CN104266680A - Microfluidics droplet detection system and method based on capacitive sensor - Google Patents
Microfluidics droplet detection system and method based on capacitive sensor Download PDFInfo
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Abstract
A microfluidics droplet detection system based on a capacitive sensor is characterized by comprising a droplet microfluidics chip, a direct-current voltage stabilizing circuit unit, a signal detection circuit unit and a computer, and the droplet microfluidics chip is of a structure according to which the capacitive sensor is integrated with a microchannel used for generating micro-droplets. A droplet detection method comprises the steps of sample pumping, droplet formation and droplet detection. The system and method have the advantages that the structure is simple, detection is conducted by means of the change of the capacitance, detection is quick, the size of the system is small, integration can be realized, the system and method are suitable for analysis of expensive samples and reagents, and manufacturing and implementation are easy.
Description
(1) technical field:
The invention belongs to microfluidic chip analysis field, particularly a kind of Microfluidic droplet detection system based on capacitive transducer and detection method.
(2) background technology:
Micro-fluidic chip is integrated on the chip of a piece several square centimeters by the basic operation unit such as sample preparation, reaction, separation, detection, cell chulture, sorting, cracking involved by biological and chemical field.Form network by microchannel, run through whole system with controlled fluid, in order to replace the various functions of conventional chemical or biology laboratory.Micro-fluidic chip sharpest edges are that multiple monotechnics flexible combination, scale on the small platform that entirety is controlled are integrated, and this makes micro-fluidic chip likely become the Important Platform of following biochemical analysis technological development.Drop is micro-fluidic is the emerging technology grown up in nearly ten years in the past, and main research is in the microchannel network closed, generate and manipulate the drop received and rise even skin upgrading.
The micro-fluidic maximum feature of drop is two kinds of liquid of formation drop is immiscible, such as water and oil, drop internal liquid and outside liquid are without diffusion, each drop can be regarded as an independent reaction chamber like this, reaction conditions in drop is not finished to be affected, and does not have cross pollution between sample.For drop, the size of drop, shape, the feature such as speed and inclusions concentration affect significantly for final biochemical expression and assay.So, carry out detecting in real time being very important to Liquid Drop Features.Researcher proposes a lot of detection method, as optical detecting method.Huebner etc. utilize the method for laser-induced fluorescence (LIF) to detect drop, can capture the change of drop geometric shape.Tkaczyk etc. are mixed with fluorescein in drop, and the laser excited through laser instrument irradiates back reflection to photon counter and photomultiplier by all kinds of means, thus the information such as the average length of detection drop and equispaced phase.The detection method of laser-induced fluorescence (LIF) detects that another name is all very high can reach Single Molecule Detection.But fluorescence labeling likely can cause the change of the biochemical activity of amalyzing substances, affects the confidence level of result.It is the average information of drop that photomultiplier detects what obtain, accurately can not control drop.And above two kinds of detection methods all need large-scale experimental apparatus, are unfavorable for integrated.
(3) summary of the invention:
The object of the present invention is to provide a kind of Microfluidic droplet detection system based on capacitive transducer and detection method, it can overcome the deficiencies in the prior art, be the system that a kind of structure that can be applicable to Microfluidic droplet is simple, be easy to processing and fabricating and realization, and the fast precision of the detection speed of its detection method is high.
Technical scheme of the present invention: a kind of Microfluidic droplet detection system based on capacitive transducer, is characterized in that it comprises drop micro-fluidic chip, direct current regulation circuit unit, signal deteching circuit unit and computing machine; Wherein, described drop micro-fluidic chip is the chip structure become one with the microchannel producing microlayer model by capacitive transducer; Described drop micro-fluidic chip by mutual bonding upper slice, bottom sheet and capacitive transducer form; Described bottom sheet is microchannel sheet, is welded with sample I entrance, sample II entrance, drop outlets, cross junction, electrode terminal, sample I passage, sample II passage and drop formation passage; Described sample I entrance is connected with sample I passage; Described sample II entrance is connected with sample II passage; Described sample I passage, sample II passage are by cross junction and drop formation expanding channels; Described drop formation expanding channels drop outlets; Described capacitive transducer is placed in the top of drop formation passage, and is connected with electrode terminal; Described upper slice on have and place the conduit of capacitive transducer; The output terminal of described direct current regulation circuit unit and the input end of signal deteching circuit unit are connected with the electrode terminal on drop micro-fluidic chip respectively; Described computing machine and signal deteching circuit unit are in being bi-directionally connected, and its output terminal is connected with the input end of direct current regulation circuit unit.
