When it comes to
sending and receiving information, man-made devices utilize negatively-charged
particles commonly known as electrons. Biological systems such as human bodies,
on the other hand, use protons via positively charged hydrogen atoms or ions. This
would indicate that there is something of a language barrier, when we try to
develop electronic devices that can communicate with living systems. That
barrier could be on its way down, however, as scientists from the University of
Washington have developed a transistor that can conduct pulses of protons - and
they've done it with some help from our friends the cephalopods.
The prototype device
is tiny, at just 5 microns in width - about one twentieth the width of a human
hair. It is a field-effect transistor, in that it incorporates a gate, a drain
and a source terminal for the current. Its proton current can be switched on
and off, just like the electron current in a regular field-effect transistor.
Its active
ingredient is chitosan, which is derived from chitin, a compound found in squid
pen (part of the squid's body that is left over from when they had shells) and
crustacean shells. Chitosan is very good at moving protons, as it forms
numerous hydrogen bonds as it absorbs water, the protons then hopping from one
bond to the next. The compound is biocompatible, is reportedly easy to
manufacture, and can be extracted from squid pens and crab shells discarded by
the food industry.
While the current
version has a silicon base, future incarnations could be made completely
biocompatible. In the immediate future, it could be used to study cells in
laboratories. Down the road, however, it could conceivably be used to monitor
or control biological processes within the body, or even to control prosthetic
limbs. Chitosan is also,
incidentally, the active ingredient in experimental self-healing paint.
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