IPMC materjali hp-FEM mudel

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Ioonjuhtivaid polümeer-metall komposiitmaterjale (edaspidi lühendatud IPMC ehk ionic polymer-metal composite) on uuritud juba vähemalt kaks aastakümmet nende huvipakkuvate omaduste tõttu. Võimalikeks kasutusaladeks on vaiksed aktuaatorid või sensorid. IPMC eelised teiste elektroaktiivsete polümeeride ees on töötamine madalal pingel (1...5V), suur paindeulatus, ja toimimine veekeskkonnas. Kuigi põhiliselt on uuritud materjalide omadusi aktuaatoritena, on hiljuti materjalide sensor-omadused rohkem tähelepanu saanud. Et materjali toimimisest aru saada ning seda kirjeldada erinevate rakenduste tarbeks, on vajalik füüsikal baseeruvat mudelit. Sellest lähtuvalt on välja töötatud Poisson-Nernst-Planck-Navier võrranditel baseeruva IPMC mudel. See baseerub füüsikalistel printsiipidest, ehk et saab kasutada võimalikult palju mõõdetavaid suurusi ääretingimustena (nagu materjali paindumine, rakendatud pinge jne). Lisaks on oluline, et meetod millel mudel baseerub, oleks efektiivne ning võimaldaks arvutusi väikese või vähemalt teadaoleva maksimaalse arvutusveaga. Käesoleva töö keskendub peamiselt just arvutusmeetodil ja annab ülevaate uudsest hp-FEM (finite element method) ehk hp lõplike elementide meetodist ja sellel baseeruvast IPMC mudelist. Kõigepealt on täielikult tuletatud võrrandid ja nende integraalne esitus Newtoni meetodi jaoks. Seejärel antakse lühike ülevaade hp-FEM meetodist adaptiivse väljapõhise võrguga ning kogu süsteemi Jakobiaani tuletus hp-FEM tarkvara Hermes jaoks. On näidatud kuidas automaatne adaptiivne hp-FEM võimaldab probleemi suuruse hoida väiksena (süsteemi vabadusastmeid ja kasutatud mälu silmas pidades). Kõige pealt on lahendatud Poisson-Nernst-Plancki võrrandisüsteem ja on käsitletud erinevaid adaptiivusalgoritme. Üks huvitav tulemus on, et adaptiivsed algoritmid võimaldavad lahendada probleemi tingimustel, kus Debye pikkus jääb nanomeetri suurusjärku – seda süsteemis mille mõõtmed on millimeetri skaalas. Nendest tulemustest lähtuvalt esitatakse lahendus terve Poisson-Nernst-Planck-Navier võrrandite süsteemile IPMC paindumise arvutustes. Taaskord on lõplikud võrrandid koos tuletuskäiguga esitatud. Lisaks on analüüsitud suur hulk simulatsiooni tulemusi arvutusprobleemi suurust ja kulutatud arvutusaega silmas pidades ja sellest lähtuvalt leitud parim adaptiivuse algoritm seda liiki probleemide jaoks. On ka näidatud kuidas meetod võimaldab arvutusdomeeni geomeetriat arvesse võtta – domeeni pikkuse ja laiuse suhtest tulenevad ääreefektid on automaatselt arvutustes käsitletud. Kokkuvõtteks, käesolevas töös on detailselt kirjeldatud kuidas kasutades uudne hp-FEM meetod koos adaptiivsete algoritmide ja väljapõhise võrguga võimaldab Nernst-Planck-Poisson-Navier probleemi lahendada efektiivselt, samal ajal hoides lahenduse arvutusvea etteseatud piirides.Ionic polymer-metal composites (IPMC) have been studied during the past two decades for their potential to serve as noiseless mechanoelectrical and electromechanical transducers. The advantages of IPMC over other electroactive polymer actuators are low voltage bending, high strains (>1%), and an ability to work in wet environments. The main focus has been on the electromechanical transduction property – the material’s ability to exhibit large bending deformation in response to a low (typically 1...5 V) applied voltage. However, lately research on the mechanoelectrical transduction properties of the material has gained more attention. In order to describe both deformation in response to applied voltage (electromechanical transduction) and induced voltage in response to applied deformation (mechanoelectrical transduction) properties of IPMC, an advanced physics based model of the material is necessary. Ongoing research has been focused on creating such model where real measurable quantities can be imposed as boundary conditions in order to reduce the number of unknown parameters required for calculations. In this dissertation, a physics based model that is based on novel hp-FEM (finite element method) is proposed. From the fundamental aspect, previously proposed and validated physics based model consisting of a system of Poisson-Nernst-Planck-Navier’s equations is described in detail and used in IPMC deformation calculations. From the mathematical aspect, a novel hp-FEM method was researched to model the equations efficiently. The main focus of this disseration is on the mathematical aspect. Full derivation of the equations with an in-depth study of the benefits of using higher order FEM with automatic adaptivity is presented. The explicit weak form of the Poisson-Nernst-Planck system for Newton’s method is presented. Thereafter, a brief overview of the adaptive multi-mesh hp-FEM is introduced and the residual vector and Jacobian matrix of the system is derived and implemented using hp-FEM library Hermes. It is shown how such problem benefits from using individual meshes with mutually independent adaptivity mechanisms. To begin with, a model consisting of only the Poisson-Nernst-Planck system is solved using different adaptivity algorithms. For instance, it is demonstrated that the problem with set of constants that results Debye’s length in the nanometer scale can be successfully solved. What makes it even more remarkable is the fact that the calculation domain size is in the millimeter scale. Based on those results, the complete Poisson-Nernst-Planck-Navier’s system of equations is studied for IPMC electromechanical transduction calculations. Again, the entire mathematical derivation including weak forms, the residual vector and Jacobian matrix are presented. Thereafter, a number of simulations are analyzed in terms of problem size and consumed CPU time. The best automatic adaptivity mode for such problem is determined. It is also shown how hp-FEM helps to keep the problem geometrically scalable. Additionally, it is demonstrated how employing a PID controller based time step adaptivity helps to reduce the total calculation time. Overall, by using hp-FEM with adaptive multi-mesh configuration the Nernst-Planck-Poisson-Navier’s problem size in IPMC deformation calculations is reduced significantly while a prescribed precision of the solution is maintained

