CN1987416A - Method and device for measuring trace matter in liquid by micro suspension arm sensor - Google Patents

Abstract

The method includes steps: through channels, water pump drives samples of liquid to be tested and normal fluid into liquid pools respectively; placing micro cantilevers to liquid pools; using laser to hit reflection face, and using 2D photo detector to detect reflected light in order to know displacements of micro cantilevers; turning off, on channel of liquid to be detected, and turning on channel of normal fluid, when liquid to be detected passes, there will be fluctuation of micro cantilevers since sorption of matter in liquid, thus fluctuation of reflection of laser beam follows; position sensitive photo detector receives reflected laser signal; after calculation, magnification, and process, the method compares signal from the fluid to be tested with signal from normal fluid under same process mode so as to obtain information of ion density. By applying AFM technique to water contamination detection the invention measures content of ion in minute quantities in water in real time.

Description

The method and apparatus of trace materials in the micro-cantilever sensor measurement liquid

Technical field

The present invention relates to measure in the environmental protection tests field method of trace materials in the liquid, particularly relate to the method for a kind of micro-cantilever sensor trace materials in measuring liquid.

Background technology

In rapid economic development, environmental pollution is also increasingly sharpening.The balance of ecologic environment is constantly destroyed, and therefore the economic development that is just threatening human existence and continuing strengthens ecological environmental protection and construction, and it is one of main task of China's new period that promotion economy is coordinated continuously and healthily to develop in a healthy way.The quality of water quality is directly connected to the healthy of its people of country, also is one of progressive sign of country.The water target of our country should progressively proceed to " everybody drinks high-quality potable water " from " the village village leads to tap water ".The expert thinks that the pollution of drinking-water is to cause cancer, and heart disease and saturnine number one threaten, and the absorption of health has caused all chronic diseases.Water pollutes the health not only influence us, can also corrode apparatus, makes dirty and corrode clothing and apparatus, makes food and drinks water spoiledly, and makes hair variable color gradually.In a lot of surface water, except that the pollution factor of routine, also have the poisonous and harmful substances (trace materials) of a lot of trace, comprise " three cause " (carcinogenic, teratogenesis, mutagenesis) material.The trace materials difficult degradation, high toxicity can be accumulated in human body by food chain, can move at the atmospheric environment middle and long distance, its harm that human body and environment are brought has become the environment focal issue that countries in the world are in recent years paid close attention to, and causes decision maker's and scientist concern all over the world.

But present monitoring method and monitoring instrument far away can not practical requirement, and environment supervision instrument is as the new branch in the instrument and meter subject, compare with other subject instrument also to be in relatively backward state.Advanced industrial country has just dropped into a large amount of funds and manpower at environmental areas such as air, water quality, ocean and ecologies since the eighties in last century, carries out the fundamental research of environment measuring and the exploitation of instrument system.And have advanced and mature product to introduce to the market in succession, formed the new industry of enviromental protection instrument.Domestic environment cause is started late, and has lagged behind more than ten years, and is also relatively backward generally.The on-line instrument of more than 100 Automatic Water Quality Monitoring Stations in the important basin of country and each province's construction almost all adopts import instrument.According to the interrelated data report, the environment supervision instrument of introduction and equipment are up to nearly 2,000,000,000 yuan.Therefore the great market of domestic high-caliber environment supervision instrument is captured by offshore company at present.Existing water quality detection method has a lot: chemical oxygen consumption (COC) method, biological oxygen demand (BOD) method, coulometric titration, spectrophotometric method, colourimetry, vapor-phase chromatography, liquid phase chromatography, mass spectroscopy etc., but all there is such or such shortcoming in they, and are many as operation steps, process is numerous and diverse, monitoring periods is long, are difficult for realizing real-time field monitoring, precision is not high, does not reach the requirement of accurate monitoring.The concentration of trace materials is very low, and from ppm (part-per-million) to ppb (part-per-billion) even ppt (part-per-trillion) order of magnitude, the material of this pettiness content is difficult to measure with conventional sensing detection method.Therefore press for the trace materials detection technique and the monitoring instrument of research and development high sensitivity, high precision, high selectivity.

