Tunable material properties through feedback control of conducting polymers

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 159-168).Mammalian skeletal muscle is an amazing actuation technology that can controllably modify its force and position outputs as well as its material properties such as stiffness. Unlike muscle, current engineering materials are limited by their intrinsic properties, dictated at the molecular level.This work is focused on developing an integrated device, called a programmable material, which mirrors the capabilities of natural co-fabricated controlled actuation systems such as muscle. While such a device may have the external appearance of a homogeneous material, it can possess unique properties not existing in any currently manufactured material. When actuation, sensing, and control capabilities are integrated within a closed-loop system, the mechanical properties of the system such as stiffness, viscosity, and inertia will arise from the dynamics of the feedback loop rather than from any inherent mechanical properties of the materials from which the device was fabricated. Moreover, these properties may be 'tuned' by altering the feedback parameters embedded in the material system. With this approach properties such as negative stiffness may be generated which do not exist in bulk materials.The most promising of the existing artificial muscle technologies is actuation with conducting polymer. Additionally, conducting polymer has been used to fabricate the position sensor and control electronics. Creating these components from a single type of material has made it possible to co-fabricate the system into an integrated device. This is the first research to attempt to create a co-fabricated, fully integrated conducting polymer feedback device. This work establishes the feasibility of building the device and answers many of the questions of fabrication and design.by Nathan Scott Wiedenman.Ph.D

Mission oriented R and D and the advancement of technology: The impact of NASA contributions, volume 2

NASA contributions to the advancement of major developments in twelve selected fields of technology are presented. The twelve fields of technology discussed are: (1) cryogenics, (2) electrochemical energy conversion and storage, (3) high-temperature ceramics, (4) high-temperature metals (5) integrated circuits, (6) internal gas dynamics (7) materials machining and forming, (8) materials joining, (9) microwave systems, (10) nondestructive testing, (11) simulation, and (12) telemetry. These field were selected on the basis of both NASA and nonaerospace interest and activity

An ultra-high throughput mutational spectrometer for human genetic diagnostics

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.Includes bibliographical references (p. 221-243).Discovering the genetic causes of common diseases may require scanning for mutations in all of the genes in a million people, a significant undertaking. Such discoveries would revolutionize biotechnology, potentially enabling simple genetic tests for risk and targeted preventative or therapeutic strategies. An increase in throughput of genetic analysis instrumentation by several orders of magnitude is essential to undertake such an ambitious task. In this thesis, progress will be presented towards the creation of such a "mutational spectrometer" instrument containing up to 10,000 capillary channels and enabled with subsystems for loading, separating, and detecting fluorescently-labeled DNA. Challenges include DNA manipulation, optical signal detection, macro/micro design integration, precision alignment and assembly, and thermal control. To manipulate DNA, we have utilized a bioMEMS design platform for interfacing to an array of separation channels that enables electrokinetic biomolecule loading, detection, and fraction collection in independent wells.(cont.) Signal detection is accomplished by a sensitive (107 molecule limit-of-detection), scalable (to 10,000 independent channels), end-of-column fluorescence detection technology that accommodates tightly packed capillary arrays as required for ultra-high throughput electrophoretic separation. Capillary array assembly and constraint technologies have been developed for 2-D arrays containing as many as 10,000 replaceable capillaries. Thermal control requirements of 0.3 °C over the entire 10,000 channel array are met with a cross-flow water heat exchanger. Additional subsystems for forcing a viscous polymer matrix into the capillaries, and interfacing the capillary array to a fluid reservoir for electrophoresis have also been developed, as required. This work lays the foundation for the realization of a mutational spectrometer instrument that will enable population-wide pangenomic analyses to uncover the genetic causes of common diseases.by Craig Richard Forest.Ph.D

OPTICAL-BASED TACTILE SENSORS FOR MINIMALLY INVASIVE SURGERIES: DESIGN, MODELING, FABRICATION AND VALIDATION

Loss of tactile perception is the most challenging limitation of state-of-the-art technology for minimally invasive surgery. In conventional open surgery, surgeons rely on their tactile sensation to perceive the tissue type, anatomical landmarks, and instrument-tissue interaction in the patient’s body. To compensate for the loss of tactile feedback in minimally invasive surgery, researchers have proposed various tactile sensors based on electrical and optical sensing principles. Optical-based sensors have shown the most compatibility with the functional and physical requirements of minimally invasive surgery applications. However, the proposed tactile sensors in the literature are typically bulky, expensive, cumbersome to integrate with surgical instruments and show nonlinearity in interaction with biological tissues. In this doctoral study, different optical tactile sensing principles were proposed, modeled, validated and various tactile sensors were fabricated, and experimentally studied to address the limitations of the state-of-the-art. The present thesis first provides a critical review of the proposed tactile sensors in the literature with a comparison of their advantages and limitations for surgical applications. Afterward, it compiles the results of the design, modeling, and validation of a hybrid optical-piezoresistive sensor, a distributed Bragg reflecting sensor, and two sensors based on the variable bending radius light intensity modulation principle. The performance of each sensor was verified experimentally for the required criteria of accuracy, resolution, range, repeatability, and hysteresis. Also, a novel image-based intensity estimation technique was proposed and its applicability for being used in surgical applications was verified experimentally. In the end, concluding remarks and recommendations for future studies are provided

NASA Tech Briefs, Spring 1985

Topic include: NASA TU Services; New Product Ideas; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Life Sciences; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences

Proceedings of the 40th Aerospace Mechanisms Symposium

The Aerospace Mechanisms Symposium (AMS) provides a unique forum for those active in the design, production and use of aerospace mechanisms. A major focus is the reporting of problems and solutions associated with the development and flight certification of new mechanisms. Organized by the Mechanisms Education Association, responsibility for hosting the AMS is shared by the National Aeronautics and Space Administration and Lockheed Martin Space Systems Company (LMSSC). Now in its 40th symposium, the AMS continues to be well attended, attracting participants from both the U.S. and abroad. The 40th AMS, hosted by the Kennedy Space Center (KSC) in Cocoa Beach, Florida, was held May 12, 13 and 14, 2010. During these three days, 38 papers were presented. Topics included gimbals and positioning mechanisms, CubeSats, actuators, Mars rovers, and Space Station mechanisms. Hardware displays during the supplier exhibit gave attendees an opportunity to meet with developers of current and future mechanism components. The use of trade names of manufacturers in this publication does not constitute an official endorsement of such products or manufacturers, either expressed or implied, by the National Aeronautics and Space Administratio