CN117949204A - System and method for improving detection accuracy of on-off performance of film micro valve - Google Patents
System and method for improving detection accuracy of on-off performance of film micro valve Download PDFInfo
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Abstract
The invention relates to a system and a method for improving the detection precision of the on-off performance of a film micro valve, comprising the following steps: the liquid path device is connected with a tested micro valve channel with M thin film micro valves, the gas path control device, the amplifying device with M signal amplifiers and the waveform generator; the signal amplifier is sequentially connected with the data acquisition card and the computer; the gas circuit control device and the liquid circuit device are respectively and electrically connected with the acquisition card; the power supply of the signal amplifier is integrated in the system power supply together with the waveform generator. Compared with the prior art that only the envelope of the signal voltage can be seen, the invention can detect the instantaneous change single-point numerical value of the signal voltage and further judge the time change of the micro valve when the micro valve is turned off or turned on. The invention can detect the micro valves in the multiple paths at the same time, and can know the opening and closing characteristics of the corresponding micro valves by measuring the voltages at two ends of the detection resistor in each path of micro-channel detection circuit.
Description
Technical Field
The invention relates to a system and a method for improving the detection precision of the on-off performance of a film micro valve, in particular to a detection system and a method for a fluid control device, which are detection systems and methods for micro flow control components.
Background
In the micro-flow control and detection system, hundreds of sample injection channels are highly concentrated and distributed in a very small area, and the micro-flow control and detection system is structurally characterized in that at least one dimension of a micro-channel for accommodating fluid is in a micron level, and different sample can be ensured to rapidly and accurately perform different analysis requirements. The micro valve is an important executive component in the micro fluid, is a component for controlling the on and off states of the micro channel, and is an important link of a micro flow control and detection system. Since the microsystem is a system in the order of micrometers or even nanometers, the control amount is also minute, so that the microsystem is difficult to observe by naked eyes and can only be measured indirectly.
The existing detection of the micro valve adopts a conductivity method. Such as the detection device and method for the opening/closing characteristics of a thin film micro valve in a micro channel in China patent (patent number: ZL201010603487.4, publication date: 2011.07.20). The conductivity method has the advantages of simple operation, visual result and the like, and the detection principle is as follows: the micro-electrode is etched in the micro-flow channel, when the micro-valve acts, the electric conduction of the solution in the micro-channel changes, and the dynamic characteristic of the opening and closing of the micro-valve can be obtained by observing the change of the current at the two ends of the electrode. Although the existing conductivity measurement system can obtain some results to a certain extent, because of the tiny characteristics of the microsystem, the measurement requires extremely high precision, any interference and noise inside and outside the system can interfere with the accuracy of the data, and even submerge the measured data, so how to improve the measurement precision of the measurement system is a problem to be solved.
Disclosure of Invention
In order to overcome the problems in the prior art, the invention provides a system and a method for improving the detection precision of the on-off performance of a film micro valve. The system and the method carefully design the micro-flow electrode, the micro-flow channel and the position of the measuring electrode in the micro-flow channel, set damping on the micro-channel, add a gas flowmeter and a liquid pressure sensor, improve an operational amplification circuit and an acquisition circuit, reduce the noise-to-noise ratio, realize high-precision signal acquisition and improve the measuring precision.
The purpose of the invention is realized in the following way: a system for improving the detection accuracy of the on-off performance of a thin film micro valve, comprising: the liquid path device is connected with a tested micro valve channel with M thin film micro valves, the gas path control device, the amplifying device with M signal amplifiers and the waveform generator; the signal amplifier is connected with the data acquisition card and the computer in sequence, M is 1, 2,3 or more tested film micro valves, and each signal amplifier comprises: the detection resistor MR is electrically connected with the detection electrode, the detection resistor MR is electrically connected with the negative input end of the operational amplification chip MOP, the positive input end of the operational amplification chip is electrically connected with the output end of the amplification chip and is electrically connected with one input end of the acquisition card, the voltage high end +Vcc of the operational amplification chip is electrically connected with the waveform generator SG and the other input end of the acquisition card, the other end of the waveform generator is electrically connected with the electrode of the liquid circuit terminal, the voltage low end-Vcc of the operational amplification chip is grounded, and a reference resistor MRef is connected between the negative input end and the output end of the operational amplification chip in parallel; the gas circuit control device comprises: the device comprises a gas circuit terminal with M gas circuit channels, a solenoid valve island with a high-precision pressure reducing valve, a gas circuit flowmeter and a gas source, wherein the gas circuit terminal is connected with a detected micro valve channel pipeline in sequence; the liquid path device comprises: a liquid path terminal with M liquid path channels and M electrodes, a liquid path pressure sensor LPM, a pulse damper LEP, a liquid supply pump SP with a pressure regulating valve and a solution tank which are sequentially connected with a detected micro valve channel pipeline; the gas circuit control device and the liquid circuit device are respectively and electrically connected with the acquisition card; the power supply of the signal amplifier is integrated in the system power supply together with the waveform generator.
Further, the electrode in the motor module is a platinum electrode.
Further, the waveform generator is a square wave generator; the output bandwidth is 10MHz to 2GHz, and the output voltage range is 20mV to 10.0V based on the accurate noise-free signal and the 5GS/s16 bit performance.
Further, the air source is a nitrogen cylinder with a flow regulating valve.
Further, the solution in the solution tank is sodium chloride solution.
Further, the liquid supply pump is a peristaltic pump or a syringe pump.
Furthermore, the electromagnetic valve island is provided with a micro pneumatic sample injection pump, a two-stage high-precision pressure reducing valve and a pump valve electric controller.
