Engineers at Northwestern University have detailed the first ever battery-less microflier design. An article (opens in new tab) published by Nature this week lays bare the research and development process of what are being billed as the smallest-ever human-made flying structures, which are planned to eventually function as "large, distributed collections of miniaturized, wireless electronic devices", or swarms, of environmental do-gooders. They're planned to be able to carry data, scan their surroundings, and provide for wireless communication as well.
Potential usages for these swarms are near-infinite: air quality monitoring (and potential interaction with weather formations), airborne disease spread control, automated seed dispersal for agriculture, non-intrusive wild-life monitoring, explosive detection solutions for law enforcement, as massive data dispersal systems...or as mass surveillance mechanisms and tools for biological warfare right out of a Bond movie.
As time and history have shown us, while technology is often argued as being neutral by nature; human usage of it is another matter entirely. Doomsday scenarios for wonder tech are certainly easy to imagine, as Black Mirror has already done with a similar concept.
But the plus side to such imaginings is that they show us exactly what we have to avoid in our interaction with technology, so we can look to its advantages instead.
The microchips' powerless design was inspired by the maple tree's free-falling propeller seeds — samara fruit. These chips don't have controllable boosters or anything of the like. Instead, the tiny electronics are moved and sustained on air currents by physics alone. Perhaps it would be more accurate to call them gliders rather than microfliers, but we're not Northwestern researchers.
"As these structures fall through the air, the interaction between the air and those wings cause a rotational motion that creates a very stable, slow-falling velocity," said John A. Rogers, one of the engineers behind the devices.
Optimizations for the microfliers were done via computer modeling, looking for the correct design that would enable them to both fall slowly and disperse widely. “The computational modeling allows a rapid design optimization of the fly structures that yields the smallest terminal velocity,” Yonggang Huang, who created the computer models, said. “This is impossible with trial-and-error experiments.”
For the actual fliers, the engineers first created a 2D, planar base, where all the electronics are contained. The electronics contents here can be customized, packed with ultra-miniaturized technology, including sensors, power sources, antennas for wireless communication and embedded memory to store data. This is particularly important for mass manufacturing capabilities: planar processes are the bread and butter of the semiconductor manufacturing industry. “This strategy of building 3D structures from 2D precursors is powerful because all existing semiconductor devices are built in planar layouts,” Rogers said. “We can thus exploit the most advanced materials and manufacturing methods used by the consumer electronics industry to make completely standard, flat, chip-like designs. Then, we just transform them into 3D flying shapes by principles that are similar to those of a pop-up book.”
The base is then bonded to "a slightly stretched rubber substrate", which when relaxed, initiates "a controlled buckling process (...) that causes the wings to “pop up” into precisely defined three-dimensional forms." The microfliers have to be released in the air; the higher this is done, the farther their dispersal potential. And the slower the microfliers fall, the farther they'll be able to disperse from the release point as well. So lengthening the flight time was one of the major goals for the engineers.
"We think that we beat nature," Rogers said. "At least in the narrow sense that we have been able to build structures that fall with more stable trajectories and at slower terminal velocities than equivalent seeds that you would see from plants or trees."
However, should this sort of technology be pushed further and enter active usage, what of all the electronic detritus? Should clouds, swarms of these microfliers just fall towards the ground to lay crushed beneath our sneakers as we run towards the Metro? Well, it so happens that Notrtwestern University has also had research done into transient electronics - electronics that are biodegradable in nature after they have finished their intended usage.
“We fabricate such physically transient electronics systems using degradable polymers, compostable conductors and dissolvable integrated circuit chips that naturally vanish into environmentally benign end products when exposed to water,” Roger said. “We recognize that recovery of large collections of microfliers might be difficult. To address this concern, these environmentally resorbable versions dissolve naturally and harmlessly.”