Encapsulation of Biosensor for Stress Monitoring in Fish: A Study on Design and Material Evaluation

This paper presents the packaging of an implantable fish-health monitoring system, called FishTag. The FishTag consists of biosensors, electronics, batteries, and an acoustic signal transmitter. For this system to function, it is vital for both the system and the fish that the tag is packaged properly. It is necessary to prove that the packaging approaches chosen will survive the environment inside a fish for the expected lifetime. The materials chosen for encapsulation were epoxy resin and biocompatible liquid silicone rubber. FishTag with a capsule shape was the main focus of this work. In addition, an alternative design of the tag was also proposed. The materials' capability to withstand the working environment of the tag was evaluated by water absorption and functional tests. The water absorption tests showed that the mean weight increase after 7 days was 2.4% and 0.2% for the epoxy and silicone, respectively. The FishTag packaged in epoxy functioned properly after being subjected to water and vibrations for a week during the functional test. Both silicone and epoxy in capsule-shape perform satisfactorily at keeping the system safe from the environment. Silicone is preferred as it absorbs less water, is flexible, and allows for change of battery and remoulding.