1982 scanning tunnel microscope occur; 1986, people such as Binnig utilized scanning tunnel microscope to measure nearly 10 ^-18The surface force of N combines scanning tunnel microscope with the probe-type contourgraph, invented atomic force microscope (AFM), measures in air, reaches the resolution of transverse precision 3nm and vertical direction 0.1nm.The atomic force microscope that people such as the S.Alexander of California university utilize optical lever to realize has obtained the surface image of atomic resolution first.With STM and AFM is the microscope of base growth, can be referred to as scanning probe microscopy (SPM).They can both observe nanoscale greatly, with them serves as that suitable transformation is carried out on the basis, can carry out nano measurement, as laser force microscope, magnetic force microscopy, electrostatic force microscope, the bullet of later appearance conduct electricity sub-emission microscope, the scan ion electricity is led microscope, optical microscope for scanning near field, photon scanning tunneling microscope, scanning thermal microscope etc., all is physics and the chemical property of utilizing the probe and the different interactions of sample to come searching surface or interface to show on nanoscale.The diameter of their contactless probe is very little, thereby has greatly improved Measurement Resolution.

At present, AFM and STM are mainly used in studying the physics interaction between high resolution detection and surface and the microstructure both at home and abroad, thereby provide the measurement of micromorphology, shape and size.The research starting of surface adsorption induction but is the thing in nearly ten years.In addition, because the characteristic length of nano material and device is very little, produce very big disturbance during measurement, so that the information that produces can not be represented itself characteristic fully.These all are the bottlenecks of technology universalization of restriction nano measurement and applicationization, and therefore, no matter the measurement under the nanoscale is in theory, still all need further investigation and development on technology and equipment.

Also begin to turn to environment measuring and the biology based on the AFM of micro-cantilever (micro-cantilever) probe and develop rapidly from the micromorphology measurement, it is advantageous that: (1) specimen preparation is simple, need not sample is carried out special processing, therefore, its destructiveness is much smaller than other common technology (as electron microscope); (2) can operate in multiple environment (comprising air, liquid and vacuum), biomolecule can also can be carried out Real-time and Dynamic to living cells and observe in direct imaging under the physiological condition; (3) can provide the 3-D view of the molecule/submolecule resolution of biomolecule and biological surface; (4) can observe local electric density and physical characteristics with the resolution of nanoscale, measure the interaction force of intermolecular (as micro-cantilever and water intermediate ion, acceptor and part); (5) can handle single biomolecule; In addition, the information that obtains by AFM can also with other analytical technology and microscopy complementation.

The micro-cantilever sensor, as it in AFM, showed, can be used as the favourable instrument of the real-time online measuring of physics, biochemical property fully.Because the absorption induction force causes the atomic primary deflector of micro-cantilever, cause variation of resonant frequency owing to adsorbed molecular mass is different, these extremely responsive variations can reach the sensitivity of ppb to ppt fully.It seems by list of references, the research of this respect carried out that domestic also have the scientific research personnel of part biological medical science nanometer technology specialty to carry out the research that AFM measures the biomolecule interphase interaction abroad.

Summary of the invention

The method and apparatus that the purpose of this invention is to provide a kind of micro-cantilever sensor trace materials in measuring liquid.From the accurate sensing of micro-cantilever, in conjunction with the AFM technology, it is applied in the liquid trace materials detects, utilize that the micro-cantilever sensor is real-time, online, the trace materials content in the measure water.

