Intelligent Machines

From the Labs: Materials

New publications, experiments and breakthroughs in information technology–and what they mean.

Better Batteries
Nanotube ­electrodes deliver more power

Supercharged: Nanotube electrodes like the one shown here in cross-­section could boost battery power.

Source: “High-power lithium batteries from functionalized carbon-nanotube electrodes”
Yang Shao-Horn et al.
Nature Nanotechnology 5: 531-537

This story is part of our September/October 2010 Issue
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Results: A lithium-ion battery with a positive electrode made of carbon nanotubes delivers 10 times as much power as a conventional battery and can store five times as much energy as a conventional ultracapacitor.

Why it matters: Researchers have been trying to make battery electrodes from carbon nanotubes because they are highly conductive and have a large surface area, two characteristics that are important for power density and storage capacity. Lithium-ion batteries with nanotube electrodes could extend the range of electric vehicles and allow electronic gadgets, including smart phones, to work longer without recharging.

Methods: MIT scientists made dense, porous nanotube films by dipping a glass slide alternately in solutions of positively and negatively charged nanotubes. The films were then heat-treated and incorporated into a lithium-ion battery with a conventional negative electrode and electrolyte. When current was passed through the battery, lithium ions reacted with oxygen on the surface of the nanotubes. The electrodes’ porous structure improves energy density by providing a large number of reaction sites for the lithium ions, as well as an easy route in and out of the electrode.

Next steps: The researchers are developing a technique for spraying the nanotube solutions on the slide, which should speed up the process of making the films from days to hours. They have licensed the technology to an undisclosed battery company.

Artificial Antibodies
A polymer binds to toxins in the blood

Source: “Recognition, neutralization, and clearance of target peptides in the bloodstream of living mice by molecularly imprinted polymer nanoparticles: a plastic antibody”
Yu Hoshino et al.
Journal of the American Chemical Society 132: 6644-6645

Results: Studies in mice provide the first evidence that a lab-made antibody designed to bind to the bee-sting toxin melittin behaves like a natural antibody in animals.

Why it matters: Antibodies–proteins that bind tightly to specific targets–are widely used in diagnostics such as HIV tests and in treatments for cancer and other diseases. But they’re fragile and must be produced by living organisms, an expensive process. Stable artificial polymers that bind to specific molecules could bring down the price of medical diagnostics and broaden access to antibody therapies.

Methods: The researchers made a polymer with a high affinity for melittin by mixing the toxin with the polymer’s building blocks and triggering chemical reactions that link the building blocks together. The polymer grew around its target so that it was “imprinted” with the molecule’s shape. After being purified and tagged with a fluorescent molecule, the polymer was injected into mice that had previously been injected with melittin labeled in a different color. The researchers then used fluorescence imaging to track the molecules’ paths in real time. They determined that the artificial antibody bound to melittin in the blood and was then carried to the liver, the same path taken by natural antibodies.

Next steps: The researchers will use the same methods to make “plastic antibodies” that target other toxins more commonly associated with health risks.

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