Need energy? Just bounce the ball

The accelerated development of the internet of things (IoT) and big data over recent decades has seen huge change to a range of things in everything from homes to healthcare, security, environmental monitoring and communication.

But one of the most influential – and in many cases quite a bit more visible – applications of big data is to sports.

Data-driven services such as exercise performance, training statistics and play-by-play analysis have been turned to assist athletes and coaches in developing training and game strategies and are an increasingly indispensable tool for gaining a competitive edge.

So it was probably only a matter of time for someone to build a “smart” table tennis table – one that detects the impact of the ball and can measure its velocity, trace its path, and detect “edge ball” (whether the ball hits the top or side edge of the table).

Such a table has just been unveiled in a paper published in Nature Communications.

The smart table can provide real-time data to assist athletes in training, and referees in decision-making.

But the really cool thing is that its detection system is powered by the impact of the ball, thanks to triboelectric nanogenerators (TENGs).

Just think about that for a moment.

In order to acquire data in real time, most sports services rely on widely distributed sensors that are generally powered by conventional energy storage devices, such as batteries.

But batteries have a limited lifetime, high replacement or recharging costs and negative environmental impacts.

TENGs represent a sustainable and maintenance-free sensing technology. They can convert mechanical energy into electricity, with unique advantages of low cost, high efficiency, simple structure, and diverse material options.

By directly converting mechanical stimuli to electrical signals, TENGs can function as self-powered sensors for pressure, tactile, or motion sensing without extra power supply – a boon for the development of maintenance-free systems.

This means that TENG technology can be an effective power solution for the era of IoT.

The joint Chinese-American team, which was led by Zhong Lin Wang from the Georgia Institute of Technology, US, developed a wood-based triboelectric sensor for use in the smart table tennis table.

Most of the materials currently used in TENGs are synthetic polymers, which are non-degradable. Their extensive use could result in severe environmental pollution.

The study team chose to use natural wood – one of the most abundant resources on Earth. Wood is renewable, sustainable, and biodegradable, and it’s been widely used for a range of purposes.

However, it isn’t a naturally perfect material for fabricating TENGs.

The report details a simple and effective two-step process for fabricating wood films with excellent mechanical and triboelectric properties, enabling flexible, durable, and high-performance wood-based triboelectric nanogenerators (W-TENGs).

Using this special wood film, the smart table tennis table uses energy from the impact of table tennis balls to power a battery-free statistical collection system and an edge-ball judgement system.

The authors show that the system can collect data and display real-time statistics for impact position, velocity and motion-path tracing. Sensors were also strategically placed to distinguish between two kinds of edge balls: side edge ball and top edge ball.

The authors suggest that the work could lead to opportunities in athletic analytics and open up new avenues for wood-based electronics combined with self-powered systems.

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