CN111156912A

CN111156912A - Self-driven strain sensor based on flexible photoelectric nano film

Info

Publication number: CN111156912A
Application number: CN201911383410.8A
Authority: CN
Inventors: 张鹤; 沈昕昳; 全力威
Original assignee: Zhejiang University ZJU
Current assignee: Zhejiang University ZJU
Priority date: 2019-12-28
Filing date: 2019-12-28
Publication date: 2020-05-15
Anticipated expiration: 2039-12-28
Also published as: CN111156912B; WO2021129370A1

Abstract

The invention provides a self-driven strain sensor based on a flexible photoelectric nano film, which is used for measuring the strain of a member to be measured and comprises a chute unit and a slide sheet unit arranged in the chute unit, wherein a slide sheet body can move along the chute unit, a connecting end at one end of a bottom plate is used for fixedly connecting the member to be measured, and a bulge at the end part of the slide sheet body is also used for fixedly connecting the member to be measured; the surface of the slip sheet body, which is attached to the sliding chute unit, is provided with a photosensitive layer, and the bottom surface of the bottom plate is provided with a light shielding layer; the sliding groove unit and the surface of the sliding sheet body which is attached to the sliding sheet body are provided with conducting layers. The photosensitive layer is manufactured based on a heterojunction structure, when a component to be detected generates strain, the photosensitive layer partially receives illumination, and the component strain can be obtained through inverse calculation according to an output current signal. Compared with the traditional strain measurement method, the strain sensor provided by the invention has the advantages of simple structure, high measurement precision, high response speed and wide application range.

Description

Self-driven strain sensor based on flexible photoelectric nano film

Technical Field

The invention relates to the field of bridge engineering, in particular to a self-driven strain sensor based on a flexible photoelectric nano film.

Background

The strain measurement of the structure is an important link for knowing the stress state of the structure, maintaining and optimizing the design of the structure and guaranteeing the safety of the structure, and has important significance in engineering. In the current engineering industry, strain gauges are widely used for strain measurement of bridges, railways, dams, and various building facilities. The currently commonly used strain measuring instruments mainly comprise a dial gauge, a resistance strain gauge, a vibrating wire strain gauge and the like. The micrometer strain gauge is a mechanical strain measuring instrument, and the difference between two measurements is compared to obtain the deformation. However, before each measurement, the micrometer gauge must be marked and read on the standard gauge so as to measure on the structure to be measured, which is tedious, and the limitation in practical application is large due to the limitation of marking length and installation. The resistance strain gauge works by using the strain resistance effect of a certain metal wire conductor, but has the defects of nonlinearity, weak output signal, poor interference resistance, large environmental influence and the like, and can only measure the strain of one point on the surface of a component along a certain direction and cannot carry out global measurement. The vibrating wire strain gauge can sense the stress change in the structure, the deformation of the vibrating wire strain gauge is transferred to a vibrating wire through the front end seat and the rear end seat to be converted into the change of the stress of the vibrating wire, so that the vibration frequency of the vibrating wire is changed, a frequency signal of the vibrating wire strain gauge is transmitted to the reading device through a cable, and the strain in the structure is measured.

Disclosure of Invention

Aiming at the defects of the prior art, the invention provides a self-driven strain sensor based on a flexible photoelectric nano film, which can convert the deformation energy of a component to be measured into electric energy and output the electric energy in the form of an electric signal, and has the advantages of simple structure, high measurement precision, high response speed and wide application range. The specific technical scheme is as follows:

a self-driven strain sensor based on a flexible photoelectric nano film is used for measuring the strain of a component to be measured and comprises a chute unit and a slip sheet unit arranged in the chute unit, wherein the chute unit comprises a bottom plate, a connecting end arranged at one end of the bottom plate and a limiting sleeve arranged in the middle of the bottom plate, the slip sheet unit comprises a slip sheet body and a protrusion arranged at the end part of the slip sheet body, the slip sheet body can move along the chute unit, the slip sheet body is attached to the chute unit through the limiting sleeve, the connecting end at one end of the bottom plate is used for fixedly connecting the component to be measured, and the protrusion at the end part of the slip sheet body is also used for fixedly connecting the component to be measured; the surface of the slip sheet body, which is attached to the sliding chute unit, is provided with a photosensitive layer, and the bottom surface of the bottom plate is provided with a light shielding layer; the sliding groove unit and the surface of the sliding sheet body which is attached to the sliding sheet body are provided with conducting layers.