Described sample I entrance is continuous phase entrance, is made up of continuous phase sample I entrance and continuous phase sample I entrance II; Described sample I entrance I and sample I entrance II pumps into sample I respectively by pump I; Described sample II entrance is discrete phase entrance, and sample II entrance pumps into sample II by pump II; Described pump I is connected with sample I entrance and sample II entrance respectively by pipeline with pump II, is pumped into by sample in drop micro-fluidic chip passage.
Described electrode terminal has two, is electrode terminal I and electrode terminal II respectively; Described electrode terminal I is connected with the output terminal of direct current regulation circuit; Described electrode terminal II is connected with the input end of signal deteching circuit.
The Ψ type passage that the microchannel producing microlayer model in described drop micro-fluidic chip is made up of sample I passage, sample II passage and drop formation passage.
Described sample I passage has two, is sample I passage I and sample I passage II respectively.
Described sample II passage and drop formation passage are straight channel.
Described sample I passage I and sample I passage II is the curved passage in straight rear end, front end; Described front end straight passage portion is parallel to each other, and is parallel relation with sample II passage; The curved channel part in described rear end is the curved passage of 1/4 circle; Described sample I passage I, sample I passage II, sample II passage are connected at cross junction place with drop formation passage.
The size of described cross junction is less than the sectional dimension of sample I passage I, sample I passage II, sample II passage and drop formation passage on chip, is easy to form drop in process prepared by drop.
The sectional dimension of described sample I passage I, sample I passage II, sample II passage and drop formation passage is 200 μm * 200 μm; Described cross junction is of a size of 100 μm * 100 μm.
The center line of described capacitive transducer overlaps with the center line of drop formation passage, does not have interlayer therebetween; The capacitor plate of described capacitive transducer is positioned at the outlet ends place of drop formation passage, and the center line of capacitor plate overlaps with the center line of drop formation passage.
The making material of described drop micro-fluidic chip is dimethyl silicone polymer; Described capacitive transducer is plane interdigital structure, and material is the potpourri of silver and dimethyl silicone polymer.
Described signal deteching circuit unit is made up of the FM circuit containing concussion module, voltage to frequency f/V change-over circuit and low-pass filter circuit; The input end of described FM circuit receives the signal of drop microfluidic chip electrode terminals II, and its output terminal is connected with low-pass filter circuit by voltage to frequency f/V change-over circuit; The output terminal of described low-pass filter circuit is connected with computing machine.
Based on a Microfluidic droplet detection method for capacitive transducer, it is characterized in that it comprises the following steps:
1. pump I is connected with sample I entrance II with the entrance I of sample I respectively by two Teflon, pump II is connected with sample II entrance by Teflon, sample is pressed into the passage of drop micro-fluidic chip, sample I enters drop micro-fluidic chip by sample I entrance I and sample I entrance II, simultaneously, sample II enters drop micro-fluidic chip from sample II entrance, and two kinds of samples are respectively by sample I passage I, sample I passage II; Sample II passage flows into, and forms drop at cross junction place, and the size of drop, shape, generation frequency, speed are subject to the impact of the inlet velocity of sample I, the viscosity of sample I, the interfacial tension between sample I and sample II;
2. by direct current regulation circuit for sensor capacitance provides power supply, step 1. in the drop that obtains flow through capacitive transducer by drop formation passage, due to the difference of two kinds of liquid dielectric, cause the electric capacity of capacitive transducer to change, the electric capacity of change can drive outside signal deteching circuit to carry out work;
3. the FM circuit of signal deteching circuit unit receives the signal of capacitance variations, and the electric capacity of change also makes the concussion module in FM circuit produce different frequency value when resonance;
4. different frequency values is after voltage to frequency f/V change-over circuit, the frequency inverted produced during these resonance is become voltage signal and exports to low-pass filter circuit, signal lower than cutoff frequency passes through by low-pass filter circuit, signal higher than cutoff frequency filters out, and makes the signal of output smoothing to computing machine;
5. computing machine exports control signal to direct current regulation circuit unit, makes the DC voltage of direct current regulation circuit unit stable output; Computer export control signal is to signal deteching circuit unit, the capacitance change signal that the difference of drop causes is passed to signal deteching circuit unit by capacitive transducer, computing machine is passed to after signal deteching circuit unit, computing machine shows testing result intuitively, thus realizes the detection to sample;
6. last, the step 1. middle drop generated is flowed out by drop outlets by drop formation passage.
