CN102954829A - Micro-particle weighing sensor of V-shaped folding cantilever beam structure - Google Patents

Abstract

The invention discloses a micro-particle weighing sensor of a V-shaped folding cantilever beam structure, belonging to the field of a precise particle mass detection sensor. A micro mass sensor comprises a fixed block, a V-shaped folding cantilever beam structure and a piezoelectric thin film, and is characterized in that the upper surface of the V-shaped folding cantilever beam connected to the fixed block is connected with the piezoelectric thin film, wherein the top or tops of a single or a plurality of V-shaped folding grooves which are arranged along the axis is or are used as a main detection point or main detection points; and the mass of a detected object is accurately calculated through data output of the piezoelectric thin film. The rigidity and the effective mass distribution state of the sensor are effectively changed through introduction of the V-shaped folding cantilever beam, so that the detection sensitivity of the sensor is greatly improved. Specific examples show that the sensitivity can be improved by 227 percent compared with the conventional sensor of the rectangular section cantilever beam structure. The micro mass sensor has the characteristics of simple structure, accuracy in positioning of the detected object, high sensitivity and the like, so that the sensor can be widely applied to detection of atoms, fine particles, environmental dust and microbial cells such as bacteria or viruses.

Description

A kind of microparticle LOAD CELLS of V-type foldable suspension arm girder construction

Technical field

The present invention relates to a kind of microparticle LOAD CELLS of V-type foldable suspension arm girder construction, belong to accurate granular mass acquisition sensor field, be mainly used in that atom is weighed, detection and the identification of size-measure of small particle, ambient dust and the microbial cells such as bacterium or virus.

Background technology

The piezo-electric resonance type micro-mass sensor mainly is attached to structural resonance frequency that the quality of the material of sensor surface causes by measurement to be changed and comes the detection material composition, and ultimate principle can be explained with following formula, Δ f _i=-f _iΔ m/M _e, f wherein _iBe sensor i rank resonance frequency, M _eBe the semi-girder equivalent mass, m is that unit area increases quality, f _iThe sensor resonant frequency variation that causes for increasing quality m.This shows the resonance frequency f of key elastic element _iWith effective mass M _eDirectly determine sensitivity and the measuring accuracy of sensor.For the measurement of particulate material, usually adopting the beam type micro-mass sensor is matrix, by specific adsorbent thin film, fixes the mensuration that measured object carries out Tiny Mass by suction-operated.Yet the quality of adsorbent thin film and size can directly increase the effective mass of sensor, and then reduce the detection sensitivity of sensor.Simultaneously, because the randomness of molecule adsorption process, so that the position of measured object can't accurately locate, and then reduce the measuring accuracy of sensor, had a strong impact on that the beam type micro-mass sensor is demarcated at atom, the application in ambient dust such as the fields such as PM2.5 identification and microbial cell detection.International monopoly WO 2005/043126 A2 and US Patent No. 7935191 propose to adopt the square-section cantilever beam sensor of single piezoelectric patches excitation, because the rigidity mass ratio of square-section semi-girder is fixing and the characteristics of planar structure, carry out the material measurement so that sensor can only depend on adsorption film, have the weakness that sensitivity is low and measured object can't be located.US Patent No. 6722200 proposes a kind of silicon materials sensor of measuring monatomic quality, the sensitivity of semi-girder marginal position will be starkly lower than the center, because this sensor mainly relies on the mode of absorption to fix tested atom, so that absorption position can directly affect measurement result.US Patent No. 6389877 B1, US 20090235746 and domestic patent CN1250156A increase adsorption area by the way that single head, double end impact load and non-piezoelectric layer physics extend, but have also increased the effective mass M of system of semi-girder simultaneously _e, reduced the sensitivity of sensor.Nearest domestic patent of invention publication number CN 1609555A proposes to adopt to measure to adsorb has the method for the oscillator displacement difference of surveying thing to come measurement quality, but wherein needs complicated optical displacement measurement system, increases and measures cost.Document " optical precision engineering " first phase in 2012 " based on the design of the micro-mass sensor of slot type cantilever beam structure " although described in sensor effectively promoted the sensitivity of sensor, but sensitivity is subject to the impact of measuring position easily, the weakness that exists the small material of individual particle shape accurately to locate.

