CN203337513U - Micro-fluidic chip particle counting system based on electrical impedance technology - Google Patents
Micro-fluidic chip particle counting system based on electrical impedance technology Download PDFInfo
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- CN203337513U CN203337513U CN2013203174078U CN201320317407U CN203337513U CN 203337513 U CN203337513 U CN 203337513U CN 2013203174078 U CN2013203174078 U CN 2013203174078U CN 201320317407 U CN201320317407 U CN 201320317407U CN 203337513 U CN203337513 U CN 203337513U
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Abstract
The utility model discloses a micro-fluidic chip particle counting system based on an electrical impedance technology. The micro-fluidic chip particle counting system comprises a micro-fluidic chip and a signal detection circuit, wherein the micro-fluidic chip comprises a glass substrate, a PDMS (Polydimethylsiloxane) substrate and two pairs of metal needles taken as electrodes. The micro-fluidic chip utilizes the common conductive metal needles as the electrodes so as to generate an electric field for generating a cross micro-channel, so that the manufacturing process of the chip is relatively simple and the cost of the chip is relatively low. The signal detection circuit comprises two I/V switching circuits, a difference circuit, an envelope detection circuit, a high-pass filtering circuit, a low-pass filtering circuit and an amplification circuit. According to the micro-fluidic chip particle counting system based on the electrical impedance technology, a signal differential detection method is used for detecting an impedance signal in the signal detection circuit so as to guarantee the accuracy of signal detection.
Description
Technical field
Utility model relates to a kind of counting micro particles system, is specifically related to a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology, belongs to the electrical detection technical field.
Background technology
The electrical impedance counting technology is the earliest for particulate/Cytometric automatic technology.Because particulate/cell can be used as insulating bodies to a certain extent, when particulate/cell passes through a certain fixed area electric field, can make the impedance in this stationary electric field zone become large; When particulate/cell leaves electric field region, it is normal that impedance recovers again; The size of impedance signal and the volume of particulate/cell are directly proportional.Therefore people utilize this characteristic particulate/cell is counted and classified.But present commercial electrical impedance counter is generally relatively large, can't meet portable requirement; And the counting technology based on the micro-fluidic chip technology provides for this requirement the possibility solved.
The micro-fluidic chip technology refers to integrated basic operation units such as sample preparation related in the fields such as biological and chemical, reaction, separation, detections or substantially is integrated on the chip of more than square centimeters (even less), form network by microchannel, run through whole system with controlled fluid, in order to a kind of technology platform of the various functions that replace conventional biological or chemical laboratory.Obviously, the micro-fluidic chip technology has the series of features such as volume is little, portable high, application is convenient, and making becomes possibility to instant detection the in the scene of some pathology parameters, and application space is very extensive.Nearly ten years, the micro-fluidic chip technical development is very rapid, especially in the research field for particulate/cell count and sorting.
But the micro-fluidic chip counting micro particles device of present stage all need to be electroplated on micro-fluidic chip or splash-proofing sputtering metal as electrode, and by electrode for generation of the electric field across microchannel.This design makes chip manufacturing process and cost relative complex, and cost compare is high.This design simultaneously, the electrode each interval is very near, easily causes passage internal induction electric field intensity inhomogeneous.Even the particulate of same class size, due to the position difference of the microchannel of flowing through, also can cause signal intensity to differ; Have a strong impact on the concrete application of counting assembly.In order to solve this class problem, the researchist introduces various focus methods, and for example dielectrophoresis focuses on, and the methods such as ultrasound wave focusing are focused on particulate/cell, although improved so to a certain extent signal stabilization, also improved complexity and the cost of package unit simultaneously.
Simultaneously, in the micro-fluidic chip counting micro particles device of present stage, because signal to noise ratio (S/N ratio) is lower, so detection system generally adopts the technology of more complicated, synchronous detection technology for example, or use very expensive instrument, realize the detection to feeble signal such as lock-in amplifier etc.Make the cost burden of whole device very large, special-purpose instrument, also can't meet portability, requirement cheaply simultaneously.
Summary of the invention
In view of this, the utility model provides a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology, and this system architecture is simple, easily manufactured, cost is low and be easy to carry.
