Electropolymerization

In recent years, great focus has been placed upon polymer thin films. These polymer thin films are important in many technological applications, ranging from coatings and adhesives to organic electronic devices, including sensors and detectors. Electrochemical polymerization is preferable, especially if the polymeric product is intended for use as polymer thin films, because electrogeneration allows fine control over the film thickness, an important parameter for fabrication of devices. Moreover, it was demonstrated that it is possible to modify the material properties by parameter control of the electrodeposition process. Electrochemistry is an excellent tool, not only for synthesis, but also for characterization and application of various types of materials. This book provides a timely overview of a current state of knowledge regarding the use of electropolymerization for new materials preparation, including conducting polymers and various possibilities of applications

Tindiprinditud pehmed täiturid

Väitekirja elektrooniline versioon ei sisalda publikatsiooneTuleviku biomeditsiini- ja robootikarakenduste täiturite jaoks on vaja usaldusväärseid, korratavaid ja skaleeritavaid valmistamismeetodeid. Johannes Gutenbergi näitel võib printimine ka tehislihaste tootmist revolutsioneerida: printimine võimaldab valmistada ühtlase paksuse ja keeruka mustriga täitureid. Selle doktoritöö raames arendati välja prinditud kolmekihilised kahest elektroodist ja neid eraldavast membraanist koosnevad juhtivpolümeeridel põhinevad täiturid. Tänu analoogsele käitumisele looduslike lihastega kutsutakse neid kuju muutvaid materjale ka tehislihasteks ning just selle funktsionaalse sarnasuse põhjal on tõenäolisteks rakendusvaldkondadeks robootika ja meditsiinitehnoloogia. Prinditud mikrotäiturite elektrilisi, mehaanilisi ja täituromadusi saab muuta kolme peamise strateegia abil. Esiteks modifitseeriti selles doktoritöös kommertsiaalse juhtivpolümeertindi koostist, lisades sinna süsinikaerogeeli. Saadud juhtivpolümeer-süsinik-komposiidil põhineval täituril näitas võrreldes ainult juhtivpolümeertäituriga suuremat jõudu. Teiseks varieeriti täituromaduste täppisreguleerimiseks elektroodi paksust, mis oli vähemalt 20 kihi ulatuses lineaarses sõltuvuses kihtide arvust. Paksuse kasvades suurenesid ka täituri jõud, liigutusulatus, pinnajuhtivus ja mahtuvus. Kolmandaks häälestati täituri sooritusvõimet sobivate alus- ehk membraanimaterjalide valikuga. Nitriilbutadieenkautšukile prinditud õhukesel täituril oli lineaarses liigutusrežiimis suurusjärgu võrra suurem liigutusulatus võrreldes tööstusliku polüvinülideendifluoriidmembraaniga täituriga. Selles töös näidati, et piisksadestusprintimise teel on võimalik valmistada pehmeid elektromehaanilisi süsteeme, hoolimata meetodi mõningatest piirangutest. Sobivalt valitud tindimaterjalid ja häälestatud printimisprotsess võimaldavad juba lähitulevikus valmistada pehmeid ja integreeritud elektromehaanilisi süsteeme täielikult printimise teel.Future soft micro actuator applications for biomedical and soft robotic applications need reliable, repeatable, cost-effective and scalable production methods. As an example of Johannes Gutenberg, printing could also revolutionize the production of artificial muscles – printing allows fabrication of homogeneous actuators with intricate patterns. In this thesis technology for fabricating actuators composed of two conducting polymer-based electrodes and a membrane separating them was developed. The actuators change their shape in response to electrical stimuli. Due to this functional similarity to natural muscles, applications in the fields of medicine and robotics are possible. The properties of printed micro actuators are tunable using various strategies. First, the composition of the conducting polymer ink was modified by adding carbon aerogel to the mix. The resulting composite showed superior force compared to pure conducting-polymer actuators. Second, the electrode thickness was controlled to fine-tune the properties. Increasing the thickness also increased the force, strain and capacitance of the actuator and conductivity of the electrodes. Third, the actuator performance was tailored by the selection of various membrane materials. Printing on spin-coated membranes from nitrile butadiene rubber resulted in extremely thin trilayer actuators that had an order of magnitude higher linear strain compared to commercial polyvinylidene based actuators. This work has showed that despite the known limitations of drop-on-demand printing, it is possible to prepare soft electromechanical systems using this technology. With the selection of compatible materials, and by using various strategies to tune the functional properties of the composite towards more preferred outcome it will be possible in the nearest future to realize applications with fully printed and integrated soft electromechanically active component

