Biomedical Engineering Reference
In-Depth Information
CHAPTER
11
Structural Colors
Natalia Dushkina
a
and
Akhlesh Lakhtakia
b
a
Department of Physics, Millersville University, Millersville,
PA 17551, USA
b
Department of Engineering Science and Mechanics, Pennsylvania State University,
University Park, PA 16802, USA
Prospectus
Structural colors originate in the scattering of light
from ordered microstructures, thin films, and even
irregular arrays of electrically small particles, but
they are not produced by pigments. Examples
include the flashing sparks of colors in opals and
the brilliant hues of some butterflies such as
Morpho
rhetenor
. Structural colors can be implemented indus-
trially to produce structurally colored paints, fabrics,
cosmetics, and sensors.
in nature. A visit to a large aquarium or an
extended stroll in a garden during spring reveals
the extensive panoply of bright colors that are
used for signaling and camouflage in the biologi-
cal world. Most of the colors in the animal world
are due to chemical pigmentation by dyes and
pigments. With a few exceptions, floral colors are
also of chemical origin
[1]
. Other colors--such as
the glowing reds and ochres of sunsets, the blue
and green hues of ocean water, the spectral colors
of rainbows, and the intense colors of some min-
erals, animals, and plants--have purely physi-
cal origins based on optical phenomena such as
refraction, reflection, scattering, interference, and
polarization of light. Our eyes cannot distinguish
colors based on their origin--physical, chemical,
or mixed--since ocular mechanisms are entirely
stimulated by rays or photons that seemingly
emanate from an object but carry no information
as to the mechanism of color production in that
object. Moreover, mental imagery is created by
electrical potentials and migrating ions in such
ways that make
color
, as opposed to frequency or
free-space wavelength, a partially psychological
construct.
Keywords
Beetle, Bird, Bragg filter, Bragg phenomenon, Butterfly,
Cholesteric liquid crystal, Circular Bragg phenomenon,
Colloid, Cosmetics, Diffraction, Dragonfly, Electrically
small particle, Fabric, Incoherence,
Infinite Color
TM
,
Inkjet printing, Interference, Jellyfish, Layer-by-layer
assembly, Latex, Multilayers, Nacre, Nacreous pigment,
Opal, Optical sensing, Physical vapor deposition, Play
of colors, Scattering, Sculptured thin film, Structural
color, Thermal imaging
11.1 INTRODUCTION: COLORS
IN NATURE
Humans, not to mention other animals, are fas-
cinated by and make use of colors that abound