Micro-fluidic chip counting micro particles system based on electrical impedance technology, comprise micro-fluidic chip and signal deteching circuit; Described micro-fluidic chip comprises: glass substrate, polydimethylsiloxane substrate and two pairs of metal needles as electrode; Described signal deteching circuit comprises: two I/V change-over circuits, difference channel, envelope detection circuit, high-pass filtering circuit, low-pass filter circuit and amplifying circuits.
In described micro-fluidic chip, the PDMS substrate is bonded in the upper surface of glass substrate, at the PDMS substrate upper surface, is processed with respectively sample flow entrance, liquid flow export, sprue, sheath fluid inflow entrance and electrode mounting hole; Be specially: in the center of PDMS substrate upper surface, process along its length strip groove as sprue; Symmetria bilateralis processing two arrays of electrodes mounting hole at sprue, be embedded in a metal needle at each electrode mounting hole; Between four electrode mounting holes and sprue, by rectangular recess, connect.At an end end processing of sprue and the sample flow entrance of sprue perforation, the liquid flow export that end processing and the sprue of the other end connects.Symmetria bilateralis at described sample flow entrance is processed with the sheath fluid inflow entrance, and two sheath fluid inflow entrances and sprue connect; The degree of depth of above-mentioned sample flow entrance, liquid flow export, sheath fluid inflow entrance and electrode mounting hole all with the consistency of thickness of PDMS substrate; Be referred to as microchannel by the sprue on described micro-fluidic chip and with the passage that sprue connects, the degree of depth of described microchannel is all consistent; In two pairs of metal needles on described micro-fluidic chip, two metal needles that are positioned at sprue one side are connected with outside sine wave AC driving source respectively, and each is connected two metal needles of opposite side with an I/V change-over circuit.
In described signal deteching circuit, the output terminal of two I/V change-over circuits is connected with two input ends of difference channel respectively, the output terminal of difference channel is connected with envelope detection circuit, envelope detection circuit is connected with low-pass filter circuit by high-pass filtering circuit, the amplifying circuit of the output termination afterbody of low-pass filter circuit; Described I/V change-over circuit is for being converted to voltage signal by the current signal collected, and the two-way voltage signal produces into differential signal by difference channel.Described envelope detection circuit is used for extracting the impedance signal of differential signal, and the impedance signal extracted is carried out to the amplification of the first order; After flip-flop in the received impedance signal of high-pass filtering circuit filtering, impedance signal is carried out to the amplification of the second level; After carrier signal in the impedance signal that the low-pass filter circuit filtering receives, by amplifying circuit, impedance signal is carried out the amplification of afterbody, the number of the last impedance signal according to output realizes the counting to particulate.
The degree of depth of described sprue and width are 1.5 times to 3 times of mean particle dia to be detected; Between through electrode mounting hole and sprue, the width of rectangular recess is 10 μ m to 50 μ m; Described electrode mounting hole and and sprue between the distance be 20 μ m; Distance H between two groups of metal needles
1be 100 μ m to 200 μ m.
In described signal deteching circuit, the version of two I/V change-over circuits is identical; The I/V change-over circuit comprises operational amplifier A and sampling resistor; The electrode input end ground connection of operational amplifier A wherein, negative input is connected with the metal needle as electrode, between its output terminal and negative input, is connected sampling resistor R0; Described difference channel comprises differential amplifier U1, operational amplifier C, resistance R 3 and resistance R 4; In two I/V change-over circuits, the output terminal of operational amplifier is connected with two input ends of differential amplifier U1 respectively, the output terminal of differential amplifier U1 is connected with the electrode input end of operational amplifier C, the negative input of operational amplifier C passes through resistance R 3 ground connection, simultaneously contact resistance R4 between its negative input and output terminal; The output terminal of operational amplifier C is connected with envelope detection circuit.
Described envelope detection circuit comprises diode D6, resistance R 2, capacitor C 1 and operational amplifier D; The output terminal of operational amplifier C is connected with the negative electrode of diode D6, and the anode of diode D6 is connected with the electrode input end of operational amplifier D; After resistance R 2 and capacitor C 1 parallel connection, be connected between the anode and ground of diode; The output terminal of described operational amplifier D is connected with high-pass filtering circuit.
