ERI: Integrable Nano-Optical Particle Sizer for Measuring Ultrafine Airborne Particles

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。超细颗粒是指空气中直径小于100纳米的颗粒。它们存在于我们呼吸的环境空气中，可以从许多不同的来源产生，如化石燃料的燃烧、野火烟雾和香烟烟雾。超细颗粒物可能对人体造成严重的健康风险。吸入超细颗粒可引起肺部炎症、全身炎症和心血管疾病。为了调查和监测由超细颗粒引起的健康风险，迫切需要能够在感兴趣点测量超细颗粒大小的可穿戴传感器。这种传感器应该经济、紧凑、低功耗，并可集成到数字移动设备和气溶胶输送设备中。在各种测量空气中颗粒的技术中，光学粒度仪对实现这种传感器平台具有很大的希望。光学粒子尺寸仪通过探测粒子穿过聚焦激光束时散射的光来测量单个空气粒子的大小。然而，在现有的基于传统光学和低成本光电元件的光学粒度仪中，最小的可检测粒度约为300纳米，而小于100纳米的超细颗粒由于其光散射太弱而无法测量。针对这些挑战和局限性，本研究项目提出了一种基于纳米光学传感器结构的光学粒度仪的新方案，该方案可以大幅增强超细颗粒诱导的光信号。这项研究的目的是开发一种光学传感器平台，能够测量环境空气和香烟烟雾中存在的超细颗粒，这对改善公众健康有很大影响。拟议的研究活动将为光学、纳米技术和气溶胶传感器领域的研究生和本科生提供培训机会，并将通过外展活动鼓励K-12学生参与STEM。本课题将研究空气中超细粒子位于强聚焦光的纳米级热点上时纳米光学结构的光学响应。具体来说，它将对如何使用金属薄膜中的亚波长孔径来精确测量流过该孔径的超细颗粒的大小产生基本的理解。该项目包括三个研究目标：1)模拟、制造和表征亚波长孔径。2)验证和校准传感器对超细颗粒的响应。3)研究超细粒子通过亚波长孔径的输运。该项目将评估所提出的传感器方案的性能，包括最小可检测粒度和可检测浓度，并研究亚波长孔径大小等关键因素的影响。提出的研究将通过将传感能力扩展到所需的超细颗粒范围，从而导致光学粒度仪的突破。提出的研究也将推动等离子体传感器领域的发展，使其能够在传感空气中的粒子方面有新的应用。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).Ultrafine particles refer to airborne particles with diameters smaller than 100 nanometers. They are present in the ambient air we breathe and can be generated from many different sources such as combustion of fossil fuels, wildfire smoke, and cigarette smoke. Ultrafine particles can potentially pose severe health risks to a human body. Inhalation of ultrafine particles can cause pulmonary inflammation, systemic inflammation, and cardiovascular diseases. In order to investigate and monitor the health risks caused by ultrafine particles, wearable sensors that can measure the sizes of ultrafine particles at points of interest are highly demanded. Such sensors should be economic, compact, low-power, and integrable into digital mobile devices and aerosol delivery devices. Out of various techniques for measuring airborne particles, optical particle sizers hold great promise for realizing such sensor platforms. An optical particle sizer measures the sizes of individual airborne particles by detecting the light scattered from particles when they travel across a focused laser beam. However, in existing optical particle sizers based on conventional optics and low-cost optoelectronic components, the smallest detectable particle size is about 300 nanometers while ultrafine particles, being smaller than 100 nanometers, cannot be measured because of too weak light scattering from them. Responding to these challenges and limitations, this research project proposes a novel scheme of optical particle sizer based on a nano-optical sensor structure which can drastically boost the optical signals induced by ultrafine particles. The proposed research is aimed at developing an optical sensor platform capable of measuring ultrafine particles present in the ambient air and cigarette smoke, which can have great impacts on the improvement of the public health. The proposed research activities will provide training opportunities for graduate and undergraduate students in the field of optics, nanotechnology, and aerosol sensors, and will also encourage STEM participations for K-12 students through an outreach activity.This research project will investigate the optical response of nano-optical structures when airborne ultrafine particles are located on the nanoscale hot spots of strongly focused light. Specifically, it will generate fundamental understanding on how to use subwavelength apertures in metal films to accurately measure the sizes of ultrafine particles flowing through the apertures. The project consists of three research objectives: 1) Model, fabricate, and characterize the subwavelength apertures. 2) Validate and calibrate the sensor's response to ultrafine particles. 3) Investigate the transport of ultrafine particles through subwavelength apertures. The project will evaluate the performance of the proposed sensor scheme including the smallest detectable particle size and detectable concentration, and study the effects of crucial factors such as the size of subwavelength apertures. The proposed research will lead to a breakthrough in optical particle sizers by extending the sensing capability into the desired ultrafine particle range. The proposed research will also advance the field of plasmonic sensors by enabling new applications in sensing airborne particles.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.