Engineers from Johns Hopkins University in Maryland have take a second look at insect flight, and over-turned received wisdom in a way that could benefit micro aerial vehicles (MAVs).
"Earlier published research pointed out that an insect's delicate wings possess very little mass compared to the bug's body," said the University. "As a result, those scholars concluded that changes in spatial distribution of mass associated with wing flapping did not need to be considered in analysing an insect's flight manoeuvrability and stability."
The effect under the microscope is the change in moment of inertia that allows a skater to spin faster by bringing their arms closer to their body.
By videoing painted lady butterflies (above) at 3,000 frame/s, with three cameras to get 3D data, the researchers found that even insects with big stiff wings use the skater trick.
"We learned that changes in moment of inertia play an important role in insect flight," said Tiras Lin the undergraduate engineer who lead the filming, and recently presented his findings to the American Physical Society.
"MAVs will have to fly through environments with tight spaces and turbulent gusts of wind," he said. "These flying robots will need to be able to turn quickly. But one area in which MAVs are lacking is manoeuvrability."
Constructing a MAV suitable for such sophisticate flight might seem a long way off, but developments in fabrication are squeezing remarkable complexity into small volumes.
The self-assembling Harvard Monolithic Bee is an example.
The Bee starts life as a sandwich created by PCB fabrication techniques.
In the sandwich are five structural layers of carbon fibre, two layers of flexible plastic for hinges, two layers of brass - more of which later, and a lace-like titanium sheet for wings.
Each layer of the laminate is laser-cut to a different pattern, stacked, and glued.
In an origami-like move reminiscent of a child's pop-up book, forces are applied to fold flat structures surrounding the proto-robot.
As these are folded, they push and pull the 2D robot parts into its final 3D shape, which is held temporarily by latches formed in the brass layers, and made permanent by soldering the latches - by dipping the whole robot into a solder bath.
Flight power comes from two piezoelectric motor layers (triangular in the photo) which are deposited through apertures in the outer layers while the assembly is still flat.
There is a video decribing the Harvard Monolithic Bee.