Described high-pass filtering circuit comprises operational amplifier E, resistance R 5, resistance R 6, capacitor C 2 and capacitor C 3; The output terminal of operational amplifier D passes through resistance R 5 and is connected with the electrode input end of operational amplifier E after resistance R 6 successively, the electrode input end of operational amplifier E is by capacitor C 3 ground connection simultaneously, one end of capacitor C 2 is connected with the output terminal of operational amplifier E, and the other end is connected between resistance R 5 and resistance R 6; Contact resistance R7 between the negative input of operational amplifier E and ground, connecting resistance R8 between its negative input and output terminal; The output terminal of operational amplifier E is connected with low-pass filter circuit.
Described low-pass filter circuit comprises resistance R 9, resistance R 12, capacitor C 4, capacitor C 5 and operational amplifier F; The output terminal of operational amplifier E is connected with the electrode input end of operational amplifier F with capacitor C 5 by capacitor C 4, and the electrode input end of operational amplifier F is by resistance R 9 ground connection simultaneously; One end of resistance R 12 is connected with the output terminal of operational amplifier F, and the other end is connected between capacitor C 4 and capacitor C 5; Contact resistance R10 between operational amplifier F negative input and ground, connecting resistance R11 between operational amplifier F negative input and output terminal; The output terminal of operational amplifier F is connected with amplifying circuit.
Described amplifying circuit comprises operational amplifier H, resistance R 13 and resistance R 14; The output terminal of described operational amplifier F is connected with the electrode input end of operational amplifier H, and the negative input of operational amplifier H is by resistance R 13 ground connection, simultaneously contact resistance R14 between the output terminal of operational amplifier H and negative input.
Described sine wave AC driving source frequency is 500KHz～1.2MHz, and peak value is 3V～5V.
In described I/V change-over circuit, the resistance of sampling resistor is 30K Ω～300K Ω, and the enlargement factor of described differential amplifier U1 is less than or equal to 10 times, and described low-pass filter circuit cutoff frequency is 1/10th of sine-wave excitation frequency input signal.
The described metal needle as electrode is acupuncture needle or platinum pin.
Beneficial effect:
This system directly is arranged on the conducting metal pin on micro-fluidic chip as electrode, thereby produces the electric field across microchannel, makes that chip manufacturing process is simple, cost is low; This kind of design simultaneously, electrode interval to each other is by the width decision of sprue, and two electrode symmetries are installed on the sprue both sides, make the induction field even intensity in induction zone, guarantee the stability of impedance signal.
For guaranteeing the accuracy of input, in this system, at the symmetria bilateralis processing sheath fluid inflow entrance of sample flow entrance, utilize sheath fluid stream that particulate is one by one gathered to more fixing fluid position, thereby be convenient to the detection of signal.
In this system, adopt differential signal detection circuit to improve the degree of accuracy of detection simultaneously, not only can improve the sensitivity of input, make the cost of whole system little simultaneously, can meet portability, cheaply requirement.
The accompanying drawing explanation
Fig. 1 is the structural representation for the micro-fluidic chip of counting micro particles;
The vertical view that Fig. 2 is the PDMS substrate;
The enlarged drawing that Fig. 3 is the induction of signal district;
The integrated connection figure that Fig. 4 is this system;
The circuit theory diagrams that Fig. 5 is I/V conversion, differential amplification and envelope detection part;
The circuit theory diagrams that Fig. 6 is high-pass filtering and low-pass filtering part;
Fig. 7 passes through for the particulate that adopts system of the present utility model to detect the differential signal that the electro-induction district forms;
Fig. 8 is for adopting the testing result comparison diagram of the utility model and prior art.
Wherein, 1-glass substrate, 2-PDMS substrate, 3-sample flow entrance, 4-liquid flow export, 5-sprue, 6-sheath fluid inflow entrance, 7-electrode mounting hole, 8-respond to core space, 9-sense blind area, 10-metal needle, 11-induction of signal district
Embodiment
Below in conjunction with the accompanying drawing embodiment that develops simultaneously, the utility model is described in detail.
The present embodiment provides a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology, this system is utilized the electrode of common conducting metal pin as micro-fluidic chip, and utilize the method that signal differential detects to be detected its impedance signal, there is simple, the with low cost and feature such as be easy to carry of chip manufacturing process.
