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Flexible microwires fabricated from conducting polymers have a wide range of potential applications, including smart textiles that incorporate sensing, actuation, and data processing. The development of garments that integrate these functionalities over wide areas (i.e. the human body) requires the production of long, highly conductive, and mechanically robust fibers or microwires. This thesis describes the development of a microwire slicing instrument capable of producing conducting polymer wires with widths as small as a few micrometers and lengths ranging from tens of millimeters to meters. To ensure high conductivity and robustness, the wires are sliced from thin polypyrrole films electrodeposited onto a glassy carbon crucible. Extensive testing was conducted to determine the optimal cutting parameters for producing long, fine wires with cleanly cut edges. This versatile fabrication process has been used to produce free-standing microwires with cross-sections of 2 [micro]m x 3 [micro]m, 20 [micro]m x 20 [micro]m, and 100 [micro]m x 20 [micro]m with lengths of 15 mm, 460 mm, and 1,200 mm, respectively. An electrochemical dynamic mechanical analyzer was used to measure the static and dynamic tensile properties, the strain-resistance relationship, and the electrochemical actuation performance of the microwires. The measured gage factors ranged from 0.4 to 0.7 and are suitable for strain sensing applications. Strains and forces of up to 2.9% and 2.3 mN were recorded during electrochemical actuation in BMIMPF6 . These monofilament microwires may be spun into yarns or braided into 2- and 3- dimensional structures for use as actuators, sensors, micro antennas, and electrical interconnects in smart fabrics.
A novel method to fabricate uniform, biodegradable microspheres from poly(lactic-co-glycolic acid) (PLGA) 85:15 using an electrospraying process is outlined in this thesis. Initial optimization of PLGA solution parameters discovered that 4wt% PLGA in chloroform yielded microstructures with a smooth, spherical morphology. The addition of benzyltriethylammonium chloride (BTEAC, 2% (w/w) PLGA) increased the conductivity of the solution, and reduced the coefficient of variance (CV) for microsphere diameter from >20% to 14%. Furthermore, modifications of applied potential and spinneret-collector separation distances during electrospraying improved the microsphere diameter to 11% CV. The fabrication parameters were finalized by the addition of silicon wafer substrates bearing Ti/Au (10/100nm) dual layer electrodes with 1.5mm diameter working areas. Resulting microspheres had an average diameter of 3.23±0.23[mu]m and showed a 7% CV. This method was then applied to exploratory research in fabricating conductive biomedical devices through the electrochemical polymerization of polypyrrole (PPy) for 1 minute on PLGA microspheres. Electrical Impedance Spectroscopy (EIS) and Cyclic Voltammetry (CVt) was performed using a bare gold reference electrode to characterize the electrical properties. The fabricated conducting polymer-based electrodes showed promising 10% and 23% impedance decreases at 1 kHz and 100 Hz respectively relative to the bare gold reference. The charge storage capacity of these devices was improved over bare gold electrodes by 20%. Based on these observations, the PLGA microsphere fabrication route presented in this thesis shows promise for the development of conductive biomedical devices.
Providing a vital link between nanotechnology and conductive polymers, this book covers advances in topics of this interdisciplinary area. In each chapter, there is a discussion of current research issues while reviewing the background of the topic. The selection of topics and contributors from around the globe make this text an outstanding resource for researchers involved in the field of nanomaterials or polymer materials design. The book is divided into three sections: From Conductive Polymers to Nanotechnology, Synthesis and Characterization, and Applications.
