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

Lawrence Technological University, Southfield MI

Investigators

Abstract

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.