This system comprises micro-fluidic chip and signal deteching circuit.Wherein micro-fluidic chip comprises: glass substrate, PDMS(dimethyl silicone polymer) substrate and two pairs of metal needles as electrode.Signal deteching circuit comprises: two I/V change-over circuits, difference channel, envelope detection circuit, high-pass filtering circuit, low-pass filter circuit and amplifying circuits.The integrated connection of this system closes: in two pairs of metal needles on micro-fluidic chip, two metal needles that are positioned at sprue one side are connected with outside sine wave AC driving source respectively, and each is connected two metal needles of opposite side with an I/V change-over circuit.Described sine wave AC driving source frequency range is chosen as between 500KHz～1.2MHz, the peak value scope at 3V between 5V.
As shown in Figure 1, wherein metal needle requires to conduct electricity the concrete structure of the micro-fluidic chip for counting micro particles that the present embodiment provides, and certain biocompatibility and stability are arranged, and adopts acupuncture needle in the present embodiment.The PDMS substrate is bonded in the upper surface of glass substrate, is processed with respectively sample flow entrance, liquid flow export, sprue, sheath fluid inflow entrance and electrode mounting hole on the PDMS substrate, as shown in Figure 2.Be specially: in the center of PDMS substrate upper surface, process along its length strip groove as sprue; Symmetria bilateralis at sprue is processed with two groups of (two every group) electrode mounting holes (two along the sprue symmetry is a group), at each electrode mounting hole, is embedded in a metal needle.The consistency of thickness of the degree of depth of described electrode mounting hole and PDMS substrate; Between four electrode mounting holes and sprue, by rectangular recess, connect.An end end processing at sprue is used as the sample flow entrance with the circular hole that sprue connects, and the circular hole that end processing and the sprue of the other end connects is as the liquid flow export.Some particulate, be easy to be sticked together such as cell etc., affects the detection of signal; For guaranteeing the accuracy of input, in the present embodiment, utilize sheath fluid stream that particulate is one by one gathered to more fixing fluid position, symmetria bilateralis processing circular hole at the sample flow entrance is used as the sheath fluid inflow entrance for this reason, and described two sheath fluid inflow entrances connect by bar-shaped trough and the sprue tilted.The degree of depth of above-mentioned sample flow entrance, liquid flow export and sheath fluid inflow entrance all with the consistency of thickness of PDMS substrate.
Below the size Selection that directly affects system sensitivity on the PDMS substrate is described in detail.
On the PDMS substrate, along the zone between two metal needles of sprue symmetry, be the induction of signal district, the enlarged drawing in induction of signal district is as shown in Figure 3.In impedance signal detects, the volume in induction of signal district and the volume ratio of particulate/cell to be detected are very important parameters.If this ratio is too large, can cause input sensitivity low.The induction of signal district comprises induction core space and sense blind area, and wherein the zone of sprue between symmetrical two metal needles is the induction core space; Coupling part between sprue and electrode mounting hole is sense blind area.Wherein respond to the volume of core space and determined by the degree of depth, width and the electrode mounting hole of sprue and the width of the rectangular recess between sprue, ideally, the volume of particulate/cell to be detected is more approaching better with the volume of induction core space; But, in actual conditions, if too approaching, be easy to cause sprue to get clogged.Therefore, in the present embodiment, the degree of depth of sprue and width all are taken as to 1.5 times of mean particle dia to be detected, can when guaranteeing detection sensitivity, block sprue.Between electrode mounting hole and sprue, the width of rectangular recess has defined the coverage of electric field, if too little, is unfavorable for that processing realizes; If too large, make the volume of induction core space and the volume ratio of particulate to be detected increase, and then reduced the sensitivity of system; In the present embodiment, the width of this rectangular recess is set to 20 μ m.The volume of sense blind area by the degree of depth, width and the electrode mounting hole of the rectangular recess between electrode mounting hole and sprue and and sprue between distance determine.In theory, the distance between electrode mounting hole and sprue is the smaller the better.Be confined to micro fabrication, if be worked into very littlely, can cause yield rate too low, therefore under guaranteeing than the prerequisite of high finished product rate, in the present embodiment electrode mounting hole with and sprue between apart from being chosen as 20 μ m.。By the sprue on described micro-fluidic chip and and the passage that connects of sprue (comprising the bar shaped between rectangular recess between electrode mounting hole and sprue, two sheath fluid inflow entrances and sprue) be referred to as microchannel, the degree of depth of microchannel is consistent.
