Why did a nanomaterial researcher spark a passion for track cycling?

In track cycling, what have nanoscientists done to break the limit of 0.0001 seconds and make the competition fairer?

On July 21, 2024, Zhang Ting, distinguished visiting researcher at the Institute of Sports Science of the General Administration of Sports of China and member of the Suzhou Institute of Nanotechnology, Chinese Academy of Sciences, gave a speech entitled "Breaking the Limit of 0.001 Seconds" at the "Looking at the Olympics with Scientific Eyes" theme session of the Science Popularization China Starry Sky Forum.

The following is an excerpt from Zhang Ting’s speech:

Hello everyone, my name is Zhang Ting, from the Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences.

My research direction is intelligent micro-nano sensing materials and devices. Simply put, it is to use nano materials and structures to develop highly sensitive and fast-response intelligent sensor devices.

So, how do our sensors create sparks with the Olympics?

In the modern Olympic arena, every millisecond and even every microsecond counts, especially in track cycling, where modern track bikes can reach speeds of more than 20 meters per second and the difference between the top athletes is often just a matter of milliseconds.

For example, in the women's individual sprint final of the Rio Olympics in 2016, a German athlete won the gold medal with a 0.004 second advantage. Therefore, in the Olympic arena, every thousandth of a second is extremely important.

We have a slogan: "For one thousandth of a second, do everything possible." We hope to break through the limit of 0.001 seconds with the help of science and technology and interdisciplinary research.

High-precision timing system is necessary

For track cycling competitions, a high-precision timing system is essential.

At present, there are two Olympic-approved timing systems in the world, both of which are monopolized by foreign companies. Because foreign timing systems are designed for events, they are very expensive, costing more than 2 million yuan each, and require the cooperation of multiple people to operate. In addition, the current functions cannot meet the personalized needs of coaches and trainers. At the same time, our national team still relies on manual timing or video analysis, which is not only inaccurate, but also time-consuming and labor-intensive, and has slow feedback.

How does the high-precision timing system work? It is a pressure detection belt installed in the track. When the bicycle passes through the detection belt, it will generate an electrical signal, which is received and processed by the tracking box to achieve timing. This type of system is not only expensive, but also has great shortcomings.

For example, the pressure detection belt in foreign countries currently uses two layers of curved copper sheets to achieve pressure detection of bicycles through contact and separation. This will lead to two crucial problems:

One is about materials. When a bicycle passes through the detection belt at high speed, the two layers of copper sheets collide and generate strong static electricity, which will affect the system and may cause inaccurate signal monitoring.

The second key problem lies in the two layers of curved copper sheets, which make the pressure detection belt relatively thick, just like a bump when driving over a speed bump. During the competition, when a bicycle passes through this raised detection belt at high speed, it will also bring a brief impact, causing the bicycle to slow down. This may bring great safety hazards, increase the risk of athletes falling or getting injured, and is also very unfavorable for racing.

Therefore, we urgently need to develop a more advanced high-precision timing system with independent intellectual property rights to achieve domestic substitution, which is of great significance for improving the core competitiveness of my country's track cycling.

To achieve this goal, the key is to break through the independent research and development of core sensor components of high-precision timing systems, including high-performance pressure detection belts, tracking boxes, start-up command consoles and software systems, etc.

How to achieve the goal?

In order to develop a more advanced pressure detection belt, we innovatively used nanotechnology to design a carbon nanotube composite material that is very sensitive to pressure.

Carbon nanotubes are a very unique conductive nanomaterial with a diameter 10,000 times thinner than a hair and a tensile strength 100 times that of steel, which can just solve the problem of the pressure belt being too thick.

The next step is to solve the problem of accuracy.

To this end, our team thought of many ways, and finally, it was the game sticks that brought us a lot of joy when we were young that gave us inspiration. Scattered game sticks can be connected together to form a network. You can imagine that if carbon nanotubes are also connected together to form such a network, stirring any one of them may significantly affect the performance of the entire network.

The sophisticated material composite process makes this conductive carbon nanotube nanomaterial scatter and interweave into a network. When a bicycle wheel passes quickly, tens of millions of carbon nanotubes will change their morphology and electrical properties in the small space under the wheel, causing the conductive network to fluctuate rapidly and significantly. In this way, we can accurately record the moment when the bicycle touches the detection belt.

Making carbon nanotubes into conductive ink

With the above design principles, the next step is to realize the high-sensitivity flexible pressure sensor belt device and batch production through repeated experiments, which is also one of the core challenges. To this end, we need long-term repeated exploration, trial and error, and iteration.

First, we disperse the carbon nanotubes in a reagent to make a uniform composite conductive ink. Its advantages are good uniformity and controllable fluidity. It can also be printed on many flexible substrate materials through printing or 3D printing.

Then, we continuously optimized the printing process and regulated the physical and chemical properties of the flexible substrate material to make the flexible substrate and the carbon nanotube composite film have a very strong bond, thereby increasing the stability of the device, so that the sensitive material will not fall off the surface of the flexible substrate during bending and use. Thus, we obtained this new type of thin and soft flexible pressure sensor.

