Breakthrough: Mini device converts molecular movement into electricity

The device was able to generate a small amount of current

Molecules are constantly in motion because they have thermal energy — even when they seem stationary to our eyes.

For instance, even though a glass of water appears to be still, the individual water molecules continually vibrate and clash with one another, resulting in this seemingly undetectable motion. This underlying molecular mobility is a basic property of matter at every temperature above absolute zero.

“We thought it would be interesting and meaningful to see if this motion can be harvested and converted into electricity,” Wei Li at Nankai University in China told New Scientist. 

The study team created a small energy-harvesting device that is only one square centimeter, called a molecular thermal motion harvester (MTMH). 

This device has two electrodes, one on top and one on the bottom, each having several 25-nanometer-wide strands of zinc oxide attached to it. Reportedly, zinc oxide was chosen as the material because of its ability to generate an electrical charge when mechanically deformed.

The harvesting device was then placed in a container filled with n-octane – a hydrocarbon comparable to propane or butane but with a longer chain of carbon and hydrogen atoms. This process occurred at room temperature.

The experiment results indicated that when the molecules in the liquid came into contact with the microscopic zinc oxide strands, they generated a small voltage of 2.28 millivolts and a current of 2.47 nanoamperes.

“The energy of the thermal motion of octane can be converted into electrical energy through the device based on the piezoelectric properties of ZnO and a nano-array structure,” mentioned the study. 

The team also aims to examine whether different solvents or liquids can efficiently serve as power sources for this device.

The researchers believe the gadget might provide energy for nano-scale devices such as implants for medicine delivery and therapeutic purposes. 

The team hopes to advance this technology further to power more complex applications with high efficiency. 

The results were reported in the journal APL Materials.

Study abstract:

Molecular thermal motion has been studied yet never utilized as an energy source. In this work, we demonstrate that the energy of liquid molecular thermal motion can be converted into electrical energy by a novel harvesting device, the molecular thermal motion harvester (MTMH). The MTMH was made by using two ZnO-based nano-arrays and one of which was gold coated to form a Schottky junction. The assembled electrodes were immersed in different liquid phase environments. The device was demonstrated to convert the molecule thermal energy of the liquid into a continuous and stable electric current. The output voltage and current can achieve 2.28 mV and 2.47 nA, respectively, and increase with the liquid temperatures. This strategy opens new insights into the development of mini- and micro-scale energy sources, and it can be expected the MTMH will have broad applications in the future.