Triboluminescence
Encyclopedia
Triboluminescence is an optical phenomenon
in which light
is generated when material is pulled apart, ripped, scratched, crushed, or rubbed (see tribology
) through the breaking of chemical bonds in the material. The phenomenon is not fully understood, but appears to be caused by the separation and reunification of electrical charges. The term comes from the Greek
τριβείν (to rub
) and the Latin
lumen (light). Triboluminescence can be observed when breaking sugar crystals (especially Wint-O-Green Life Savers
) and peeling adhesive tapes.
Triboluminescence is often used as a synonym for fractoluminescence (a term sometimes used when referring only to light emitted from fractured crystals). Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when it is deformed, as opposed to broken. These are examples of mechanoluminescence
, which is luminescence
resulting from any mechanical action on a solid
.
Indians from Central Colorado are one of the first documented groups of people in the world credited with the application of mechanoluminescence
involving the use of quartz crystals to generate light. The Ute constructed special ceremonial rattles made from buffalo rawhide which they filled with clear quartz crystals collected from the mountains of Colorado and Utah. When the rattles were shaken at night during ceremonies, the friction and mechanical stress of the quartz crystals impacting together produced flashes of light visible through the translucent buffalo hide.
when he recorded in his 1620 Novum Organum
that "It is well known that all sugar
, whether candied or plain, if it be hard, will sparkle when broken or scraped in the dark." The scientist Robert Boyle
also reported on some of his work on triboluminescence in 1663. In the late 1790s, sugar
production began to produce more refined sugar crystals. These crystals were formed into a large solid cone for transport and sale. This solid cone of sugar had to be broken into usable chunks using a device known as sugar nips
. People began to notice that as sugar was "nipped" in low light, tiny bursts of light were visible.
A historically important instance of triboluminescence occurred in Paris in 1675. Astronomer Jean-Felix Picard
observed that his barometer
was glowing in the dark as he carried it. His barometer consisted of a glass tube that was partially filled with mercury. Whenever the mercury slid down the glass tube, the empty space above the mercury would glow. While investigating this phenomenon, researchers discovered that static electricity could cause low-pressure air to glow. This discovery revealed the possibility of electric lighting.
have not yet arrived at a full understanding of the effect, but the current theory of triboluminescence — based upon crystallographic, spectroscopic, and other experimental evidence — is that upon fracture of asymmetrical materials, charge
is separated. When the charges recombine, the electric discharge ionizes the surrounding air, causing a flash of light. Research further suggests that crystals which display triboluminescence must lack symmetry (in order to permit charge separation) and be poor conductors. However, there are substances which break this rule, and which do not possess asymmetry, yet display triboluminescence anyway. It is thought that these materials contain impurities, which confer properties of asymmetry to the substance. Much of the recent work on triboluminescence was done by Linda M. Sweeting at Towson University
.
may begin to glow while being rubbed. This occasionally happens to diamonds while a facet is being ground or the diamond is being sawn during the cutting process
. Diamonds may fluoresce blue or red. Some other rocks are triboluminescent, emitting light when rubbed together.
Ordinary friction tape
(the cloth type — not the shiny electrician
's tape) displays a glowing line where the end of the tape is being pulled away from the roll. In 1953, Russian scientists showed that triboluminescence caused by peeling a roll of Scotch Tape
in a vacuum
can produce energy equivalent to X-ray
s. In 2008, scientists working at UCLA performed an experiment that showed actual X-rays were produced, which were strong enough to leave an X-ray image of a finger on dental photographic paper
; they hoped to use their research to create a new type of x-ray imaging device.
Many self-sealing postal envelopes will produce a blue glow when opened in the dark or in low-light conditions.
Also, when sugar crystals are crushed, tiny electrical fields are created, separating positive and negative charges that then create spark
s while trying to reunite. Wint-O-Green Life Savers
work especially well for creating such sparks, because wintergreen
oil (methyl salicylate
) is fluorescent and converts ultraviolet light into blue light.
Some Band Aid wrappers and Breathe Right wrappers also glow bluish-green when unwrapped swiftly.
