Harpoon Your Brain
If you want to monitor overall brain activity, the standard way is to strap a headset on the victim, hook him up to an
electroencephalography (EEG) apparatus, and watch what
comes through the channels. Sometimes, though, scientists
want to study interactions between individual neurons to, e.g.,
better understand the computational complexity of the brain.
That can be a little tricky as it involves inserting tiny electrodes
into the cells, and existing ones have some shortcomings.
Metal electrodes record spikes but can't record the
computations performed by the cells. Glass probes can do
both but are fragile and can break off, leaving your brain full
of little shards.
Recently, a couple of professors at Duke University
( duke.edu) constructed a brain cell "nano-harpoon" out of
increasingly ubiquitous carbon nanotubes. The result is an
improved probe that is only a millimeter long and a few
"To our knowledge, this is the first time scientists have
used carbon nanotubes to record signals from individual
neurons — what we call intracellular recordings — in brain
slices or intact brains of vertebrates," noted Prof. Bruce
Donald, one of the probe's developers. "The new carbon
nanotubes combine the best features of both metal and glass
electrodes. They record well both inside and outside brain
cells, and they are quite flexible. Because they won't shatter,
scientists could use them to record signals from individual
brain cells of live animals," added Duke neurobiologist
To make the probe, they started with the tip of an
electrochemically sharpened piece of tungsten wire and
extended it with self-entangled multiwall carbon nanotubes,
which were further sharpened using a focused ion beam.
They then jabbed it into mouse brains to demonstrate that this
type of probe works at least as well as its glass counterparts —
so well that the team has applied for a patent. According to
the developers, the probes may be useful in applications
ranging from basic science to human brain-computer
interfaces and brain prostheses. ▲
■ Brain cell harpoon developed at Duke University.
Small Size, More Power
Also on the tiny side is a new microbattery developed by a research team from Harvard's
Wyss Institute ( wyss.harvard.edu) and the University
of Illinois at Urbana-Champaign ( illinois.edu). There
has always been a tradeoff between the size of a
battery and the amount of power it can provide,
which is a limitation for many miniaturized devices
such as flying insect-like robots, built-in microphones
and cameras, and other gadgets for which weight is
critical. One approach is to create very thin,
lightweight batteries using thin-film deposition
techniques. Because they are super thin, they just
don't pack enough power for many designs. The
Harvard/Illinois team reasoned that, if they could
come up with inks that have the right combination of
chemical and electrical properties, it would be
possible to create more powerful batteries using 3D
printing techniques. Turns out they were right.
They concocted one ink for the anodes and
another for the cathodes — each containing a
different lithium metal oxide compound. These were
deposited as layers on two gold combs to create an
interlaced stack of anodes and cathodes. Then, all
they had to do was drop the electrodes into a
container and fill it with electrolyte. The result is
functioning lithium-ion microbatteries the size of a
grain of sand.
According to one of the team members,
"The electrochemical performance is comparable to
commercial batteries in terms of charge and
discharge rate, cycle life, and energy densities.
We're just able to achieve this on a much smaller
scale." This breakthrough should be useful in the
development of many types of smaller devices in
medical and other fields. ▲
■ A Harvard/University of Illinois team creates
the first 3D printed microbattery.
■ BY JEFF ECKERT TECHKNOWLEDGEY 2013
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8 September 2013