Cantilever-enhanced photoacoustic measurement of light-absorbing aerosols

TL;DR

This paper introduces a highly sensitive photoacoustic measurement technique for light-absorbing aerosols using a cantilever microphone, achieving significantly lower noise levels and enabling detection in ultra-clean environments.

Contribution

The study presents a novel cantilever-based photoacoustic detection method that surpasses traditional diaphragm microphones in sensitivity, eliminating the need for resonant acoustic cells.

Findings

Achieved a noise level of 0.013 Mm$^{-1}$ with 20 s sampling.

Demonstrated detection of black carbon and nigrosin particles.

Enhanced sensitivity by up to two orders of magnitude.

Abstract

Photoacoustic detection is a sensitive method for measurement of light-absorbing particles directly in the aerosol phase. In this article, we demonstrate a new sensitive technique for photoacoustic aerosol absorption measurements using a cantilever microphone for the detection of the photoacoustic signal. Compared to conventional diaphragm microphones, a cantilever offers increased sensitivity by up to two orders of magnitude. Here we reached a noise level of 0.013 Mm$^{-1}$ (one standard deviation) with a sampling time of 20 s, using a simple single-pass design without a need for a resonant acoustic cell. We demonstrate the method in measurements of size-selected nigrosin particles and ambient black carbon. Due to the exceptional sensitivity, the technique shows great potential for applications where low detection limits are required, for example size-selected absorption measurements and black carbon detection in ultra clean environments.