Powders in gel capsules can emit flashes of light that are visible in the dark. It may make a difference what the powder is. L-Tryptophan
is a sleep aid and essential amino acid. The house brand of L-Tryptophan gel capsules from the US chain store Vitamin Shoppe do this when being shaken out of the bottle.
from the fracture
(rather than rubbing) of a crystal
, but fracturing often occurs with rubbing. Depending upon the atom
ic and molecular
composition of the crystal, when the crystal fractures a charge separation can occur making one side of the fractured crystal positively charged and the other side negatively charged. Like in triboluminescence, if the charge separation results in a large enough electric potential
, a discharge across the gap and through the bath gas between the interfaces can occur. The potential at which this occurs depends upon the dielectric
properties of the bath gas.
This phenomenon can be demonstrated by removing ice from a freezer in a darkened room, under conditions in which the ice makes cracking sounds from sudden thermal expansion. If the ambient light is dim enough, flashes of white light from the cracking ice can be observed.
Optical phenomenon
An optical phenomenon is any observable event that results from the interaction of light and matter. See also list of optical topics and optics. A mirage is an example of an optical phenomenon....
in which light
Light
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
is generated when material is pulled apart, ripped, scratched, crushed, or rubbed (see tribology
Tribology
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear...
) through the breaking of chemical bonds in the material. The phenomenon is not fully understood, but appears to be caused by the separation and reunification of electrical charges. The term comes from the Greek
Greek language
Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...
τριβείν (to rub
Tribology
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study and application of the principles of friction, lubrication and wear...
) and the Latin
Latin
Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...
lumen (light). Triboluminescence can be observed when breaking sugar crystals (especially Wint-O-Green Life Savers
Life Savers
Life Savers is an American brand of ring-shaped mints and artificially fruit-flavored hard candy. The candy is known for its distinctive packaging, coming in aluminum foil rolls....
) and peeling adhesive tapes.
Triboluminescence is often used as a synonym for fractoluminescence (a term sometimes used when referring only to light emitted from fractured crystals). Triboluminescence differs from piezoluminescence in that a piezoluminescent material emits light when it is deformed, as opposed to broken. These are examples of mechanoluminescence
Mechanoluminescence
Mechanoluminescence is light emission resulting from any mechanical action on a solid. It can be produced through ultrasound, or through other means.* Fractoluminescence is caused by stress that results in the formation of fractures....
, which is luminescence
Luminescence
Luminescence is emission of light by a substance not resulting from heat; it is thus a form of cold body radiation. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. This distinguishes luminescence from incandescence, which is light emitted by a...
resulting from any mechanical action on a solid
Solid
Solid is one of the three classical states of matter . It is characterized by structural rigidity and resistance to changes of shape or volume. Unlike a liquid, a solid object does not flow to take on the shape of its container, nor does it expand to fill the entire volume available to it like a...
.
History
Uncompahgre Ute Indians
The Uncompahgre UteUte Tribe
The Ute are an American Indian people now living primarily in Utah and Colorado. There are three Ute tribal reservations: Uintah-Ouray in northeastern Utah ; Southern Ute in Colorado ; and Ute Mountain which primarily lies in Colorado, but extends to Utah and New Mexico . The name of the state of...
Indians from Central Colorado are one of the first documented groups of people in the world credited with the application of mechanoluminescence
Mechanoluminescence
Mechanoluminescence is light emission resulting from any mechanical action on a solid. It can be produced through ultrasound, or through other means.* Fractoluminescence is caused by stress that results in the formation of fractures....
involving the use of quartz crystals to generate light. The Ute constructed special ceremonial rattles made from buffalo rawhide which they filled with clear quartz crystals collected from the mountains of Colorado and Utah. When the rattles were shaken at night during ceremonies, the friction and mechanical stress of the quartz crystals impacting together produced flashes of light visible through the translucent buffalo hide.
Later descriptions
The first recorded observation is attributed to English scholar Francis BaconFrancis Bacon
Francis Bacon, 1st Viscount St Albans, KC was an English philosopher, statesman, scientist, lawyer, jurist, author and pioneer of the scientific method. He served both as Attorney General and Lord Chancellor of England...
when he recorded in his 1620 Novum Organum
Novum Organum
The Novum Organum, full original title Novum Organum Scientiarum, is a philosophical work by Francis Bacon, written in Latin and published in 1620. The title translates as new instrument, i.e. new instrument of science. This is a reference to Aristotle's work Organon, which was his treatise on...
