In this work, researchers 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.

In the era of the Internet of Things (IoT) and 5G, energy demands are decentralized, mobile, and ubiquitous. Some mini- and micro-scale energy sources, such as airflow, human movement blood flow, ultrasound, etc., have already been explored and converted into electricity by various nano-energy generator technologies based on different schemes/mechanisms. Most of these conversions are based on mechanical energy.

Molecular thermal motion is a special kind of dynamic motion that is essentially different from ordinary mechanical motion. It is a component of the internal energy of the physical system, which means that the molecules of all substances are in constant and random movement above absolute zero temperature. Brownian motion of particles is one example that is caused by the molecule thermal motion of the surrounding liquid or gaseous molecules. Molecule thermal motion contains an enormous amount of energy, taking an ideal gas as an example, the average kinetic energy of thermal motion per mole of gas molecules at room temperature (27 °C) is 3.7 kiloJoules. If this form of energy could be utilized from the huge amounts of liquids and gases on the planet effectively, this would provide a new source of energy on an enormous scale.