For the degree of accuracy improve detected, this system is carried out difference processing to two groups of impedance signals, and the distance H between two groups of metal needles directly affects the effect of input.Although the position of electric field is limited by the size of sprue, electric field outwards itself needs an attenuation process at the induction core space; If two pairs of electrode contacts are too near, the electric field produced between the two pairs of electrodes easily interferes with each other, and is unfavorable for input; If but at a distance of too far away, the detection rates of reduction particulate that can be serious.Distance H in the present embodiment between two groups of metal needles
1be 100 μ m, under this distance, guaranteed the detection rates of particulate, the electric field produced between while two pairs of electrodes can not interfere with each other yet.
When the nonconductors such as particulate/cell pass through the induction of signal district, the anti-increase of the overall resistance in induction of signal district; Once particulate/cell leaves, it is normal that the electrical impedance in induction of signal district is recovered again; A projection on the time impedance signal has been reacted above-mentioned whole process.Because the electric field at induction zone is an AC field, and particulate/cell flow rate is corresponding very fast, so impedance signal on feature, approaches an amplitude-modulated signal very much.For this judgement, the utility model utilizes the principles of modulation and demodulation of envelope detection, designs the respective impedance signal deteching circuit.In order to improve accuracy of detection and sensitivity, utilize difference detecting method simultaneously, utilize two pairs of electrode needle to combine to realize differential signal.In signal deteching circuit, wherein the output terminal of two I/V change-over circuits is connected with two input ends of difference channel respectively, the output terminal of difference channel is connected with envelope detection circuit, the output signal of envelope detection circuit is after amplifying circuit amplifies, by high-pass filtering circuit and low-pass filter circuit, signal is processed again the amplifying circuit of the output termination afterbody of low-pass filter circuit.
Described I/V change-over circuit is for being converted to voltage signal by current signal, and the two-way voltage signal produces into differential signal by difference channel, and envelope detection circuit is for extracting the rough envelope of differential signal, and particulate/cell passes through the impedance signal of electric field; Then by high-pass filtering circuit filtering flip-flop, amplifying circuit subsequently amplifies signal, then sends to the further filtering carrier signal of low-pass filter circuit, finally utilizes amplifying circuit to be amplified signal, so that identification; Then just can or show signals collecting.The parameter of envelope detection circuit and filtering circuit depends on the speed of particulate/cell to be measured through the electro-induction district.The selection of operational amplifier in circuit must meet higher gain bandwidth product and lower bias current input requirements simultaneously, and the noise inputs error is also as much as possible little.
The concrete structure of signal deteching circuit as shown in Figure 5 and Figure 6.Described I/V change-over circuit is realized by operational amplifier and sampling resistor.Selected the integrated operational amplifier U2 that contains four operational amplifiers (being respectively operational amplifier A, B, C, D) in the present embodiment.Wherein operational amplifier A and operational amplifier B are respectively used to two I/V change-over circuits, two I/V change-over circuits identical version of sampling.Take operational amplifier A as example, the electrode input end ground connection of operational amplifier A, negative input is connected with the metal needle as electrode, be connected sampling resistor R0 between its output terminal and negative input, in order to reduce error, R0 selects high-accuracy resistance, and its resistance is directly proportional to the volume in induction of signal district, scope at 30K Ω between 300K Ω.Described difference channel comprises differential amplifier U1 and operational amplifier C; The output terminal of operational amplifier A and operational amplifier B is connected with two input ends of differential amplifier U1 respectively, and the enlargement factor of differential amplifier U1 can not arrange too large, take interior as good for 10 times.The output terminal of differential amplifier U1 is connected with the electrode input end of operational amplifier C, the negative input of operational amplifier C is by resistance R 3 ground connection, contact resistance R4 between its negative input and output terminal, utilize operational amplifier C and resistance R 3, R4 further to amplify 23 times to the output signal of differential amplifier U1 in the present embodiment simultaneously.The output terminal of operational amplifier C is connected with envelope detection circuit, and described envelope detection circuit comprises diode D6, resistance R 2, capacitor C 1 and operational amplifier D.The output terminal of operational amplifier C is connected with the negative electrode of diode D6, and the anode of diode D6 is connected with the electrode input end of operational amplifier D; After resistance R 2 and capacitor C 1 parallel connection, be connected between the anode and ground of diode D6.In the envelope detection circuit of the present embodiment, diode opposite direction in the direction of diode D6 and envelope detector commonly used; Because the signal of I/V change-over circuit collection is a current signal, while due to particulate/stream of cells, crossing the induction of signal district, this zone impedance increases, and current value reduces, and the signal therefore collected is a signal that peak value is downward; Here utilize reverse diode to arrange signal is swung to processing, make the peak value of signal upwards.The value of resistance R 2 and capacitor C 1 has determined the detection scope of envelope detection, so the selection of its value should, much smaller than the incoming frequency of sine-wave excitation, also be greater than particulate cutting induction zone electric field frequency simultaneously.Operational amplifier D, for follower, plays the effect of impedance matching.