The application of described drop micro-fluidic chip comprises the size, shape, speed, the inclusion characteristics that detect drop; Drop in Microfluidic droplet system accurately controls and the composition of sample introduction sample of biological, chemistry, field of medicaments controls.
Principle of work of the present invention: based on the Microfluidic droplet detection chip of capacitive transducer principle, integrate drop formation and drop detection, the type of drive of all passages of micro-fluidic chip is all gas driven injection mode, chip is made up of upper and lower two panels and electric capacity three part, at upper processing electric capacity conduit, bottom sheet processing microchannel, in the conduit that electric capacity is embedded in slice, by upper slice and bottom sheet bonding, form the microchannel closed.
On chip, microchannel is used for producing the drop be separated, and capacitor on chip sensor is used for detecting drop; The effect of direct current regulation circuit (see Fig. 3) is the direct current of output voltage stabilization, is the normal work supply capacity of capacitive transducer; FM circuit (see Fig. 4) is using the part of capacitive transducer as alternator resonant loop, and when input quantity causes the electric capacity of capacitive transducer to change, the concussion frequency f of oscillator changes; F/V change-over circuit (see Fig. 5) converts frequency f variable signal to the voltage signal changed in proportion, and when incoming frequency f change makes, output voltage is response change also; Its effect the frequency f of oscillator in FM circuit is converted to voltage signal to export; Signal lower than cutoff frequency passes through by low-pass filter circuit (see Fig. 6), and the signal higher than cutoff frequency filters out, and the effect of low-pass filter circuit is here smoothed output signals.
Power supply in direct current regulation circuit (see Fig. 3) is 220V50Hz, for the energy of whole circuit inputs, be connected with transformer T-phase, single phase bridge type rectifier circu is formed by diode D1, D2, D3, D4, output single-phase sinusoidal voltage, single-phase sinusoidal voltage carries out filtering by C1, C2, C3, C4 tetra-electric capacity, and three terminal regulator U1, U2 and electric capacity C5, C6, C7, C8 form voltage stabilizing link, output DC stabilization ± 12V voltage.
R1, R2, R3, R4 and transistor Q1 form oscillatory circuit, and the frequency selection network forming oscillator by C10, C11, C12, L1 and variable capacitance Cx, completes He Ne laser.The resonance frequency change of the resonant circuit that variable capacitance Cx change causes inductance L 1 and variable capacitance Cx to form is thus the output frequency of realizing circuit changes (see Fig. 4).
But stablize electric capacity C14, integrating capacitor C13, the value exporting pull-up resistor R5 and R9 determines that frequency inverted is the scope of output voltage.C15, C16, C17, R7 are filter actions, play Anti-Jamming.Regulate R8 to trigger the operational amplifier of TD650 inside, TD650 is the chip (see Fig. 5) of a integrated voltage to frequency (F/V) translation circuit.
In low-pass filter circuit, R11, C18 and R12, C19 form Order RC filtering circuit, and in circuit, R10 forms feedback network (see Fig. 6).
