Chameleon-like camouflage: 'Nano-camo' for fashionistas and environmentalists

Apr 17, 2009
Sandia researcher George Bachand examines an enlargement of actual images of light-emitting quantum dots. These ride microtubules that have spontaneously formed stable circles of about 5 microns diameter. The picture superimposes two separate images - one of green rings and one of red - for visual effect. The images were processed to remove noise and maximize contrast. (Photo by Randy Montoya)

(PhysOrg.com) -- Certain fish species blend with their environment by changing color. Sandia National Laboratories researchers have demonstrated that, in theory, they could cause synthetic materials to change color like fish do.

“Camouflage outfits that blend with a variety of environments without need of an outside power source — say, blue when at sea and then brown in a desert environment — is where this work could eventually lead,” says principal investigator George Bachand. “Or the same effect could be used in fabricating chic civilian clothing that automatically changes color to fit different visual settings.”

Such clothing could be a reality in five to ten years, he says.

The power source for both the biological and the lab method relies on the basic cellular fuel called ATP, which releases energy as it breaks down. Fifty percent (roughly) is absorbed by the motor proteins — tiny molecular motors able to move along surfaces.

When fish change colors, motor proteins aggregate and disperse skin pigment crystals carried in their “tails” as they walk with their “feet” along the microtubule skeleton of the cell. By this means, they rearrange the color display.

Introducing an on/off switch

To put motor proteins in motion or switch them off, nature uses complex signaling networks. The Bachand group’s method is simpler. It involves the simple genetic insertion of a kind of docking port in the motor protein’s structure. What docks are zinc ions. Bound zinc ions turn the protein’s action to “off.” Stripping zinc ions out with chemical agents allows the motor protein to work again. The effect is controllable, and even reversible.

“We essentially reengineered the to introduce a switch into the motor,” says Bachand. “So we can now turn our nanofluidic devices on and off.”

Previous efforts at regulating motor activity have used fuel intake as a control mechanism: the less the fuel, the slower the process. The Bachand group’s switch, operated independently of fuel changes, resembles the improvement in early automobile technologies when a simple ignition switch took over for more complicated rheostats. The paper describing this work was a spotlighted article in the journal Biotechnology and Bioengineering (vol. 100, p. 478).

But what is it that the switch operates?

Scanning electron microscope image (tinted) of forming rings (Photo by Bonnie McKenzie and Erik Spoerke, Sandia National Laboratories)

Like crowd surfers at a rock concert

In a cover article in the high-profile journal Advanced Materials (Dec. 2, 2008), the Sandia team describes a kind of inverted cellular world, where motor proteins do not run about but instead are upended so that their tails are embedded in a protein-modified layer on a glass slide. Free-ranging microtubules — cylindrical protein filaments — instead of forming the cellular skeleton of cells, are passed along by the waving feet of the motor proteins like crowd surfers at a rock concert, or like buckets passed hand-to-hand along a line of firefighters.

The traveling microtubules are coated with quantum dots — nanoscopic groups of atoms that emit light, their frequency dependent on dot size.

The dots emit different frequency of light than they adsorb, while the biological system merely reflects incoming wavelengths. But they perform similar coloring functions.

The telephone cord twist

When motor-transported microtubules collide, the microtubules stick together and twist until they resemble a desk phone cord. The twisting process ultimately forces the formation of stable rings approximately five micrometers in diameter. Their docked quantum dots (cadmium selenide) produce a range of light frequencies.

When mechanical strain in the rings causes them to rupture, the cracked segments are tugged out by the nearby motors until the ring is completely disassembled. The formation and destruction of the two states — free microtubules and rings — can be reversibly controlled.

Thus the dots can be tightly packed or dispersed — optically, an essential ingredient in the perception of color change.

Mimicking fish

The process resembles the action of fish color changes, which require one group of motor proteins carrying pigments to be “on” all the time while a second group of is turned on by complex biological processes at the right time. This produces a tug-of-war between motor groups that results in pigment dispersion and ultimately a color change. When the second motor is switched off, the color returns to the ground aggregate state.

“Our overall process mimics the fish,” says Bachand. “We essentially go from a dispersed particle state to a concentrated one and then back again to dispersed, similar to the fish. Thus, in principle, the mechanism could produce a color change. The underlying science provides a new basis for materials scientists to begin working toward real-world applications.”

Provided by Sandia National Laboratories (news : web)

Explore further: Thinnest feasible nano-membrane produced

add to favorites email to friend print save as pdf

Related Stories

One-dimensional Diffusion Accelerates Molecular Motors

May 12, 2006

Max Planck scientists have identified a new strategy which motor proteins use to move. The research was carried out by Prof. Jonathon Howard and Stefan Diez at the Max Planck Institute of Molecular Cell Biology ...

Biological motors sort molecules one by one on a chip

May 11, 2006

Researchers from Delft University of Technology’s Kavli Institute of Nanoscience have discovered how to use the motors of biological cells in extremely small channels on a chip. Based on this, they built ...

Motor proteins may be vehicles for drug delivery

Mar 20, 2009

Specialized motor proteins that transport cargo within cells could be turned into nanoscale machines for drug delivery, according to bioengineers. Chemical alteration of the proteins' function could also help inhibit the ...

Roadworks on the motorways of the cell

Dec 28, 2006

A cell is a busy place. In a permanent rush hour, molecules are transported along a dynamic motorway system made up of filaments called microtubules. Microtubules constantly grow and shrink and are rapidly ...

Recommended for you

Thinnest feasible nano-membrane produced

4 hours ago

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

7 hours ago

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Making 'bucky-balls' in spin-out's sights

Apr 16, 2014

(Phys.org) —A new Oxford spin-out firm is targeting the difficult challenge of manufacturing fullerenes, known as 'bucky-balls' because of their spherical shape, a type of carbon nanomaterial which, like ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

JoPrints
not rated yet Jun 15, 2009
Just amazing, I am trying to develop temporary printing inks that could offer the same sorts of capabilities as this... However the above technology, unlike my conceptual idea, is actually a real possibility now. I would love to no more about this facinating research! Any papers published yet?

More news stories

Thinnest feasible nano-membrane produced

A new nano-membrane made out of the 'super material' graphene is extremely light and breathable. Not only can this open the door to a new generation of functional waterproof clothing, but also to ultra-rapid filtration. The ...

Wiring up carbon-based electronics

Carbon-based nanostructures such as nanotubes, graphene sheets, and nanoribbons are unique building blocks showing versatile nanomechanical and nanoelectronic properties. These materials which are ordered ...

Hackathon team's GoogolPlex gives Siri extra powers

(Phys.org) —Four freshmen at the University of Pennsylvania have taken Apple's personal assistant Siri to behave as a graduate-level executive assistant which, when asked, is capable of adjusting the temperature ...

Better thermal-imaging lens from waste sulfur

Sulfur left over from refining fossil fuels can be transformed into cheap, lightweight, plastic lenses for infrared devices, including night-vision goggles, a University of Arizona-led international team ...

Researchers discover target for treating dengue fever

Two recent papers by a University of Colorado School of Medicine researcher and colleagues may help scientists develop treatments or vaccines for Dengue fever, West Nile virus, Yellow fever, Japanese encephalitis and other ...