Further, the photosensitive layer comprises a photoetching substrate and electrodes arranged on two sides of the photoetching substrate, wherein one electrode is provided with a graphene layer, the other electrode is provided with a Pa-type silicon layer, the Pa-type silicon layer and the graphene layer are sequentially laid between the two electrodes on the photoetching substrate, and the Pa-type silicon layer is close to the photoetching substrate.

Further, the electrode is an aluminum electrode.

Furthermore, the slide body is made of high-pressure polyethylene, and the sliding chute unit is made of ethylene-vinyl acetate copolymer with the vinyl acetate content of more than 30%.

Further, the chute unit is made of propylene-ethylene random copolymer.

Further, the length of the sliding sheet body is equal to that of the bottom plate, and the width of the sliding sheet body is equal to that of the limiting sleeve.

Further, the strain sensor further comprises a measuring circuit, wherein the measuring circuit comprises an electric wire and an electric signal measuring device, and the electric signal measuring device measures the induced current of the strain sensor.

Further, the measuring circuit is integrated at the bottom of the chute.

The invention has the beneficial effects that:

the invention converts the mechanical rule of the strain of the component into an electric signal according to the mechanical-electrical conversion characteristic, and the electric signal passes through a signal processing device in the device, so that the strain can be represented by the electric signal through an output device and output. Compared with other strain measurement devices, the self-driven strain sensor based on the flexible photoelectric nano film has the advantages of simple structure, high measurement precision, high response speed, wide application range and the like. The self-driven strain sensor based on the flexible photoelectric nano film has extremely high response speed and extremely high sensitivity due to the heterojunction structure. Simultaneously because the gleitbretter body all adopts flexible macromolecular material to make with the spout unit, have better ductility and deformability, can warp along with the deformation of the component that awaits measuring, compare in traditional rigidity strain measurement method, have better suitability.

Drawings

FIG. 1 is a block diagram of a self-driven strain sensor based on flexible optoelectronic nano-films;

FIG. 2 is a structural view of a photosensitive layer;

FIG. 3 is a spectral response plot of a photosensitive layer;

FIG. 4 is a perspective view and a cross-sectional view of a tensile strain measurement state of the sensor;

FIG. 5 is a perspective view and a cross-sectional view of a compressive strain measurement state of the sensor;

reference numbers in the figures: the sliding vane type photoelectric detector comprises a base plate 1, a base plate connecting end 2, a limiting sleeve 3, a sliding vane body 4, a sliding vane protrusion 5, a shading layer 6, a photosensitive layer 7, a Pa type silicon layer 7-1, a graphene layer 7-2, an aluminum electrode 7-3 and a PI substrate 7-4; l₀Initial labeling of the strain sensor; x (t) is the stretching/shortening of the member at time t.

Detailed Description

The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments, and the objects and effects of the invention will become more apparent. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

