DESIGN AND CHARACTERIZATION OF MAGNETIC FIELD ACTUATED MULTILAYERED POLYMERS.

DESIGN AND CHARACTERIZATION OF MAGNETIC FIELD ACTUATED MULTILAYERED POLYMERS.
Author: Rui Leng
Publisher:
Total Pages: 0
Release: 2022
Genre:
ISBN:

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This thesis investigates multi-field actuated smart materials for potential biomedical applications. Magneto-active elastomers (MAEs) consisting of magnetic particles and a two-part elastomer were first designed and tested for their degree of actuation as unimorphs. The study considered two types of magnetic particles, hard and soft. For hard magnetic particles, barium hexaferrite (BHF) microparticles were chosen based on their responsiveness to magnetic field and their hard magnetic properties. The permanent magnetic dipoles of BHF resulting in large remanent magnetization can be polarized by magnetic field into designed directions. For soft magnetic particles, iron oxide microparticles were chosen where application of magnetic field results in induced dipoles. The elastomer matrix for the MAEs was fabricated using a two-part polydimethylsiloxane (PDMS) base and curing agent. BHF-PDMS and iron oxide-PDMS were fabricated using conventional casting method, processed into unimorphs and actuated as proof of concept. A unimorph structure is a layered structure where a substrate material is deformed using an active material and designed for large bending deformation. Bending and folding actuation was elicited with BHF-PDMS thin films as the particle magnetic dipoles were poled in a uniform direction beforehand. The film then reacts to external magnetic field by aligning the dipole directions with the external magnetic field direction. Iron oxide-PDMS was also studied and actuated using external magnetic field. Other actuation configurations designed included gripping and flower blooming motions. Large bending actuation was achieved with both hard and soft MAEs, and the next step was to test for printability. Iron oxide-PDMS was chosen for the printability test and the material compositions was tuned by adjusting base to curing agent ratio and by the addition of thickening agent. The printability study considered parameters such as temperature and number of printed layers, and results showed that printable iron oxide-PDMS slurries were obtained with 5wt% fumed silica added. The matrix of the magneto-active polymer-based materials was also investigated by comparing PDMS with mechanically stiffer polyvinyl alcohol (PVA) in degree of actuation. In the last step, multi-field actuation was studied using both conventional casting and additive manufacturing (AM) methods. Shape memory polymers (SMPs) were chosen to act as the "active" substrate for their shape fixing and recovery abilities under different temperatures. Unimorph structures were again used to test actuation of MAE-SMP under both magnetic and thermal fields. A gripping configuration was designed and demonstrated using conventionally cast iron oxide-PDMS and SMPs. Printed iron oxide-SMP thin films were actuated to assess the impact of the functional gradient design, showing different degree of actuation with different compositions of materials. The outcome of this research aims at potential biomedical applications using smart materials to allow non-contact control with large actuations. Additive manufacturing will enable the facile fabrication of actuators using these multiple materials, and would allow more customized devices to be printed for ease of use, while adapting to each patient's unique condition and requirement.

Multi-filed Actuation of Polymer Based Structures

Multi-filed Actuation of Polymer Based Structures
Author: Sarah Masters
Publisher:
Total Pages:
Release: 2016
Genre:
ISBN:

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In this project, active materials and sample configurations were explored with the goal of creating multi-field actuators, i.e., materials that respond to multiple stimuli to deform and change shape. Specifically, PVDF-TrFE- CTFE (terpolymer) and PDMS with barium ferrite particles were the two types of active materials used. Terpolymer is an electroactive polymer material, which actuates when an electric field is applied, and the PDMS with barium ferrite particles is a magnetoactive material, which actuates when placed in a magnetic field. By building different actuator configurations using these active materials, deformation and shape change can be achieved using both electric and magnetic fields. The main two motions observed throughout this project were bending (curvature across the entire sample) and folding (localized curvature at a notch). First, bending in a unimorph was explored; the unimorph was fabricated using solution cast terpolymer as the active material with scotch tape added to the sample as the inactive material. When an electric field is applied to this type of sample, the nanodomains present in the terpolymer cause it to contract in the thickness and expand in the length of the sample. Attaching a layer of scotch tape (inactive substrate) to the terpolymer restricts the planar expansion of the terpolymer when electric field is applied. This configuration, referred to as a unimorph, results in a bending motion towards the inactive substrate under electric field. Next, notches are introduced in the unimorph to transform the bending into folding; specifically, two smaller pieces of scotch tape were added on to the single layer of tape that was first placed on the terpolymer. A gap, i.e., notch, is left in between the two smaller pieces of tape that are added to the top of the sample. In the notched area, since there is less inactive substrate, these areas will exhibit more localized bending than the rest of the samples. Both single notch and double notch folding were explored. Double notch samples showed greater actuation, to the point where the sample curled up on itself because a large amount of folding was produced in both notches. Next, PDMS with barium ferrite particles was used to create a unimorph bender that would actuate when a magnetic field was applied. The barium ferrite particles are permanent magnetic particles, so when they are added to the PDMS and the entire sample is cured under a magnetic field, the resulting material has a magnetic pole direction. When the sample is then placed in an applied magnetic field, the sample actuates (bends) to try to align the poled direction of the sample with the direction of the external magnetic field. Finally, terpolymer and PDMS with barium ferrite particles were combined (attached together using an adhesive spray) into a bimorph structure. Both bending and folding actuators were investigated using this bimorph configuration. These multi-field actuators respond to both electric and magnetic fields. In conclusion, multi-field actuation of a single bimorph sample was achieved using both an electric and magnetic field. Both multi-field bending and folding were successfully demonstrated and quantified.

