An insect’s internal chemicals can be converted to
electricity, potentially providing power for sensors, recording devices, or to
control the bug, a group of researchers at Case Western Reserve
The finding is yet another in a growing list from
universities across the country that could bring the creation of insect cyborgs—touted
as possible first responders to super spies—out of science fiction and into
reality. In this case, the power supply, while small, doesn’t rely on movement,
light, or batteries, just normal feeding.
The work is published online in the Journal of
the American Chemical Society.
“It is virtually impossible to start from
scratch and make something that works like an insect,” said Daniel
Scherson, chemistry professor at Case Western Reserve and senior author of the
“Using an insect is likely to prove far
easier,” Scherson said. “For that, you need electrical energy to
power sensors or to excite the neurons to make the insect do as you want, by
generating enough power out of the insect itself.”
Scherson teamed with graduate student Michelle
Rasmussen, biology professor Roy E. Ritzmann, chemistry professor Irene Lee,
and biology research assistant Alan J. Pollack to develop an implantable
biofuel cell to provide usable power.
The key to converting the chemical energy is using
enzymes in series at the anode.
The first enzyme breaks the sugar, trehalose,
which a cockroach constantly produces from its food, into two simpler sugars,
called monosaccharides. The second enzyme oxidizes the monosaccharides,
The current flows as electrons are drawn to the
cathode, where oxygen from air takes up the electrons and is reduced to water.
After testing the system using trehalose
solutions, prototype electrodes were inserted in a blood sinus in the abdomen
of a female cockroach, away from critical internal organs.
“Insects have an open circulatory system so
the blood is not under much pressure,” Ritzmann explained. “So,
unlike say a vertebrate, where if you pushed a probe into a vein or worse an
artery (which is very high pressure) blood does not come out at any pressure.
So, basically, this is really pretty benign. In fact, it is not unusual for the
insect to right itself and walk or run away afterward.”
The researchers found the cockroaches suffered no
long-term damage, which bodes well for long-term use.
To determine the output of the fuel cell, the
group used an instrument called a potentiostat. Maximum power density reached
nearly 100 microwatts per square centimeter at 0.2 volts. Maximum current
density was about 450 microamps per square centimeter.
The study was five years in the making. Progress
stalled for nearly a year due to difficulties with trehalase—the first enzyme
used in the series.
Lee suggested they have the trehalase gene
chemically synthesized to generate an expression plasmid, which is a DNA
molecule separate from chromosomal DNA, to allow the production of large
quantities of purified enzyme from Escherichia
coli. “Michelle then began collecting enzyme that proved to have much
higher specific activities than those obtained from commercial sources,”
Lee said. “The new enzyme led to success.”
The researchers are now taking several steps to
move the technology forward: miniaturizing the fuel cell so that it can be
fully implanted and allow an insect to run or fly normally; investigating
materials that may last long inside of an insect, working with other
researchers to build a signal transmitter that can run on little energy; adding
a lightweight rechargeable battery.
“It’s possible the system could be used intermittently,” Scherson
said. “An insect equipped with a sensor could measure the amount of
noxious gas in a room, broadcast the finding, shut down and recharge for an
hour, then take a new measurement and broadcast again.”
SOURCE – Case Western Reserve University