the component and transducer electrical impedance accurately modeled variations in contributing processes and material interfaces to estimate the evolution of effective capacitance based on the electrode composition. Combination of optimized electrode composition, ionic liquid uptake, and the series of linear and branched sulfonated polysulfones allowed for fabrication of a tailored set of novel ionic polymer transducers. Effects of the fabrication process on the ionic conductivity of the membranes and transducers are evaluated using electrical impedance spectroscopy, which also allowed for equivalent circuit modeling to calculate effective capacitance for the series of IPTs that varied in composition, topology, and uptake for both types of fabrication processes. The transducers described in this dissertation are the first IPTs to be designed and actuated with novel ionomers, specifically linear and branched sulfonated polysulfones, in the presence of ionic liquids. Use of sulfonated polysulfones allowed for realization of transducers with high uptakes of the ionic liquid diluent that retained significant hydrated modulus on the order of 2 GPa. Characterization of electromechanical transduction for the series of sBPS – IPTs was demonstrated in cantilever bending through frequency response analysis and step responses in the time domain to low input voltages. Both the ion content and polymer topology of the sBPS ionomeric matrix demonstrated a significant effect on the final actuation performance in relation to variations in charge transport. Also, IPTs constructed with a co-diluent swelling method which emphasized the formation and stability of the ionomer's charge transport pathway demonstrated the greatest actuation responses, up to a peak-to-peak strain of ~0.45 % and strain rates on the order of 0.1 % / s while producing significant blocked force (180 N/Vm). Combination of these actuation performance metrics resulted in maximum energy densities of 1150 mJ/kg and 2.23 mJ/mm³ for the corresponding IPT. / Ph. D.

Detecting heart and respiratory rates is an essential means of providing emergency medical care. Current methods of detecting such signals include the widely used electrocardiography (ECG) method. Other more manual methods of heart and respiratory rate estimation require a practitioner to constantly observe the patient. These methods are time consuming and detract valuable time from emergency medical care. This thesis presents a novel, hands off, heart and respiratory monitor (HARMONI). It uses pressure transducers and medical tubing placed on a person's chest. The tubing is plugged off at one end, and then attached to a pressure transducer at the other end. The transducer sees spikes in voltage whenever the pressure inside the tubing changes. Heart and respiratory rates both cause expansion in the chest, increasing the pressure in the tubing, and causing the transducer to see a change in voltage. The method was first validated, and then tested in a simulated environment. Finally, the device was transformed in to a full system prototype. Human tests were conducted to correlate the signal with that of an industry standard ECG device. This thesis explains how heart and respiratory rates can be derived using signal processing techniques and a simple non-invasive sensor. This device is a rapidly deployable tool that has the potential to save lives specifically in mass casualty situations. It would be a force multiplier, allowing a single responder to monitor multiple casualties, saving time and lives. / Master of Science

In an increasingly data-driven society, sensors and actuators are the bridge between the physical world and the world of "data." Electroacoustic transducers convert acoustic energy into electrical energy (or vice versa), so it can be interpreted as data. Piezoelectric materials are often used for transducer manufacturing, and recent advancements in additive manufacturing have enabled this material to take on complex geometric forms with micro-scale features. This work advances the additive manufacturing of piezoelectric materials by developing a model for predictive success of complex 3D printed geometries in Mask Image Projection-Stereolithography (MIP-SL) by accounting for mechanical wear on Polydimethylsiloxane (PDMS). This work proposes a framework for the rapid manufacture of 3D printed transducers, adaptable to a multitude of transducer element forms. Using the print model and transducer framework, latticed hydrophone elements are designed and tested, showing evidence of selectively tunable sensitivity, resonance, and directivity pattern. These technology advancements are extended to enable a workflow for users to input polar coordinates and receive an acoustic element of a continuously tuned directivity pattern. Investigation into customer problem spaces via tech-push methods are adapted from the NSF's Lean Launchpad to reveal insight to the problems faced in hydrophone applications and other neighboring problem spaces. / Master of Science / In an increasingly data-driven world, sensors are the bridge between the physical world and the world of "data." The better the sensor; the better the data. Electroacoustic transducers are sensors that convert acoustic sound energy into electrical energy or vice versa. These are observed in the world around us as microphones, speakers, ultrasound devices, and more. In the early 1900's, piezoelectric materials became one of the dominant methods for transducer creation, and recent advancements in additive manufacturing have enabled this material to take on highly complex geometric forms with micro-scale feature sizes. Further advancements to additive manufacturing of piezoelectric materials are contributed through development of a model for predicting the success of complex 3D printed geometries in an Mask Image Projection-Stereolithography (MIP-SL) by accounting for mechanical wear on the Polydimethylsiloxane (PDMS) print window. This work proposes a framework for the rapid manufacture of 3D printed transducers, adaptable to a multitude of element forms. Using the developed print model and transducer framework, latticed hydrophone elements are designed and tested, showing evidence of selectively tunable sensitivity, resonance and beampattern. The advancements in technology are extended to enable a workflow for users to input polar coordinates and receive an acoustic element of continuously tuned beampattern. Investigation into customer problem spaces via tech-push methods are adapted from NSF's Lean Launchpad and reveals great insight to the problems faced in hydrophone applications and other neighboring industry spaces.

