Wearable electronic vest turns fish into underwater spies

• An underwater vest containing an antioxidant MXene hydrogel captures disturbances in the water flow caused by the movements of fish to understand their adaptive behaviours and ethological characteristics.
• The device features a pair of pseudocapacitive pressure-sensing units, offering a robust and noninvasive approach for the in-depth study of aquatic behaviours.

Researches from National University of Defense Technology have pioneered a wearable tagging electronic device, referred to as an underwater vest, which adeptly captures disturbances in the water flow caused by the movements of fish to understand their adaptive behaviours and ethological characteristics.

The device utilises an advanced MXene hydrogel known for its remarkable sensitivity to changes in water pressure. The device features a pair of pseudocapacitive pressure-sensing units, offering a robust and noninvasive approach for the in-depth study of aquatic behaviours.

The hybrid hydrogel electrodes were developed through cross-linking MXene with holey-reduced graphene oxide nanosheets and further modification with 1-ethyl-3-methylimidazolium dicyanamide ionic liquids, which increased the interfacial capacitance and long-term interfacial activity of the MXene.

Consequently, the sensing unit exhibited ultrahigh sensitivity in an aquatic environment for 60 days and superior high-pressure resolution (10 Pa) within a wide working range of 1 MPa.

Ultimately, an underwater vest integrated with such sensing units clearly distinguished and recorded fish locomotion. 

Advancing aquatic research

A koi fish with a length of about 30 cm was placed in the sensing vest and used as the experimental subject, and it was placed in a water tank with a depth of about 40 cm.

Moreover, an underwater camera (S3, Ezviz Technology Co., Ltd.) was placed in the tank to track changes in the locomotion of the fish.

Whether a fish turns, speeds up, or dips, the vest’s pseudocapacitive pressure-sensing units register these actions with unparalleled precision.

“This wearable device significantly advances aquatic research. It transcends the constraints of traditional systems and paves the way for comprehensive studies on fish behaviour and their ecological interactions,” Dr. Jiafei Hu, the lead researcher from the National University of Defense Technology, said.

Moreover, he said the introduction of the underwater vest signifies a major advancement in research methodologies, enabling precise, real-time insights into fish behaviours and their environmental dynamics.

“Its implications for environmental conservation, aquatic ecosystem studies, and the development of sophisticated monitoring technologies are profound and far-reaching.”

The potential applications of underwater vests are promising and attractive; additionally, the underwater vests can be used for recording fish movements and migration routes and even for monitoring weak flow fields, such as seismic waves and ocean currents.