Because sample I and sample II is two kinds of inconsistent liquid, the dielectric constants of two kinds of liquid is very large, general difference is tens times, flowing through capacitive transducer 5 specific inductive capacity only having sample I is a fixing number, when the stream of liquid droplets that contain sample II in sample I is through capacitive transducer 5, specific inductive capacity changes thus the capacitance of capacitive transducer 5 changes.The signal of change is connected the external circuit detection of electrode terminal 7 and 8, thus realizes the detection to drop, and the analogous diagram that drop produces as shown in Figure 7.
Know-why involved in the present invention: drop detection schematic diagram as shown in Figure 2, it utilizes two kinds of different sample solutions to form microlayer model at chip cross junction place, there is very large otherness in two kinds of sample solution self specific inductive capacity, when flowing through the capacitive transducer being connected (as shown in Figure 3) with direct current regulation circuit at drop, cause the change of capacitance, electric capacity forms LC sine wave oscillation circuit with outside FM circuit (as shown in Figure 4), the change of capacitive transducer makes the oscillation frequency of LC sine wave oscillation circuit change, through f/V change-over circuit (as shown in Figure 5), the oscillation frequency of LC sine wave oscillation circuit is converted into voltage signal, voltage signal after conversion is with the undesired signal of a lot of low frequency, through the undesired signal filtering of low-pass filter circuit (as shown in Figure 6) by low frequency, obtain level and smooth voltage signal, thus realization realizes the change to drop by the change of Detection capacitance.
1. Microfluidic droplet produces technology
Microlayer model technology is in microscale channel, utilize the interaction between the Osima jacoti, Osima excavata of liquid and surface tension that continuous fluid is separated into discrete micro updating, receive upgrading and with a kind of microlayer model generation technology of the drop of lower volume.It is the technology of a kind of manipulation fine liquid volume completely newly that development in recent years is got up.By the size, shape, generated frequency etc. that regulate the condition such as geometry, surface chemical property, rate of flow of fluid of chip microchannel can regulate drop flexibly.Drop produces and mainly contains three kinds of modes, and namely knot structure (T-junction), streaming focus on (flow-focusing) and coaxial stream (co-axial flow) altogether.Microlayer model type mainly contains gas and liquid phase drop and liquid-liquid phase drop two kinds.Gas and liquid phase drop owing to easily volatilizing and causing cross pollution and limit its application in microchannel.Liquid-liquid phase drop is difference divided into again oil-in-water (O/W) according to continuous phase and discrete phase, Water-In-Oil (W/O), Water-In-Oil bag oil (O/W/O) and W/O/W (W/O/W) etc., the shortcomings such as drop volatilization, cross pollution can be overcome, because of but the emphasis place of Microfluidic droplet technical development.Liquid-liquid phase microlayer model because volume is little, between droplet sample without diffusion, the cross pollution of sample room can be avoided, stable reaction conditions, suitably manipulation are lower can realize the advantages such as rapid mixing, it is a kind of very good microreactor, be widely used in the reaction under the microscale condition in the fields such as chemistry and life science, as: chemosynthesis, micro-extraction, crystallization of protein, enzymic synthesis and activity analysis, cell embedding, drop PCR etc.
2. Microfluidic droplet detection technique
Liquid drop microfluidic system has the advantages such as mixing velocity is fast, low without cross pollution, reagent and sample consumption, the generated frequency of drop fast (can reach hundreds of to few kilohertz), be widely used in the research fields such as single cell analysis, enzyme kinetics, protein synthesis and high flux screening, these relevant applications are very high to the requirement of the precision controlling of sample, so detecting the information of drop is the very important guarantee of of liquid drop microfluidic system widespread use.Microfluidic droplet detects and mainly carries out infomation detection to the concentration etc. of the size of drop, shape, speed and drop inclusions, and the detection of these information plays vital effect to experimental result.
3. capacitance signal is converted to voltage signal technology
The difference of drop information causes the capacitance of capacitive transducer to change, because the variable quantity directly measuring capacitance is very difficult and precision is very low, we directly can not measure the change of capacitance to measure the information of drop, utilize external circuit capacitance to be converted to the magnitude of voltage easily measured to measure, there is the advantages such as directly perceived, simple, convenient.