The output terminal of operational amplifier D is connected with high-pass filtering circuit.As shown in Figure 6, this part has been selected the integrated operational amplifier U3 that contains four operational amplifiers to the detailed construction of described high-pass filtering circuit and low-pass filter circuit, has only used wherein three in the present embodiment, is respectively operational amplifier E, F, H.Wherein operational amplifier E and resistance R 5, resistance R 6, capacitor C 2, capacitor C 3 form the Order RC high-pass filtering circuit, the output terminal of operational amplifier D passes through resistance R 5 and is connected with the electrode input end of operational amplifier E after resistance R 6 successively, the electrode input end of operational amplifier E is by capacitor C 3 ground connection simultaneously, one end of capacitor C 3 is connected with the output terminal of operational amplifier E, and the other end is connected between resistance R 5 and resistance R 6.In the present embodiment, the cutoff frequency of high-pass filtering circuit is in the 10Hz left and right, for the DC component after the filtering envelope detection.Then utilize negative input and the resistance R between ground 7 that is connected on operational amplifier E, and the resistance R between negative input and output terminal 8 is put and is twice to its output signal.
The output terminal of operational amplifier E is connected with low-pass filter circuit.The Order RC low-pass filter that described low-pass filter circuit forms for the operational amplifier F in resistance R 9, resistance R 12, capacitor C 4, capacitor C 5 and operational amplifier U3.The output terminal of operational amplifier E is connected with the electrode input end of operational amplifier F with capacitor C 5 by capacitor C 4, and the electrode input end of operational amplifier F is by resistance R 9 ground connection simultaneously.One end of resistance R 12 is connected with the output terminal of operational amplifier F, and the other end is connected between capacitor C 4 and capacitor C 5.Low-pass filter circuit is for the sine wave exciting signal component of further filtered signal, and its cutoff frequency is relevant with the input sine wave excitation components, elects 1/10th of sine-wave excitation frequency input signal in the present embodiment as.Then utilize the resistance R 10 between operational amplifier F negative input and ground, and the resistance R 11 between operational amplifier F negative input and output terminal is put and is twice to its output signal.
The output terminal of operational amplifier F is connected with the electrode input end of operational amplifier H, the negative input of operational amplifier F is by resistance R 13 ground connection, contact resistance R14 between the output terminal of operational amplifier H and negative input simultaneously, 14 pairs of signals of operational amplifier H and resistance R 13 and resistance R form the amplification of final step, and the output terminal of operational amplifier G outputs to final signal on display device or collecting device.
The principle of work of this counting micro particles system is:
Before measuring process starts, first in microchannel, be full of conducting solution, two electrodes of sprue one end connect sine wave AC excitation (frequency range is chosen as between 500KHz～1.2MHz, peak value scope at 3V between 5V), and two electrodes of the other end connect the impedance signal testing circuit.Like this, just formed an electric field between the electrode of every two symmetries, this electric field and microchannel intersection form the induction of signal district.
, now there is impedance signal to produce, and, in the electric field of second pair of create electrode subsequently, owing to there is no particulate/stream of cells mistake, occur so have any signal during through the electric field of first pair of create electrode when particulate/stream of cells.Signal deteching circuit utilizes the difference of this two paths of signals to be counted the particulate/cell in the induction of signal district that flows through, and can effectively increase system sensitivity.
