Highly Sensitive Photoacoustic Methane Detection Based on Fish-Ear-Inspired Differential Photoacoustic Cell

In this article, we report a novel fish-ear-inspired differential photoacoustic cell (FED-PAC)-based photoacoustic spectroscopy (PAS) sensor. Inspired by the opposing-phase responses of the otolithic organs (e.g., utricle and saccule) in the fish inner ear, we designed two acoustically antiphase resonators for differential signal extraction. This innovative design significantly enhances the photoacoustic signal while effectively suppressing in-phase noise interference. Methane (mathrm{CH}-{{4}} was selected as the target analyte for performance evaluation. Experimental results demonstrate that the second-harmonic (2 {f}{)} signal amplitude of the differential module reaches 1178.53μ V, representing a 2.46-and 1.62-fold increase compared to microphone 1 and microphone 2, respectively. With an integration time of 1000 s, the FED-PAC-based PAS sensor achieves a minimum detection limit (MDL) of 256 ppb, underscoring its exceptional potential for trace gas detection. These findings confirm that fish-ear-inspired biomimetics offer a transformative path to optimize acoustic resonance and boost photoacoustic detection.