Analysis-by-synthesis is found, is subjected to the restriction of self structure and adsorption film shape, and pure square-section declines that there is complex structure in mass sensor, sensitivity is low and minim is blamed deficiency with accurate location, has had a strong impact on its scope of application.Therefore, the development trend of novel micro-mass sensor is: in the situation that promotes sensitivity, simplify the sensor construction form, accurately locate measured object and reduce the measuring position to the influence degree of sensitivity.

Summary of the invention

The present invention is directed to that existing micro-mass sensor measured object can't be located, sensitivity is low and depend critically upon the weakness of adsorption film shape and absorption position, a kind of microparticle LOAD CELLS of V-type foldable suspension arm girder construction is provided, introduce the V-type folding cantilever beam of special, utilize the location characteristics of structure self accurately to locate the position of measured matter, and make sensor reach the maximum sensitivity output state, effectively reduce the measured object uncertainty problem that is caused by adsorbent thin film.Find with simulation comparison that by experiment the sensitivity of the micro-mass sensor of V-type foldable suspension arm girder construction is 3.3 times at same scale square-section cantilever beam sensor.That the micro-mass sensor that proposes has is highly sensitive, accurate positioning and the high characteristics of measuring accuracy, efficiently solve conventional planar cantilever beam structure sensor monatomicly weigh, the larger problems of aspect error such as cell measurement and the measurement of particle size of dust size.

Technical scheme of the present invention is: a kind of microparticle LOAD CELLS of V-type foldable suspension arm girder construction, it mainly comprises a V-type folding cantilever beam of special that is connected with fixed block, connect piezoelectric membrane on the semi-girder as driving and detecting unit, adsorption film is connected in the extension folded slot inside surface of semi-girder.When adsorption film is adsorbed onto the detection thing, measures the resonance frequency changing value of sensor by piezoelectric membrane, and calculate thus the quality of surveying thing.

Described foldable suspension arm girder construction is folded to form the V-type cross section along center section, and the width of V-type groove and highly adjustable.

Described foldable suspension arm girder construction has single or multiple continuously folding V-type grooves along axis direction.

Described V-type folded beam structure one end is connected in fixed block, forms cantilever beam structure;

Described piezoelectric membrane is connected in the upper surface of folding cantilever beam of special, and the length of piezoelectric membrane is less than semi-girder length;

The drift angle of the V-type groove of described foldable suspension arm girder construction is spent less than 180 greater than 0 degree;

The horizontal surface on described piezoelectric membrane and the semi-girder edge of a wing interconnects, and seamless;

The lap of described folding cantilever beam of special and piezoelectric membrane is composite bed, is the extension without the semi-girder of piezoelectric membrane cover part, and both resonance frequencies equate.

The method for designing of the microparticle LOAD CELLS of described V-type foldable suspension arm girder construction is as follows:

$f_{1i}=\frac{{\mathrm{\&lambda;}}_{1i}^2}{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="1"\; label="L"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">L</figure-callout>}}_1^2}\sqrt{\frac{\mathrm{\&Sigma;}{E}_i{I}_i}{\mathrm{\&Sigma;}{A}_i{\mathrm{\&rho;}}_i}}---\left(1\right)$

Parameter in the formula (1) is respectively by following various expression:

$\begin{array}{c}\mathrm{\&Sigma;}{E}_i{I}_i=E_1\{{\mathrm{<figure-callout\; id="1"\; label="I"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">I</figure-callout>}}_1+[{\left(\frac{H_e}{2}\right)}^2-{(\frac{H_{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">e</figure-callout>}}}{2}+t_n)}^2\left]\right[w_{1}h+w_{3}h+2h\sqrt{{\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">w</figure-callout>}}_2}{2}\right)}^2+H^2}\left]\right\}\\ +E_p[\frac{{\mathrm{bt}}_p^3}{12}+{(\frac{t_p}{2}-t_n)}^2{\mathrm{bt}}_p]\end{array}---\left(2\right)$

$I_1=\left(\frac{w_1+w_3}{3}\right)h^3+\frac{w_2}{12}{(H+h)}^3-\frac{w_2}{12}{H}^3---\left(3\right)$