Superiority of the present invention: 1. structure is simple, makes simple, is easy to generate drop; 2. utilize the sample solution of two kinds of differing dielectric constants to form microlayer model in chip, when making it flow through capacitive transducer, cause the change of capacitance, realize the change to drop by the change of Detection capacitance; 3. this detection method has detection fast, is easy to realize the miniaturization of whole detection system, integrated advantage; 4. owing to adopting Microfluidic droplet chip, required sample and reagent volume few; Possess sample and the few advantage of reagent consumption, be applicable to very much the analysis of expensive samples and reagent; 5. the outer detecting circuit of drop detection method can be on a circuit board integrated, and its structure is simple, is easy to processing and fabricating, and easily realize structural miniaturization, integrated.
(4) accompanying drawing illustrates:
Fig. 1 is a kind of structural representation based on drop micro-fluidic chip in the Microfluidic droplet detection system of capacitive transducer involved by the present invention.
The one-piece construction block diagram of Fig. 2 a kind of Microfluidic droplet detection system based on capacitive transducer involved by the present invention.
Fig. 3 is a kind of principle of work schematic diagram based on direct current regulation circuit unit in the Microfluidic droplet detection system of capacitive transducer involved by the present invention.
Fig. 4 is a kind of principle of work schematic diagram based on FM circuit in the Microfluidic droplet detection system of capacitive transducer involved by the present invention.
Fig. 5 is a kind of principle of work schematic diagram based on f/V change-over circuit in the Microfluidic droplet detection system of capacitive transducer involved by the present invention.
Fig. 6 is a kind of principle of work schematic diagram based on low-pass filter circuit in the Microfluidic droplet detection system of capacitive transducer involved by the present invention.
The emulation drop of Fig. 7 a kind of Microfluidic droplet detection method based on capacitive transducer involved by the present invention produces schematic diagram.
Fig. 8 is a kind of relation schematic diagram based on droplet size and sample I inlet velocity in the Microfluidic droplet detection method of capacitive transducer involved by the present invention.
Fig. 9 is a kind of relation schematic diagram based on droplet size and sample I viscosity in the Microfluidic droplet detection method of capacitive transducer involved by the present invention.
Figure 10 is a kind of based on droplet size in the Microfluidic droplet detection method of capacitive transducer and the relation schematic diagram of interfacial tension between sample I and sample 2II involved by the present invention.
Wherein, 1 is continuous phase sample I entrance I; 2 is continuous phase sample I entrance II; 3 is sample II entrance; 4 is drop outlets; 5 is capacitive transducer; 6 is cross junction; 7 is electrode terminal I; 8 is electrode terminal II; 9 is sample I passage I; 10 is sample I passage II; 11 is sample II passage; 12 is drop formation passage.
(5) embodiment:
Embodiment: a kind of Microfluidic droplet detection system based on capacitive transducer, is characterized in that it comprises drop micro-fluidic chip, direct current regulation circuit unit, signal deteching circuit unit and computing machine; Wherein, described drop micro-fluidic chip is the chip structure become one with the microchannel producing microlayer model by capacitive transducer; Described drop micro-fluidic chip by mutual bonding upper slice, bottom sheet and capacitive transducer 5 form (see Fig. 1); Described bottom sheet is microchannel sheet, is welded with sample I entrance, sample II entrance 3, drop outlets 4, cross junction 6, electrode terminal, sample I passage, sample II passage 11 and drop formation passage 12; Described sample I entrance is connected with sample I passage; Described sample II entrance 3 is connected with sample II passage 11; Described sample I passage, sample II passage 11 are connected with drop formation passage 12 by cross junction 6; Described drop formation passage 12 connects drop outlets 4; Described capacitive transducer 5 is placed in the top of drop formation passage 12, and is connected with electrode terminal; Described upper slice on have and place the conduit of capacitive transducer 5; The output terminal of described direct current regulation circuit unit and the input end of signal deteching circuit unit are connected with the electrode terminal on drop micro-fluidic chip respectively; Described computing machine and signal deteching circuit unit are in being bi-directionally connected, and its output terminal is connected (see Fig. 2) with the input end of direct current regulation circuit unit.