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Model development for numerical simulation of the behaviors of pH-stimulus responsive hydrogels

Ph.DDOCTOR OF PHILOSOPH

Design and application of a cellular, piezoelectric, artificial muscle actuator for biorobotic systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 219-227).One of the foremost challenges in robotics is the development of muscle-like actuators that have the capability to reproduce the smooth motions observed in animals. Biological muscles have a unique cellular structure that departs from traditional electromechanical actuators in several ways. A muscle consists of a vast number of muscle fibers and, more fundamentally, sarcomeres that act as cellular units or building blocks. A muscle's output force and displacement are the aggregate effect of the individual building blocks. Thus, without using gearing or transmissions, muscles can be tailored to a range of loads, satisfying specific force and displacement requirements. These natural actuators are desirable for biorobotic applications, but many of their characteristics have been difficult to reproduce artificially. This thesis develops and applies a new artificial muscle actuator based on piezoelectric technology. The essential approach is to use a subdivided, cellular architecture inspired by natural muscle. The primary contributions of this work stem from three sequential aims. The first aim is to develop the operating principles and design of the actuator cellular units. The basic operating principle of the actuator involves nested flexural amplifiers applied to piezoelectric stacks thereby creating an output length strain commensurate with natural muscle. The second aim is to further improve performance of the actuator design by imparting tunable stiffness and resonance capabilities. This work demonstrates a previously unavailable level of tunability in both stiffness and resonance. The final aim is to showcase the capabilities of the actuator design by developing an underwater biorobotic fish system that utilizes the actuators for resonance-based locomotion. Each aspect of this thesis is supported by rigorous analysis and functional prototypes that augment broadly applicable design concepts.by Thomas William Secord.Ph.D

Proceeding Of Mechanical Engineering Research Day 2016 (MERD’16)

This Open Access e-Proceeding contains a compilation of 105 selected papers from the Mechanical Engineering Research Day 2016 (MERD’16) event, which is held in Kampus Teknologi, Universiti Teknikal Malaysia Melaka (UTeM) - Melaka, Malaysia, on 31 March 2016. The theme chosen for this event is ‘IDEA. INSPIRE. INNOVATE’. It was gratifying to all of us when the response for MERD’16 is overwhelming as the technical committees received more than 200 submissions from various areas of mechanical engineering. After a peer-review process, the editors have accepted 105 papers for the e-proceeding that cover 7 main themes. This open access e-Proceeding can be viewed or downloaded at www3.utem.edu.my/care/proceedings. We hope that these proceeding will serve as a valuable reference for researchers. With the large number of submissions from the researchers in other faculties, the event has achieved its main objective which is to bring together educators, researchers and practitioners to share their findings and perhaps sustaining the research culture in the university. The topics of MERD’16 are based on a combination of fundamental researches, advanced research methodologies and application technologies. As the editor-in-chief, we would like to express our gratitude to the editorial board and fellow review members for their tireless effort in compiling and reviewing the selected papers for this proceeding. We would also like to extend our great appreciation to the members of the Publication Committee and Secretariat for their excellent cooperation in preparing the proceeding of MERD’16

