Nanogap electrode sensor for single ultrafine particulate matter by electromigration

Abstract

Ultrafine particulate matter is a mixture of liquid and solid particles with 100nm or less diameter. The insignificant size and mass, the high toxicity, and surface area per mass of ultrafine particulate matter have been thoroughly investigated and are more dangerous than larger particulate matter. The smaller aerodynamic diameter allows ultrafine particulate matter to penetrate deeper into alveoli and blood, leading to high blood pressure, ischemic and stroke. Therefore, the characterization and measurement of ultrafine particulate matter is key to understanding and reducing the risk of particles' exposure. Characterization of ultrafine particulate matter by transmission electron microscopy is profoundly used in research for understanding the model of ultrafine particulate matter, there is still lacking measurement methods and standards due to the limitation of commercial optical sense and Mie's theory. To fill the research gap, this work proposed to construct a new electrical sensing method by using nanogap electrode and metal-particle-metal configuration to measure the electrical signal of single ultrafine particulate matter. Electromigration and E-beam lithography is used to fabricate nanogap electrode. Keithley 2400 and the self-made programme is used for electrical measurement. The result of electrical signal was being compared with commercial optical sensor based on weather condition. Three implications can be derived from the electrical signal analysis: the number of counting particulate matter, the amplitude of current spike, and the morphology of current spike. The result is matched the relative humidity and weather information. This work starts a new chapter in detecting single ultrafine particulate matter by electrical measurement.