Chromophorism
by Heather - Thursday, August 9, 2012, 02:45 AM
Chromatophores of the squid
Chromophorism is a fascinating strategy employed by
several species to change their appearance rapidly in
order to camoflauge themselves, distract attackers or
attract mates. Researchers Jonathan Rossiter, Bryan Yap
and Andrew Conn explored how these abilities could be
artificially recreated. By doing so the possibility for usage
in camouflage, thermal regulation and photovoltaics
could become more available to us.
Two different mechanisms are employed by organisms to
achieve these types of optical metamorphoses.
Cephalopod chromatophores, pigment containing cells,
utilize muscle contraction in their surface soft tissues. These specialized muscles are connected to small
packs of pigment called saccules. When the muscles are stimulated to contract, they allow the saccules
to expand and the pigment within to cover more surface area, thus changing the look of the organism.
This technique is very fast responding and allows for intricate patterns to form. Zerbrafish, on the other
hand, utilize hydrostatic pressure to pump pigmented fluid located below the skin surface to the surface
to manifest a color change. This is a slower acting means of color change but the color intensity is
greater as the pigment isn’t simply spread out but input directly into the specialized display cells.
Typical Cephalapod Chromatophore
In the lab, dielectric elastomers, or DEs, were utilized to
artificially simulate the behavior of the chromatophores
in both cases explained above. DEs are a polymer
material which when connected to electric circuit
change shape when a voltage is applied and then return
to their original shape when the voltage is disengaged.
For the cephalopod chromatophores, a disc of DE
membrane was designed and connected to a voltage
supply. When the voltage was applied, the pigment
spot expanded. This process was performed with three
discs of artificial chromatophore, as well, and expansion
again occurred when voltage was applied.
Click here to see a clip of the lab-simulated behavior of the cephalapod chromatophores
Success was also achieved when mimicking the zerbrafish melanophores (called melanophores since
color change only occurs between black and white). Two DEs were connected to both sides of a silicon
molded ink cell sandwiched between two glass slides. The researchers were able to successfully pump
two inks – one clear, the other black – in alternating fashion, in and out of the ink cell, thus changing the
color.
Click here to see a lab-simulated clip of the behavior in the lab of a zebrafish melanophore.
The bioinspired products that could emerge from this technology could go far beyond color change.
Thermal regulation products that can regulate the movement of heating or cooling substances could be
created. One usage I thought of was a covering that would aid in the regulation of the body
temperatures of premature babies who are unable to do so for themselves, yet. Because one of the
unique uses of this technology is that is requires soft tissues, blankets could be developed so that
mothers could hold their tiny infants much earlier whereas now the infant is often sequestered to its
incubator.
Photovoltaic skins were another suggestion made by the researchers. Regulating the exposure of
photosensitive material to light could allow for a more efficient a capturing role in new solar energy
technologies.
Finally, camouflage is an obvious product that could emerge. The new technology would benefit the
camouflage in that it is active and able to respond to different conditions and, as noted earlier, it is a
technology utilized in soft tissue, thus in flexible, movable materials like uniforms.
These product possibilities will find their way into further development and usage, from my vantage
point for two reasons:
1) If the military (and the government that funds the military) sees the benefit to the safety of
its troops the development will be funded. Many of our technologies came out of development
for military usage and this would be another example. In fact, in one article I found, research
was being performed by the Air Force Research Laboratory.
2) If energy conservation and clean energy demands increase need for more efficient solar
energy capture could meet some of this demand. The harvesting of solar energy is quite
inefficient at this time. The usage of photovoltaic materials that are able to respond to changing
conditions could improve this making it more useful and beneficial to the consumer.
I would definitely classify chromophorism as a bioinspired technology. The researchers were exploring
and developing artificial mechanisms that mimic the fluctuations in chromatophores – not the other
functions and abilities of the organisms of interest. They also discussed other means of using the
phenomena they recreated other than simply for color change but for thermal regulation and
photovoltaics as well.
References
Biomimetic chromatophores for camouflage and soft active surfaces. Jonathan Rossiter et al 2012
Bioinspir. Biomim. 7 036009 doi:10.1088/1748-3182/7/3/036009
Halford, Bethany. “Cephalopod camouflage inspires materials research.” Chemical and Engineering
News 85.46 (2007): 49-50. http://pubs.acs.org/cen/science/85/8546sci2.html
Squid and zebrafish cells inspire camouflaging smart materials. Phys.org, 2 May 2012. Web. 05 Aug.
2012. http://phys.org/news/2012-05-squid-zebrafish-cells-camouflaging-smart.html .