Roboticists and military planners have dreamed of tiny insect robots for years — ones that walk, fly, or both. But while there's been a lot of advances in hose fields nothing seems to beat the design nature came up with — and no wonder, since evolution has had millions of years to perfect it. So researchers are also looking at ways to equip insects with the technology that might otherwise go on an insect-sized vehicle. However, when you load up a bug with equipment you need a way to power it without weighing it down so much it can't fly.
Ethem Aktakka and his team at the University of Michigan came up with a solution: use the insect itself for power. They used a green June beetle (Cotinis nitida) to test the kit, which consists of a piece of piezoelectric material (in this case a lead-zirconium-titanate mix) attached to the beetle's back. The tip of the spiral touches the beetle's wing sheath, or elytra.
Piezoelectric materials generate current when they are bent or deformed, so as the beetle flies, bending the material, it generates power. Atkakka and his team tested two prototypes, one shaped like a crossbar and one in a spiral. The crossbar version, which was actually tested on a beetle, generated a total of about 7.5 microwatts, while the spiral version which was tested on a lab table produced between 18 and 22.5 microwatts, or, the researchers say, about 45 microwatts per insect — enough to power a small bit of electronic equipment.
Other methods of picking up energy from the bugs have been tried. Small solar panels could be put on the wing sheaths, but they don't work in the dark or on overcast days, and using the bug's body heat (they generate small amounts when flying) doesn't produce enough power. Batteries can be quite heavy relative to the insect. The piezoelectric system seems to produce the most bang for the buck — the spiral pieces weigh only 0.2 grams, compared to an average weight of 1.3 grams for the beetle. That leaves a lot more for payloads, such as the small controllers that scientists have learned to implant in the insect's brain.
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