Ultra-High Efficiency Microwave Plasma for Extreme Low-Power Applications

冷等离子体是等离子体医药、食品保鲜、水处理、可重构电子、高品质照明、电力推进系统、杀菌和微制造等领域的关键技术。然而，产生稳定的等离子体并不是一项微不足道的任务，因为通常需要庞大、昂贵和耗能的单元。为了促进广泛使用，特别是在低资源环境中，需要高效率、低功率和低成本的等离子体。初步结果表明，通过适当地采用微波谐振结构，确实有可能以非常低的输入功率获得所需密度的等离子体，甚至在毫瓦范围内也是如此。因此，这项工作的首要目标是利用理论、计算和实验方法从根本上研究极低功率和高效的共振微波等离子体。这项研究将促进对低温共振微波等离子体的基本认识，并有望阐明电磁波与包括自持共振微波等离子体在内的等离子体之间的相互作用。这项研究的结果将为下一代低成本和容易获得的等离子体发生器铺平道路。这个项目预计将不仅改变等离子社区的理解，也将改变依赖于传统的笨重和笨重的等离子体源的工程界的理解，这些等离子体源固有地限制了它们的应用。研究成果还将用于本科生和研究生的教育目的，以及向孩子们进行科学示范，以增加他们对等离子体的知识，并潜在地吸引他们进入STEM领域。尽管已经广泛地探索了直流、脉冲和射频等离子体，但对微波等离子体，特别是共振模式下的微波等离子体还没有全面的了解。共振微波等离子体发生在阿尔法放电区域，具有极低的鞘压降，确保被点燃的等离子体稳定，没有电极侵蚀，这是一个重要的寿命问题。这项研究的目的是建立一个极高效率和低功率等离子体的理论框架，对其行为进行计算模拟，并通过实验验证理论和计算模型。这种等离子体可能由低功率和容易获得的电源供电，包括手机、太阳能电池，甚至电池，这使得它安全、低成本、便携，并随时可供许多最终用户使用。为了将这一愿景变为现实，正在追求四个主要目标：(1)发展对谐振微波放电物理的基本了解，(2)评估和利用适当的高质量因数微波谐振结构，(3)设计和实施创新的工程电极，以及(4)研究预电离(例如，直流和射频)和脉冲微波技术。此外，可伸缩谐振器阵列将用于更大的等离子体区域。这项研究的结果预计将有助于实现可直接供许多最终用户使用的超低功率等离子体源。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Cold plasma is a critical technology in many application fields such as plasma medicine, food preservation, water treatment, reconfigurable electronics, high-quality lighting, electric propulsion systems, sterilization, and microfabrication. However, generating stable plasma is not a trivial task as bulky, expensive, and energy-hungry units are often required. To facilitate widespread use, particularly in low resource settings, there is a need for high efficiency, low power, and low-cost plasmas. Preliminary results indicate that it is indeed possible to achieve plasma of required density with very low input power, even in the milliwatts range, by properly employing microwave resonant structures. Hence, the overarching objective of this effort is to fundamentally investigate extremely low-power and highly efficient resonant microwave plasmas using theoretical, computational, and experimental approaches. This research will advance the knowledge on the fundamental understanding of low-temperature resonant microwave plasmas and is expected to elucidate the interactions between electromagnetic waves and plasmas including self-sustained resonant microwave plasmas. The outcomes of this research will pave the road for the next generation of low-cost and readily available plasma generators. This project is expected to change the understanding of not only the plasma community but also the engineering community that rely on conventional bulky and cumbersome plasma sources that inherently limit their applications. The research results will also be utilized for educational purposes, both at the undergraduate and graduate levels, as well as for scientific demonstrations to children to increase their knowledge about plasma and potentially attract them to the STEM field.Although DC, pulse, and RF plasmas have been extensively explored, there is no comprehensive understanding of microwave plasmas, especially in resonant mode. Resonant microwave plasma occurs in the alpha–discharge regime with an extremely low sheath voltage drop, ensuring that the ignited plasma is stable with no electrode erosion as an important lifetime issue. The proposed research is aimed at developing a theoretical framework for extreme high efficiency and low power plasmas, simulating their behavior computationally, and experimentally validating the theory and computational models. Such plasma can potentially be powered by low-power and readily available supplies including cell phones, solar cells, or even batteries, which makes it safe, low cost, portable, and readily available to many end users. To turn this vision into reality, four major objectives are being pursued: (1) development of a fundamental understanding of resonant microwave discharge physics, (2) assessment and utilization of proper high quality-factor microwave resonant structures, (3) design and implementation of innovative engineered electrodes, and (4) investigation of pre-ionization (e.g., DC and RF) and pulsed microwave techniques. In addition, arrays of scalable resonators will be employed for larger plasma regions. The results of this research are expected to facilitate the realization of ultra-low power plasma sources that can become directly available to many end users.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.