CN102457207B

CN102457207B - Vibration energy collector

Info

Publication number: CN102457207B
Application number: CN201010521658.9A
Authority: CN
Inventors: 冯雪; 王永; 陆炳卫; 蒋东杰
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2010-10-27
Filing date: 2010-10-27
Publication date: 2014-05-07
Anticipated expiration: 2030-10-27
Also published as: CN102457207A

Abstract

A vibration energy collector belongs to the technical fields of electronic devices and new energy sources. The invention comprises a series of strip-shaped thin films, a series of piezoelectric ceramic sheets with upper and lower electrodes and a flexible substrate with inclined groove pattern on the surface. The piezoelectric ceramic sheet is pasted on the surface of the strip-shaped film, and the strip-shaped film is laid in parallel on a flexible substrate with a chute-shaped pattern on the surface. The fundamental frequency of each strip-shaped film placed above the same chute is different, and each strip-shaped film resonates under different environmental excitation frequencies. The piezoelectric ceramic sheet pasted on the surface of the film converts the vibration energy into electrical energy, thus providing energy for the load. The present invention rationally utilizes the dynamic characteristics of the fixed-branch film at both ends under axial pressure, and can reduce the fundamental frequency to an extremely low level, even to zero, which is beyond the reach of traditional vibration energy harvesters; on the other hand, due to the Drawing lessons from the idea of flexible electronics, the flexible substrate is introduced, so it has a certain degree of flexibility and effectively expands its application range.

Description

A kind of vibrational energy collector

Technical field

The present invention relates to a kind of vibrational energy collector, belong to electronic device, novel energy technical field.

Background technology

In daily life, for small portable electronic device (such as mobile phone, MP4 etc.), if do not need regularly charging, be bound to so bring great convenience to people.In industrial circle, for providing the energy to be one, long distance distributed wireless micro sensing device has challenging problem, this is because traditional energy supply method based on battery or battery pack is accompanied by many problems, wherein most important one is: once the energy content of battery exhausts, it is impossible replacing one by one them.Based on above-mentioned consideration, the energy of electronic equipment is supplied with the direction that problem had become global scientific circles and technos effort already immediately.Notice, in surrounding environment, spread all over energy source, such as electromagnetic energy, solar energy, heat energy and mechanical energy etc., if can collect these energy with reasonable manner is used, can solve the Power supply problem of aforementioned small portable electronic device and wireless microsensor part.The utilization of solar energy launches in high gear, but the photoenvironment of its inevitable requirement abundance, and for flush type device, this condition is impossible meet.Due to mechanical oscillation ubiquity in environment around, the utilization of mechanical oscillation is subject to any environmental limitations hardly, is therefore more and more subject to people's attention.Power conversion mechanism by certain, realizes the collection for vibrational energy, and Here it is, and so-called vibrational energy is collected.Current application the most widely vibrational energy collector part is cantilever type piezoelectric girder construction, and this structure is selected the cantilever the way of restraint that fundamental frequency is minimum, and by further reducing fundamental frequency in free end configuration lumped mass.Such structure can only be collected the energy of characteristic frequency in external environment.Yet ambient environment vibrations is generally random vibration, Energy distribution is on very wide frequency band.In order to collect the energy of each frequency, people have made cantilever design array, and each unit in array has different length and/or end counterweight, and each unit has different fundamental frequencies.For different driving frequencies, unit different in array resonate, thereby realize the collection to each frequency energy.The shortcoming of above-mentioned vibrational energy collector comprises: due to the constraint of several how factors, the mode of free end counterweight is unable its fundamental frequency is dropped to very low; This device is perfect rigidity, does not have any flexibility, and this has greatly limited its application scenario.

Summary of the invention

The object of this invention is to provide a kind of vibrational energy collector, can collect the broadband vibration energy that comprises ultralow frequency, can be small portable electronic device and wireless microsensor part etc. instant energy is provided.

Technical scheme of the present invention is as follows:

A vibrational energy collector, is characterized in that: described vibrational energy collector comprises band-like film, with piezoelectric ceramic piece and the flexible substrate of upper/lower electrode; The surface of described flexible substrate is with spot figure, and this spot figure is comprised of at least one skewed slot, and the width of skewed slot is gradual change shape, and skewed slot is arranged by same direction or rightabout; At the matrix surface multi-ribbon shape film that be arranged in parallel, the axis of band-like film is vertical with the center line of groove; The part that every ribbon film is across on skewed slot forms a beam with both ends built-in; The number of the beam with both ends built-in that every ribbon film forms equals the number of skewed slot; Upper surface or lower surface at each beam middle part arrange piezoelectric ceramic piece, or in the upper and lower surface at each beam with both ends built-in middle part, the piezoelectric ceramic piece with upper/lower electrode are all set.