Electroactive Polymer-based Materials for Responsive Origami-inspired Structures

Electroactive Polymer-based Materials for Responsive Origami-inspired Structures
Author: Saad Ahmed
Publisher:
Total Pages:
Release: 2017
Genre:
ISBN:

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With the ever-growing usage of technology in our day-to-day life, the demands on existing energy sources, sustainable technology, and space requirements are also increasing. As a result, increasing interests are focused on technologies with benefits such as reduced space requirements, reduced material consumption, and improved energy efficiency. Origami-inspired engineering has gained much attention among scientists, engineers and mathematicians as an emerging form of technology with potential advantages such as relatively simple assembly process, realization of a large number of structures/shapes from a single sheet and finally, capability of folding into a compact shape and then unfolding (deploy or launch) into a larger-complex shape. Self-folding mechanism coupled with origami-inspired engineering is of particular interest where the structure has the ability to fold and unfold in response to an external stimulus without manual assistance. Researchers have investigated several self-folding mechanisms to realize origami-inspired engineering. In this work, an electroactive polymer (EAP), more specifically poly (vinylidende fluoride-trifluoroehtylene-chlorotrifluoroethylene) P(VDF-TrFE-CTFE), is studied and implemented to achieve origami-inspired self-folding structures.P(VDF-TrFE-CTFE) is used to realize electric field driven origami-inspired smart structures because of high room temperature dielectric constant (~50), fast response and reversible actuation mechanism. Processing condition of P(VDF-TrFE-CTFE) is studied based on the microstructure and electromechanical properties. Then a detail electrical, electromechanical, analytical, thermal, mechanical characterization on P(VDF-TrFE-CTFE) is performed and presented. Through dielectric spectroscopy it is observed that the Curie transition of terpolymer shows a broad peak unlike normal ferroelectric polymer. Polarization study reveals very slim (less lossy) hysteresis loop. The current understanding of the origin of electrostrictive strain is attributed to phase transition from paraelectric to ferroelectric phases. In this work, electric field in-situ X-ray diffraction (XRD) and sum frequency generation (SFG) study are conducted to investigate and confirm the switching of and phases to polar -phase. To enable electric field-driven on-demand bending and folding of P(VDF-TrFE-CTFE), various approaches are undertaken. First, electric field-driven large bending is achieved using a one layered unimorph actuator. Two approaches are pursued to convert the bending actuation into folding: notches and stiffener. While stiffener approach was not very successful, the notch approach showed more pronounced folding actuation. However, EAP actuators also possess drawbacks that impede their implementation in applications, namely they induce relatively low force and require high actuation voltages. To address these issues, a multilayered unimorph concept is proposed. Due to the complex fabrication process of multilayered unimorph actuator and the large number of experimental parameters, a universal analytical model is developed in this work to guide the experimental design and fabrication of these actuators. The model is based on a set of non-dimensional equations for electric field-induced curvature, tip displacement and blocked force, taking into account the wide range of design parameters (such as thickness, modulus, number of layers, electric field magnitude, etc.). First, analytical results are validated with experimental studies, then the model is used to predict the displacement, curvature, blocked force and maximum work output of multilayered unimorph actuators for various input parameters such as thickness, modulus, number of layers, electric field and stiffness contrast. An advantage of this combined modeling and experimental approach is the ability to maximize the performance of the designed actuator for the particular application of interest; for example, whether displacement or force is the goal would determine the number of layers and type of substrate used. Finally, origami-inspired smart structures are actuated using the insights from the developed electromechanical model. Although the multilayered actuator concept improves the electromechanical performance of P(VDF-TrFE-CTFE) actuator, with the increase of number of polymer layers the possibility of defect driven premature electrical breakdown also increases due to the requirement of high driving voltage. Polymer-based capacitors have the ability to clear defects with partial electrical breakdown and subsequent removal of a localized electrode section near the defect, which is known as self-clearing. A methodical approach to self-clear P(VDF-TrFE-CTFE) terpolymer to delay premature defect-driven electrical breakdown of the terpolymer actuators at high operating electric fields is proposed in this study. Breakdown results show that electrical breakdown strength is improved up to 18% in comparison to a control sample after self-clearing. Furthermore, the electromechanical performance in terms of blocked force and free displacement of terpolymer-based benders are examined after self-clearing and precleared samples show improved blocked force, free displacement and maximum sustainable electric field compared to control samples. The study demonstrates that controlled self-clearing of EAPs improves the breakdown limit and reliability of the EAP actuators for practical applications without impeding their electromechanical performance. In this study, the limitations of P(VDF-TrFE-CTFE) terpolymer are addressed and studied to achieve origami-inspired self-folding structures. First, processing conditions of terpolymer is studied and 9 hours annealing condition is selected based on the improved electromechanical performance. Electric field driven in-situ XRD and SFG is implemented which gives direct experimental evidence of the electric field induced reversible transition of and phases to phase. The feasibility of P(VDF-TrFE-CTFE) to achieve electric field driven on-demand bending and folding is experimentally demonstrated using various geometric approaches. Then, a universal analytical model for an EAP based on beam bending theorem is developed which can also be implemented to design multilayered actuators driven by other physical fields such as magnetic or thermal. The concept to couple active multilayered actuators with inactive origami-inspired structures is introduced and successfully actuated. Finally, a systematic method is introduced to induce controlled self-clearing of P(VDF-TrFE-CTFE), which improves electric field sustaining capability and reliably of P(VDF-TrFE-CTFE) devices.