This thesis aims at providing a better understanding of the micro- and nanofabrication of conducting polymers for biomedical devices and presents novel processes that widen the application range of conducting polymers in this field. The thesis is divided in four chapters, namely "Materials and Methods", "Biocatalytically-produced polypyrrole thin films and microelectrodes on insulating surfaces", "Azide-PEDOT electrodes. Application to DNA sensors" and "Fabrication of polypyrrole single nanowire devices". Chapter 1, entitled "Materials and Methods", describes the materials used in this work and the fabrication and characterization methods required for the development of the thesis. Here, theoretical and experimental details about the techniques employed, are provided. Chapter 2, entitled "Biocatalytically-produced polypyrrole thin films and microelectrodes on insulating surfaces", presents a new on-surface biocatalytical procedure for the fabrication of polypyrrole microelectrodes on insulating surfaces, with resolutions comparable to the ones of conventional photolitography. This is an environmentally respectful microfabrication method that allows the entrapment of biomolecules during the polymer synthesis in a single step. As a proof of concept, biotin was trapped in the polypyrrole matrix and then released in a controlled way through electrical stimulation. It was proven that the polymer keeps its electroactivity after the fabrication and functionalization processes. This biocatalytical-based technique represents a straightforward method for the microfabrication of biological-active conducting polymers, which could be implemented in implantable devices for remotely controlled tissue interactions. Chapter 3, entitled "Azide-PEDOT electrodes. Application to DNA sensors", describes the fabrication and testing of an electrochemical label-free DNA hybridization sensor, based on novel azidomethyl-modified poly(3,4-ethylenedioxythiophene) electrodes (azide-PEDOT electrodes). These azide-PEDOT electrodes were used as platforms for the immobilization of acetylene-DNA probes, complementary to the "Hepatitis C" virus. The acetylene-DNA probes were covalently grafted to the polymer backbone via the robust "Click" reaction, which a part from being a very selective functionalization method, preserves DNA from denaturation during the synthesis of the polymer. DNA hybridization was detected by Differential Pulse Voltammetry (DPV), where the electrochemical change of the polymer behaviour, produced by the recognition event, was directly evaluated. This fabrication procedure is a powerful tool for the preparation of label-free DNA sensors able to selectively recognize a specific DNA sequence, down to the nanomolar range. Finally, Chapter 4, entitled "Fabrication of polypyrrole single nanowire devices", discusses the fabrication of polypyrrole at the nanoscale. Two fabrication techniques were investigated here, namely dip pen nanolithography and electrochemical polymerization on template-assisted surfaces. On one hand, the dip pen nanolithography proved to be a simple deposition technique with good control over size and location of the polypyrrole nanowires. On the other hand, the electrochemical polymerization on template-assisted surfaces provided as well nanoscaled polypyrrole, but added the possibility to chemically manipulate the polymer. This chemical manipulation was translated into polymer devices with different electrical properties. By the use of these techniques, the capability of fabricating single nanowire devices (ready to use in different applications) and arrays of ordered nanowires based on conducting polymers is demonstrated. Additionally, two appendixes can be found at the end of the thesis: Appendix A: "Fabrication of azide-PEDOT microwire-based devices" and Appendix B: "Fabrication of nanopatterns by electron-sensitive silanes". They provide short experimental results obtained during the course of this work, which are first steps for future investigations. A general conclusions section can be found at the end of the thesis, where a summary of the main achievements and contributions of this thesis are listed.
(Cont.) The synthetic scheme was also utilized to produce a monomer that could be electrochemically cross-linked in a controlled fashion. In chapter four, a variety of polythiophene derivatives that incorporated azaferrocenes complexes into the main polymer chain were synthesized. These polymers were then used to ascertain the effect of a n-bound metal on the main chain of a conducting polymer. The oxidation of the metal centers in the polymer produced a significant change in the conductivity of the polymer film. Changing the length and oxidation potential of the polythiophene section of the monomer appeared to alter the charge delocalization of the polymers. In chapter five, a series of polythiophene derivatives containing cyclobutadiene cobalt cyclopentadiene complexes in the main polymer chain were synthesized. The viability of the electropolymerization of the complexes was determined by the relative position of organic section's oxidation potential versus the oxidation of the metal centers. The metal coordinated cyclobutadiene ring of the complex appeared to have a modest charge transport ability.