Flexible substrate of the present invention adopts high molecular polymer, at least low order of magnitude of modulus of elasticity of the modular ratio band-like film of high molecular polymer.

The present invention compared with prior art, have the following advantages and high-lighting effect: traditional cantilever type piezoelectric girder construction with end counterweight, because its fundamental frequencies of constraint of several how factors can not drop to very low, and the present invention has rationally utilized the dynamic characteristic of axial compression two fixed ends film, fundamental frequency can be dropped to extremely low, zero even; The semiconductor technology of traditional cantilever type vibrational energy collector based on traditional make, because of but perfect rigidity, and the present invention is owing to having used for reference the thinking of flexible electronic, has introduced flexible substrate, thereby has certain flexibility, has effectively expanded its range of application.

Accompanying drawing explanation

Fig. 1 is overall structure schematic diagram of the present invention (stereoscopic figure).Skewed slot in figure and band-like film are only example, and the number of the two can suitably be chosen according to the size of flexible substrate.

Fig. 2 is with the flexible substrate vertical view of arranging in the same way skewed slot.

Fig. 3 is the flexible substrate vertical view with reversed arrangement skewed slot.

In figure: 1-band-like film; 2-piezoelectric ceramic piece; 3-flexible substrate; 4-skewed slot; 5-beam with both ends built-in.

Embodiment

Below in conjunction with accompanying drawing, structure of the present invention, principle and preparation method are further illustrated.

Fig. 1 is the overall structure schematic diagram of the vibrational energy collector that improves of the present invention, and it comprises band-like film 1, the flexible substrate 3 with the piezoelectric ceramic piece 2 of upper/lower electrode and surface with spot figure.Spot figure is comprised of at least one skewed slot 4, and the width of skewed slot is gradual change shape, and skewed slot is arranged (referring to Fig. 2, Fig. 3) by same direction or rightabout.Skewed slot in figure and band-like film are only example, and the number of the two can suitably be chosen according to the size of flexible substrate.

At the matrix surface multi-ribbon shape film that be arranged in parallel, the axis of band-like film is vertical with the center line of groove; The part that every ribbon film is across on skewed slot forms a beam with both ends built-in; The beam with both ends built-in number that every ribbon film forms equals the number of skewed slot; Upper surface or lower surface at each beam with both ends built-in middle part arrange piezoelectric ceramic piece 2, or in the upper and lower surface of each beam with both ends built-in, piezoelectric ceramic piece are all set.Described flexible substrate adopts high molecular polymer, at least low order of magnitude of modulus of elasticity of the modular ratio band-like film of high molecular polymer.Such as conventional, there are organic high molecular polymers such as dimethyl silicone polymer (PDMS) and polyimides (PI).

The thickness of note band-like film is h, width is b, length is

.The characteristic size of skewed slot upper surface is ,

with

, the degree of depth of skewed slot is w, the distance between adjacent skewed slot is

.

Theory analysis shows, the beam with both ends built-in that is subject to axial compression has peculiar dynamic characteristic: the suitable variation of axial compression load can significantly change the fundamental frequency of beam.Axial compression strain is started from scratch and is increased gradually, and the fundamental frequency of beam declines rapidly; When axial compression strain reaches the critical buckling strain of beam with both ends built-in, the fundamental frequency of beam deteriorates to zero; Along with the further increase of axial compression strain, the fundamental frequency of beam is fast rise again.The critical buckling strain here refers to: in axial loading procedure, exist and make the configuration of beam with both ends built-in by the straight critical strain values that sports non-straight.Critical buckling strain is determined by constraint and the physical dimension of structure.For length, be

beam with both ends built-in, its critical strain is .In the preparation process of device, can adopt the thermal mismatching between film and flexible substrate, all band-like films are applied to identical compression strain

