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。超细颗粒物是指直径小于100纳米的空气中颗粒物。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，例如化石燃料的燃烧，野火烟雾和香烟烟雾。超细颗粒可能对人体造成严重的健康风险。吸入超细颗粒物可引起肺部炎症、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，非常需要能够在感兴趣的点测量超细颗粒尺寸的可穿戴传感器。这样的传感器应该是经济的、紧凑的、低功率的，并且可集成到数字移动的设备和气溶胶递送设备中。在用于测量空气中颗粒的各种技术中，光学颗粒粒度仪对于实现这种传感器平台具有很大的希望。光学粒度仪通过检测颗粒穿过聚焦激光束时散射的光来测量单个空气传播颗粒的大小。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，最小可检测的颗粒尺寸约为300纳米，而小于100纳米的超细颗粒由于太弱的光散射而无法测量。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测量仪的新方案，该结构可以大大提高超细颗粒诱导的光学信号。这项研究旨在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。该研究项目将为光学、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，并通过推广活动鼓励K-12学生参与STEM。该研究项目将调查当空气中的超细颗粒位于强聚焦光的纳米级热点时，纳米光学结构的光学响应。具体而言，它将产生基本的理解，如何使用金属薄膜中的亚波长孔径，以准确地测量流过孔径的超细颗粒的尺寸。本计画包含三个研究目标：1）亚波长孔径之建模、制作与特性分析。2)测量和校准传感器对超细颗粒的响应。3)研究超微粒子通过亚波长孔径的传输。该项目将评估拟议传感器方案的性能，包括最小可检测颗粒尺寸和可检测浓度，并研究亚波长孔径尺寸等关键因素的影响。拟议的研究将导致突破光学粒度仪的传感能力扩展到所需的超细颗粒范围。该研究还将推动等离子体传感器领域的新应用，使其能够感应空气中的颗粒物。该奖项反映了NSF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.