Vector hydrophones are essential tools for underwater acoustic detection because they can directly measure the direction and velocity of sound waves. Electrochemical vector hydrophones are particularly attractive due to their high sensitivity, low mechanical noise, and strong performance at very low frequencies, where many conventional sensors struggle. However, existing designs are often limited by poorly controlled electrode spacing, restricted reaction areas, and narrow effective bandwidths, reducing their ability to capture weak and broadband underwater signals. Improving sensitivity without sacrificing bandwidth has therefore remained a key technical bottleneck. Based on these challenges, there is a clear need to conduct in-depth research into new microelectrode structures and system-level optimization strategies.
In a study published (DOI: 10.1038/s41378-025-01040-z) in Microsystems & Nanoengineering in November 2025, researchers from the Chinese Academy of Sciences and the University of Chinese Academy of Sciences report a new co-oscillating electrochemical vector hydrophone with markedly improved performance. The team introduced microgroove-based integrated microelectrodes and combined them with a force-balanced negative feedback mechanism. This approach enables precise control of electrode geometry while extending the operational bandwidth. Experimental results show that the device achieves higher sensitivity and a much wider working frequency range than previously reported electrochemical vector hydrophones.
The core innovation of the study lies in the redesign of the hydrophone's sensitive microelectrodes. By introducing deep microgrooves between anode and cathode electrodes, the researchers achieved micron-scale spacing that is difficult to control using conventional fabrication methods. This geometry not only reduces the distance ions must travel during electrochemical reactions but also creates additional effective cathode surfaces along the microgroove sidewalls. Numerical simulations and theoretical modeling showed that smaller electrode spacing and enlarged cathode areas directly enhance output current and sensitivity, especially at low frequencies.
To further overcome bandwidth limitations, the team implemented a force-balanced negative feedback system based on a coil–magnet configuration. While negative feedback typically reduces sensitivity, the enhanced electrode design compensated for this loss, allowing the hydrophone to maintain strong signal response while significantly extending its frequency range. Experimental testing demonstrated that the device achieved approximately twice the peak sensitivity of state-of-the-art electrochemical vector hydrophones, while expanding the −3 dB bandwidth from below 100 Hz to as wide as 1–450 Hz.
Additional measurements confirmed stable “figure-eight” directivity, low self-noise comparable to shallow-sea background levels, and reliable operation under simulated harsh underwater conditions equivalent to depths of 200 meters.
“This work shows how micro-scale structural design can unlock system-level performance gains,” said one of the study's senior researchers. “By carefully engineering the microelectrode geometry and combining it with an optimized feedback mechanism, we were able to break the usual trade-off between sensitivity and bandwidth. The result is a vector hydrophone that performs exceptionally well in low-frequency ranges while remaining robust and practical for real underwater environments. This approach could inspire new designs not only in hydrophones, but also in other electrochemical sensing systems.”
The improved hydrophone has broad implications for underwater acoustic technologies. Its high sensitivity and wide bandwidth make it well suited for applications such as ocean environmental monitoring, underwater target detection, sonar systems, and unmanned underwater vehicles. In particular, the ability to detect very low-frequency signals with low noise could enhance long-range acoustic sensing and improve situational awareness in complex marine soundscapes. Beyond hydrophones, the microgroove-based electrode design strategy may also be applied to other MEMS electrochemical sensors, opening new opportunities for high-performance sensing in geophysics, marine science, and environmental monitoring.
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References
DOI
10.1038/s41378-025-01040-z
Original Source URL
https://doi.org/10.1038/s41378-025-01040-z
Funding information
This study was supported in part by the Strategic Priority Research Program (B) of the Chinese Academy of Sciences under Grant XDB1110201, in part by the National Natural Science Foundation of China under Grant 62201549, Grant 52335012, and Grant U23A20362, in part by Beijing Natural Science Foundation under Grant 4242012, in part by the Youth Innovation Promotion Association CAS under Grant 2023134.
About Microsystems & Nanoengineering
Microsystems & Nanoengineering is an online-only, open access international journal devoted to publishing original research results and reviews on all aspects of Micro and Nano Electro Mechanical Systems from fundamental to applied research. The journal is published by Springer Nature in partnership with the Aerospace Information Research Institute, Chinese Academy of Sciences, supported by the State Key Laboratory of Transducer Technology.