Color Control Technology using Candy Light-emitting Principle
team led by Dr. Soon Moon Jeong developed a mechanoluminescence color control
technology that can change green light to red light by simulating the candy
light-emitting principle. The technology is expected to be used for displays
and lights that require no external electricity.
mechanoluminescence: a method of light emission that requires no external
electric power and which applies a mechanical force to a material to cause motion
and the recombination of electrons in the material that in turn transmits
mechanical energy to light energy.
The research team noted that blue light is emitted when
wintergreen-flavored candy (ex. Lifesavers) is bitten or smashed. In general,
it is known that mechanoluminescence in the ultraviolet region is generated
when the sugar component in the candy is broken. Natural vegetable oil is a
material that generates a blue color by absorbing ultraviolet, thus
wintergreen-flavored candy containing natural vegetable oil emits a blue light
when it is smashed.
The research team thus combined this phenomenon with
mechanoluminescence research and developed a color control technology that
allows the existing green light in the mechanoluminescence material to be
absorbed and red light to be generated by mixing single green
mechanoluminescence material and organic fluorescent dye.
When rubbing a substrate that is coated with organic
fluorescent dye with a mixture of mechanoluminescence materials (ex. ZnS and PDMS)
and silicone rubber, the mechanoluminescence materials that are heavier than the
silicon rubber will sink to the bottom of the substrate, while the silicon
rubber is being hardened and the organic fluorescent dye will be evenly spread over
its top forming a natural double-layered structure. An experiment confirmed
that when mechanical force is applied on the substrate, the light-emitting
layer in the mechanoluminescence material generates green light, and the color
conversion layer where the organic fluorescent dye is spread on the rubber converts
this green light into red light.
Through these experiments, the team proved that it is
possible to express a variety of colors depending on the mixture ratio of the single
mechanoluminescence materials and organic fluorescent dye. Color conversion
efficiency can also be increased through the diffusion of the organic
fluorescent dye. Further, this structure can be applied to an electric field
that generates light electrically, so the team also developed a hybrid element
implementing patterns that enable mechanoluminescence light-emission and
electrical light emission simultaneously yet independently.
In contrast to existing studies that relied on the
development of mechanoluminescence materials based on the fact that
mechanoluminescence material affects the color of light produced, the findings
of this study have been evaluated highly in the sense that they pioneered
mechanoluminescence color control technology by enabling a larger variety of
color expression by combining organic fluorescent dye.
This mechanoluminescence light-emitting phenomenon can
be applied to displays, lights, and sensors without external electric power;
thus, it is expected to be used in the development of environment-friendly
displays that cause no energy or environmental problems.
Dr. Soon Moon Jeong from Division of Nano and Energy
Convergence Research said, “The core of this study is that we discovered that a
variety of colors can be generated by combining mechanoluminescence materials
as well as organic fluorescent dye that are widely and commonly used. I’ll
continue to conduct research that improves energy and environmental issues by
using mechanoluminescence phenomena.”
This research outcome was published in Advanced Functional Materials, a world-renowned
international journal in the materials science field, on July 19, 2016.
Soon Moon Jeong, Seongkyu Song, et.
al., “Mechanoluminescence Color Conversion by Spontaneous
Fluorescent-Dye-Diffusion in Elastomeric Zinc Sulfide Composite”, Advanced
Functional Materials 2016.