A tiny engine which works on changes in bacterial activity

Researchers from Indian Institute of Science (IISc) and the Jawaharlal Nehru Centre for Advanced Scientific Research have designed a microscopic heat engine that relies on changes in bacterial activity.

BREAKTHROUGH ACHIEVED: Scientist Ajay K. Sood (seated) with scholars Subho Ghosh (left) and Sudeesh Krishnamurthy in Bengaluru

some of the key points of the research are:-

• It relies on changes in bacterial activity.
• It operates at 50-60 per cent efficiency, which is quite high as compared to the engines we use at present

Working :

• It relies on very small changes in temperature input to impact bacterial activity to achieve large work done by the engine against the other existing engines which require a very high amount of temperature difference. 
• This engine uses a colloidal particle of 5 micro-metre size, optically trapped using a laser beam
• The extent to which the particle can move is controlled by varying the intensity of the laser beam — the more the intensity the less the particle can move and vice versa.
• At high temperature the intensity of the laser beam is reduced and the particle can get displaced more; leading to increased intensity at lower temperature.

Process: 

The change in temperature, which is carried out every four seconds, leads to changes in bacterial activity and hence the work done by the engine.

Key Factor : Efficiency

• “The temperature difference is too small to get work done. The efficiency of the engine will be around three per cent at this temperature difference. But due to bacterial activity the efficiency is over 50 per cent,” says Prof. Ajay K. Sood, the corresponding author of the paper from the Department of Physics, IISc.
• He further adds "When the bacterial activity is high at 40 degree C the effective temperature is around 2000 degree C; at 17 degree C the bacterial activity is significantly diminished leading to low effective temperature"
• But still challenges are there :While the tiny heat engine outperformed a conventional engine in efficiency, it is still far less efficient compared with biological motors that operate in our bodies at 100 per cent efficiency even when the temperature remains constant.

"The next step is to connect the heat engine to some nano device or electromechanical device,” Prof. Sood says.