32 research outputs found
Closed loop performance of polypyrrole linear contractile actuators
No full textConducting polymer actuators such as polypyrrole can generate stresses over 10 times larger than skeletal muscle and have typical repeatable strains between 1% and 12%, making them potential candidates for lightweight, low-cost, robotic applications. Polypyrrole linear actuators under closed loop control have not been previously reported. Here we report the open and closed loop performance of polypyrrole linear contractile actuators evaluated at pre-loaded stresses of 1 MPa to 3 MPa. A standard PI control scheme driving a potentiostat was implemented in conjunction with positioning feedback from a DC/DC linear variable differential transformer (LVDT). A dynamic positioning range of 3400 is reported, with a positioning resolution of 125 nm (0.001% strain) and a maximum repeatable displacement of 427 microns (3.6% strain). The open loop frequency response of actuator strain shows characteristics of a first-order low pass filter with a log gain versus log frequency slope near -1 for frequencies tested between 0.05 Hz to 2 Hz. The closed loop frequency response of actuator strain when tracking a sinusoidal set-point signal of 0.5% strain shows characteristics of a first order system with one zero, with a corner frequency near 0.08 Hz and an operating bandwidth up to 1 Hz. Step responses at various controller output maximum voltages show a reduction in contractile response times by a factor of four, where higher voltages yield faster contractile responses.United States. Intelligence Advanced Research Projects Activity (Grant NBCHC080001
Conducting Polymer-Based Multifunctional Materials
No full textConducting polymers are employable as low-voltage actuators, sensors, energy storage and delivery components, structural elements, computational circuitry, memory, and electronic components, making them a versatile choice for creating integrated, multifunctional materials and devices. Here we show one such conducting polymer-based, multifunctional system, derived from the versatility of the conducting polymer polypyrrole. Three functions of polypyrrole (actuation, length sensation, and energy storage) have been individually evaluated and cooperatively combined in the synthesis of a multifunctional, polymeric system that actuates, senses strain deformation, and stores energy. The system operates whereby the strain of a polypyrrole actuator is measured by a polypyrrole length sensor, whilst being powered by an array of polypyrrole supercapacitors. Independently, polypyrrole actuators were evaluated at 250 discrete frequencies ranging from 0.01 to 10 Hz using fixed, ±1 V sinusoidal excitation. Polypyrrole length sensors were evaluated using a thin-film dynamic mechanical analyzer for the same range of frequencies with a 2% sinusoidal input strain. Polypyrrole supercapacitors were evaluated using cyclic voltammetry (-1.0 V to +1.0 V; 12.5 to 100 mV/sec) and galvanostatic charge-discharge cycling (0.5 to 2 mA/mg). As an actuator, polypyrrole samples showed measureable actuation strain between 0.001% and 1.6% for the frequency range tested, with amplitude versus frequency decay behavior similar to a first-order low-pass filter. As a length sensor, polypyrrole samples showed linear-elastic behavior up to 3% strain and gauge factors near 4. As a symmetric supercapacitor, polypyrrole had capacitance values higher than 20 kF/kg, energy densities near 20 kJ/kg, and power densities near 2 kW/kg. The evaluation of each component, independently, justified creating a cooperative system composed of these three components operating simultaneously. Polypyrrole supercapacitors provided ample power to excite polypyrrole actuators. Polypyrrole length sensors attached in series to polypyrrole actuators were capable of measuring strain from coupled polypyrrole actuators. Performance metrics and future possibilities regarding conducting polymer-based multifunctional materials are discussed. Topics: Polymers , Multifunctional materialsUnited States. Intelligence Advanced Research Projects Activity (Grant NBCHC080001
Design, fabrication, and characterization of controllable conducting polymer actuation systems
