[Object] To provide a technology such as a piezoelectric coil having higher energy conversion efficiency.

[Solving Means] A piezoelectric coil according to the present technology includes a coil-like core material and a plurality of band-like piezoelectric materials. The plurality of piezoelectric materials is helically wound around the core material so as to be alternately arranged along the core material.

Provided is a piezoelectric structure including a braid composed of a conductive fiber and piezoelectric fibers, the braid being a covered fiber having the conductive fiber as the core and the piezoelectric fibers covering the periphery of the conductive fiber, wherein the covered fiber has at least one bent section, and when the piezoelectric structure is placed on a horizontal surface, the height from the horizontal surface to the uppermost section of the piezoelectric structure is greater than the diameter of the covered fiber.

A very small piezoelectric sensor capable of being mass produced includes a core, a piezoelectric layer on a surface of the core; and a conductive layer on a surface of the piezoelectric layer away from the core. The core is flexible and threadlike, the core is a first electrode of the piezoelectric sensor, and the conductive layer is a second electrode of the piezoelectric sensor. An array of such sensors allows the “skin” of a robot for example to simulate the sensitivity of hair-covered human skin. A method for making the piezoelectric sensor and an electronic device using the piezoelectric sensor are also disclosed.

A structure includes an oriented piezoelectric polymer arranged in a circular tubular or circular columnar shape, wherein the orientation angle of the piezoelectric polymer with respect to the central axis of the structure is 15° to 75°, the piezoelectric polymer includes a crystalline polymer having an absolute value of 0.1 to 1000 pC/N for the piezoelectric constant d14 when the orientation axis is the third axis, and the piezoelectric polymer includes a P-body containing a crystalline polymer with a positive piezoelectric constant d14 value and an N-body containing a crystalline polymer with a negative value, wherein for the portion of the central axis of the structure having a length of 1 cm, the value of T1/T2 is 0 to 0.8, T1 being the smaller and T2 being the larger of (ZP+SN) and (SP+ZN), where ZP, SP, ZN, and SN are particularly defined masses.

A hydrophone may include a first piezoelectric cable including alternating sections of positive polarity and negative polarity, and a second piezoelectric cable including alternating sections of negative polarity and positive polarity. At least a portion of each section of positive polarity of the first piezoelectric cable may be bonded or adhered to at least a portion of a section of negative polarity of the second piezoelectric cable. A method of manufacturing a hydrophone may include winding or coiling a first piezoelectric cable and a second piezoelectric cable at the same time to create a series of wound sections including cables, the wound sections alternating with a series of not wound sections including the cables.

A piezoelectric coaxial sensor includes: a sensor portion including a center conductor having a linear shape, a polymer piezoelectric layer containing polyvinylidene fluoride and that covers an outer peripheral surface of the center conductor, and a first outer conductor that surrounds an outer peripheral surface of the polymer piezoelectric layer; and jacket layers that each include a film having a tape shape wound to surround an outer peripheral surface of the sensor portion. The film of at least one of the jacket layers exposed to the outside of the piezoelectric coaxial sensor among the other jacket layers is adhered to a member in contact with an adhesive layer by the adhesive layer. The adhesive layer includes a thermoplastic resin having a melting point of 120° C. or lower.

A piezoelectric coaxial sensor includes: a sensor portion including a center conductor having a linear shape, a polymer piezoelectric layer containing polyvinylidene fluoride and that covers an outer peripheral surface of the center conductor, and a first outer conductor that surrounds an outer peripheral surface of the polymer piezoelectric layer; and jacket layers that each include a film having a tape shape wound to surround an outer peripheral surface of the sensor portion. The film of at least one of the jacket layers exposed to the outside of the piezoelectric coaxial sensor among the other jacket layers is adhered to a member in contact with an adhesive layer by the adhesive layer. The adhesive layer includes a thermoplastic resin having a melting point of 120° C. or lower.

A piezoelectric substrate attachment structure including a press section pressed by contact, a piezoelectric substrate provided adjacent to the press section, and a base section provided adjacent to the piezoelectric substrate on an opposite side from the press section. The following relationship Equation (a) is satisfied:
da/E′a<db/E′b  (a) wherein da is a thickness of the press section in a direction of adjacency to the piezoelectric substrate, E′a is a storage modulus of the press section from dynamic viscoelastic analysis, db is a thickness of the base section in the adjacency direction, and E′b is a storage modulus of the base section from dynamic viscoelastic analysis.

A piezoelectric coaxial sensor includes: a center conductor including a conductive wire; a polymer piezoelectric layer covering an outer peripheral surface of the center conductor; a first outer conductor surrounding an outer peripheral surface of the polymer piezoelectric layer; a first jacket layer covering an outer peripheral surface of the first outer conductor; and a second outer conductor surrounding an outer peripheral surface of the first jacket layer. A voltage is generated between the center conductor and the first outer conductor based on induced charges generated in the polymer piezoelectric layer.

A piezoelectric coaxial sensor includes: a center conductor including a conductive wire; a polymer piezoelectric layer covering an outer peripheral surface of the center conductor; a first outer conductor surrounding an outer peripheral surface of the polymer piezoelectric layer; a first jacket layer covering an outer peripheral surface of the first outer conductor; and a second outer conductor surrounding an outer peripheral surface of the first jacket layer. A voltage is generated between the center conductor and the first outer conductor based on induced charges generated in the polymer piezoelectric layer.