 |
|
MIT researchers have created a new
structured gel that can rapidly change color in response to a variety of
stimuli, including temperature, pressure, salt concentration and humidity.
(File Photo)
|
WASHINGTON, Oct. 21 (Xinhua) -- MIT researchers have created a new structured
gel that can rapidly change color in response to a variety of stimuli, including
temperature, pressure, salt concentration and humidity.
A paper describing the research work is published in
the Oct. 21 online edition of Nature Materials.
Among other applications, the structured gel could be
used as a fast and inexpensive chemical sensor, says Edwin Thomas, a professor
of materials Science and engineering at MIT.
One place where such an environmental sensor could be
useful is a food processing plant, where the sensor could indicate whether food
that must remain dry has been overly exposed to humidity.
A critical component of the structured gel is a
material that expands or contracts when exposed to certain stimuli. Those
changes in the thickness of the gel cause it to change color, through the entire
range of the visible spectrum of light.
Objects that reflect different colors depending on
which way you look at them already exist, but once those objects are
manufactured, their properties can't change. The MIT team set out to create a
material that would change color in response to external stimuli.
To do that, they started with a self-assembling block
copolymer thin film made of alternating layers of two materials, polystyrene and
poly-2-vinyl-pyridine. The thickness of those layers and their refractive
indices determine what color light will be reflected by the resulting gel.
By keeping the thickness of the polystyrene layer
constant and altering the thickness of the poly-2-vinyl-pyridine layer with
external stimuli such as PH and salt concentration, the researchers were able to
change the gel's color in fractions of a second.
The research team is also working on a gel that
changes color in response to applied voltages.