Above-mentioned purpose of the present invention is achieved through the following technical solutions:

One, the method for a kind of micro-cantilever sensor trace materials in measuring liquid

(1) water pump respectively through testing liquid and normal fluid through passage, by a switch, sample is squeezed into liquid cell;

(2) bottom surface is to place micro-cantilever in the transparent material liquid cell, beats at the micro-cantilever reflective surface with beam of laser, surveys the displacement that reflected light is learnt micro-cantilever with the 2 D photoelectric detector of a position sensing;

(3) switch has the third gear passage, promptly close, open the testing liquid passage and open the normal fluid passage, when testing liquid through out-of-date because the suction-operated of material therebetween, micro-cantilever has fluctuation, so the reflection of laser beam also just rises and falls thereupon;

(4) the position sensing photodetector receives the reflector laser signal, and control circuit as calculated amplifies, handles and normal fluid is compared with the same manner gained signal, can obtain to represent the information of ion concentration.

Two, the device of a kind of micro-cantilever sensor trace materials in measuring liquid

Water pump connects normal fluid and testing liquid respectively through passage, connect the conversion switch more respectively, the switch outlet connects the liquid cell that the bottom surface is a transparent material, and micro-cantilever is set in the liquid cell, laser beam enters from the liquid cell bottom surface through the micro-cantilever bottom reflection to detector, and detector is electrically connected with computing machine.

The present invention compared with prior art, the beneficial effect that has is: detect from the precision of trace materials, the AFM technology is applied to the water pollution detection, utilize micro-cantilever sensor absorption induction, in real time, the micro ion content in online, the measure water, the present invention helps real-time water pollution detection fast.

Description of drawings

Fig. 1 is a micro-cantilever principle schematic of the present invention; Micro-cantilever side view before Fig. 1 a micro-cantilever vertical view, Fig. 1 b suction-operated, Fig. 1 c absorption causing micro-cantilever bending;

Fig. 2 is a measuring method schematic representation of apparatus of the present invention.

Among the figure: 1, water pump, 2, normal fluid, 3, testing liquid, 4, switch, 5, liquid cell, 6, micro-cantilever, 7, laser, 8, detector, 9, computing machine, 10, liquid outlet.

Embodiment

The invention will be further described below in conjunction with drawings and Examples.

As shown in Figure 2, water pump 1 connects normal fluid 2 and testing liquid 3 respectively through passage, connect conversion switch 4 more respectively, switch 4 outlets connect the liquid cell 5 that the bottom surface is a transparent material, micro-cantilever 6 is set in the liquid cell, laser beam enters from liquid cell 5 bottom surfaces through micro-cantilever 7 bottom reflections to detector 8, and detector 8 is electrically connected with computing machine 9, and 10 is the liquid outlet of liquid cell.

Micro-cantilever (as shown in Figure 1a) has shown that in atomic force microscope it is as the unusual huge power of sensitive force transducer.Equally, micro-cantilever also can be used as biochemical sensor and comes surface measurements pressure: biological sample produces surface pressing in the suction-operated meeting on micro-cantilever (shown in Fig. 1 b) surface, thereby causes the bending (shown in Fig. 1 c) of micro-cantilever.It can measure 10 ^-4The pressure of N/m changes, and chemical bond is about 10 ^-9～10 ^-11Between the N.As seen the elastic constant of the bending that causes of ion adsorption and micro-cantilever is in same magnitude.

The length of supposing micro-cantilever is L, and wide is w, and thick is t, and have L＞＞w＞＞t.The micro-cantilever bending radius that absorption causes is R (as shown in Figure 1).

Relation between micro-cantilever surface pressing g and the surface free energy γ, can represent with the Shuttleworth formula:

$g=\mathrm{\γ}+\frac{\∂\mathrm{\γ}}{\∂\mathrm{\ϵ}}$

Surface tension  ε is defined as the variation of surface area: $\∂\mathrm{\ϵ}=\frac{\mathrm{dA}}{A}$

Bending that micro-cantilever causes and its length are compared very little.Can ignore surface tension effect, think that the variation of micro-cantilever free energy equals the variation of its surface pressing.

