Defying Gravity with Attraction

Today’s unmanned aerial vehicles (UAVs) have some hefty limitations when it comes to flight time. Keeping their rotors spinning longer requires larger batteries, but larger batteries add weight that decrease flight time. Breaking free from this vicious cycle might be achieved by some as yet unimagined breakthrough in energy storage technology. But we need solutions now, so we cannot wait for a new technology that may or may not ever materialize.

Fortunately, there are some options that can help us to make the most of what we currently have available to us. One of the chief methods employed by UAV developers involves cutting weight wherever possible. If you can get by without a given system or component, simply toss it aside to boost flight times. A group of engineers at the University of California, Berkeley has taken this approach to the extreme with their novel robot design. Consisting of little more than a rotor and a pair of magnets, their robot is the lightest and smallest untethered and controllable UAV ever developed — although the simple design limits its capabilities.

The insect-scale robot measures just 9.4 millimeters across and weighs a mere 21 milligrams. Unlike traditional UAVs that rely on onboard batteries or a power tether, this prototype operates by using an external alternating magnetic field. This magnetic field induces rotation in the rotor by interacting with a pair of tiny magnets that are attached to it. This, in turn, generates lift. By adjusting the frequency of the applied field, researchers can make the robot hover or ascend, while lateral movement is controlled by fine-tuning the magnetic forces.

Although it may not replace traditional drones anytime soon, this system offers some promising potential applications. Miniature UAVs like this could be used for search and rescue missions, inspecting industrial equipment, or even aiding in plant pollination. The robot has also demonstrated an impressive lift-to-weight ratio, allowing it to carry tiny payloads, such as infrared sensors for environmental scanning.

But before anything so practical as these applications becomes realistic, the team needs to overcome some limitations of their approach. One of the biggest limitations of this flying robot is its range. It can only operate within about 10 centimeters of the magnetic coils that power it. However, the researchers believe this can be improved to some extent by enhancing the strength and configuration of the coils. With further refinements, the UAV could potentially fly up to a meter away from the power source — although that is still quite limiting.

Another avenue for improvement involves further miniaturization. By making the robot even smaller and lighter, the power requirements could decrease, allowing for new wireless energy transfer methods, such as electromagnetic waves from radio or cell signals. Future advancements may also include integrating onboard energy conversion systems to power sensors and other electronics, making these robots more autonomous.

Should a wireless energy transfer method be shown to be practical, perhaps the team could integrate the world’s smallest microcontroller into their world’s smallest UAV. It seems like a match that was just meant to be. But for now, this tiny UAV will remain no more than a proof of concept that reminds us that sometimes, less truly is more when it comes to cutting-edge technology.