Marine animals play a crucial role in ecosystem dynamics and are essential for understanding ocean health and biodiversity. However, attaching sensors to these animals, especially soft and fragile species like squid and jellyfish, has been challenging due to the invasive nature of traditional sensor attachment methods.
a–c Shear strength (a), tensile strength (b), and interfacial toughness (c) between the BIMS and various marine animal tissues. d–f Schematic illustration (d) and representative images (e, f) for a mock sensor adhered on a squid mantle with simulated respiration. g, h Representative images of robust and non-invasive adhesion on squid mantle before (g) and after (h) 40 cycles of simulated respiration. i, j Squid (i) and jellyfish (j) after tagging (left image in each panel) and freely swimming immediately upon release (right image of each panel). k Tag deployment time in water for squid and jellyfish. Values in (a, b, c, and k) represent the mean and the standard deviation (n ≥ 2 independent samples). Image Credit: https://www.nature.com/articles/s41467-024-46833-4
In a recent article published in the Journal Nature Communications, researchers from the US have developed a soft hydrogel-based bioadhesive interface that enables rapid, robust, and non-invasive adhesion on a variety of marine animals. This development would enable the facilitation of large-scale sensor deployments for studying biomechanics, collective behaviors, interspecific interactions, and multi-species activities.
Background
Soft and fragile marine species, such as squid and jellyfish, constitute a significant portion of ocean biomass and are integral to marine ecosystems. Existing methods for attaching sensors to these species often involve invasive physical anchors, suction cups, and rigid glues, which can lead to unreliable fixation, tissue trauma, and behavioral changes in the animals.
The limitations of these traditional attachment methods have hindered research on soft-bodied marine organisms, limiting the understanding of their interactions. The development of a bioadhesive interface addresses these challenges by providing a gentle and efficient way to attach sensors to fragile marine species, expanding the scope of marine biosensing research to include a broader range of organisms.
The Current Study
The bioadhesive interface was prepared using a specialized soft hydrogel material tailored for marine applications. To test and develop the interface, the following steps were taken:
Preparation of the Bioadhesive Interface: The composition of the interface involved two distinct entangled polymer networks: one was physically crosslinked poly (vinyl alcohol) (PVA), and another was covalently crosslinked poly (acrylic acid). Both the polymers were grafted with N-hydroxysuccinimide ester (PAA-NHS ester). This unique combination of polymers was selected to optimize adhesion properties while ensuring compatibility with marine species.
Application Process: The application of the bioadhesive interface to marine species was a critical step in ensuring rapid and reliable sensor attachment. Prior to application, the dried-hydrogel adhesive interface, with a thickness of 150 μm, was carefully positioned on the target area of the marine organism. The interface was designed to absorb seawater from the surface of the species, promoting hydration and swelling to enhance adhesion. Gentle pressure was applied to facilitate contact between the adhesive interface and the marine organism, allowing for rapid integration within a remarkable timeframe of less than 22 seconds.
Mechanical Testing: To evaluate the performance of the bioadhesive interface, three mechanical tests were conducted on ex vivo tissues from marine animals. These tests included measurements of interfacial toughness, shear strength, and tensile strength, following established testing standards specific for tissue adhesives such as 90-degree peel tests, lap-shear tests, and tensile tests.
Species Compatibility Testing: The efficacy of the bioadhesive interface was further assessed through compatibility testing on a diverse range of marine species, including squid, jellyfish, ray-finned fish, skates, and lobsters. The interface demonstrated robust adhesion, and by testing the interface on various marine organisms, the study confirmed its ability to provide non-invasive and reliable attachment, enabling researchers to analyze behaviors and interactions across different species with minimal disturbance.
Data Collection and Analysis: Following the application of the bioadhesive interface, data collection procedures were implemented to gather information on sensor performance, adhesion strength, and animal responses. The collected data was then analyzed using appropriate statistical methods to assess the effectiveness of the bioadhesive interface in facilitating sensor deployment and monitoring marine animals.
Results and Discussion
The findings demonstrated the successful application of the bioadhesive interface on various marine species, including squid, jellyfish, ray-finned fish, skates, and lobsters. The rapid adhesion provided by the bioadhesive interface allowed for multi-animal sensor deployments to study group behaviors, motion dynamics, and interactions between species.
The non-invasive nature of the interface minimized disruptions to normal animal activities, enabling researchers to collect high-quality data on eco-physiological measurements and comparisons across different species. The versatility and reliability of the bioadhesive interface open new possibilities for researching marine ecosystems and understanding the dynamics of underwater environments without causing harm to the animals.
Conclusion
In conclusion, the development of the soft hydrogel-based bioadhesive interface represents a significant advancement in marine sensor technology, offering a gentle and efficient method for attaching sensors to soft and fragile marine species. This innovative approach not only enhances the ability to explore marine animals but also expands the scope of marine biosensing research to include a wider range of organisms.
By enabling rapid, robust, and non-invasive adhesion on various marine animals, the bioadhesive interface holds great promise for advancing the understanding of marine ecosystems, behaviors, and interactions. The application of this technology has the potential to revolutionize marine research and conservation efforts, paving the way for new discoveries and insights into the underwater world.
Journal Reference
Duque Londono, C., Cones, S.F., Deng, J. et al. (2024). Bioadhesive interface for marine sensors on diverse soft fragile species. Nature Communications 15, 2958. https://doi.org/10.1038/s41467-024-46833-4, https://www.nature.com/articles/s41467-024-46833-4