The 83rd JSAP Autumn Meeting 2022 Highlighted Presentations
October 24, 2022

Discovery of static-electricity-induced luminescence (SEL) sensing materialFirst Material Capable of Visualizing Static Electricity inApproximately 2,600 Years
Tadashi Terasaki, Kazuya Kikunaga
Sensing System Research Center, National Institute of Advanced Industrial Science and Technology (AIST)

summary• Discovered and developed static-electricity-induced luminescence (SEL), an electrostatic
luminescence material that can visualize static electricity under visible light.
• For the first time in the world, the distribution of static electricity can be visualized byluminescence.
• This research has the potential to open up a variety of application fields, including
industrial applications such as improving the aerodynamics of automobiles andelucidating the mechanism of static-electricity-related accidents.

A research group led by Tadashi Terasaki and Kazuya Kikunaga at the Sensing System Research Center of
the National Institute of Advanced Industrial Science and Technology (AIST) has discovered and developed
static-electricity-induced luminescence (SEL), an electrostatic emitting material that can visualize static
electricity under visible light. SEL is the world’s first electrostatic sensor that has succeeded in capturing andvisualizing the distribution of static electricity on various curved surfaces. It has the potential to open up
various application fields, including industrial applications in device development and improvement of
aerodynamic characteristics of automobiles, elucidation of the mechanism of static-electricity-relatedaccidents, and solution development.

detailRemoving static electricity improves automobile performance! The mystery of static
electricity around us
Static discharge is a very familiar phenomenon. For example, when you try to touch a doorknob inwinter, you get a momentary shock. However, many things about static electricity remain unclear.
A research group at the Sensing System Research Center of the National Institute of Advanced
Industrial Science and Technology (AIST) has developed SEL, a paint- or sheet-type sensor thatcan visualize static electricity under visible light (Figure). It has the potential to open up a variety ofapplication fields, including industrial applications such as device development and elucidation of
the mechanism of static-electricity-related accidents.
You may wonder, “What is the point of knowing about static electricity if it is so familiar?” Further,you may think, “What is the use of knowing about static electricity?” Elucidating the mechanism ofstatic electricity has great value because static electricity is believed to affect the aerodynamic
characteristics of automobiles and to cause serious fires.
Studying static electricity is difficult because it is invisible. Consequently, although static electricity
has long been studied, much about it remains unknown. The philosopher Thales provided the mostclassical description of the mechanical phenomenon of electrostatics in around 600 BC upon
discovering that frictional charges attract feathers. However, the phenomenon of electrostatic
charge itself was not treated as a natural science until the 16th century. The original idea ofelectrostatic precipitation was born at this same time; however, it was only realized in the 20thcentury.
Static electricity is a well-known phenomenon, but there are many aspects about it that are notunderstood. SEL is a fine ceramic particle that can be used as a paint and can therefore be applied
to any curved surface. Further, Tadashi Terasaki of the research group noted that it has theadvantage of being observable in visible light.
Kazuya Kikunaga of the research group noted that the ability to apply the coating to curved
surfaces and to obtain information on the distribution of electrostatic charges is very useful inresearch. Capacitance-type electrostatic sensors have been developed previously; however,measuring static electricity accurately on objects with uneven surfaces is difficult.
For example, attaching an aluminum tape to automobiles is empirically known to improve theiraerodynamic characteristics by eliminating static electricity. However, the location on the car where
static can be eliminated most efficiently is unclear. We aim to quantify this empirical phenomenon
by using SEL electrostatic sensing and linking it to industrial applications. For this purpose,knowing the distribution of the electrostatic charges on curved surfaces is important.
Static Electricity Has Become Visible after 2600 Years
The search for novel materials began with the arrangement of all shiny candidate materials on atable. The discovery ultimately resulted from a miraculous coincidence.
We tried all glowing materials, including EL materials that emit light when exposed to electricity,light-storing materials that store and emit light, and stress-emitting agents that emit light in
response to the force applied to them. Coincidentally, we found that the material SrAl2O4:Eu2+

glows in response to weak electricity from ions and charged particles in the air. The chemical
formula of this material is very similar to that of afterglow materials such as luminescent tape.
Terasaki noted that they are currently surprised by the discovery that this sensor represents andare analyzing its luminescence mechanism in detail.
The research team is currently repeating electrostatic sensing experiments by applying SEL tovarious objects. The experimental process involves a series of interesting discoveries. For
example, experiments using SEL have shown that charge transfer already occurs between
charged and discharged objects before the static electricity shock occurs. Kikunaga noted that they
are currently very interested in observing the actual state of static electricity for the first time in theworld.
Kikunaga now hopes to apply SEL to improve the aerodynamic characteristics of automobiles andto prevent industrial accidents.
Kikunaga stated that the fastest application of SEL can be expected in the automotive industry, as
major automotive companies have already commercialized aluminum tapes for static electricity
removal. Further, static-electricity-related accident prevention is a socially significant application.
For example, in 2017, an explosion accident caused by static electricity resulted in death andinjury. The use of this technique to prevent such accidents from happening would be beneficial.
Now that static electricity has become visible some 2,622 years after its description by thephilosopher Thales, it will be very exciting to see how SEL unravels the nature of static electricity inthe future.

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figures

SEL is characterized by its ability to visualize the distribution of static electricity under visible light by emitting light. The
above photo was taken with a smartphone camera, and not a specialized camera.

A film to which SEL is added is irradiated with a static electricity generating gun. Static electricity can be observed as
green luminescence.