$H_e=\sqrt[3]{\frac{3I_1}{w_1+w_2+w_3}}---\left(4\right)$

$t_n=\frac{\frac{1}{2}{E}_p{t}_p^2-\frac{1}{2}{E}_1{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">t</figure-callout>}}_1^2}{E_1{\mathrm{<figure-callout\; id="1"\; label="t"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">t</figure-callout>}}_1+E_2{\mathrm{<figure-callout\; id="2"\; label="t"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">t</figure-callout>}}_2}=\frac{\frac{1}{2}{E}_p{t}_p^2-\frac{1}{2}{E}_1{H}_e^2}{E_1{H}_e+E_p{t}_p}---\left(5\right)$

$\mathrm{\&Sigma;}{A}_i{\mathrm{\&rho;}}_i=\mathrm{\&rho;h}[w_1+w_3+2\sqrt{{\left(\frac{w_2}{2}\right)}^2+H^2}]+{\mathrm{\&rho;}}_p{\mathrm{bt}}_p---\left(6\right)$

Wherein, λ _1iThe coefficient relevant with each rank mode eigenvalue, E _p, E ₁Be respectively the elastic modulus of piezoelectric and semi-girder material, t _p, h, b, w ₂, H, w ₁, w ₃, be respectively piezoelectric film thickness, folded beam thickness, folded beam width, folded slot width, groove height, folded beam arranged on left and right sides wing width, t _n, m ₁, H _eBe respectively neutral line position, equivalent mass and semi-girder equivalent thickness, A _i, ρ _iBe the corresponding area of section of each layer and density of material.

Resonance frequency f for the semi-girder extension _2i, computing formula is:

$f_{2i}=\frac{{\mathrm{\&lambda;}}_{2i}^2}{2\mathrm{\&pi;}{\mathrm{<figure-callout\; id="2"\; label="L"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">L</figure-callout>}}_2^2}\sqrt{\frac{\mathrm{\&Sigma;}{E}_i{I}_i}{\mathrm{\&Sigma;}{A}_i{\mathrm{\&rho;}}_i}}---\left(7\right)$

Wherein,

$\mathrm{\&Sigma;}{E}_i{I}_i=E_1\{I_1+[{\left(\frac{H_e}{2}\right)}^2-{(\frac{H_{\mathrm{<figure-callout\; id="2"\; label="e"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">e</figure-callout>}}}{2}+t_n)}^2\left]\right[w_{1}h+w_{3}h+2h\sqrt{{\left(\frac{{\mathrm{<figure-callout\; id="2"\; label="w"\; filenames="HDA00002422462100013.png"\; state="\{\{state\}\}">w</figure-callout>}}_2}{2}\right)}^2+H^2}\left]\right\}---\left(8\right)$

$\mathrm{\&Sigma;}{A}_i{\mathrm{\&rho;}}_i=\mathrm{\&rho;h}[w_1+w_3+2\sqrt{{\left(\frac{w_2}{2}\right)}^2+H^2}]---\left(9\right)$

Make the resonance frequency of composite portion and extension equate, can determine the resonance frequency f of V-type foldable suspension arm girder construction _i, measured object is placed the top of V-type groove, can determine to load the sensor resonant frequency f ' behind the measured object, determined the sensitivity of sensor by difference on the frequency.By adjusting the height H of V-type folding groove, the number of width W and V-type folding groove promotes the sensitivity of sensor, reaches 3.3 times of square-section.

The present invention compared with prior art has following advantage:

[1] the present invention adopts V-type foldable suspension arm girder construction to substitute traditional square-section girder construction as the key elastic element of mass sensor, adjust rigidity and the effective mass distribution of sensor, realize that larger sensitivity promotes amplitude, can reach 3.3 times of square-section transducer sensitivity;

[2] the present invention adopts V-type foldable suspension arm girder construction to substitute traditional square-section girder construction, top by V-type folding groove, need not additional adsorbent thin film and can determine the fixed position of measured object, simplify sensor construction, when reducing cost, Effective Raise the measuring accuracy of original sensor;

[3] the present invention can realize the continuous coverage of multiple measured object in the continuous method of arranging a plurality of V-types folding grooves of the axis direction of cantilever beam structure, the simplified measurement process, and promote detection efficiency.

