Whitesides also wants to develop tests for
infectious diseases such as tuberculosis.
To disseminate the technology,
Whitesides cofounded the nonprofit
Diagnostics for All in Brookline, MA, in
2007. It plans to deploy the liver function
tests in an African country around the end
of this year. The team hopes that eventually, people with little medical training
can administer the tests and photograph
the results with a cell phone. Whitesides
envisions a center where technicians and
doctors can evaluate the images and send
back treatment recommendations.
“This is one of the most deployable
devices I have seen,” says Albert Folch,
an associate professor of bioengineering at the University of Washington, who
works with microfluidics. “What is so
incredibly clever is that they were able to
create photoresist structures embedded
inside paper. At the same time, the porosity of the paper acts as the cheapest pump
on the planet.”
Recently, the Harvard researchers have made the paper chips into a
three-dimensional diagnostic device by
layering them with punctured pieces of
waterproof tape. A drop of liquid can
move across channels and into wells on
the first sheet, diffuse down through the
holes in the tape, and react in test wells on
the second paper layer. The ability to perform many more tests and even carry out
two-step reactions with a single sample
will enable the device to detect diseases
(like malaria or HIV) that require more
complicated assays, such as those that use
antibodies. Results appear after five minutes to half an hour, depending on the test.
The researchers hope the advanced
version of the test can eventually be mass
produced using the same printing technology that churns out newspapers. Cost
for the materials should be three to five
cents. At that price, says Folch, the tests
“will have a big impact on health care in
areas where transportation and energy
access is difficult.” —Kristina Grifantini
DISCHARGED
■ Magnesium
■ Electrolyte
■ Antimony
1 The molten active components (colored bands) of a new grid-scale
storage battery are held in a container that delivers and collects electrical current. Here, the battery is ready to be charged, with positive
magnesium and negative antimony ions dissolved in the electrolyte.
ENERGY
Liquid Battery
Donald Sadoway conceived of a novel battery that
could allow cities to run on solar power at night.
Without a good way to store
electricity on a large scale,
solar power is useless at
night. One promising storage option
is a new kind of battery made with
all-liquid active materials. Prototypes
suggest that these liquid batteries
will cost less than a third as much as
today’s best batteries and could last
significantly longer.
The battery is unlike any other. The
electrodes are molten metals, and
the electrolyte that conducts current between them is a molten salt.
This results in an unusually resilient
device that can quickly absorb large
amounts of electricity. The electrodes
can operate at electrical currents
“tens of times higher than any [bat-
tery] that’s ever been measured,” says
Donald Sadoway, a materials chemistry professor at MI T and one of the
battery’s inventors. What’s more, the
materials are cheap, and the design
allows for simple manufacturing.
The first prototype consists of a
container surrounded by insulating
material. The researchers add molten
raw materials: antimony on the bottom, an electrolyte such as sodium
sulfide in the middle, and magnesium at the top. Since each material
has a different density, they naturally
remain in distinct layers, which sim-plifies manufacturing. The container
doubles as a current collector, delivering electrons from a power supply,
such as solar panels, or carrying them
