Electrical energy is normally generated through heat, motion, nuclear transformation, or chemical reactions, but now scientists at VTT Technical Research Center of Finland have devised a new method that involves mechanical vibrations. They figured out how to “harvest” the vibrational energy that occurs naturally when two surfaces with different work functions are connected via electrodes, and this energy could potentially be used to power wearables and other low-power electronics.
A work function is a property of the surface of a material that is defined as the difference between the energy of an electron at rest and the minimum thermodynamic work (another form of energy) that is required to remove said electron from the material. It’s often applied in photoelectric devices and cathode-ray tubes, and is sometimes guarded against in electronic circuits involving different metals, but it had not before been used in vibration energy harvesting.
For more detail: New technique for generating electricity from mechanical vibrations