that "It is well known that all sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
, whether candied or plain, if it be hard, will sparkle when broken or scraped in the dark." The scientist Robert Boyle
Robert Boyle
Robert Boyle FRS was a 17th century natural philosopher, chemist, physicist, and inventor, also noted for his writings in theology. He has been variously described as English, Irish, or Anglo-Irish, his father having come to Ireland from England during the time of the English plantations of...
also reported on some of his work on triboluminescence in 1663. In the late 1790s, sugar
Sugar
Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...
production began to produce more refined sugar crystals. These crystals were formed into a large solid cone for transport and sale. This solid cone of sugar had to be broken into usable chunks using a device known as sugar nips
Sugar nips
Before the introduction of granulated and cube sugars in the second half of the 19th century, the domestic consumer purchased sugar in the form of a sugarloaf , or at least a part of one, and pieces were cut from it by hand using sugar nips, pliers-like cutters...
. People began to notice that as sugar was "nipped" in low light, tiny bursts of light were visible.
A historically important instance of triboluminescence occurred in Paris in 1675. Astronomer Jean-Felix Picard
Jean Picard
Jean-Felix Picard was a French astronomer and priest born in La Flèche, where he studied at the Jesuit Collège Royal Henry-Le-Grand. He was the first person to measure the size of the Earth to a reasonable degree of accuracy in a survey conducted in 1669–70, for which he is honored with a...
observed that his barometer
Barometer
A barometer is a scientific instrument used in meteorology to measure atmospheric pressure. Pressure tendency can forecast short term changes in the weather...
was glowing in the dark as he carried it. His barometer consisted of a glass tube that was partially filled with mercury. Whenever the mercury slid down the glass tube, the empty space above the mercury would glow. While investigating this phenomenon, researchers discovered that static electricity could cause low-pressure air to glow. This discovery revealed the possibility of electric lighting.
Mechanism of action
Materials scientistsMaterials science
Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
have not yet arrived at a full understanding of the effect, but the current theory of triboluminescence — based upon crystallographic, spectroscopic, and other experimental evidence — is that upon fracture of asymmetrical materials, charge
Electric charge
Electric charge is a physical property of matter that causes it to experience a force when near other electrically charged matter. Electric charge comes in two types, called positive and negative. Two positively charged substances, or objects, experience a mutual repulsive force, as do two...
is separated. When the charges recombine, the electric discharge ionizes the surrounding air, causing a flash of light. Research further suggests that crystals which display triboluminescence must lack symmetry (in order to permit charge separation) and be poor conductors. However, there are substances which break this rule, and which do not possess asymmetry, yet display triboluminescence anyway. It is thought that these materials contain impurities, which confer properties of asymmetry to the substance. Much of the recent work on triboluminescence was done by Linda M. Sweeting at Towson University
Towson University
Towson University, often referred to as TU or simply Towson for short, is a public university located in Towson in Baltimore County, Maryland, U.S...
.
Examples
A diamondDiamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
may begin to glow while being rubbed. This occasionally happens to diamonds while a facet is being ground or the diamond is being sawn during the cutting process
Diamond cutting
Diamond cutting is the art, skill and, increasingly, science of changing a diamond from a rough stone into a faceted gem. Cutting diamond requires specialized knowledge, tools, equipment, and techniques because of its extreme difficulty....
. Diamonds may fluoresce blue or red. Some other rocks are triboluminescent, emitting light when rubbed together.
Ordinary friction tape
Friction tape
Friction tape is a type of adhesive tape made from cloth impregnated with a rubber-based adhesive and is mainly used to increase grip or friction. Because the adhesive is impregnated in the cloth, friction tape is sticky on both sides. The rubber based adhesive makes it an electrical insulator and...
(the cloth type — not the shiny electrician
Electrician
An electrician is a tradesman specializing in electrical wiring of buildings, stationary machines and related equipment. Electricians may be employed in the installation of new electrical components or the maintenance and repair of existing electrical infrastructure. Electricians may also...