No full textThesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2010.Cataloged from PDF version of thesis.Includes bibliographical references (p. 144-148).The geometric, hierarchal, multifunctional composition of mammalian skeletal muscle and the neuromuscular system consists of actuation elements, length sensors, force sensors, localized energy storage, controlled energy delivery, computational components, and intercommunication pathways. Conducting polymer materials are versatile enough to perform all of the above functions. This work explores the design, characterization, and implementation of three conducting polymer components in building artificial muscle actuation systems: actuators, length sensors, and energy storage. The first systematic strain characterization of polypyrrole actuators at voltages above 1 V for a frequency range of 0.01 Hz to 100 Hz is reported. Material, mechanical, and electrical properties of polypyrrole length sensors are evaluated over the same frequency range. Polypyrrole supercapacitors are evaluated as a function of dopant, electrolyte, geometry, and mass, enabling the determination of their capacitance, charge-discharge lifetime, and self-discharge. Fabrication techniques for combining multiple conducting polymer components (actuators, length sensors, and energy storage elements) by means of electrically insulated, mechanical attachments are developed and demonstrated. An all-polymer, open loop linear contractile actuation system is presented, along with the first conducting polymer powered conducting polymer actuators, and the first tripolymer system. These results build a foundation upon which large, scalable, self-powered, all polymer electro-chemo-mechanical actuation systems can be developed for a future set of conducting polymer artificial muscle systems.by Eli Paster.S.M
Development of a miniature, continuous measurement, stochastic perturbation gas chromatograph
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 150-154).Gas chromatography is one of the most widely used analytical chemistry techniques for separating and analyzing chemical compounds. Chromatographic methods are used to identify constituent species within a compound and determine the purity and relative concentrations of those species. Current gas chromatographs are heavy, bench top instruments that require large capital expenditures, kilowatt power sources, and trained technicians. Additionally, traditional chromatographic measurements are non-continuous. The first part of this thesis explores the application of stochastic system identification techniques applied to chromatography to enable continuous chromatographic measurements, multiplexing of instrument components, and the ability to optimally tune instrumentation parameters and reduce chromatogram noise. The second part of this thesis explores the development of a miniaturized, standalone gas chromatograph. A handheld, low-cost gas chromatograph has been developed over the course of five device generations, through the implementation of localized heating techniques, on-demand gas generation, and the integration of electrical, mechanical, and chemical processes into a compact volume. Characterization of the device shows comparable operating parameters and performance to equivalent bench top instruments at 0.5% total cost and 0.03% total volume. These contributions reduce the barrier-to-entry for performing high quality chemical measurements, and enable more widespread use of chromatography in monitored, closed-loop, remote operation and automated systems.by Eli Paster.Ph. D
Multi-component single-substrate conducting polymer actuation systems and fabrication techniques
No full textConducting polymer materials can be employed as actuation elements, length sensors, force sensors, energy storage devices, and electrical components. Combining the various functionalities of conducting polymers to create singlesubstrate, integrated systems remains a challenge, as chemical and electrical insulation barriers, adhesion techniques, and the possibility of scaling need to be taken into consideration. Here fabrication techniques for combining multiple conducting polymer components by means of electrically insulated, mechanical attachments are developed. Electrochemically synthesized polypyrrole substrates were coated with thin films of polystyrene, Parylene, and polyimide. The isotonic actuation performance of each coated film was evaluated in comparison to non-coated films, with an observed decrease in peak-to-peak maximum strain output near 95% (polystyrene and Parylene), 20% (vacuum, 0.8 Pa), 50% (curing at 110°C) and 20% (localized polyimide deposition). The chemical barrier properties of each manufacturing technique were evaluated by exposing the coated polypyrrole substrates to an oxidative chemical vapor deposition of Poly(3,4-ethylenedioxythiophene) (PEDOT). Vapor-deposited PEDOT made the insulation layers of polystyrene and Parylene conductive at thicknesses up to four microns. Spin-coated films of polyimide, greater than ten microns thick, maintained electrical insulation properties after PEDOT depositions. Conducting polymer film-to-film attachments using each manufacturing technique were attempted, with polyimide working successfully when employed under a specific deposition, drying, and curing protocol, as discussed. Three dimensional conducting polymer actuation systems composed of actuators, length sensors, and energy storage devices were constructed on flexible, single substrates. These results build a foundation upon which scalable, self-powered, polymer actuation systems can be developed.United States. Intelligence Advanced Research Projects Activity (Grant NBCHC080001
