Go, Fish
A waterproof smart vest for fish was created with an MXene-based hydrogel to track their movements and give insights into their behavior.
Research and conservation efforts focused on fish and their aquatic environments play a vital role in understanding and protecting these ecosystems, which are crucial for biodiversity and human well-being. Central to these efforts is the monitoring of fish behavior, as it provides valuable insights into their ecological roles, interactions with their environment, and responses to anthropogenic pressures. One of the most significant challenges in this endeavor is capturing the movements of fish, which is the key to understanding their behavior.
Traditionally, vision-based monitoring systems utilizing cameras have been the primary method for capturing data on fish movement. However, underwater environments present unique challenges, as visible light does not travel far underwater, severely limiting the effectiveness of this approach. This limitation has spurred innovation in recent years towards the development of wearable devices capable of monitoring fish behavior over large areas and extended time frames.
However, building effective wearable devices for this purpose presents significant technical challenges. One such challenge is the rapidly changing pressure in underwater environments, which can affect the performance and durability of the devices. Additionally, detecting the minuscule motions made by slowly swimming fish requires extremely sensitive and sophisticated sensors and data processing techniques.
A practical wearable device is on the horizon that may overcome many of these challenges, thanks to the efforts of a team at the National University of Defense Technology in China. They have created a waterproof smart vest for fish that can accurately track their behavior over long periods of time. Moreover, it was shown that this vest is capable of capturing very subtle nuances of fish movement due to its unique design.
The vest is made of a novel MXene-based hydrogel material, which is composed of MXene, holey-reduced graphene oxide, N-acetyl-L-cysteine, and 1-ethyl-3-methylimidazolium dicyanamide as an ionic liquid. The MXene material provides an ultrahigh interfacial pseudocapacitance effect, which enables the vest to sense pressure changes with high sensitivity. The remainder of the chemicals suppress self-stacking and improve the antioxidant properties of the vest. They also serve to further modify the surface and enhance the performance of the hydrogel in underwater environments.
The hydrogel serves as the active electrode material with a highly resilient double-network acidic hydrogel dielectric layer integrated into an ultrasensitive pressure-sensing unit. The hydrogel's interlayer spacing and surface properties are optimized for durability in underwater environments for extended periods, making it well-suited for this application.
Sensing units are embedded into holes arranged along the left and right sides of the vest. By monitoring small fluctuations in pressure, fish locomotion can be detected. Experimentation demonstrated that this system can recognize a number of activities, like swimming, turning, sinking, and surfacing.
Looking to the future, the researchers believe that in addition to tracking fish behavior, their core technology will also be useful in understanding the migration routes of sea creatures, and for monitoring weak flow fields, like those exhibited by seismic waves and ocean currents.