As shown in fig. 1, the self-driven strain sensor based on a flexible photoelectric nano-film of the present invention is used for measuring the strain of a member to be measured, and includes a sliding slot unit and a sliding sheet unit disposed in the sliding slot unit, where the sliding slot unit includes a bottom plate 1, a connecting end 2 disposed at one end of the bottom plate 1, and a limiting sleeve 3 disposed in the middle of the bottom plate 1, the sliding sheet unit includes a sliding sheet body 4 and a protrusion 5 disposed at an end of the sliding sheet body 4, the sliding sheet body 4 can move along the sliding slot unit, and the sliding sheet body 4 is attached to the sliding slot unit by the limiting sleeve 3, the connecting end 2 at one end of the bottom plate is used for fixedly connecting the member to be measured, and the protrusion 5 at an end of the sliding sheet body is also used for fixedly connecting the member to be measured; a photosensitive layer 7 is arranged on the surface of the sliding sheet body 4, which is attached to the sliding chute unit, and a shading layer 6 is arranged on the bottom surface of the bottom plate; the sliding groove unit and the surface attached to the sliding sheet body 4 are provided with a conducting layer.

In order to improve the photoelectric conversion efficiency of a silicon-based material, graphene is used as another conductive material to form a heterojunction, and the heterojunction is used as a photosensitive layer of the self-driven strain sensor provided by the invention. As shown in fig. 2, the photosensitive layer 7 includes a photolithography substrate and electrodes disposed on two sides of the photolithography substrate, one of the electrodes is provided with a graphene layer 7-2, the other electrode is provided with a Pa-type silicon layer 7-1, and between the two electrodes on the photolithography substrate, the Pa-type silicon layer 7-1 and the graphene layer 7-2 are sequentially laid, and the Pa-type silicon layer 7-1 is close to the photolithography substrate.

Fig. 4 and 5 respectively show the deformation state of the flexible photoelectric nano-film based self-driven strain sensor of the present invention when the self-driven strain sensor is fixed on a member to be measured, wherein fig. 4 is the stretching state of the member to be measured, fig. 5 is the compression state of the member to be measured, and during the stretching or compressing process of the member to be measured, the sliding chute unit and the sliding vane unit are relatively displaced, and the photosensitive surface can receive external light to generate induced current; the magnitude of the induced current can be measured by an electric signal measuring device. The strain amount of the member to be measured can be obtained by conversion based on the induced current.

The self-driven strain sensor based on the flexible photoelectric nano film disclosed by the invention is matched with a visible light to near infrared short wave as an optical signal source (with the wavelength of 400-1100nm), wherein the signal has two peaks (as shown in figure 3) when the wavelength is 680nm and 960nm, namely the signal represents the best response of the sensor. Considering that the laser light has a wavelength of 960nm in the invisible wavelength range, the laser light having a wavelength of 680nm may be selected as the light source for the convenience of the layout of the device.

The self-driven strain sensor based on the flexible photoelectric nano film has extremely short response speed (5ns) to optical signals, and has extremely high sensitivity as a strain sensing technology. The photoelectric conversion of the device is realized through a heterojunction between graphene and a silicon material, when an optical signal is received, valence electrons in the silicon absorb photon energy in incident light to generate energy level transition, so that electron-hole pairs are formed, and under the action of an internal electric field, the electron-hole pairs are separated to generate induced current, so that the conversion of the optical signal and an electric signal is realized.

The principle of the self-driven strain sensor based on the flexible photoelectric nano film to realize strain measurement is as follows:

taking the measurement state of the tensile strain shown in fig. 4 as an example, at a certain time t, the relative displacement between the photosensitive surface and the light-shielding material is x (t), and the strain expression of the member at this time is:

where ε (t) is the strain of the component to be measured at time t, l₀The member measures the initial length of the segment when the strain sensor apparatus is installed.

In the self-driven strain sensor based on the flexible photoelectric nano film, when the photosensitive layer receives illumination, the photosensitive layer generates photocurrent due to a photoelectric effect, and the expression is as follows:

wherein r is a polar coordinate, W_pIs the P region thickness. J. the design is a square_L(r) is the lateral current density.

The forward current is divided into two parts, namely a first part which can be obtained according to the forward current of an ideal PN junction:

wherein J_sIs the reverse saturation current of a PN junction, which has the form:

wherein

And

the thermal equilibrium electron and hole concentrations of the P and N regions, respectively; q is single electron electric quantity, D_nAnd D_pThe diffusion coefficients of electrons and holes, respectively; l is_nAnd L_pDiffusion lengths of electrons and holes, respectively; k and T are the Boltzmann constant and temperature, respectively; r is a polar coordinate.