Historia fucorum
No full textError in pagination: p. 237 misnumbered 227First 4 plates numbered: IA, IB, IIA, IIBMode of access: Internet.Special Collections copy formerly owned by John Crerar LibrarySpecial Collections copy bound in period mottled calf, gilt spine, and paste paster endpaper
Tortoise versus Hare: Pop-up Coloring Book
No full textThis 8½ x 11 book is in a series that also includes, up until now, Red Riding Hood and Three Pigs. Sturdy cardstock allows for cutting out sections and gluing them in clearly marked places for the effects of a pop-up book. The version of TH here is strange to me. The tortoise is clumsy. The hare slips on apples and sends them flying. One of the apples lands on the tortoise and shoots him out of his shell. The young cutter-and-paster can decide who wins the race. And the young reader can color in these black-and-white designs.Çlirim Muça; English translation by Besjana Gorreja and Myfanwy Woods-Jac
The role of business in the development of the welfare state and labor markets in Germany : containing social reforms
No full textThis book assesses the role of employers in the development of welfare state and labour market institutions. Building on an in-depth analysis of Germany, a market economy known to often provide economic benefits to firms, this book explores one of the most contested issues in the comparative and historical literature on the welfare state. In a departure from existing employer-centered explanations, the author applies new empirical data to contend that the variation in acceptance of social reform depends more on changes in the types of political challenges faced by employers, than on changes in the type of institutions considered economically beneficial. Covering major reforms spanning more than a century of institutional development in unemployment insurance, accident insurance, pensions, collective bargaining, and codetermination, this book argues that employers support social policy as a means to contain political outcomes that would have been worse, including labour unrest and more radical reform plans. Using new and controversial findings on the role of employers in welfare state development, this book considers the conditions for a peaceful coexistence of a generous welfare state and the business world.1. Introduction
2. Theory: Economic Interests and Political Constraints
3. The Origins of Employers’ Associations: Coordinating against Organized Labor
4. Bismarck’s Social Reforms: Employers and Social Pacification
5. World War I and Its Consequences: Class Collaboration in Exceptional Times
6. Business and the Origins of Unemployment Insurance: Protecting Work Incentives
7. Business after World War II: The "Social Market Economy"
8. Post-War Social Policy Reforms: Containing Welfare Expansion
9. Codetermination: Employers against Economic Democracy
10. Employers and the German Model Today
11. Conclusions: How Employers Shaped the Welfare StatePublished version of EUI PhD thesis, 200
I-voting and Public Policy Approach: Cross-case comparative analysis of i-voting policy in Norway, Estonia and Switzerland
No full textThis report analyses what factors determine the termination of the i-voting policy in Norway by employing a cross-case analysis of the i-voting policy in Norway, Estonia and Switzerland using a method of difference. It employs the public policy approach, basing the theoretical framework on Lowi’s (1972) thesis “Policies determine politics” and conceptualises the i-voting policy type, as a governance policy following Tolbert’s (2002) contribution, adding to Lowi’s (1972) policy typology. The study finds that political will and its relation to the intention of the policy was able to show effects on different stages of the policy cycle, like the adoption of the policy to the legal framework and its specifications, policy implementation in terms of different choices in target groups and approaches, and lastly, policy evaluation/ termination in terms of what metrics were the policy evaluated upon. The author also suggests the relevance of further research on stakeholder influence in i-voting policymaking could utilise this governance policy concept broader, showing its comprehensive applicability. Moreover, a better understanding of what exact implications the change in government had in Norway’s case could tell us more about the political costs and associated risks that (at the time) the newly elected government did not intend to take and why
The improvement of propionic acid safety and use during the preservation of stored grains
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