A transducer consisting of multiple layers of ionic polymer material is developed for applications in sensing, actuation, and control. The transducer consists of two to four individual layers each approximately 200 microns thick. The transducers are connected in parallel to minimize the electric field requirements for actuation. The tradeoff in deflection and force can be controlled by controlling the mechanical constraint at the interface. Packaging the transducer in an outer coating produces a hard constraint between layers and reduces the deflection with a force that increases linearly with the number of layers. This configuration also increases the bandwidth of the transducer. Removing the outer packaging produces an actuator that maintains the deflection of a single layer but has an increased force output. This is obtained by allowing the layers to slide relative to one another during bending. A Finite Element Analysis (FEA) method capable of modeling the structure of the multilayer transducers is developped. It is used to model the interfacial friction in multilayer transducers. Experiments on transducers with one to three layers are performed and the results are compared to Newbury's equivalent circuit model, which was modified to accommodate the multilayer polymers. The modification was performed on four different boundary conditions, two electrical the series and the parallel connection, and two mechanical the zero interfacial friction and the zero slip on the interface. Results demonstrate that the largest obstacle to obtaining good performance is water transport between the individual layers. Water crossover produces a near short circuit electrical condition and produces feedthrough between actuation layers and sensing layers. Electrical feedthrough due to water crossover eliminates the ability to produce a transducer that has combined sensing and actuation properties. Eliminating water crossover through good insulation enables the development of a small (5 mm x 30 mm) transducer that has sensing and actuation bandwidth on the order of 100 Hz. Due to the mechanical similarities of ionic transducers to biological muscles and their large flapping displacement capabilities we are studying the possibility of their use in flapping Micro Air Vehicle (MAV) application, as engines, controllers and sensors. The FEA modeling technique capable is used to design two ionic polymers actuated flapping wings. / Master of Science

Histotripsy is a non-invasive, non-thermal, and non-ionizing therapy that utilizes converging high-pressure ultrasound waves at a focal point to produce cavitation and induce mechanical tissue destruction. Currently, rapid prototyped histotripsy transducers consist of multiple elements and are made using 3D printing methods. Multi-element transducers introduce size constraints and 3D printing has limitations in material choice, cost, and time for larger scale manufacturing. This thesis investigates the development of rapid prototyped single element histotripsy transducers and the use of injection molding for transducer fabrication, utilizing an in-house metal CNC mill for mold manufacturing and a desktop injection molding machine. Nylon 101 and 30% glass-filled nylon were chosen as the plastics to inject as these were found to have the most similar acoustic properties to WaterShed, an ABS-like plastic currently used. Six single-element transducers were constructed with a 2 MHz curved Pz26 piezoceramic disc: two with SLA 3D printed housing, two with SLS 3D printed housing, and two with injection molded housing. Electrical impedance, beam dimensions, focal pressure output, and cavitation were characterized for each element. The results show that rapid prototyped single element transducers can generate enough pressure to perform histotripsy. This marks the development of the first rapid prototyped single element histotripsy transducer and further confirms that injection molding can produce transducers comparable, if not identical or potentially superior, to 3D printed counterparts. Future work aims to further characterize these transducers, explore more material options, and apply injection molding to various transducer designs while optimizing both CNC and injection molding parameters. / Master of Science / Histotripsy is a form of cancer therapy that can non-invasively treat tumors using focused ultrasound waves. Focused ultrasound transducers are used to achieve this and are currently prototyped using 3D printing. However, these methods are limiting in material options and upscale manufacturing. Many of these devices currently used tend to be larger in size, comparable to the size of a mixing bowl, which limits its applications. This thesis investigates the development of single element histotripsy transducers and the use of injection molding for transducer fabrication, using an in-house metal CNC mill for mold manufacturing and desktop injection molding machine. Nylon 101 and 30% glass-filled nylon were chosen as the plastics to inject due to their ideal acoustic properties. Six single-element transducers were constructed: two with SLA 3D printing, two with SLS 3D printing, and two with injection molding. All transducers were tested and compared against each other. The results show that 3D printed single element transducers can perform histotripsy and that injection molding can produce comparable results. Future work should continue to test and characterize these transducers, explore more material options for injection molding, apply injection molding to other transducer designs, and optimize CNC and injection molding parameters.