Fig. 7 is while adopting native system, 10 μ m particulates are by the testing result after electric field region, and this curve has meaned that a particulate passes through the electro-induction district and the differential signal that forms.
Fig. 8 further tests comparing result by native system and existing flow cytometer, adopt hybrid fine particles sample (5 μ m, 10 μ m and 15 μ m), then sample is divided into to two parts, a part utilizes flow cytometer to be tested, and a part utilizes system of the present utility model to be tested in addition.Fig. 8 (a) is the Output rusults of flow cytometer, and horizontal ordinate is forward scattering light, and ordinate is side scattered light; Clearly demonstrate three sample collection districts in figure, it represents respectively 5 μ m(A), 10 μ m(B) and 15 μ m(C) particulate samples, its ratio is respectively 54.3%(9), 28.5%(10) and 12.6%(11).Measurement result is turned to the histogram based on forward scattering light, as shown in Figure 8 (b) shows.Adopt the measurement result of system described in the utility model as shown in Figure 9 (c), very obvious three piecemeals are arranged, every ratio that accounts for whole quantity is respectively 49.7%, 32.4%, 14,1%, and with Fig. 8 (a) with (b), consistance is very good.
Micro-fluidic chip counting micro particles device described in the utility model, simplicity of design, easily manufactured, with low cost, can meet people to the instant needs that detect in scene, at aspects such as environment measuring, biological study and medical diagnosiss, wide using value arranged.
In sum, these are only preferred embodiment of the present utility model, be not intended to limit protection domain of the present utility model.All within spirit of the present utility model and principle, any modification of doing, be equal to replacement, improvement etc., within all should being included in protection domain of the present utility model.
Claims (6)
1. the micro-fluidic chip counting micro particles system based on electrical impedance technology, is characterized in that, comprises micro-fluidic chip and signal deteching circuit; Described micro-fluidic chip comprises: glass substrate, polydimethylsiloxane substrate and two pairs of metal needles as electrode; Described signal deteching circuit comprises: two I/V change-over circuits, difference channel, envelope detection circuit, high-pass filtering circuit, low-pass filter circuit and amplifying circuits;
In described micro-fluidic chip, the PDMS substrate is bonded in the upper surface of glass substrate, at the PDMS substrate upper surface, is processed with respectively sample flow entrance, liquid flow export, sprue, sheath fluid inflow entrance and electrode mounting hole; Be specially: in the center of PDMS substrate upper surface, process along its length strip groove as sprue; Symmetria bilateralis processing two arrays of electrodes mounting hole at sprue, be embedded in a metal needle at each electrode mounting hole; Between four electrode mounting holes and sprue, by rectangular recess, connect; At an end end processing of sprue and the sample flow entrance of sprue perforation, the liquid flow export that end processing and the sprue of the other end connects; Symmetria bilateralis at described sample flow entrance is processed with the sheath fluid inflow entrance, and two sheath fluid inflow entrances and sprue connect; The degree of depth of above-mentioned sample flow entrance, liquid flow export, sheath fluid inflow entrance and electrode mounting hole all with the consistency of thickness of PDMS substrate; Be referred to as microchannel by the sprue on described micro-fluidic chip and with the passage that sprue connects, the degree of depth of described microchannel is all consistent; In two pairs of metal needles on described micro-fluidic chip, two metal needles that are positioned at sprue one side are connected with outside sine wave AC driving source respectively, and each is connected two metal needles of opposite side with an I/V change-over circuit;
In described signal deteching circuit, the output terminal of two I/V change-over circuits is connected with two input ends of difference channel respectively, the output terminal of difference channel is connected with envelope detection circuit, envelope detection circuit is connected with low-pass filter circuit by high-pass filtering circuit, the amplifying circuit of the output termination afterbody of low-pass filter circuit; Described I/V change-over circuit is for being converted to voltage signal by the current signal collected, and the two-way voltage signal produces into differential signal by difference channel; Described envelope detection circuit is used for extracting the impedance signal of differential signal, and the impedance signal extracted is carried out to the amplification of the first order; After flip-flop in the received impedance signal of high-pass filtering circuit filtering, impedance signal is carried out to the amplification of the second level; After carrier signal in the impedance signal that the low-pass filter circuit filtering receives, by amplifying circuit, impedance signal is carried out the amplification of afterbody, the number of the last impedance signal according to output realizes the counting to particulate.