The Stoney formula has been described the displacement (Δ z) of the micro-cantilever after the bending and the variation of surface pressing, the relation of the variation of free energy in other words (δ g):

$\mathrm{\&Delta;z}=\frac{3(1-v)L^2}{\mathrm{<figure-callout\; id="2"\; label="E\; t"\; filenames="A20061015551000081.png"\; state="\{\{state\}\}">E</figure-callout>}{t}^{}{}^2}\mathrm{\&delta;g}$

V is the Poisson coefficient, and E is a Young modulus.Like this, the variation of its surface pressing is learnt in the displacement that can measure micro-cantilever.And the micro-cantilever surface pressing is closely related with the concentration of trace materials, i.e. the concentration of displacement of micro-cantilever and trace materials is closely related.

Specific embodiments, as shown in Figure 2

(1) micro pump by a switch, is slowly squeezed into liquid cell with sample through passage (comprising testing liquid and normal fluid), discharges by the outlet of liquid cell opposite side at last;

(2) make with transparent material the liquid cell bottom surface, places micro-cantilever therein.With a branch of wavelength 680nm, the semiconductor laser of power 10mW is beaten at the micro-cantilever reflective surface, surveys the displacement that reflected light is learnt micro-cantilever with the 2 D photoelectric detector (as the shore pine S1743 of company model) of a position sensing.Because the shake of liquid level will influence the trend of laser optical path, cause serious error, ad hoc meter laser enters from the bottom surface, reduces to the influence that liquid flow causes minimum;

(3) switch has 3 grades: close, open the testing liquid passage and open the normal fluid passage.When testing liquid through out-of-date because the suction-operated of material therebetween, micro-cantilever has fluctuation, so the reflection of laser beam also just rises and falls thereupon;

(4) the position sensing photodetector receives the reflector laser signal, output current signal.Amplify through control circuit, be converted into voltage signal, finally gather into computer and handle, obtain the deformation quantity size of micro-cantilever by the A/D interface.By and normal fluid (pure water) compare with the same manner gained signal, can obtain to represent the information of aspects such as ion concentration;

(5) micro-cantilever is made by one 100～500 μ m silicon chip or nitrogenize silicon chip long and that approximately 500nm～5 μ m are thick.There is a sharpened tip on the micro-cantilever top, is used for interaction force between test sample one needle point.Micro-cantilever has certain specification, as: the shape of length, width, elasticity coefficient and needle point, select dissimilar probes according to the characteristic of sample.

(6) with the known sample that contains variable concentrations or trace materials kind, reach dissimilar micro-cantilevers and do test, set up corresponding database, deposit in the computer software.Can detect unknown sample.

Claims (2)

1. the method for trace materials in the micro-cantilever sensor measurement liquid is characterized in that the step of this method is as follows:

(1) water pump respectively through testing liquid and normal fluid through passage, by a switch, sample is squeezed into liquid cell;

(2) bottom surface is to place micro-cantilever in the liquid cell of transparent material, beats at the micro-cantilever reflective surface with beam of laser, surveys the displacement that reflected light is learnt micro-cantilever with the 2 D photoelectric detector of a position sensing;

(3) switch has the third gear passage, promptly close, open the testing liquid passage and open the normal fluid passage, when testing liquid through out-of-date because the suction-operated of material therebetween, micro-cantilever has fluctuation, so the reflection of laser beam also just rises and falls thereupon;

(4) the position sensing photodetector receives the reflector laser signal, and control circuit as calculated amplifies, handles and normal fluid is compared with the same manner gained signal, can obtain to represent the information of ion concentration.

2. the device of trace materials in the micro-cantilever sensor measurement liquid, it is characterized in that: water pump (1) connects normal fluid (2) and testing liquid (3) respectively through passage, connect conversion switch (4) more respectively, switch (4) outlet connects the liquid cell that the bottom surface is a transparent material (5), micro-cantilever (6) is set in the liquid cell, laser beam enters from liquid cell (5) bottom surface through micro-cantilever (7) bottom reflection to detector (8), and detector (8) is electrically connected with computing machine (9).

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