Download The Piezoelectric Effect

The Sustainable Dance Floor
If you have ever set foot in a dance club, you understand
the importance of bright lights, stimulating music and
speakers that blast music so loud you can feel it vibrating
beneath your skin. Now imagine that the dance floor could
sense your energy and replay it back. As you dance harder,
the floor glows brighter. As you jump up and down, beams
of light explode through the room to the beat of your
movement. This idea is no longer trapped in the idealistic
imaginations of club hounds; the Sustainable Dance Floor
has recently become a reality.
Figure 1: Sustainable Dance Floor
The Sustainable Dance Floor (SDF) morphs dancing and
moving people into a sustainable source of energy using a phenomenon called the piezoelectric effect.
The energy produced by movement is converted into electricity that is used to make the dance floor
react to the public in an interactive way. As you move, it moves. To create electricity, the floor will
compress slightly when being stepped on. In order for this compression to produce power, the floor
must be made with a special material called a piezoelectric. To properly explain the piezoelectric effect
and how it is used for sustainable energy, a few foundational engineering principles must be explained
as a preface.
1.0 Engineering Principles
With the global attempt to make most of the world a ‘greener’ place, piezoelectricity has been recently
pushed into the limelight as an undeniable source for sustainable energy. The science behind this theory
can be a little difficult to wrap your mind around, but it can be broken down into two basic engineering
principles. Understanding the physics behind the dipole moment and net polarization is imperative in
the effort to grasp the idea behind piezoelectric effect.
1.1 The Dipole Moment
Ions exist in all materials, acting as building blocks of a molecular structure. These charged atoms move
throughout the material and can induce a polarity within a specific grain at any time. A polarity is
created when there is a noticeable concentration of positive ions on one side of a molecule and negative
ions on the other. Therefore, it can be said that one half of the molecule has a positive charge and the
other has a negative charge. This occurrence, a dipole moment, can be defined as the measure of
polarity in a chemical bond or molecule, equal to the product of one charge and the distance between
the two charges. Figure 2A displays a material in which the dipoles within each grain are randomly
oriented. This property is referred to as non-symmetric polarization. Materials must exhibit this quality
in order to be able to demonstrate the piezoelectric effect.
1.2 Polarization
In order for a material to be able to exhibit an electric field when placed under mechanical stress, a net
polarization must exist throughout the structure. A net polarization is the displacement of positive and
negative electric charge to opposite ends of a system, especially by subjection to an electric field (Figure
2B). This polarization can be accredited to a series of dipoles present in each individual grain of the
crystal structure. If the structure has a center of symmetry, any dipole moment generated in one
direction would be forced by symmetry to be zero; therefore, piezoelectric materials must be nonsymmetric. In order for a material to exhibit a net polarization, the material requires that the central
atom be in a non-equilibrium position. If this is the case, there exists an inherent dipole moment in the
structure, resulting in a polarization.
Figure 2: A. Series of random dipole moments within a material B. When an electric field is applied
across the material, a net polarization is induced C. The polarized piezoelectric material, exhibiting
the net charge among the individual grains
2.0 Piezoelectric Materials
When a piezoelectric material is placed under a mechanical stress (stretching, squeezing or twisting), the
atomic structure of the crystal changes and a dipole moment is formed. These dipoles are created
throughout the entire material, inducing a net polarization by the process explained in sections 1.1 and
1.2. This polarization results in an electric field across the material, which can be utilized as an energy
source immediately, or stored for later use. Voila, a sustainable source of energy.
2.1 The Piezoelectric Effect Dance Floor
Figure 3: Piezoelectric effect on the SDT
Figure 3 explains how the Sustainable Dance Floor
utilizes the piezoelectric effect in four simple
steps. In the first image, the dance floor is
presented, constructed with piezoelectric blocks
sitting on springs that compress when someone
steps on them. In the second and third images, it
is shown how a slight compression of the floor
triggers the electrical current through the
piezoelectric material, which is then sent to
battery generators nearby. The fourth and final
image explicates how the batteries are used to
power various parts of the nightclub (including
the dance floor), and are continually recharged as
the dance floor is occupied.
The Sustainable Dance Floor is just one method of using piezoelectric materials for sustainable energy
purposes. Ultimately, this concept could be applied to sidewalks, athletic fields, subway stations,
anything with heavy human traffic. If society continues to strive for a sustainable lifestyle, piezoelectric
materials will, without a doubt, grow more and more prevalent. The Sustainable Dance Floor proves that
technology remains a relentless source of improvement of life on a daily basis; however, it is the
innovative thinking behind that technology, which is the true foundation for our development towards a
more efficient way of life.