Vibration-driven energy harvester

A vibration-driven energy harvester, comprising:

• a fixed electrode;
• a movable electrode that is disposed so as to face opposite the fixed electrode and is allowed to move relative to the fixed electrode;
• and
• an ionic liquid disposed between the fixed electrode and the movable electrode which face opposite each other,
• wherein:
• the moveable electrode and the fixed electrode are arranged such that power is generated when an external vibration moves the movable electrode toward and away from the opposite-facing fixed electrode such that a distance between the movable electrode and the fixed electrode changes, the change in the distance causing a change in an area of an electrical double layer formed on two sides of an interface of the fixed electrode and the ionic liquid and an area of an electrical double layer formed on two sides of an interface of the movable electrode and the ionic liquid,
• one of the fixed electrode and the movable electrode facing opposite each other is an electret electrode, and
• a surface potential at the electret electrode is set within a potential window of the ionic liquid.