A Fitbit for Fish? A Protein-Based KELM Hydrogel Sensor Shows Promise for Sub-Sea Health-Tracking

Researchers from the Chinese Academy of Fishing Sciences, Shanghai Ocean University, the Chinese Academy of Sciences, and Tsinghua University have come up with a way to build what is, effectively, a Fitbit for fish — or, more accurately, a health-tracking implantable for aquatic organisms.

"Wearable electronics incorporating proteins for biocompatibility have garnered significant research attention, given their potential applications in biocompatible medical devices, artificial skin, humanoid robots, and other fields," the researchers explain. "However, a notable challenge exists, as many wearable electronics currently lack those essential properties due to issues such as non-biological compatibility, as well as insufficient mechanical and conductive performance. Here, we have developed a hybrid keratin (KE) hydrogel by incorporating a liquid metal (LM, eutectic gallium-indium alloy) to design a wearable electronic device with excellent biocompatibility, enhanced conductivity, and good mechanical properties."

The team's KELM hydrogel was proven through the creation of a health-tracking wearable for scallops — bivalve shellfish of the family Pectinidae. Rather than tracking movement, though, the wearable was used instead to track the creatures' heartbeat — doing so with, the researchers claim, high sensitivity and a low detection limit. Further experiments extended the testing to vertebrates including sturgeons and amphibians including giant salamanders — with each transmitting their heart beats accurately to a nearby Bluetooth receiver.

The technology has potential beyond underwater creatures, though: the team says it could also be used for human health monitoring, exhibiting the ability to adhere to human skin and biological tissues with "remarkable" strength and to stretch up to 2,600% of its original size. It's also highly sensitive to strain and shows a high conductivity — which is how it was monitoring the aquatic animals' heartbeats in the first place.

There's only one catch: where we can just strap a Fitbit to our wrist, the team's work required vertebrates to have the KELM hydrogel sensor surgically implanted. This, the researchers say, will be the focus of future work, developing minimally-invasive ways to use the technology and working on using arrays of multiple KELM hydrogel sensors to enable more precise behavioral monitoring.

The team's work has been published in the journal Engineering under open-access terms.