Described sample I entrance is continuous phase entrance, is made up of continuous phase sample I entrance I1 and continuous phase sample I entrance II2; Described sample I entrance I1 and sample I entrance II2 pumps into sample I respectively by pump I; Described sample II entrance 3 is discrete phase entrances, and sample II entrance 3 pumps into sample II by pump II; Described pump I is connected with sample I entrance and sample II entrance respectively by pipeline with pump II, is pumped into by sample in drop micro-fluidic chip passage.
Described electrode terminal has two, is electrode terminal I7 and electrode terminal II8 respectively; Described electrode terminal I7 is connected with the output terminal of direct current regulation circuit; Described electrode terminal II8 is connected with the input end of signal deteching circuit.
The Ψ type passage that the microchannel producing microlayer model in described drop micro-fluidic chip is made up of sample I passage, sample II passage 11 and drop formation passage 12.
Described sample I passage has two, is sample I passage I9 and sample I passage II10 respectively.
Described sample II passage 11 is straight channel with drop formation passage 12.
Described sample I passage I9 and sample I passage II10 is the curved passage in straight rear end, front end; Described front end straight passage portion is parallel to each other, and with sample II passage 11 in parallel relation; The curved channel part in described rear end is the curved passage of 1/4 circle; Described sample I passage I9, sample I passage II10, sample II passage 11 are connected at cross junction 6 place with drop formation passage 12.
The size of described cross junction 6 is less than sample I passage I9, sample I passage II10 on chip, sample II passage 11 and the sectional dimension of drop formation passage 12, is easy to form drop in process prepared by drop.
Described sample I passage I9, sample I passage II10, sample II passage 11 are 200 μm * 200 μm with the sectional dimension of drop formation passage 12; Described cross junction 6 is of a size of 100 μm * 100 μm.
The center line of described capacitive transducer 5 overlaps with the center line of drop formation passage 12, does not have interlayer therebetween; The capacitor plate of described capacitive transducer 5 is positioned at the outlet ends place of drop formation passage 12, and the center line of capacitor plate overlaps with the center line of drop formation passage 12.
The making material of described drop micro-fluidic chip is dimethyl silicone polymer; Described capacitive transducer is plane interdigital structure, and material is the potpourri of silver and dimethyl silicone polymer.
Described signal deteching circuit unit is made up of the FM circuit containing concussion module, voltage to frequency f/V change-over circuit and low-pass filter circuit; The input end of described FM circuit receives the signal of drop microfluidic chip electrode terminals II8, and its output terminal is connected with low-pass filter circuit by voltage to frequency f/V change-over circuit; The output terminal of described low-pass filter circuit is connected with computing machine.
Based on a Microfluidic droplet detection method for capacitive transducer, it is characterized in that it comprises the following steps:
1. air driven pump I is connected with sample I entrance II2 with the entrance I1 of sample I respectively by two Teflon, air driven pump II is connected with sample II entrance by Teflon, sample is pressed into the passage of drop micro-fluidic chip, sample I hexadecane enters drop micro-fluidic chip by sample I entrance I1 and sample I entrance II2, simultaneously, sample II distilled water enters drop micro-fluidic chip from sample II entrance 3, and two kinds of samples are respectively by sample I passage I9, sample I passage II10; Sample II passage 11 flows into, and forms drop at cross junction 6 place, and the size of drop, shape, generation frequency, speed are subject to the impact of the inlet velocity of sample I, the viscosity of sample I, the interfacial tension between sample I and sample II; Distilled water is subject to the impact of the interfacial tension between the shearing force of hexadecane and hexadecane and water at cross junction 6 place, is independent droplet by water cut; And size, the shape of drop formation in chip can be changed by the pressure size changing air driven pump;
2. by direct current regulation circuit for sensor capacitance provides power supply, step 1. in the drop that obtains flow through capacitive transducer by drop formation passage 12, due to the difference of two kinds of liquid dielectric, cause the electric capacity of capacitive transducer to change, the electric capacity of change can drive outside signal deteching circuit to carry out work;
3. the FM circuit of signal deteching circuit unit receives the signal of capacitance variations, and the electric capacity of change also makes the concussion module in FM circuit produce different frequency value when resonance;
4. different frequency values is after voltage to frequency f/V change-over circuit, the frequency inverted produced during these resonance is become voltage signal and exports to low-pass filter circuit, signal lower than cutoff frequency passes through by low-pass filter circuit, signal higher than cutoff frequency filters out, and makes the signal of output smoothing to computing machine;
5. computing machine exports control signal to direct current regulation circuit unit, makes the DC voltage of direct current regulation circuit unit stable output; Computer export control signal is to signal deteching circuit unit, the capacitance change signal that the difference of drop causes is passed to signal deteching circuit unit by capacitive transducer 5, computing machine is passed to after signal deteching circuit unit, computing machine shows testing result intuitively, thus realizes the detection to sample;
6. last, the step 1. middle drop generated is flowed out by drop outlets 4 by drop formation passage 12.