2. a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology according to claim 1, it is characterized in that: the degree of depth of described sprue and width are 1.5 times to 3 times of mean particle dia to be detected; Between through electrode mounting hole and sprue, the width of rectangular recess is 10 μ m to 50 μ m; Described electrode mounting hole and and sprue between the distance be 20 μ m; Distance H between two groups of metal needles
1be 100 μ m to 200 μ m.
3. a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology according to claim 1, it is characterized in that: in described signal deteching circuit, the version of two I/V change-over circuits is identical; The I/V change-over circuit comprises operational amplifier A and sampling resistor; The electrode input end ground connection of operational amplifier A wherein, negative input is connected with the metal needle as electrode, between its output terminal and negative input, is connected sampling resistor R0; Described difference channel comprises differential amplifier U1, operational amplifier C, resistance R 3 and resistance R 4; In two I/V change-over circuits, the output terminal of operational amplifier is connected with two input ends of differential amplifier U1 respectively, the output terminal of differential amplifier U1 is connected with the electrode input end of operational amplifier C, the negative input of operational amplifier C passes through resistance R 3 ground connection, simultaneously contact resistance R4 between its negative input and output terminal; The output terminal of operational amplifier C is connected with envelope detection circuit;
Described envelope detection circuit comprises diode D6, resistance R 2, capacitor C 1 and operational amplifier D; The output terminal of operational amplifier C is connected with the negative electrode of diode D6, and the anode of diode D6 is connected with the electrode input end of operational amplifier D; After resistance R 2 and capacitor C 1 parallel connection, be connected between the anode and ground of diode; The output terminal of described operational amplifier D is connected with high-pass filtering circuit;
Described high-pass filtering circuit comprises operational amplifier E, resistance R 5, resistance R 6, capacitor C 2 and capacitor C 3; The output terminal of operational amplifier D passes through resistance R 5 and is connected with the electrode input end of operational amplifier E after resistance R 6 successively, the electrode input end of operational amplifier E is by capacitor C 3 ground connection simultaneously, one end of capacitor C 2 is connected with the output terminal of operational amplifier E, and the other end is connected between resistance R 5 and resistance R 6; Contact resistance R7 between the negative input of operational amplifier E and ground, connecting resistance R8 between its negative input and output terminal; The output terminal of operational amplifier E is connected with low-pass filter circuit;
Described low-pass filter circuit comprises resistance R 9, resistance R 12, capacitor C 4, capacitor C 5 and operational amplifier F; The output terminal of operational amplifier E is connected with the electrode input end of operational amplifier F with capacitor C 5 by capacitor C 4, and the electrode input end of operational amplifier F is by resistance R 9 ground connection simultaneously; One end of resistance R 12 is connected with the output terminal of operational amplifier F, and the other end is connected between capacitor C 4 and capacitor C 5; Contact resistance R10 between operational amplifier F negative input and ground, connecting resistance R11 between operational amplifier F negative input and output terminal; The output terminal of operational amplifier F is connected with amplifying circuit;
Described amplifying circuit comprises operational amplifier H, resistance R 13 and resistance R 14; The output terminal of described operational amplifier F is connected with the electrode input end of operational amplifier H, and the negative input of operational amplifier H is by resistance R 13 ground connection, simultaneously contact resistance R14 between the output terminal of operational amplifier H and negative input.
4. a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology according to claim 1, it is characterized in that: described sine wave AC driving source frequency is 500KHz～1.2MHz, and peak value is 3V～5V.
5. a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology according to claim 1, it is characterized in that: in described I/V change-over circuit, the resistance of sampling resistor is 30K Ω～300K Ω, the enlargement factor of described differential amplifier U1 is less than or equal to 10 times, and described low-pass filter circuit cutoff frequency is 1/10th of sine-wave excitation frequency input signal.
6. a kind of micro-fluidic chip counting micro particles system based on electrical impedance technology according to claim 1 is characterized in that: the described metal needle as electrode is acupuncture needle or platinum pin.
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