Electropolymerizing conducting polymers is one of the fastest and most controllable nanofabrication techniques for functional coatings and interfaces. Intrinsically conducting polymers with highly conjugated architectures are unique smart materials that can reversibly switch between an insulating (reduced) state and a conducting (oxidized) upon doping. Depending on its oxidation state, the polymer exhibits distinct changes in optical, electrical and mechanical properties, which are the foundation of various electrochromic, actuator, and electronic applications. Among synthetic methods for conducting polymers, electrochemical synthesis via an oxidative coupling mechanism is preferred because of its simplicity and the high control it offers toward the resulting film thickness and morphology. Considering these advantages, this dissertation focuses on the formation, characterization, and applications of electropolymerized conducting polymer films particularly in developing molecularly imprinted polymer (MIP) sensors and multi-component patterning. Chapter 1 provides a background overview on conducting polymers, molecular imprinting and colloidal sphere or nanosphere lithography, which is the primary patterning technique used in this work. Chapter 2 reports the use of electropolymerized polyterthiophene films as MIP sensors for pyrene, a representative polycyclic aromatic hydrocarbon (PAH) compound and environmental contaminant. Chapter 3 incorporated nanosphere lithography into developing electropolymerized poly(terthiophene-carboxylic acid) arrays as MIP sensors for aspartame, a well-known peptide sweetener that allegedly has harmful health effects. The last three chapters were devoted toward multi-component patterning with inorganic and biological materials. Chapter 4 demonstrates the stepwise fabrication and characterization of binary co-patterns made up of an inverse honeycomb polycarbazole array backfilled with electrodeposited gold. The polycarbazole was subsequently etched thus revealing a periodic array of gold islands. Chapter 5 details the fabrication of a freely standing membrane demonstrating the hierarchical assembly of Cowpea mosaic virus nanoparticles on a nanopatterned polypyrrole array. Chapter 6 demonstrates a different approach in fabricating conducting polymer/virus arrays by decorating the outer protein surface of CPMV with electrochemically cross-linkable pyrrole units and co-electrodepositing the virions with polypyrrole to form nanopatterns. Finally, Chapter 7 presents a general summary of the dissertation and some general insights on the future direction of the research.
This book provides a comprehensive overview on the recent significant advancements of conductive polymers and their composites in terms of conductive mechanism, fabrication strategies, important properties, and various promising applications. The corresponding knowledge was systematically compiled in the logical order and demonstrated as seven chapters. The special structure, influencing factors of the conductivity, the charge carrier transport model, the wettability and classical categories of the conductive polymers are narrated. Both conventional and novel strategies undertaken to fabricate the conductive polymers are introduced, as provided the overall master of the progress. In comparison with the bulk counterpart, nanostructured conductive polymers with different dimensions such as nanospheres, nano-networks, nanotubes and nanowire arrays are produced through distinct methods, thus presenting unique and distinct performance endowed by the nanometer scale. The combination of conductive polymers with other functional materials results in a number of the composites with improved properties by synergistic effect. The superior performance of conductive polymers and their composites greatly facilitates their development toward various important applications in the advanced and sophisticated fields such as biological utilization, energy storage and sensors. Due to their excellent biocompatibility, conductive polymers and their composites stand out to be useful in the biological field including tissue engineering, drug delivery and artificial muscle. To meet the urgent demand of the energy storage, conductive polymers and their composites play an important role in the devices including supercapacitors, solar cells and fuel cells. Finally, development of conductive polymers and their composites in the modern industry is greatly enhanced by their applications in smart sensors such as conductometric sensors, gravimetric sensors, optical sensors, chemical sensors and biosensors. This book has significant value for researchers, graduate students, and engineers carrying out the fundamental research or industrial production of conductive polymers and their composites.
Learn how recent advances are fueling new possibilities in textiles, optics, electronics, and biomedicine! As the field of conjugated, electrically conducting, and electroactive polymers has grown, the Handbook of Conducting Polymers has been there to document and celebrate these changes along the way. Now split into two vo