Jan
9
A Higher Form of Life to Produce Electricity
January 9, 2012 | 6 Comments
The past decade has seen ingenious devices described in the literature to accomplish the goal. Methods for converting chemical or mechanical energy are either present in, or generated by living organisms for generating electricity, and are expected to open exciting new prospects for the development of autonomous ways to produce power.
The Case Reserve team’s work is another in a growing list from universities across the country that could bring the creation of insect cyborgs out of science fiction and into reality.
What stands out this time is the power supply, while small, doesn’t rely on movement, light or batteries, just normal insect feeding. Enter the formidable cockroach.
Biocell Implantation Into a Cockroach. Click image for the largest view.
Daniel Scherson, chemistry professor at Case Western Reserve and senior author of the paper explains, “It is virtually impossible to start from scratch and make something that works like an insect. Using an insect is likely to prove far easier. 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.”
So Scherson organized a team 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 – inside the insect.
The principle the team exploits is converting the insect’s own chemical energy using enzymes in a series of steps 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, releasing electrons.
Biocell in Insect Enzyme Based Schematic. Click image for more info.
The current flows as electrons are drawn to the cathode, where oxygen from the air takes up the electrons and is in turn reduced to water. After testing the system design using trehalose solutions, prototype electrodes were inserted in a blood sinus in the abdomen of a female cockroach, away from critical internal organs.
Ritzmann takes up the explanation; “Insects have an open circulatory system so the blood is not under much pressure. 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.
That out of the way, how much power? 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.
Doing this is much harder than it seems. The research has been ongoing for 5 years, and trehalase – the first enzyme used in the series was quite difficult to manage stalling progress for nearly a year.
So Professor 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 Rasmussen then set about “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 Case Western team is 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 would last a long time inside of an insect, and working with other researchers to build a signal transmitter that can run on little energy plus adding a lightweight rechargeable battery.
All that might make one feel a little compassion for the insect – but we’re looking at cockroaches for now.
For those with a challenge to imagine a first adopter use, Professor Scherson said, “It’s possible the system could be used intermittently. 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.”
The overarching news is a biocell can in fact convert trehalose contained within an insect and oxygen from the air into electricity that, in principle, could be collected and stored and subsequently used to power a variety of microdevices. That’s a clue for other ideas, too.
The future will see more miniaturization, now it seems all the way down to the lowly, but formidable and resilient cockroach. It’s about time those creatures came up with something useful to be doing. Imagine the resiliency of the cockroach and humanities’ ingenuity bonded together . . .
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