's tape) displays a glowing line where the end of the tape is being pulled away from the roll. In 1953, Russian scientists showed that triboluminescence caused by peeling a roll of Scotch Tape
Scotch Tape
Scotch Tape is a brand name used for certain pressure sensitive tapes manufactured by 3M as part of the company's Scotch brand.- History :The precursor to the current tapes was developed in the 1930s in Minneapolis, Minnesota by Richard Drew to seal a then-new transparent material known as...
in a vacuum
Vacuum
In everyday usage, vacuum is a volume of space that is essentially empty of matter, such that its gaseous pressure is much less than atmospheric pressure. The word comes from the Latin term for "empty". A perfect vacuum would be one with no particles in it at all, which is impossible to achieve in...
can produce energy equivalent to X-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s. In 2008, scientists working at UCLA performed an experiment that showed actual X-rays were produced, which were strong enough to leave an X-ray image of a finger on dental photographic paper
Photographic paper
Photographic paper is paper coated with light-sensitive chemicals, used for making photographic prints.Photographic paper is exposed to light in a controlled manner, either by placing a negative in contact with the paper directly to produce a contact print, by using an enlarger in order to create a...
; they hoped to use their research to create a new type of x-ray imaging device.
Many self-sealing postal envelopes will produce a blue glow when opened in the dark or in low-light conditions.
Also, when sugar crystals are crushed, tiny electrical fields are created, separating positive and negative charges that then create spark
Electric spark
An electric spark is a type of electrostatic discharge that occurs when an electric field creates an ionized electrically conductive channel in air producing a brief emission of light and sound. A spark is formed when the electric field strength exceeds the dielectric field strength of air...
s while trying to reunite. Wint-O-Green Life Savers
Life Savers
Life Savers is an American brand of ring-shaped mints and artificially fruit-flavored hard candy. The candy is known for its distinctive packaging, coming in aluminum foil rolls....
work especially well for creating such sparks, because wintergreen
Wintergreen
Wintergreen is a group of plants. Wintergreen once commonly referred to plants that continue photosynthesis throughout the winter...
oil (methyl salicylate
Methyl salicylate
Methyl salicylate is a natural product of many species of plants. Some of the plants which produce it are called wintergreens, hence the common name.-Botanical background:...
) is fluorescent and converts ultraviolet light into blue light.
Some Band Aid wrappers and Breathe Right wrappers also glow bluish-green when unwrapped swiftly.
Powders in gel capsules can emit flashes of light that are visible in the dark. It may make a difference what the powder is. L-Tryptophan
Tryptophan
Tryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
is a sleep aid and essential amino acid. The house brand of L-Tryptophan gel capsules from the US chain store Vitamin Shoppe do this when being shaken out of the bottle.
Fractoluminescence
Fractoluminescence is often used as a synonym for triboluminescence. It is the emission of lightLight
Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Visible light has wavelength in a range from about 380 nanometres to about 740 nm, with a frequency range of about 405 THz to 790 THz...
from the fracture
Fracture
A fracture is the separation of an object or material into two, or more, pieces under the action of stress.The word fracture is often applied to bones of living creatures , or to crystals or crystalline materials, such as gemstones or metal...
(rather than rubbing) of a crystal
Crystal
A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions. The scientific study of crystals and crystal formation is known as crystallography...
, but fracturing often occurs with rubbing. Depending upon the atom
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
ic and molecular
Molecule
A molecule is an electrically neutral group of at least two atoms held together by covalent chemical bonds. Molecules are distinguished from ions by their electrical charge...
composition of the crystal, when the crystal fractures a charge separation can occur making one side of the fractured crystal positively charged and the other side negatively charged. Like in triboluminescence, if the charge separation results in a large enough electric potential
Electric potential
In classical electromagnetism, the electric potential at a point within a defined space is equal to the electric potential energy at that location divided by the charge there...
, a discharge across the gap and through the bath gas between the interfaces can occur. The potential at which this occurs depends upon the dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...
properties of the bath gas.
This phenomenon can be demonstrated by removing ice from a freezer in a darkened room, under conditions in which the ice makes cracking sounds from sudden thermal expansion. If the ambient light is dim enough, flashes of white light from the cracking ice can be observed.
External links
- Page on "wintergreen candy and other triboluminescent materials" from Towson University department of chemistry by Dr. Sweeting.
- 1997 article from science news explaining Dr. Sweeting's work.
- 2006 article "Sound science behind glowing sugar" on PhysicsWeb.
- Correlation between nanosecond X-ray flashes and stick–slip friction in peeling tape. Nature 455, 1089-1092 (23 October 2008) | doi:10.1038/nature07378