Recently, the Madrid University of Technology (UPM) has collaborated with scientists at the University of Florence in Florence to develop a machine fish designed to track the pH level in aquaculture settings to help keep fish healthy. Researchers at the Madrid Polytechnic University said that the percentage of pH in the fish farm is very important because it shows the acidity of the water and affects other water quality factors. Aquaculture water tends to cause fish to become ill, and a recent study has even shown that it allows fish to "give up" their own instincts and to swim them to predators.

UPM researchers collaborated with scientists at the University of Florence to create a fish-shaped underwater robot to monitor pH in real time and on site. The robot is designed to mimic fish, and even adapt to its movement in response to water quality as a way of revealing anomalies in specific areas.

A robot with a length of 30 cm (12 in.) (Excluding the tail) uses a shape memory alloy actuator to bend the "skeleton" made of 1 mm thick polycarbonate, all of which are wrapped in latex material. When it comes to how to drive the robot underwater, the system gets its hint from a dedicated sensor.

This sensor is made of a polyaniline film (a conductive polymer) on the surface of the graphite electrode which, by monitoring the nearby pH, converts these chemical information into an electronic signal and then determines the swimming mode of the robot. The team has conducted a preliminary experiment, which uses a pH sensor to control the tail movement of the machine fish.

"Because this system provides early information on environmental change, we can control water quality parameters and improve management decisions in fish farms, thereby improving the health of these animals," said Claudio Rossi of UPM.

The team's research was published in the journal Sensors and Actuators B: Chemical.