Is the potential distribution of the P region, the potential of the N region can be considered as 0 in the formula of the forward current, and the forward photovoltage between the P region and the N region can be directly used

Instead.

The second component is the forward current density at which photogenerated electron-hole pairs are separated in the space charge region:

where f is the rate at which electron-hole pairs are separated in lateral unit area (the fraction of current is 0 in the area where there is no illumination).

Then the total forward photocurrent is:

the lateral current i (t) can then be derived from ohm's law:

where ρ is_PIs the resistivity of the P region, b is the width of the photosensitive layer, d₀Is the P region thickness.

Combining the above formulas, we can get:

the dynamic strain epsilon (t) of the component to be measured can be solved as follows:

from the above equation, it can be obtained that the mapping relation between the current i (t) and the strain amount epsilon (t) exists in epsilon (t) → i (t) at a certain time t, that is, at the certain time t, by measuring the current i (t), the strain amount epsilon (t) at that moment can be obtained so as to express the strain amount as an electric signal through the measuring circuit.

The principle of the compressive strain measurement state shown in fig. 5 is the same as described above.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and although the invention has been described in detail with reference to the foregoing examples, it will be apparent to those skilled in the art that various changes in the form and details of the embodiments may be made and equivalents may be substituted for elements thereof. All modifications, equivalents and the like which come within the spirit and principle of the invention are intended to be included within the scope of the invention.

Claims

1. A self-driven strain sensor based on a flexible photoelectric nano film is used for measuring the strain of a member to be measured and is characterized by comprising a chute unit and a slide unit arranged in the chute unit. The sliding chute unit comprises a bottom plate, a connecting end arranged at one end of the bottom plate and a limiting sleeve arranged in the middle of the bottom plate, the sliding vane unit comprises a sliding vane body and a protrusion arranged at the end part of the sliding vane body, the sliding vane body can move along the sliding chute unit, the sliding vane body is attached to the sliding chute unit through the limiting sleeve, the connecting end at one end of the bottom plate is used for fixedly connecting a component to be detected, and the protrusion at the end part of the sliding vane body is also used for fixedly connecting the component to be detected; the surface of the slip sheet body, which is attached to the sliding chute unit, is provided with a photosensitive layer, and the bottom surface of the bottom plate is provided with a light shielding layer; the sliding groove unit and the surface of the sliding sheet body which is attached to the sliding sheet body are provided with conducting layers.

2. The self-driven strain sensor according to claim 1, wherein the photosensitive layer comprises a photo-etching substrate and electrodes disposed on two sides of the photo-etching substrate, wherein one electrode is provided with a graphene layer, the other electrode is provided with a Pa-type silicon layer, and the Pa-type silicon layer and the graphene layer are sequentially laid between the two electrodes on the photo-etching substrate, and the Pa-type silicon layer is close to the photo-etching substrate.

3. The self-driven strain sensor of claim 1, wherein the electrodes are aluminum electrodes.

4. The self-driven strain sensor of claim 1, wherein the slider body is made of high pressure polyethylene and the runner unit is made of ethylene vinyl acetate copolymer having a vinyl acetate content greater than 30%.

5. The self-driven strain sensor of claim 1, wherein the chute unit is made of propylene-ethylene random copolymer.

6. The self-driven strain sensor of claim 1, wherein the length of the slider body is equal to the length of the base plate, and the width of the slider body is equal to the width of the limiting sleeve.

7. The self-driven strain sensor of claim 1, further comprising a measurement circuit comprising an electrical wire and an electrical signal measurement device that measures an induced current of the strain sensor.

8. Self-driven strain sensor according to claim 1, wherein the measuring circuit is integrated in the bottom of the chute.