Thesis (M.S.)--Mechanical Engineering, Georgia Institute of Technology, 2004. / Berthelot, Committee Chair; Lynch, Committee Member; Jacobs, Committee Member. Includes bibliographical references (leaves 111-113).

A co-polymer made from Polyvinyl Alcohol and Polyacrylic Acid (PVA-PAA) has been synthesized to form new robotic actuation systems which use the contractile and variable compliance properties of this material. The stimulation of these fibres is studied (particularly chemical activation using acetone and water), as are the factors which influence the response, especially those relating to its performance as an artificial muscle. Mathematical models and simulations of the dynamics of the polymeric strips have been developed, permitting a thorough analysis of the performance determining parameters. Using these models a control strategy has been designed and implemented, with experimental results being obtained for a gripper powered by a flexor/extensor pair formed using these polymeric actuators. An investigation of a second property of the polymer, its variable compliance is alsoincluded. Use of this feature has lead to the design, construction and testing of a multi degree-of-freedom dextrous hand, which despite having only a single actuator, can exercise independent control over each joint.

Dynamic materials which can sense changes in their surroundings and subsequently respond or adapt by autonomously altering their functionality, surface chemistry, transparency, color, wetting behavior, adhesiveness, shape, etc. are primed to be integral components of future "smart" technologies. However, such systems can be quite complex and often require intricate coordination between both chemical and mechanical inputs/outputs as well as the combination of multiple materials working cooperatively to achieve the proper functionality. It is critical to not only understand the fundamental behaviors of existing dynamic chemo-mechanical systems, but also to apply that knowledge and explore new avenues for design of novel materials platforms which could provide a basis for future adaptive technologies. Part 1 explores the use of environmentally-sensitive hydrogels, either alone or within arrays of high-aspect-ratio nano/microstructures, as chemo-mechanical actuators. Chapters 1 through 7 describe a bio-inspired approach to the design of hybrid actuating surfaces in which the volume-changing hydrogel acts as the “muscle” that reversibly actuates the microstructured "bone". In particular, the different actuation mechanisms arising from variations in how the hydrogel is integrated into the structure array, how chemical signals can be used to manipulate actuation parameters, and finally how such a system may be used for applications ranging from adaptive optics to manipulation of chemical reactions are described. Chapter 8 discusses the use of responsive hydrogel scaffolds as a means to mechanically compress cells and direct differentiation. Part II explores dynamic microsystems involving the integration of catalytic sites within intricately structured 3D microenvironments. Specifically, we explore a generalizable and straightforward route to fabricate microscale patterns of nanocrystalline platinum and palladium using multiphoton lithography. The catalytic, electrical, and electrochemical properties are characterized, and we demonstrate high resolution integration of catalysts within 3D-defined microenvironments to generate directed particle and fluid transport. / Chemistry and Chemical Biology

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Current research in experimental and computational fluid dynamics is focused in the area of flow control. Flow control devices are usually classified as either passive or active. Plasma actuators are active flow control devices that require input from an external power source. Current efforts have modeled the effects of plasma actuators as a body force near the electrode. The research presented herein focuses on modeling the fluid-plasma interaction seen in dielectric barrier discharge plasma actuators as a body force vector in the region above the embedded electrode using computational fluid dynamics (CFD). This body force is modeled as the product of the gradient of the potential due to the electric field and the net charge density. In a passive flow control study, two-dimensional simulations using CFD are done with a smooth and bumpy Eppler 398 airfoil with laminar, transition, and turbulent models in an effort to improve the understanding of the flow over bumpy airfoils and to quantify the advantages or disadvantages of the bumps.