Using Feedback Mechanism to Control Phase Transition of Vanadium Dioxide to Exploit its Full Operating Range

二氧化钒(VO2)是一种智能多功能材料，它具有金属相和绝缘体相之间的特征转变，在电学、光学和力学性能上都会发生突变和实质性的变化(几个数量级)。这在传感器、执行器和高速开关等各种应用中引起了相当大的关注。然而，VO2的金属-绝缘体相变具有尖锐而狭窄的温度窗口，其数字开关的突发性限制了其在需要具有连续可调特性的模拟操作模式的应用中的进一步发展。该项目将尝试利用反馈机制，以实现VO2的全工作范围的使用，从而显著增强其广泛的适用性，就像几十年前对运算放大器所做的那样。这项研究将利用过渡阶段VO2固有的复杂动态行为，利用反馈控制理论的进步来实现重构能力。潜在的影响是重大的，因为这项研究的结果将使更强大和能力更强的设备在几个领域的模拟应用。例如，具有可重新配置的相变光学特性的VO2将促进太赫兹光学器件的发展，这些器件在医学诊断和生物学、宽带通信、安全、防御和无损检测的成像和光谱应用中具有应用。研究成果将被纳入本科和研究生教育，并将通过教育和推广活动向公众传播。该项目将通过引入控制理论的基本反馈机制来研究赋予VO2可重新配置的相变的可行性，以实现其全部运行范围。该项目将在不确定性和滞后系统的建模和控制方面发展新的知识，以同时实现精确的连续VO2相变和高调制深度。新的知识将构成一个基本的贡献，将有益于其他几个应用，其中需要控制动态非线性，如不确定条件下的迟滞。利用德克萨斯理工大学S纳米技术中心的现有设施和资源，将建立可重新配置的VO2硬件在环和实验测试台，以验证方法。这项研究也很好地融合了理论、实验和计算工作。该项目有新的外展活动，例如将研究元素注入到针对K-12学生和代表性不足群体的新的动手实验中。

Vanadium dioxide (VO2) is a smart multifunctional material which has characteristic transition between its metal and insulator phases, which have abrupt and substantial changes (several orders of magnitude) in electrical, optical, and mechanical properties. This has led to considerable attention in a variety of applications including sensors, actuators, and high-speed switches. However, the digital ON/OFF abruptness of the metal-insulator phase transition of VO2 with a sharp and narrow temperature window limits its further development for applications that demand analog operation mode with continuously tunable properties. This project will try to exploit the mechanisms of feedback to enable the use of full operational range of VO2 and thereby significantly enhancing their wide-spread applicability like it did for operational amplifiers several decades ago. The research will leverage inherent complex dynamic behavior of VO2 in transition phase to achieve reconfiguration capability using advances in feedback control theory. The potential impact is significant as the outcomes of this research will enable more powerful and capable devices for analog applications in several fields. For example, VO2 with reconfigurable phase transition optical property will facilitate advances in terahertz optical devices with applications in imaging and spectroscopy for medical diagnostics and biology, broadband communications, security, defense, and nondestructive testing. The research results will be incorporated into both undergraduate and graduate education and will be disseminated to public through educational and outreach activities.The project will investigate the feasibility of empowering VO2 with reconfigurable phase transition via introducing the fundamental feedback mechanisms in control theory to achieve its full operational range. The project will develop new knowledge on modeling and control of systems with uncertainties and hysteresis to achieve both precise continuous VO2 phase transition and high modulation depth simultaneously. The new knowledge will constitute a fundamental contribution that will benefit several other applications where control of dynamic nonlinearities such as hysteresis under uncertainties is required. Both reconfigurable VO2 hardware-in-the-loop and experimental test beds will be built to validate the methodologies by leveraging the available facilities and resources at Texas Tech University?s Nano Tech Center. The research also has a nice blend of theoretical, experimental, and computational work. The project has novel outreach activities such as infusion of research elements into novel hands-on experiments for K-12 students and underrepresented groups.