Robotics is increasingly used in environmental monitoring. However, these tiny, inexpensive devices will often simply be abandoned after their purpose is served.
The body of conventional robots often relies on non-biodegradable materials and potentially toxic chemicals, which can possibly be a pollution risk when left in the environment. In that context, scientists from EPFL in Switzerland have developed little robots that can be consumed by fish when their job is done.
These motorboat-shaped robots, approximately 5 cm (2 inches) in length and weighing an average of 1.43 grams, are made out of commercial fish food.
The fish-feed powder is mixed with a biopolymer binder, and then is shaped into the robot’s body and freeze-dried. This is to ensure that a major part of the robot can be readily digestible to provide nutritional value to aquatic organisms.
A chamber consists of a non-toxic combination of sodium bicarbonate and citric acid, and is sealed with a gel plug where water is absorbed, then reacts with the powder inside to produce CO2. The gas then expands into a microfluidic reservoir filled with propylene glycol to push the glycol out of the robot’s tail.
The expulsion of glycol leverages the Marangoni effect, which reduces surface tension, to propel the robot forward, mimicking the locomotion of water striders. The achievement showed that the glycol used is non-toxic, minimizing any potential harm to the aquatic environment.
These edible robots are expected to deploy a batch onto the surface of a body of water to collect data on various environmental parameters. The robots with sensors could collect information such as water temperature, pH in the water, and pollutant levels once it is left on the surface of the water. The data could then be transmitted wirelessly or obtained from the robots that are collected.
Over time, the fish-food hulls would become waterlogged, soften, and eventually sink, becoming readily available for consumption by fish and other aquatic animals.
In addition, the robots could also be deployed in fish farms to deliver medicated feed directly to fish.
This achievement represents a significant step forward. However, another challenge now lies in producing sensors and other electronics that are likewise biodegradable or even edible to ensure the complete elimination of non-degradable materials from the robots.
Image & article source by EPFL
