A fiber-tip photoacoustic sensor for in situ trace gas detection

Abstract

Most trace gas detection methods developed so far largely rely on active sampling procedures, which are known to introduce different kinds of artifacts. Here, we demonstrate sampling-free in situ trace gas detection in millimeter scale volumes with fiber coupled cantilever enhanced photoacoustic spectroscopy. Our 2.4 mm diameter fiber-tip sensor is free from the wavelength modulation induced background signal (a phenomenon that is often overlooked in photoacoustic spectroscopy) and reaches a normalized noise equivalent absorption coefficient of 1.3 × 10−9 W cm−1 Hz−1/2 for acetylene detection. To validate its in situ gas detection capability, we inserted the sensor into a mini fermenter for headspace monitoring of CO2 production during yeast fermentation. Our results show that the sensor can easily follow the different stages of the CO2 production of the fermentation process in great detail.

Fully Coupled Model for Frequency Response Simulation of Miniaturized Cantilever-Based Photoacoustic Gas Sensors

“…The model was further applied to investigate how different sensor parameters were going to influence the sensor performance. According to the parametric sweep results, it seems that the signal to noise ratio of the sensor reported in [12] could be further improved by reducing the gap size, considering environmental acoustic noise as the dominant noise source [11]. Moreover, it seems that matching the acoustic and mechanical resonances of the PA cell and the pressure transducer could be an effective signal enhancement method that is worth further investigation.…”

“…Recently, we introduced a series of cantilever-based miniaturized PA sensors to the field in which customized micro-cantilevers were used as the pressure transducer and glass tubes with an inner diameter as small as 0.6 mm was used as gas cells [10,11,12]. To guide the development of such gas sensors towards further optimization and miniaturization, a fully coupled sensor model based on Comsol Multiphysics is proposed in this paper.…”

Direct Absorption and Photoacoustic Spectroscopy for Gas Sensing and Analysis: A Critical Review

“…Cantilevers have been placed at different locations in the system. These include 1) the cantilever can be placed in the PA cell at one end of the cylinder while the excitation light comes from the other end as depicted in Figure 8c, [149] 2) both the excitation and readout fibers are on the same side, [177] and 3) the cantilever can be placed at the side of the cell. [128] The detection of the cantilever's motion can be performed using a Michelson interferometer (MI), [178,179] Fabry-Perot cavity [180] or the piezoelectric effect.…”

“…[149] The experiment was repeated with a Gasera PA device which showed a comparable NNEA of 2.5 × 10 −10 cm −1 W Hz −1∕2 . Zhou and Iannuzzi [177] installed the excitation and read-out fibers on the same side. They detected acetylene with an NNEA of 1.3 × 10 −9 cm −1 W Hz −1∕2 .…”

Sub-Nanometer Acoustic Vibration Sensing Using a Tapered-Tip Optical Fiber Microcantilever

“…Among them, optical fiber-based solutions have drawn increasing attention due to their tolerance to electromagnetic interference, small size, low weight, and ability to multiplex with a single sensor probe across a long distance [ 15 , 16 , 17 , 18 , 19 , 20 , 21 ]. Recently, an optical fiber-based sensor called PAS-WRAP was developed, which uses the PA effect for methane leak detection [ 22 ]. Although this is a very promising technology, the current version has limited detection sensitivity mainly due to the insufficient acoustic response of the regular fibers.…”