It is only 0.3 mm thick, as thin as a piece of paper. Therefore, when the wheel passes quickly, it can greatly improve the accuracy of detection without causing the bicycle to slow down, which greatly improves safety. At present, our flexible pressure detection belt can be 8 meters long and can withstand more than 1 million times of repeated rolling by a bicycle at a speed of 90 kilometers per hour.

On this basis, we further overcame the difficulties of mass integrated molding of flexible pressure sensors, and through flexible packaging and interface design, we finally achieved the mass production of high-precision flexible pressure detection belts for track cycling tracking and timing.

At this point, we have completed the first step in developing a high-precision timing system.

Next, we deployed this world-first flexible pressure detection belt on the track cycling tracks in Beijing’s training venues in a distributed manner. There are more than 7 of them. This is the video of athletes passing through the flexible pressure detection belts one after another.

Control the counting error within one ten-thousandth of a second

The second step of our research is to quickly and synchronously transmit and process the signals detected by these flexible pressure detection belts, which is also a challenge.

To this end, we teamed up with Professor Zhong Daidi and Professor Huang Zhiyong from Chongqing University to establish a distributed time synchronization network to control the entire counting error to within one ten-thousandth of a second.

In addition, when riding a track bike at high speed, the tires and the floor will constantly rub against each other, accumulating a large amount of electric charge. When it comes into contact with the pressure belt, a strong discharge of more than 10,000 volts will occur, which will greatly affect the accuracy of information collection and the safety of the system.

Therefore, we adopted a variety of methods such as precise discharge, hardware isolation and software filtering to achieve harmless processing of some strong interference signals that may be generated by the outside world, ensuring the accuracy of data collection while ensuring the security of the system.

Accurately control the opening time of the launch gate

Before the start, the track bike is controlled by the starter. After the start countdown is up, the timing system delays 100 milliseconds to turn on the starter, and the athletes respond quickly and start.

This involves the third core component of the high-precision timing system: the starting command console.

In this process, the athlete's reaction speed is crucial to the performance. Generally speaking, athletes will repeatedly train based on the opening time of the starting gate to form muscle memory.

At the same time, this also requires us to accurately control the opening time of the gate when designing the starting device, and the control accuracy must reach one thousandth of a second. Otherwise, if it is too early, it will cause a "false start", and if it is too late, it will affect the athlete's performance.

The gate opening is a mechanical movement, and it is very difficult to control the accuracy of mechanical movement in such a short time. We have joined forces with the team from Chongqing University to use high-speed cameras combined with high-precision control algorithms to achieve precise control of the gate opening time, keeping the error within one ten-thousandth of a second.

Based on the above research, we collaborated with multiple groups through interdisciplinary research and finally achieved a high-precision timing system that broke the 0.001 second limit.

In the future, we will continue to optimize, such as introducing more sophisticated micro-nano structures, and by optimizing the mechanical and electrical models, further improving the pressure perception sensitivity of the flexible timing belt, and strive to increase the timing accuracy to the microsecond level.

In fact, these technologies can be used not only in track cycling competitions, but also in other sports events such as fencing and boxing. This flexible intelligent sensing technology can be used.

At the same time, our flexible intelligent sensing technology based on nanotechnology can more deeply coordinate information collection, transmission and processing systems to reduce counting errors; through intelligent algorithms, multi-technology combination and grid layout, we can achieve real-time and accurate perception of bicycle position and speed, bringing track cycling into a comprehensive intelligent era and making the sport more scientific.

How else can new materials be used to reduce resistance?

In fact, the application of new materials and new technologies in the Olympic Games is not limited to this.

We are also looking into the possibility of reducing bicycle resistance by incorporating bionic design, and have made some progress.

We teamed up with Professor Yuan Weizheng and Professor He Yang from Northwestern Polytechnical University to test and measure the frame, wheels, handlebars, cycling clothing, helmet and each rider's riding posture in a wind tunnel to find ways to reduce drag in these six areas.

We drew on the unique tongue-shaped fractal sand ridge structure of the Kumtag Desert in Xinjiang, my country. The undulating pattern of the sand ridge surface can affect the flow of wind and form a relatively smooth resistance distribution. This distribution can keep the wind at a high flow rate and flow rate when passing through the sand ridge, thereby reducing resistance and energy loss.

Inspired by this bionic design, we designed and manufactured the world's first sand-ridge-like micro-nanostructure drag-reducing film. Combining theories such as aerodynamics, we designed a unique micro-nanostructure for bicycle wheel rotors and helmets, achieving a 3% drag reduction rate.

At the same time, we have teamed up with Professor Su Weifeng's team from the Beijing Normal University-Hong Kong Baptist University United International College to use artificial intelligence methods such as motion estimation intelligent algorithms and computer vision technology to efficiently and intelligently analyze motion images. Combined with ground timing tapes, we have formed a multi-dimensional, multi-modal precise time and space judgment that can eliminate misjudgments in millisecond-level competitions.

We hope to build the most accurate clock through the intersection of multiple disciplines, combining nanotechnology, bionics, AI technology, etc., to make the competition fairer and contribute to the Olympic athletes' "faster, higher, stronger".

Planning and production

Author: Zhang Ting, Distinguished Visiting Researcher, Institute of Sports Science, General Administration of Sport of China, Member of the Board of Directors, Suzhou Institute of Nanotechnology, Chinese Academy of Sciences

Editor: Yang Yang

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