Field Responsive Polymers

Field Responsive Polymers
Author: Ishrat M. Khan
Publisher:
Total Pages: 392
Release: 1999
Genre: Medical
ISBN:

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The twenty-two chapters in this volume present state-of-the-art research and discuss some of the potential applications of electroresponsive, photoresponsive, and responsive polymers in chemistry and biology. Its comprehensive nature makes it ideal for polymer scientists, materials scientists, and physicists.

Magnetic Multilayers

Magnetic Multilayers
Author: Lawrence H Bennett
Publisher: World Scientific
Total Pages: 397
Release: 1994-12-16
Genre: Technology & Engineering
ISBN: 9814571067

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This book focuses on an increasingly important area of materials science and technology, namely, the fabrication and properties of artificial materials where slabs of magnetized materials are sandwiched between slabs of nonmagnetized materials. It includes reviews by experts on the theory and descriptions of the various experimental techniques such as those using nuclear or electron spin probes, as well as optical, X-ray or neutron probes. It also reviews potential applications such as the giant magnetoresistance, and one specialized preparation technique, the electrodeposition. The various chapters are tutorial in nature, making the subject accessible to nonspecialists, as well as useful to researchers in the field.

Advanced Mechatronics and MEMS Devices II

Advanced Mechatronics and MEMS Devices II
Author: Dan Zhang
Publisher: Springer
Total Pages: 719
Release: 2016-10-18
Genre: Technology & Engineering
ISBN: 3319321803

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This book introduces the state-of-the-art technologies in mechatronics, robotics, and MEMS devices in order to improve their methodologies. It provides a follow-up to "Advanced Mechatronics and MEMS Devices" (2013) with an exploration of the most up-to-date technologies and their applications, shown through examples that give readers insights and lessons learned from actual projects. Researchers on mechatronics, robotics, and MEMS as well as graduate students in mechanical engineering will find chapters on: Fundamental design and working principles on MEMS accelerometers Innovative mobile technologies Force/tactile sensors development Control schemes for reconfigurable robotic systems Inertial microfluidics Piezoelectric force sensors and dynamic calibration techniques ...And more. Authors explore applications in the areas of agriculture, biomedicine, advanced manufacturing, and space. Micro-assembly for current and future industries is also considered, as well as the design and development of micro and intelligent manufacturing.

Nanotechnology for Oral Drug Delivery

Nanotechnology for Oral Drug Delivery
Author: João Pedro Martins
Publisher: Academic Press
Total Pages: 536
Release: 2020-07-30
Genre: Medical
ISBN: 0128180390

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Nanotechnology for Oral Drug Delivery: From Concept to Applications discusses the current challenges of oral drug delivery, broadly revising the different physicochemical barriers faced by nanotechnolgy-based oral drug delivery systems, and highlighting the challenges of improving intestinal permeability and drug absorption. Oral delivery is the most widely used form of drug administration due to ease of ingestion, cost effectiveness, and versatility, by allowing for the accommodation of different types of drugs, having the highest patient compliance. In this book, a comprehensive overview of the most promising and up-to-date engineered and surface functionalized drug carrier systems, as well as opportunities for the development of novel and robust delivery platforms for oral drug administration are discussed. The relevance of controlling the physicochemical properties of the developed particle formulations, from size and shape to drug release profile are broadly reviewed. Advances in both in vitro and in vivo scenarios are discussed, focusing on the possibilities to study the biological-material interface. The industrial perspective on the production of nanotechnology-based oral drug delivery systems is also covered. Nanotechnology for Oral Drug Delivery: From Concept to Applications is essential reading for researchers, professors, advanced students and industry professionals working in the development, manufacturing and/or commercialization of nanotechnology-based systems for oral drug delivery, targeted drug delivery, controlled drug release, materials science and biomaterials, in vitro and in vivo testing of potential oral drug delivery technologies. Highlights the relevance of oral drug delivery in the clinical setting Covers the most recent advances in the field of nanotechnology for oral drug delivery Provides the scientific community with data that can facilitate and guide their research