.For same skewed slot, the span of the formed beam with both ends built-in of a series of band-like films is different, at band-like film, arrange enough close in the situation that, the span of beam along the centerline direction of skewed slot by

be gradient to

.The built-in beam of this series length gradual change, because critical buckling strain is separately different, in identical strain

natural frequency under effect is also different.So in strain

under effect, the fundamental frequency of these a series of beams has covered a wider frequency range, and comprises zero-frequency.This device is placed in operational environment, and in environment, the vibration of different frequency will excite the resonance of different fundamental frequency beams.The resonance of beam bring beam upper and lower surface larger alternately change tension and compression strain.The tension and compression strain of beam upper and lower surface causes the dilatation of the piezoelectric ceramic piece that sticks on beam upper and lower surface middle part.Due to piezoelectric effect, the dilatation of piezoelectric ceramic piece makes the upper and lower surface of piezoelectric ceramic piece assemble respectively opposite polarity electric charge.Due to the existence of piezoelectric ceramic piece upper and lower surface electrode, accumulation is on electrode, and this just forms a capacitor.Available conductive lead wire is connected two electrodes with external circuit, form closed-loop path, and capacitor can be supplied with the energy for external circuit like this.

Preparation method of the present invention mainly comprises following step: etch respectively flexible substrate spot figure and band-like film, band-like film is transferred on flexible substrate.The structure that the band-like film upper surface of take is below arranged piezoelectric ceramic piece describes as example.In this example, flexible substrate adopts PI matrix as acceptor, needs to adopt PDMS matrix as transfer printing carrier in transfer process.

First on silicon substrate, prepare strip-shaped thin rete.Above thin layer, the very thin metal electrode of first sputter one deck, then deposits one deck piezoelectric ceramic in the above, sputter one deck electrode more afterwards, and electrode material can be conventional platinum, gold, silver, chromium or aluminium etc.; By etch process, the film of etching band shape, the piezoceramics layer of film upper surface etching become isolated rectangle island, the size of electrode and piezoceramics layer in the same size.By etching, prepare the flexible PI matrix with width gradual change skewed slot.Flexible substrate with skewed slot is good with etching but still be trapped in together with the band-like film on silicon chip and be placed in the environment that sets temperature, insulation a period of time, make the temperature of the two all reach the ambient temperature setting.With flexible PDMS matrix, be attached on band-like film, tear up rapidly PDMS matrix after compression, band-like film is torn from silicon chip by PDMS matrix like this, and is attached to PDMS matrix surface.The relative position of matrix of skewed slot of having adjusted band-like film on PDMS matrix surface and etching, is imprinted on PDMS matrix on the flexible PI matrix with skewed slot, the PDMS matrix of slowly tearing after compression, and transfer process has just completed, and device preparation also completes substantially.Device is put under normal temperature, due to thermal mismatching effect, in film, has certain strain.By controlling the ambient temperature of transfer process, can just equal length and be so that be applied to axial strain in each clamped beam l ₀the critical buckling strain of built-in beam.Like this, length is l ₀the fundamental frequency of clamped beam level off to 0, length is less than l ₀beam keep straightened condition, length is greater than l ₀beam generation flexing, their fundamental frequency along with length with l ₀difference increase and increase rapidly.

Here provide definite method of flexible substrate intensification occurrence.

that length is l ₀the critical buckling strain of band-like film, the thermal coefficient of expansion of note flexible substrate is

, intensification value is

.That is to say, the flexible substrate thermal strain causing due to intensification equals length and is l ₀the critical buckling strain of band-like film.

Claims

1. A vibration energy harvester, characterized in that: the vibration energy harvester includes a strip-shaped film (1), a piezoelectric ceramic sheet (2) with upper and lower electrodes and a flexible substrate (3); the flexible The surface of the substrate has a spot pattern, the pattern is composed of at least one chute, the width of the chute is gradually changing, and the chute is arranged in the same direction or in the opposite direction; a plurality of strip-shaped films are arranged in parallel on the surface of the flexible substrate ( 1), the axis of the strip-shaped film is perpendicular to the center line of the chute; the part of each strip-shaped film straddling the chute forms a fixed beam at both ends; the number of fixed beams at both ends formed by each strip-shaped film is equal to The number of chutes; a piezoelectric ceramic sheet with upper and lower electrodes is arranged on the upper surface or lower surface of the middle part of each fixed beam at both ends, or a piezoelectric ceramic sheet with upper and lower electrodes is arranged on the upper and lower surfaces of the middle part of each fixed beam at both ends. Ceramics.

2. according to a kind of vibration energy collector described in claim 1, it is characterized in that: described flexible substrate adopts high molecular polymer, and the elastic modulus of high molecular polymer is at least one lower than the elastic modulus of strip film Magnitude.