The Ocean of Things

We are learning more about our planet than we ever would have thought possible as a result of the proliferation of Internet of Things (IoT) devices. These inexpensive and tiny internet-connected systems can be loaded down with sensors and widely distributed over the surface of the planet to capture all sorts of environmental data. It has been predicted that there will be as many as one trillion IoT devices in operation by the year 2035, so we can expect many new insights to come from the data that they collect.

While these devices are being distributed far and wide all over the planet, the vast majority of them are deployed on dry land. However, 71 percent of the Earth's surface is water, and understanding this area is critical to many environmental and logistical issues. Clearly the next frontier for IoT will need to be the world’s oceans, but it is a very challenging environment to work in. In particular, powering these systems presents many difficulties. Given the wide distribution of the devices in remote locations, and their shifting positions as they drift, recharging or changing batteries is not a practical option.

Alternative energy sources, like solar and kinetic energy form currents, have been extensively explored. Yet due to factors like the high levels of variability in availability, they have not been demonstrated to be viable for widespread use. A trio of researchers at the State University of New York at Binghamton have come up with a very interesting solution that could overcome these problems, however. They have developed a bug-like robot that can skim across the surface of the water to collect data. This robot is powered by a special battery that draws power from bacteria and never needs to be recharged.

The aquatic robot was designed to mimic the appearance and capabilities of a water strider. The lightweight polycarbonate plastic body gives it buoyancy. It includes a small DC motor for locomotion. Rotational movements of this motor are utilized to propel it along the surface of the water without applying force directly to the water itself.

It is the miniaturized microbial fuel cell (MFC) that is the primary innovation developed by the researchers. The MFC is filled with a bacteria known as Bacillus subtilis. It is designed such that nutrients from the water can pass into the cell to support the metabolic activities of the bacteria. Using this battery, organic materials are converted into electricity via catalytic redox reactions. When the conditions are unfavorable for the bacteria, or insufficient nutrients are available, they will form spores that allow them to survive — although less energy is produced in this state. And when conditions improve, they return to their normal cellular state.

This battery does not produce a lot of energy; the team showed that it can generate about one milliwatt of power. That is enough, however, to power an array of environmental sensors to monitor, for example, water temperature, pollution levels, and the behaviors of aquatic animals. It is also sufficient to operate the robot’s motor.

At present, aquatic IoT devices are generally anchored to one location. Using the methods described in this research, environmental data could be collected all over the planet. But before we get there, the team still has some work to do. As a next step, they plan to experiment with additional types of bacteria in the MFC to determine which work the best under stressful ocean conditions.