Piezoelectric effect happens when a material produces electric charge once mechanical stress is applied to it. The meaning of the word “piezo” is “to stress.” It is a Greek word. There are many materials that have piezoelectric property. Some of these materials are crystals, ceramics, and bones. Ceramics that can produce piezoelectricity are called piezoceramics.
It was in 1880 that physicist brothers Pierre and Jacques Curie discovered piezoelectric effect. In 1957, Dr. Ivao Yasuda made the discovery that bones possess piezoelectric property.
There are two kinds of piezoelectric effect. These are direct and inverse. Direct piezoelectricity happens when a material produces electric voltage when it is compressed or pressed. Inverse piezoelectricity, on the other hand, occurs when a piezoelectric material becomes deformed when an electric field is applied to it.
Piezoelectricity in Bones
A bone is mostly made of bone matrix. Bone matrix has two parts. These are organic and inorganic. The organic part is mostly made of Type I collagen while the inorganic part is made of hydroxyapatite. Hydroxyapatite is the reason why bone can produce piezoelectricity.
How Bones Produce Piezoelectricity
The collagen molecules are made up of charge carriers. When a bone is stressed, the charge carriers go to the bone’s surface. When this happens, piezoelectricity is produced.
How Piezoelectricity Increases Bone Density
When a bone produces piezoelectricity due to the stress applied to it, electrical dipoles are formed. Electric dipoles attract osteoblasts, the cells that build bones. Osteoblasts deposit calcium and other minerals on the part of the bone that is stressed. This increases the density of the bone.
Importance of Piezoelectricity to Bones
Piezoelectricity is good for bones because it can repair and heal bones. Also, bones can be remodeled with the help of piezoelectricity. This was discovered in 1892 by Dr. Julius Wolff. This effect of piezoelectricity to bones is also called Wolff’s Law.