‘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 University and senior author of a paper detailing the research in the online Journal of the American Chemical Society.
‘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 is said to have 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.
According to a statement, 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 oxidises the monosaccharides, releasing electrons.
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.
‘Insects have an open circulatory system so the blood is not under much pressure,’ said Ritzmann. ‘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.’
To determine the output of the fuel cell, the group used a potentiostat. Maximum power density is said to have reached nearly 100 microwatts per square centimetre at 0.2V. Maximum current density was about 450 microamps per square centimetre.
The researchers are now taking steps to move the technology forward, namely miniaturising the fuel cell so that it can be fully implanted and allow an insect to run or fly normally; investigating materials that may last a long time inside an insect; working with other researchers to build a signal transmitter that can run on little energy; and adding a lightweight rechargeable battery.
‘It’s possible that 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.’