Can microbes actually produce electricity?
Microbes have often proved to be a gift of nature. From programmed biofertilizers to being used in metabolite production, microbes have greatly aided mankind.
But have we found out everything there is to know?
Microbes have shown great adaptability. They have been found to survive in the warmest of climates to the coldest depths of the Earth. They can respire with or without oxygen, by simply pumping out electrons. So does this mean they can generate electricity as well?
Can there be small microbial power plants running machineries?
Scientists believe it can be done. The only hurdle is harnessing this power from these tiny cells.
But, where there is a will, there is a way.
MIT engineers have developed a microfluidic technique that can efficiently assess bacteria’s polarizability.
The technique can quickly process small samples of bacteria and measure the bacteria’s ability to produce electricity.
It is a safer and more efficient manner compared to our current techniques.
They believe there is a broad range of bacteria with this ability. Currently we assay a handful.
This tool could help bring the others to knowledge.
Bacteria produce electricity by extracellular electron transfer, or EET.
They generate electrons and transfer them across their cell membranes through tiny channels.
The existing techniques to measure this are time consuming and involve large samples with complicated extractions. These techniques rupture the cells and denature proteins.
Buie and his group have been on the lookout for an alternative for the past 10 years.
They made microfluidic chips etched with small channels.Through this they flow microliter-samples of bacteria. Each channel is pinched in the middle to form an hourglass configuration. When a voltage is applied across a channel, the pinched section puts a squeeze on the electric field, making it 100 times stronger than the surrounding field.
The gradient of the electric field creates a phenomenon known as dielectrophoresis.It is a force that pushes the cell against its motion induced by the electric field.
As a result, dielectrophoresis can repel a particle or freeze it in its tracks at different applied voltages.
Dielectrophoresis is used to quickly sort bacteria according to size, species etc.
In a new study, the team used this microfluidic setup to compare various strains of bacteria.
The strains included a wild-type that actively produces electricity in microbial fuel cells, and several genetically engineered strains.Very small, microliter samples of each bacterial strain were passed through the microfluidic channel. They slowly amped up the voltage across the channel, one volt per second, from 0 to 80 volts.
Through particle image velocimetry, they observed that the electric field propelled bacterial cells through the channel, until they approached the pinched section.
Here, the much stronger field acted to push back on the bacteria via dielectrophoresis and held them in place.
Some trapped at lower applied voltages, and others at higher voltages.
“Trapping voltage” for each cell and their cell sizes was simulated through computer to calculate the polarizability.
Bacteria that were more electrochemically active, tended to have a higher polarizability.
Thus a correlation was developed.
The Microfluidic technique was concluded to be an efficient and nondestructive way to gauge polarizability.
Considering further correlations holds true, this could be the first step for clean energy generation.
One day, it can be possible, that the electricity you use, would have been generated from a very tiny unicellular organism !!