That the micro-mass sensor of a kind of V-type foldable suspension arm girder construction proposed by the invention has is simple in structure, highly sensitive, the characteristics of accurate positioning and continuous coverage, weighs on molecule, Growth of Cells, microorganism detection such as bacterium and virus, little quality, the field such as danger product detection has widely application value.

Description of drawings

Fig. 1 is a kind of microparticle LOAD CELLS of V-type foldable suspension arm girder construction.

Fig. 2 is a kind of sensitivity of microparticle LOAD CELLS of V-type foldable suspension arm girder construction and the traditional rectangular comparison diagram that cuts section bar.

Fig. 3 is embodiments of the present invention 2 structural representations.

Fig. 4 is the sensitivity of sensor in the embodiment of the present invention 2 and the traditional rectangular comparison diagram that cuts section bar.

Among the figure: 1, fixed block; 2, piezoelectric membrane; 3, single V-type groove foldable suspension arm girder construction; 4, double V-shaped groove is folding cuts section bar;

Embodiment

Embodiment one

Fig. 1 has provided a kind of microparticle load cell structure synoptic diagram of V-type foldable suspension arm girder construction.Wherein, the lower surface of piezoelectric membrane 2 is connected in the upper surface of V-type folding cantilever beam of special 3, and one section of piezoelectric membrane 2 and folded beam is connected in fixed block 1, and the other end is unsettled, forms composite cantilever structure.The seamless connection between piezoelectric membrane 2 and the V-type folding cantilever beam of special, and the length of piezoelectric membrane 2 is less than folding cantilever beam of special 3.Take the free end of piezoelectric membrane 2 as boundary, composite cantilever structure is divided into two parts: i.e. composite bed and extended layer.Folding cantilever beam of special 3 is highly elastic material.

Example 1: under identical geometric parameter (as shown in table 1), the Sensitivity comparison curve of the sensitivity of embodiment of the present invention one and square-section girder construction, as shown in Figure 2.According to the definition of transducer sensitivity, the slope of figure cathetus is the sensitivity of respective sensor.When the foldable suspension arm beam length was 20.0mm, the sensitivity of remolding sensitivity rectangle plane formula sensor of the present invention improved 2.9 times, effectively raises the sensitivity of sensor.

Table 1 sensor geometric parameter

Embodiment two

Fig. 3 is embodiment two structural representations of the microparticle LOAD CELLS of a kind of V-type foldable suspension arm of the present invention girder construction.On the basis of embodiment one, single V-type groove folding cantilever beam of special is replaced with the folding cantilever beam of special of continuous a plurality of V-type grooves, can be used for the continuous coverage of many kinds of substance.

Claims (6)

1. the microparticle LOAD CELLS of a V-type foldable suspension arm girder construction, it mainly comprises V-type folding cantilever beam of special 3, piezoelectric membrane 2 and fixed block 1; It is characterized in that: the upper surface of V-type folding cantilevers 3 is connecting piezoelectric membrane 2, and an end is connected in fixed block 1, by measuring the resonance frequency poor f of cantilever design before and after thing is surveyed in absorption, and then calculates the quality m that surveys thing.

2. according to claim, the microparticle LOAD CELLS of 1 described a kind of V-type foldable suspension arm girder construction is characterized in that: the center section folding concave of described V-type folding cantilevers 3 is gone down, and forms the V-type cross section.

3. according to claim, the microparticle LOAD CELLS of 1 described a kind of V-type foldable suspension arm girder construction is characterized in that: the two edges part of V-type folding cantilevers 3 is horizontal structure, with the horizontal direction angle be zero degree.

4. according to claim, the microparticle LOAD CELLS of 1 described a kind of V-type foldable suspension arm girder construction is characterized in that: piezoelectric membrane 2 length are less than the length of semi-girder 3.

5. according to claim, the microparticle LOAD CELLS of 1 described a kind of V-type foldable suspension arm girder construction is characterized in that: the folding drift angle of V-type is spent less than 180 greater than 0 degree.

6. according to claim, the microparticle LOAD CELLS of 1 described a kind of V-type foldable suspension arm girder construction is characterized in that: the both sides flange surfaces of V-type folding cantilevers 3 is connected with the seamless surface of piezoelectric membrane 2.

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