Antenna sensing for wearable applications

As wearable technologies are growing fast, there is emerging trend to increase functionality of the devices. Antennas which are primarily component in communication systems can offer attractive route forward to minimize the number of components functioning as a sensing element for wearable and flexible electronics. Toward development of flexible antenna as sensing element, this thesis investigates the development of the flexible and printed sensing NFC RFID tag. In this approach, the sensor measurement is supported by the internal sensor and analog-to-digital convertor (ADC) of the NFC transponder. Design optimisation, fabrication and characterization of the printed antenna are described. Besides, the printed antenna, NFC transponder and two simple resistive sensors are integrated to form a fully flexible sensing RFID tag demonstrating applicability in food and health monitoring. This thesis also presents development of two antenna sensors by using functional materials: (i) An inductor-capacitor (LC) resonant tank based wireless pressure sensor on electrospun Poly-L-lactide (PLLA) nanofibers-based substrate. The screen-printed resonant tank (resonant frequency of ~13.56 MHz) consists of a planar inductor connected in parallel with an interdigitated capacitor. Since the substrates is piezoelectric, the capacitance of the interdigitated capacitor varies in response to the applied pressure. To demonstrate a potential application of developed pressure sensor, it was integrated on a compression bandage to monitor sub-bandage pressure. (ii) To investigate the realization of sensing antenna as temperature sensor simple loop antenna is designed and in this study unlike the first study that the sensing element was the substrate, the conductive body of the antenna itself is considered as a functional material. In this case, a small part of a loop antenna which originally was printed using silver paste is replaced by Poly(3,4-ethylenedioxythiophene): polystyrene (PEDOT: PSS). The sensing mechanism is based on the resonant frequency shift by varying temperature. While using functional materials is useful for realization of antenna sensor, another approach also is presented by developing stretchable textile-based microstrip antennas on deformable substrate which can measure joint angles of a human limb. The EM characteristics of the meshed patch antenna were compared with its metallic counterpart fabricated with lithography technique. Moreover, the concept of stretchable UHF RFID-based strain sensor is touched in the final part of this thesis

Shape memory polymeric nanocompsites for biological applications

The aim of this work is to develop novel shape memory polymers (SMPs) and nanocomposites for potential biological applications. A kind of commercial SMP, shape memory polyurethane (SMPU), was used to prepare nanocomposites by incorporating nano-clay into the SMPU substrate. The mechanical behaviour, thermal property and shape memory efficiency were studied with various nanofiller loadings. Chemical synthesis methods were also employed to prepare the other designable SMP and its nanocomposites, i.e. the shape memory polystyrene co-polymer (SMPS). Multiple technologies were adopted to enhance the SMPS matrix such as modifying the chemical components, introducing various functional nanoparticles into the polymeric network and improving the dispersion of the nanoparticles. Different methods were used to characterize the overall performance of the obtained materials. Mechanical tests were performed at different dimensional scales with a varied degree of localisation. Nanoindentation was firstly applied to assess the micro-mechanical properties of shape memory polymer nanocomposites at scales down to particle size. The micro-mechanical analysis provided the fundamental information on the SMPs and their nanocomposites for bio-MEMS applications. Potential applications were also explored through manufacturing different type of device models and testing their shape recovery efficiencies. Finally, theoretical contributions were made in two areas. The first one was the theoretical analysis on the nanoparticles enhancement to the soft polymeric matrix. The other was in developing a constitutive model to describe the thermo-viscoelastic property and shape memory behaviour for SMP nanocomposites

A Complex of the Electromagnetic Biosensors with a Nanowired Pickup

The proposal to measure the biosignal values of different origins with advanced nanosensors of electromagnetic quantities is justified when allowing for superconducting abilities of the devices. They are composed in full-scale arrays. The said arrays can be both implantable into ionic channels of an organism and sheathed on the sources of the electromagnetic emanation. Nanowired head sensors function both in passive mode for picking up the biosignals and with additional excitation of a defined biomedium through the same head (in reverse). The designed variety of bio-nanosensors allow interfacing a variety of biosignals with the external systems, also with a possibility to control the exposure on an organism by artificially created signals. The calculated signals lies in the range of −5 to 5 V, (7÷0)⋅1017/cm3 molecules or magnetic beads, 2÷10 pH, and stream speed 3⋅10−3÷102 m/s, flow 10−5÷10 m/s, and haemoglobin concentration of 1030÷1024 molec/cm3. The sensitivity of this micro- or nanoscope can be estimated as =10−4 (A⋅m/√Hz) with SNR equal to 104. The sensitivity of an advanced first-order biogradiometer is equal to 3 fT/√Hz. The smallest resolvable change in magnetic moment detected by this system in the band 10 Hz is 1 fJ/T

Functional Polymer Solutions and Gels–Physics and Novel Applications

“Functional Polymer Solutions and Gels—Physics and Novel Applications” contains a broad range of articles in this vast field of polymer and soft matter science. It shows insight into the field by highlighting how sticky (non-covalent) chemical bonds can assemble a seemingly water-like liquid into a gel, how ionic liquids influence the gelation behavior of poly(N-Isopropylacrylamide) as well as how the molecular composition of functional copolymers is reflected in the temperature-responsiveness. These physics were augmented by theoretical works on drag-reduction. Also, drug-release – an improved control of how fast or dependent on an external factor – and antibacterial properties were the topic of several works. Biomedical applications on how cell growth can be influenced and how vessels in biological systems, e.g., blood vessels, can be improved by functional polymers were complemented with papers on tomography by using gels. On totally different lines, also the topic of how asphalt can be improved and how functional polymers can be used for the enrichment and removal of substances. These different papers are a good representation of the whole area of functional polymers