Background

Although battery powered tennis rackets have been outlawed by the International Tennis Federation, the use of piezoelectrics that themselves generate power have been employed as the most recent development and are deemed legal by the sports’ governing body.

For the unitiated, piezoelectric materials produce an electrical current when subject to a deformation or loading such as a bending or compressive force. Under these circumstances they can be used in detectors and strain gauges. Similarly, if an electric current is applied to a piezoelectric material, it can induce a mechanical deformation. In this way thet can be used in actuators.
Incorporating Piezoelectrics Into Tennis Rackets

Piezoelectrics in the form of lead zirconate titanate (PZT) fibres have been embedded into the bodies of composite tennis racket frames, most notably in the head and throat.
How Do They Work?

When a player impacts a tennis ball with a piezoelectric equipped racket, it undergoes a slight deformation i.e. bending. The piezoelectric fibres generate an electrical current as a direct response to the deformation. The electric current is fed into a microchip located in the top of the handle. The microchip generates amplifies the piezoelectric effect and produces an electrical response that is fed back into the piezoelectric fibres producing a counterforce which in turn reduces bending. All this happening in the milliseconds while the ball is still on the strings.
What Are The Advantages of Using Piezoelectrics in Tennis Rackets?

The incorporation of piezoelectrics in tennis rackets has two advantages:

· The counterforce generated effectively produces a stiffer racket, helping the player to generate more power.

· The piezoelectric also reduced vibration that reaches the player, reducing the risk of tennis elbow, a common problem encountered by players who used aluminium framed rackets, common in the 1970’s. This also makes the racket more comfortable to use.
Who Makes Rackets Equipped with Piezoelectrics?

At the time of writing, the only manufacturer known to make rackets with piezoelectric electronics was Head.