The smallest man-made flying structure in history was born, and a dozen Chinese and foreign teams jointly tackled key problems.
It is even smaller than a pen core and can spin and fall in the air like a seed.
The micro-aircraft consists of two parts: electronic functional parts and wings. All parts are from micrometers to millimeters in size.
When it falls in the air, its wings will interact with the air, so that it can make a slow and steady rotation.
The related paper became the cover paper of the current issue of Nature, with the title of "Three-dimensional electronic micro-aircraft inspired by the seeds of wind".
"We think we defeated nature"
The poet Gu Cheng once said: "The grass is bearing its seeds, and the wind is shaking its leaves. If we stand and don't speak, it is very beautiful." The fourth volume of the West Normal University version of the text "riding a "white horse" of cocklebur" has something to say "The seeds of dandelion were sent by Granny Feng with a small umbrella."
In art works, seeds, especially flying seeds, always have romantic images. Today, the seed has inspired a Nature cover paper.
Zhang Yihui, the Dean of the Department of Engineering Mechanics of the School of Aeronautics and Astronautics, Tsinghua University, said that the reason why this paper is on the cover is that the aircraft equipped with microelectronic devices can be made so small and can stay in the air for a long time. Environmental monitoring or other information testing. In addition, science itself has a certain degree of artistry, and the artistic beauty of this device is very rare.
The decentralized micro-aircraft, which is only the size of a refill, has many capabilities for monitoring air pollution, airborne diseases, and environmental pollution. The most important thing is that it can fly.
Most of the previous electronic aerial vehicles were driven by active methods. This type of micro aerial vehicles has certain limitations in miniaturization due to complicated mechanical components and designs. In particular, it is very difficult to provide the huge energy consumed by flight while miniaturizing.
The device does not need to be driven by an engine, but relies on natural wind to fly.
It flies in the air like the seed of a maple tree. When it descends from the air to the ground, it will also be like a helicopter. After spinning continuously, it will land smoothly.
It is through the study of maple seeds that rely on wind to inoculate other plant seeds, the team optimized the micro-aircraft from the aspect of aerodynamics to ensure that it can land at a controlled low speed when it descends from a high altitude.
Controlling the landing speed not only ensures a more stable flight, but also allows it to fly in a wider range in the air, thereby increasing the time it takes to interact with the air, allowing it to better monitor air pollution and airborne diseases.
The micro-aircraft body is equipped with various ultra-miniaturization technologies, including sensors, power supplies, wireless communication antennas, and embedded memory for storing data.
John A. Rogers, a member of the U.S. Academies and Professor of the Department of Materials Science and Engineering at Northwestern University, served as the co-corresponding author of the paper. He is also one of the main leaders of the study. He told the media that the main goal of the study is to make small electronic systems capable of The function of winged flight allows it to be dispersed to farther places to perform functions such as environmental perception, pollution monitoring, population monitoring, or disease tracking.
The success of this research is because it was inspired by the biological world. In billions of years of natural history, nature has designed seeds with very complex aerodynamics. The research also draws on these design concepts and applies them to the electronic circuits of micro-aircraft.
The propeller-like seeds of maple leaves, after spinning in the air, will slowly and steadily fall to the ground. This is an example of nature's increase in the survival rate of plants. Because of this, maple seeds that could not move on their own can spread more widely, and the offspring of maple trees can reproduce farther places.
It is precisely because of this that many seeds in nature exhibit complex and ingenious aerodynamic characteristics. In the design process of this micro-aircraft, the team studied the aerodynamic characteristics of various types of plant seeds, and found the most direct inspiration from the star fruit vine.
Star fruit vine is a flowering vine plant with star-shaped seeds. Its seeds have leaf-shaped wings that can rotate slowly in the wind.
During the development and design of the equipment, the team initially designed and manufactured a number of micro-aircraft, including a three-wing aircraft that is very similar to the seeds of the star fruit vine.
In order to determine the most ideal structure, they carried out a full-scale calculation model design, by simulating the surrounding air flow, and finally simulated the slow and controllable rotation of the Samsung fruit vine seeds from the micro air vehicle.
Next to the preparation, the researchers used advanced imaging and quantitative flow mode methods to build and test the structure of the micro-aircraft in the laboratory.
On the basis of the aircraft structure model designed by Professor Zhang Yihui and the leadership of Academician Huang Yonggang of Northwestern University, the team led by Academician Rogers then proceeded further with Leonardo Chamorro, associate professor of mechanical engineering at the University of Illinois at Urbana-Champaign. In cooperation, they used advanced imaging and quantitative flow patterns to build and test structures in the laboratory.
Chip design
To make these devices, the team got inspiration from another familiar novelty, pop-up three-dimensional books that many children have read.
In the preparation, the researchers first made the precursor of the flying structure in the flat plate. Then, these precursors are glued to the slightly stretched rubber substrate.
When the originally stretched base appears to relax, a pre-controlled buckling process will occur. At this time, the wing will "pop out" and a precisely defined three-dimensional shape can be formed.
This is an ingenious strategy for making 3D structures from 2D planar structures, which was previously on the cover of Science magazine in 2015. Since existing semiconductor devices are manufactured based on planar structures, they can use advanced materials and manufacturing methods that are being used in the consumer electronics industry to design the devices in a chip. Then, based on a principle similar to pop-up books, they can be transformed into the shape of a 3D aircraft.
In addition, they placed the center of gravity of the electronic components in a lower position of the equipment to avoid falling to the ground due to loss of control.
After the above steps, structures of various sizes and shapes are finally born, some of which have properties comparable to those of natural seeds.
Academician Rogers believes that to some extent, the team defeated nature. At least in the narrow sense, the micro-aircraft designed and manufactured by them has a more stable trajectory and a slower falling speed than the seeds of plants or trees, and is smaller in volume than many natural seeds, or even not as large as sand grains. The miniaturization of equipment is the dominant development trajectory of the electronics industry.
Can be used for environmental monitoring and water quality monitoring, etc.
With the micro-aircraft, coupled with sensors, memory, a power source that can collect environmental energy, and a data cable, it can be assembled into an air particle detection device.
In fact, it is to integrate it with the Internet and throw it into the mountains and fields to monitor environmental pollution.
It can also be used to monitor water quality if it is equipped with a pH sensor. In addition, equipped with a photodetector, it can be used to measure different wavelengths of sunlight.
At present, many monitoring technologies must use large-scale equipment in practice. The team envisions that if such equipment is dropped from airplanes or buildings and widely dispersed, it will be able to perform environmental remediation monitoring after chemical spills, and it can also track pollution levels in the air at different altitudes.
In view of the "ultra-mini" size of the micro-aircraft, it can be distributed in a high-density and large-scale area, so as to realize the general detection of a wireless network.
At the same time, the team also took into account the possible e-waste problem. In terms of recycling of waste equipment, they have developed a transient electronic device that can be dissolved in water in a harmless manner after the "end of life".
At present, the device is used in bioabsorbable pacemakers, and the effect has also been verified. Currently, they are using the same materials—degradable polymers, compostable conductors, and soluble integrated circuit chips—to make micro-aircraft.
In the future, once it accidentally falls into the water, it will automatically dissolve, realizing the real "fuck away".
Zhang Yihui said that the Tsinghua team’s contribution to the work of micro-electronic aircraft is mainly in three aspects. One is the bionic structural design inspired by wind-borne seeds; the second is the reverse design and mechanical analysis of the three-dimensional assembly of the aircraft structure; and the third is the spin of the aircraft structure. Falling flow field simulation and stability analysis.