The application of described drop micro-fluidic chip comprises the size, shape, speed, the inclusion characteristics that detect drop; Drop in Microfluidic droplet system accurately controls and the composition of sample introduction sample of biological, chemistry, field of medicaments controls.
The generation of drop as shown in Figure 7, changes by the inlet velocity of change sample I, the viscosity of sample I and the interfacial tension between sample 1 (continuous phase) and sample II size, shape and the generation frequency that drop produces in the process produced.Under the condition that the inlet velocity of sample I is different, its simulation result as shown in Figure 8; Under the condition that the viscosity of sample I is different, its simulation result as shown in Figure 9; Under the condition that interfacial tension between sample I from sample II is different, its simulation result as shown in Figure 10.
Claims (10)
1., based on a Microfluidic droplet detection system for capacitive transducer, it is characterized in that it comprises drop micro-fluidic chip, direct current regulation circuit unit, signal deteching circuit unit and computing machine; Wherein, described drop micro-fluidic chip is the chip structure become one with the microchannel producing microlayer model by capacitive transducer; Described drop micro-fluidic chip by mutual bonding upper slice, bottom sheet and capacitive transducer form; Described bottom sheet is microchannel sheet, is welded with sample I entrance, sample II entrance, drop outlets, cross junction, electrode terminal, sample I passage, sample II passage and drop formation passage; Described sample I entrance is connected with sample I passage; Described sample II entrance is connected with sample II passage; Described sample I passage, sample II passage are by cross junction and drop formation expanding channels; Described drop formation expanding channels drop outlets; Described capacitive transducer is placed in the top of drop formation passage, and is connected with electrode terminal; Described upper slice on have and place the conduit of capacitive transducer; The output terminal of described direct current regulation circuit unit and the input end of signal deteching circuit unit are connected with the electrode terminal on drop micro-fluidic chip respectively; Described computing machine and signal deteching circuit unit are in being bi-directionally connected, and its output terminal is connected with the input end of direct current regulation circuit unit.
2. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, is characterized in that described sample I entrance is continuous phase entrance, is made up of continuous phase sample I entrance and continuous phase sample I entrance II; Described sample I entrance I and sample I entrance II pumps into sample I respectively by pump I; Described sample II entrance is discrete phase entrance, and sample II entrance pumps into sample II by pump II; Described pump I is connected with sample I entrance and sample II entrance respectively by pipeline with pump II, is pumped into by sample in drop micro-fluidic chip passage.
3. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, it is characterized in that described electrode terminal has two, is electrode terminal I and electrode terminal II respectively; Described electrode terminal I is connected with the output terminal of direct current regulation circuit; Described electrode terminal II is connected with the input end of signal deteching circuit; The center line of described capacitive transducer overlaps with the center line of drop formation passage, does not have interlayer therebetween; The capacitor plate of described capacitive transducer is positioned at the outlet ends place of drop formation passage, and the center line of capacitor plate overlaps with the center line of drop formation passage.
4. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, the Ψ type passage that the microchannel that it is characterized in that producing in described drop micro-fluidic chip microlayer model is made up of sample I passage, sample II passage and drop formation passage; Described sample I passage has two, is sample I passage I and sample I passage II respectively.
5. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 4, is characterized in that described sample II passage and drop formation passage are straight channel; Described sample I passage I and sample I passage II is the curved passage in straight rear end, front end; Described front end straight passage portion is parallel to each other, and is parallel relation with sample II passage; The curved channel part in described rear end is the curved passage of 1/4 circle; Described sample I passage I, sample I passage II, sample II passage are connected at cross junction place with drop formation passage.
6. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, it is characterized in that the size of described cross junction is less than the sectional dimension of sample I passage I, sample I passage II, sample II passage and drop formation passage on chip, be easy to form drop in process prepared by drop; The sectional dimension of described sample I passage I, sample I passage II, sample II passage and drop formation passage is 200 μm * 200 μm; Described cross junction is of a size of 100 μm * 100 μm.
7. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, is characterized in that the making material of described drop micro-fluidic chip is dimethyl silicone polymer; Described capacitive transducer is plane interdigital structure, and material is the potpourri of silver and dimethyl silicone polymer.
8. a kind of Microfluidic droplet detection system based on capacitive transducer according to claim 1, is characterized in that described signal deteching circuit unit forms by containing the FM circuit of concussion module, voltage to frequency f/V change-over circuit and low-pass filter circuit; The input end of described FM circuit receives the signal of drop microfluidic chip electrode terminals II, and its output terminal is connected with low-pass filter circuit by voltage to frequency f/V change-over circuit; The output terminal of described low-pass filter circuit is connected with computing machine.
9., based on a Microfluidic droplet detection method for capacitive transducer, it is characterized in that it comprises the following steps:
1. pump I is connected with sample I entrance II with the entrance I of sample I respectively by two Teflon, pump II is connected with sample II entrance by Teflon, sample is pressed into the passage of drop micro-fluidic chip, sample I enters drop micro-fluidic chip by sample I entrance I and sample I entrance II, simultaneously, sample II enters drop micro-fluidic chip from sample II entrance, and two kinds of samples are respectively by sample I passage I, sample I passage II; Sample II passage flows into, and forms drop at cross junction place, and the size of drop, shape, generation frequency, speed are subject to the impact of the inlet velocity of sample I, the viscosity of sample I, the interfacial tension between sample I and sample II;
2. by direct current regulation circuit for sensor capacitance provides power supply, step 1. in the drop that obtains flow through capacitive transducer by drop formation passage, due to the difference of two kinds of liquid dielectric, cause the electric capacity of capacitive transducer to change, the electric capacity of change can drive outside signal deteching circuit to carry out work;
3. the FM circuit of signal deteching circuit unit receives the signal of capacitance variations, and the electric capacity of change also makes the concussion module in FM circuit produce different frequency value when resonance;
4. different frequency values is after voltage to frequency f/V change-over circuit, the frequency inverted produced during these resonance is become voltage signal and exports to low-pass filter circuit, signal lower than cutoff frequency passes through by low-pass filter circuit, signal higher than cutoff frequency filters out, and makes the signal of output smoothing to computing machine;
5. computing machine exports control signal to direct current regulation circuit unit, makes the DC voltage of direct current regulation circuit unit stable output; Computer export control signal is to signal deteching circuit unit, the capacitance change signal that the difference of drop causes is passed to signal deteching circuit unit by capacitive transducer, computing machine is passed to after signal deteching circuit unit, computing machine shows testing result intuitively, thus realizes the detection to sample;
6. last, the step 1. middle drop generated is flowed out by drop outlets by drop formation passage.
10. a kind of Microfluidic droplet detection method based on capacitive transducer according to claim 9, is characterized in that the application of described drop micro-fluidic chip comprises the size, shape, speed, the inclusion characteristics that detect drop; Drop in Microfluidic droplet system accurately controls and the composition of sample introduction sample of biological, chemistry, field of medicaments controls.
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