This paper discusses basic issues of micromachined ultrasonic transducers, including their design and fabrication. First, the acoustic fundamentals of ultrasonic transducers are introduced, and relevant simulation methods are illustrated. Following these topics, important aspects of silicon micromachining are presented. Based on this knowledge, two distinctive micromachining processes for transducer fabrication are proposed. One of them, the bulk process, has been proved to be successful, whereas for the second one, a surface process, some improvements are still needed. Besides these works, an innovative direct bonding technology is also developed. This technology constitutes the basis of the bulk process. Of course, it can also be used for the packaging of other MEMS devices.

Following X-Ray, Ultrasound is now the most common of all the medical imaging technologies specifically in obstetrics and cardiology. Plus that the ultrasound hazards perceived to be insignificant compared with X-rays. Considering the fact that the study of cardiovascular diseases, blood flow patterns and the fetal development is essential for human life, the accuracy and proper functioning of ultrasonic systems is of great importance. Hence quality control of ultrasonic transducers is necessary. In this thesis, a system to standardize the acceptance criteria for quality control of ultrasonic transducers is described. On this ground a study on ultrasound images conducted to compare and evaluate the quality resulted from different types of transducers in different conditions, i.e. defective or functional. A clinical study was also carried out to evaluate our hypothesis in real cases at department of Cardiology and department of genecology. Results from this study show that the perception of quality is somewhat subjective and clinical studies are time-consuming. But quality factors such as the ability to accurately identify anatomical structure and functional capabilities are of great importance and help.

International Telemetering Conference Proceedings / October 27-30, 1997 / Riviera Hotel and Convention Center, Las Vegas, Nevada / Telemetry & Instrumentation, in conjunction with NASA’s Kennedy Space Center, has developed a commercial, intelligent, data acquisition module that performs all functions associated with acquiring and digitizing a transducer measurement. These functions include transducer excitation, signal gain and anti-aliasing filtering, A/D conversion, linearization and digital filtering, and sample rate decimation. The functions are programmable and are set up from information stored in a local Transducer Electronic Data Sheet (TEDS). In addition, the module performs continuous self-calibration and self-test to maintain 0.01% accuracy over its entire operating temperature range for periods of one year without manual recalibration. The module operates in conjunction with a VME-based data acquisition system.

Ressonância Magnética (RM) é uma técnica bastante versátil, pois é utilizada em muitas áreas de pesquisa, como biologia, física, química, engenharia e medicina. Apesar disso, constitui-se uma desvantagem o alto custo do equipamento e suas restrições físicas para alguns experimentos. Para reduzir essas desvantagens, o grupo de pesquisadores do CIERMag está desenvolvendo um equipamento de RMN multipropósito e, para complementá-lo, este trabalho vem desenvolver um subsistema non-real-time que gerencia os dispositivos periféricos de um experimento. Foi proposta uma rede de dispositivos que é controlada por um Raspberry Pi como elemento central, o qual está conectado ao terminal computadorizado do sistema através de uma rede local (Local Area Network - LAN) via Ethernet e conectado aos dispositivos periféricos via Serial Peripheral Interface (SPI). Com o objetivo de ser possível gerenciar qualquer tipo de dispositivo, foi desenvolvido um conjunto de parâmetros baseado no Transducer Electronic Data Sheet (TEDS), definido no padrão IEEE 1451, de modo que cada dispositivo, normalmente um transdutor, possui seu próprio. Foram elaboradas duas interfaces de software: uma desenvolvida em Python e a outra uma interface web HTML. Ambas as interfaces possuem as mesmas funcionalidades: editor e gerenciador de TEDS, visualização gráfica de medidas dos sensores e interface para os atuadores. / Magnetic Resonance (MR) is a very versatile technique, since it is used in many research areas such as biology, physics, chemistry, engineering and medicine. Despite this, the cost of the equipment and its physical restrictions in some experiments constitute a serious drawback. To minimize these problems, the CIERMag research team is developing multipurpose MR equipment and, to complement this equipment, this work develops a non-real-time subsystem that manages the peripheral devices of the experiment. It was proposed a network of devices controlled by a Raspberry Pi as its central element, which is connected to the terminal computer of the system. The protocol adopted for this was Ethernet via Local Area Network (LAN); communication with peripheral transducers was performed with the Serial Peripheral Interface (SPI). With the objective to be able to manage any type of device, we created parameter sets based on Transducer Electronic Data Sheet (TEDS), defined in the IEEE 1451 standard, so each device, normally a transducer, has its own parameter set. We created two software interfaces: one developed with Python and the other is a HTML web interface. Both have the same functionalities: a TEDS editor and manager, a graphical visualization of sensor measurements and also an actuator interface.