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Instability-Induced Rapid Shape Change in Heat- and Photo-Responsive Materials
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| 자료유형 | 학위논문 |
|---|---|
| 서명/저자사항 | Instability-Induced Rapid Shape Change in Heat- and Photo-Responsive Materials. |
| 개인저자 | Babaei, Mahnoush. |
| 단체저자명 | Carnegie Mellon University. Civil and Environmental Engineering. |
| 발행사항 | [S.l.]: Carnegie Mellon University., 2019. |
| 발행사항 | Ann Arbor: ProQuest Dissertations & Theses, 2019. |
| 형태사항 | 124 p. |
| 기본자료 저록 | Dissertations Abstracts International 80-12B. Dissertation Abstract International |
| ISBN | 9781392279670 |
| 학위논문주기 | Thesis (Ph.D.)--Carnegie Mellon University, 2019. |
| 일반주기 |
Source: Dissertations Abstracts International, Volume: 80-12, Section: B.
Publisher info.: Dissertation/Thesis. Advisor: Dayal, Kaushik |
| 이용제한사항 | This item must not be added to any third party search indexes.This item must not be sold to any third party vendors. |
| 요약 | The ability to use non-mechanical stimuli such as light and heat to generate mechanical work directly can enable generating smart machines that are free of onboard power sources and do not require complex micro-fabricated components and mechanisms. Amongst many soft materials, Liquid Crystal Polymers have attracted a lot of interest because of their several unique characteristics such as programmable anisotropy, reversible shape change, and soft elasticity. This class of fascinating materials has the ability to change shape in response to various stimuli such as heat, light, and solvent.Light offers multiple control knobs for photomechanical regulation, including spatiotemporal modulation of intensity, direction, polarization, and chirality. Currently, however, the attenuation length of the photons (typically, few 關m) places a bound on the thickness within which mechanical work can be produced. The generation of photomechanical strain is characteristically graded, often involving bending, with limited scalability of the work-content in actuators, which cannot be more than a few tens of 關m in thickness. Here, we first investigate the effect of light attenuation on the dynamics of various director distributions through the thickness. We show that the interplay of gradient light absorption and gradient stiffness through the thickness leads to various actuation modes such as multi-step actuation.Next, using instabilities, we use this otherwise weak bending-mode actuation in photomechanically active liquid crystalline polymers (elastomeric and glassy) to drive non- linear transformations of boundary-confined curved shells to produce torque densities greater than 102 Nm/kg and flexural actuation rates greater than 102 radians/s. These metrics place them in a property space that competes favorably with conventional rotary systems. We investigate the effect of initial structural features on the performance of the proposed configuration for the actuators. The geometrical features of the induced instabilities are also studied.Finally, the idea of using instability-induced shape change is extended to the heat- actuated bilayer systems to magnify their work content. The effect of different structural aspects is studied with the goal of designing optimized systems.The ability to harness magnified actuation in monolithic, 關m to mm-scale form factors to drive functional devices exclusively using heat or light, can enable thermally and optically powered and re-configurable machines in applications ranging from microrobotics, biomedicine and manipulation in environments hostile to electromechanical systems. |
| 일반주제명 | Engineering. Mechanical engineering. Materials science. |
| 언어 | 영어 |
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