Artificial muscle morphology : structure/property relationships in polypyrrole actuators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2007.Includes bibliographical references (leaves 183-204).We seek to improve polypyrrole and other conducting polymer actuators by discovering and exploiting the connection between nanoscale transport events and macroscale active strain. To this end we have used diffraction and electron microscopy to investigate the microstructure of polypyrrole. and propose a new description consisting of disordered polypyrrole chains held together by small crystalline bundles, around which solvent and counterions are randomly distributed. We utilize different modes of deformation to impart orientational texture to polypyrrole films, and show that by controlling polymer chain conformation and packing at a sub-micron level a conducting polymer actuator can be engineered that shows a significantly larger macroscopic electroactive response. We also alter the synthesis and doping conditions to produce films with widely varying surface morphologies, allowing us to control the rate of electroactive response. Our detailed understanding of polypyrrole morphology at different lengthscales provides valuable insight to the mechanisms of polypyrrole actuation, and has helped us process polypyrrole more intelligently for improved electroactive devices.by Rachel Zimet Pytel.Ph.D

Diffusion-limited characteristics of mechanically induced currents in polypyrrole/Au-membrane composites

A mechanically induced current (MIC) in a polypyrrole/Au-coated membrane (PPy/Au-membrane) composite with various surface morphologies was investigated, and the electrolyte conditions were determined in an electrochemical cell. A MIC was induced on porous PPy/Au-membranes with a thin layer of PPy. Conversely, relatively small MICs were observed in non-highly porous films such as freestanding films and PPy/Au-membranes with thick PPy deposits. A MIC smaller by one order of magnitude was also observed in a Au-membrane without PPy. These results indicated that the MICs was due to a charging phenomenon in both the redox and the double layer capacitances. The MIC also varied with supporting electrolyte and their concentration. The MIC was strongly reduced in solutions with diluted electrolytes and with bulky cationic electrolytes, indicating that the number and the penetration speed of mobile ions limited the magnitude of the MIC. These characteristics indicated that the MIC was essentially a diffusion limited current. A two-electrode MIC cell was also configured to investigate a power generation film in a normal saline solution, which can possibly be utilized for biomedical applications

Doctor of Philosophy

dissertationConducting polymer actuators have shown numerous improvements in mechanical performance over the last couple of decades, but can be better utilized in applications with the ability to adjust to unknown operating conditions, or improved during their lifetime. This work employs the process of sequential growth to initially fabricate polypyrrole-metal coil composite actuators, and then again for further actuator growth during its lifetime of operation. The novel synthesis process was first shown through the use of a custom testing apparatus that could support the sequential growth process by allowing different actuation and synthesis solutions to be controlled in the test cell, as well as facilitate mechanical performance testing. Open-loop testing demonstrated the actuator system performance for multiple growth stages over multiple input frequencies, and was then compared to the parameters identified to fit a simplified model during operation. The simplified model was shown to differentiate from the experimental data, but provided useful optimal growth prediction values with a performance cost evaluation algorithm. The model could predict the optimal growth determined by the experimental data to within one growth stage. Performance was improved by using a proportional-derivative feedback controller where the gains were calculated by the desired response at each growth stage for each sample. The cost performance was performed again with the closed-loop data, but did an inferior job of predicting the optimal amount of growth for each sample compared to the open-loop data. The simplified model accurately tracked the behavior changes through multiple stages of growth. The main contributions of this work include a novel testing apparatus and synthesis method for multiple growth steps, the implementation of a simplified model for tracking and optimal growth stage prediction, and the application of a model-based proportional-derivative feedback controller

Planate conducting polymer actuator based on polypyrrole and its application

In this study, we propose a planate actuator which can transform only its central part locally. We have developed a planate conducting polymer actuator based on polypyrrole (PPy) and two types of acids, such as p-phenol sulfonic acid and dodecylbenzene sulfonic acid, by electrodeposition. Its structure was patterned bimorph structure with anion-driven, cation-driven and bimorph layers. The planate conducting polymer actuator could deform only its central part locally. Moreover, we introduce a micro-pump that operates by planate conducting polymer actuator as the drive source. The water level in the flow channel of micro-pump shows the reciprocating motion measuring ±2 mm in accordance with the oscillation of the bimorph conducting polymer actuator which was approximately 28 μl/min. The oscillating volume can be controlled by the application of electrochemical potential and its scan rate applied to the actuator