:
Photo: Dave Bullock/Wired.com
PASADENA, California – For all you moonshine makers who thought your hobby was
just a guilty pleasure, a new spin on distilling may actually help save lives. Using ancient
technology reduced to a microscopic scale, scientists at Caltech have created new tools to detect
disease and purify water using tiny stills.
The creation of the still around A.D. 500 was one of humanity's earliest, and still quite
popular, technological advancements. Traditionally, a still boils liquids in order to vaporize
and separate them. Now, using nanoparticles and lasers, liquids no longer need to be boiled to be
separated.
Removing the heat requirement from distillation means the process could be used to separate
living cells without killing them, which could lead to advanced disease detection. Other
applications include extracting water cheaply and efficiently from sea water in low-energy
saltwater distillation plants.
How do they do it? Take a tour through professor David Boyd's lab and go behind the scenes of
this revolutionary process.
Left: A green laser evaporates the water from a liquid. This is the final stage
of nano distillation.
:
Here is a diagram of the basic nano still technique. At top is the initial setup with gold
nanoparticles sitting on top of a glass slide. The fluid waiting to be distilled is enclosed from
above by a silicone rubber chip.
In the bottom diagram, a green laser operating near the resonant frequency of the gold particles
is applied. The laser heats the gold nanoparticles, which then transfer the heat to the
surrounding fluid. This small amount of heat is just enough to cause controlled evaporation over
the gas bubble barrier, leaving pure water on the right-hand side of the diagram.
Click through to the next photo to take a closer look at each of these steps.
Illustration: Chemical Separations by Bubble Assisted Interphase Mass-Transfer, David A.
Boyd, James Adelman, David Goodwin, and Demetri Psaltis
:
Photo: Dave Bullock/Wired.com
This spin coater is used to spread out the thin layer of gold nanoparticles on the glass slide. A
drop of the gold solution is placed on the slide and the coater spins extremely fast. This
spinning spreads the solution evenly and coats the slide with a nearly uniform 15-nanometer layer
of gold.
To get a controlled spacing of particles there needs to be a structure in place to hold them. To
achieve this, scientists add a polymer to the gold solution. This polymer forms a uniform lattice
to structure all the gold. But observant readers will notice there was no polymer in the previous
diagram. Where does it go? Click to the next photo to find out.
:
Photo: Dave Bullock/Wired.com
This is an oxygen etcher. Once the glass slide is covered with the polymer-and-gold solution,
this etcher burns off the polymer, leaving just the gold behind.
:
Photo: Dave Bullock/Wired.com
This is a sample slide covered with a matrix of gold nanoparticles. The purple streaks on the
slide are the nanoparticles, visibly spreading out from the initial drop applied to the slide
during the spin coating. For those readers expecting the entire slide to be purple, scientists
actually need only a small portion of the slide to be covered uniformly by the gold, so these
streaks will suffice.
The particles have a unique property of rapidly dissipating heat, which is a key factor in how
the still works.
:
Photo: Dave Bullock/Wired.com
In another part of the lab, the piece of silicone rubber is made. If you think back to the second
image in this gallery, you'll recall that the silicone rubber encloses the fluid between itself
and the glass slide. This piece of silicone is called the microfluidic chip because of the fluid
channels carved into it.
The machine pictured at left is called a mask aligner. It creates a mold for the microfluidic
chip. It does this by exposing an image (in this case, the shape and design of the chip) to a
photosensitive material. The unexposed portion of the material is discarded, and the shape of the
mold is all that's left. It's similar to a photo enlarger, but instead of a two-dimensional
image, a fully formed nano structure is made. The final mold is then used to create fluid
channels in a piece of silicone rubber. This silicone rubber ends up being the microfluidic chip.
:
Photo: Dave Bullock/Wired.com
Here, the silicone rubber chip is drilled to create ports for the nano still. These ports will be
used to inject solutions for distillation and to extract the distilled liquid.
:
Photo: Dave Bullock/Wired.com
Tiny plugs of silicone are the doughnut holes of the micro-fabrication world. Sadly, these plugs
will remain uneaten.
:
Photo: Dave Bullock/Wired.com
After fabrication of the microfluidic chip, we're ready to put it all together. The chip is glued
to the gold-coated slide that we made earlier (pictured at center-left inside petri dish). Now we
have a nano still, which has an electronic sensor attached for measuring the conductivity of the
fluid.
:
Photo: Dave Bullock/Wired.com
Sometimes science is messy. This workbench is covered with a collection of syringes and gold
nanoparticle-coated glass slides. The syringes are used to inject fluids through the ports into
the channels in the still, which we'll see in the next photo.
:
Photo: Dave Bullock/Wired.com
In this photo, blue "Smurf blood" food-grade dye is injected into the nano still through a
syringe. The dye makes it easy to see when the liquid has been distilled. The distilled water
will be clear and the remaining water will become darker due to the higher concentration of dye.
:
Photo: Dave Bullock/Wired.com
A low-powered green diode laser shines down into the still. The laser is roughly the same
strength as an off-the-shelf laser pointer. Very little energy is needed in the microdistilling
process thanks to the heat-dissipating properties of the gold nanoparticles.
Professor Boyd, the lead researcher on the project, reveals that this process was largely
discovered by accident. "We had this problem with [an] air bubble, so we started hitting it with
a laser. Instead of getting rid of it, we saw that we were actually causing the distillation
process to occur, which was completely unexpected," Boyd explains.
Â
Category: Lifestyle
Recommandations
)
and reject those that you are not interested in
(
)
