As everyone from farmers to environmentalists have found, airborne drones are fantastic for monitoring wide swaths of land that are too expansive to cover by foot. But they do consume a fair amount of energy, which reduces their deployment time; the mere act of remaining airborne, even if hovering in place and not traveling at speed, requires a steady flow of juice to keep those rotors going. This can be a problem for some applications, as "Energy efficiency is essential in the environmental monitoring world," explains Gennaro Notomista, a PhD student in the Robotics and InTelligent Systems Laboratory at Georgia Tech, "where processes take place over very long periods of time."

Thus Notomista struck upon a different idea: What if the drone consumed no energy while motionless? And what if it never needed to return to base to recharge? It could then remain in the field indefinitely, gathering data at length and beaming it back to base.

For his inspiration, Notomista looked to…sloths. If a concession was made to add a small amount of infrastructure not required by a drone--in this case, a cable slung between two points--a SlothBot could travel along the cable to reach the relevant area, then literally hang out and do its monitoring thing.

"Currently deployed in the Atlanta Botanical Garden, the SlothBot can run (or climb) forever without ever needing to be charged through a power outlet. An extremely energy efficient robot, the SlothBot monitors environmental factors like temperature, weather and carbon dioxide levels.

"How does the SlothBot have such a long battery life? Number one: it hangs on a cable and switches off all motors while stationary, which would be impossible for a drone. Secondly it traverses at a slow, slothlike speed.

"Programmed with control algorithms to only move when necessary, if the SlothBot is low on charge, it will automatically move until its light intensity and current sensors communicate that enough power is flowing into the battery via its solar panels."

Notomista chose FDM 3D printing for the SlothBot's shell, selecting a weatherproof material (PLA Pro) for its construction, and outsourcing the printing to 3D Hubs. "Because the SlothBot would be deployed outdoors, we wanted a material for the shell that was at least rain and UV resistant," Notomista says.

1. Rainproof environmental sensors, off-the-shelf

2. Waterproof ultrasonic sensors, off-the-shelf

3. FDM 3D printed shell in PLA Pro with UV & rain resistant coating

4. Waterproof tube housing all electronic parts, excl. motors & environmental sensors

5. Printed Circuit Board (PCB) designed in-house, manufactured externally

6. Motors, off-the-shelf

Notomista's next goal is to create a SlothBot 2.0 that can be used for agricultural monitoring in far-flung, remote locations with no cell service. For connectivity, the plan is to add a low-power satellite link.

You can learn more about the SlothBot's development process here.