A vibration energy harvester includes: a pair of electrodes provided so as to face opposite each other, with at least one of the pair of electrodes allowed to move; and an ion gel provided between the pair of electrodes, which is formed by using an ionic liquid, wherein: as an external vibration causes the electrode to move along a direction in which a distance between the pair of electrodes changes, power is generated through a change in an area of an electric double layer formed on two sides of an interface of each electrode and the ion gel.

The present invention provides an electret sheet that exhibits excellent piezoelectricity even by light stress. The electret sheet of the invention is characterized by including a charged porous sheet, in which the electret sheet has a compressive elastic modulus of 80 to 300 MPa when compressively deformed at 25° C. and a 50% compression stress of 120 to 300 kPa at 25° C., and thus has the excellent piezoelectricity for light stress and exhibits the excellent piezoelectricity even by light stress (0.5N or less) caused by a pulse wave or a breathing.

Provided is a method of manufacturing a polymer electret. The method of manufacturing a polymer electrets includes forming a polymer thin film, which includes a block copolymer (BCP) having two or more polymer chains covalently bonded together; forming a nano-structure of the BCP in which a first block formed by first polymer chains that self-assemble together and a second block formed by second polymer chains that self-assemble together are micro-phase-separated, by performing an annealing process on the polymer thin film; forming a porous polymer film with a nano-pore by selectively removing one of the first block and the second block; and charging the porous polymer film.

Provided is a method of manufacturing a polymer electret. The method of manufacturing a polymer electrets includes forming a polymer thin film, which includes a block copolymer (BCP) having two or more polymer chains covalently bonded together; forming a nano-structure of the BCP in which a first block formed by first polymer chains that self-assemble together and a second block formed by second polymer chains that self-assemble together are micro-phase-separated, by performing an annealing process on the polymer thin film; forming a porous polymer film with a nano-pore by selectively removing one of the first block and the second block; and charging the porous polymer film.

A system is disclosed for restoring a surface field potential of an electret material. An oscillator generates an oscillating output, and a power amplifier amplifies the oscillating output. A step-up transformer generates a high voltage alternating current output from the amplified oscillating output, and a polarity controller generates one of a positive pulsating output and a negative pulsating output from the high voltage alternating current output.

A system is disclosed for restoring a surface field potential of an electret material. An oscillator generates an oscillating output, and a power amplifier amplifies the oscillating output. A step-up transformer generates a high voltage alternating current output from the amplified oscillating output, and a polarity controller generates one of a positive pulsating output and a negative pulsating output from the high voltage alternating current output.

Provided are an element applicable to a high-precision, high-sensitivity pressure detecting sensor and switch, a manufacturing method for the element; and a sensor, an electronic circuit, and an input device that include the element. The electret element of the present invention has a semiconductor sandwiched between a pair of electrodes, and an electret film disposed at a location opposite to the semiconductor via a gap. The electret element of the present invention may be structured so that the semiconductor contacts with the electret film, or so as to have micro-sized gaps therebetween. The electret film is semi-permanently kept in a positively or negatively charged state. By having a structure in which the electret film can contact with or approach the semiconductor, an amount of electric currents flowing between the pair of electrodes can be controlled.

A method of manufacturing a MEMS vibration element having a fixed electrode, a movable electrode, and an elastic supporting unit that elastically supports the movable electrode with respect to the fixed electrode includes: etching a base material having a first thickness to form the fixed electrode and the movable electrode; and etching the base material to form the elastic supporting unit having a second thickness, the second thickness being less than the first thickness.

Provision of a piezoelectric element which uses a lightweight and flexible electret material and an electrode layer which is also lightweight, has high conductivity and good flexibility to easily receive electrical signals from an electret, and has good durability. Additionally, provision of a musical instrument provided with such a piezoelectric element. A piezoelectric element comprising an electrode layer (B) on at least one surface of an electret material (A) having pores inside, wherein a porosity of the electret material (A) is 20 to 80%, the electrode layer (B) contains 20 to 70 mass % of a carbon fine particle, and a thickness of the electrode layer (B) is 2 to 100 μm.

Provision of a piezoelectric element which uses a lightweight and flexible electret material and an electrode layer which is also lightweight, has high conductivity and good flexibility to easily receive electrical signals from an electret, and has good durability. Additionally, provision of a musical instrument provided with such a piezoelectric element. A piezoelectric element comprising an electrode layer (B) on at least one surface of an electret material (A) having pores inside, wherein a porosity of the electret material (A) is 20 to 80%, the electrode layer (B) contains 20 to 70 mass % of a carbon fine particle, and a thickness of the electrode layer (B) is 2 to 100 μm.