A method for improving the detection precision of the on-off performance of a film micro valve by using the system comprises the following steps:
Step 1, a connection system: the method comprises the steps of connecting a detected micro-flow channel into a detection device, determining each micro-valve to be detected, connecting an input electrode to a liquid inlet of the micro-channel where the micro-valve is located to be in contact with liquid, wherein the liquid inlet of the micro-channel is not influenced by the flow of the liquid in the micro-channel, connecting an output end electrode to a liquid outlet of the micro-channel respectively and in contact with the liquid, and not influencing the flow of the liquid in the micro-channel, connecting a gas circuit control device and a liquid circuit device, connecting the electrodes to an amplifying device and connecting an acquisition card and a computer;
Step 2, starting the system: powering up the system and opening the computer, and setting the computer as a data acquisition interface; opening a nitrogen bottle, closing all micro-valve gas paths through an electromagnetic valve island, detecting the gas path linking tightness, adjusting the gas pressure input into each film micro-valve through the electromagnetic valve island after no gas leakage is determined, and determining that the input gas pressure value is 0.3Mpa after passing through a secondary pressure reducing valve; injecting standard sodium chloride solution into the solution tank, starting a liquid supply pump, adjusting the liquid pressure, and monitoring the pressure change through a liquid path pressure sensor; the pulse damper is adjusted to enable the liquid output to be stable; turning on a waveform generator to provide an input signal to an amplifier;
step 3, collecting data: according to experimental requirements, the solenoid valve island adjusts the gas circuit to drive each micro valve, voltage data V 0 on a detection resistor connected with a detection electrode of each micro valve on a detection liquid circuit terminal is acquired by the acquisition card in real time, voltage signals on the resistor connected between the ports are sent to a computer for data processing, and a voltage signal change curve on the detection resistor on each thin film microchannel is obtained; changing the air pressure value and the liquid flow value, observing the change of each voltage data V 0, drawing a change curve of the voltage data V 0 with different air pressure values and different liquid flow values, and recording the change curve in a computer;
Step 4, data analysis: judging whether the micro valve is completely closed or not through the voltage value change of the amplifying circuit, if the micro valve is completely closed, the voltage value is from a certain fixed value to zero, and if the micro valve is not completely closed, the micro valve is not completely closed; when the micro valve is opened, the solution flows through the micro channel; the micro valve is turned off, and the solution is blocked by the micro valve; when the micro valve is opened and closed, voltage value differences obtained by measuring voltages at two ends of the detection resistor are respectively measured, so that the opening and closing performances of the micro valve are detected:
The alternating voltage value output by the waveform generator is V i, the resistance value of the measuring resistor is R, and the equivalent resistance of the thin film micro valve liquid flow passage is R flu:
The voltage value V 0 at two ends of the detection resistor is as follows:
Wherein: kappa is the conductivity of the solution, S is the cross-sectional area of the microchannel; l is the length of the microfluidic channel to be tested;
Calculating a root mean square value V RMS of an output voltage value of the liquid path pressure sensor:
Wherein: t is the measurement duration and V (T) is the instantaneous voltage.
The invention has the advantages and beneficial effects that: compared with the prior art, only the envelope of the signal voltage can be seen, namely only the trend can be seen, the invention can detect the instantaneous change single-point numerical value of the signal voltage and further judge the time change of turning off or on the micro valve, which is an important index of the micro valve characteristic. In order to avoid the influence of the electrode on the micro-flow channel, the invention only needs to be externally connected with the electrode, thereby not only avoiding the influence on the micro-fluid flow, but also reducing the cost. The invention also adds a damper, reduces the interference of pulsation in the process of detecting the oversubsampled sample, improves the detection precision, and ensures that the characteristic index of the evaluation micro valve is more accurate. The invention can detect the micro valves in the multiple paths at the same time, and can know the opening and closing characteristics of the corresponding micro valves by measuring the voltages at two ends of the detection resistor in each path of micro-channel detection circuit. One or more micro valves can be arranged in the micro channel of the tested valve, and the opening and closing characteristics of the micro channel can be respectively detected.
Drawings
The invention is further described below with reference to the drawings and examples.
FIG. 1 is a schematic block diagram of a system according to an embodiment of the present invention;
FIG. 2 is an example of a two-fluid detection cell microvalve layout;
FIG. 3 is a schematic diagram of a structure of a thin film micro valve and a measuring electrode according to an embodiment of the present invention;
Fig. 4 is an equivalent circuit diagram for measuring the opening and closing performance of the thin film micro valve.
Detailed Description
Embodiment one:
The embodiment is a system for improving the detection precision of the on-off performance of a film micro valve, as shown in fig. 1. The embodiment comprises the following steps: a liquid path device connected with a tested micro valve channel with M thin film micro valves, a gas path control device, an amplifying device with M signal amplifiers and a waveform generator (the part with a dotted line frame in fig. 1 is the device). The signal amplifier (the part with the two-dot chain line frame in the figure 1 is an amplifier) is sequentially connected with the data acquisition card and the computer, M is 1,2, 3 or more tested film micro-valves, and each signal amplifier comprises: the detection resistor MR is electrically connected with the detection electrode, the detection resistor MR is electrically connected with the negative input end of the operational amplification chip MOP (the thin solid line in fig. 1 represents electrical connection), the positive input end of the operational amplification chip is electrically connected with the output end of the amplification chip and is electrically connected with one input end of the acquisition card, the voltage high end +Vcc of the operational amplification chip is electrically connected with the waveform generator SG and the other input end of the acquisition card, the other end of the waveform generator is electrically connected with the electrode of the liquid circuit terminal, the voltage low end-Vcc of the operational amplification chip is grounded, and a reference resistor MRef is connected between the negative input end and the output end of the operational amplification chip in parallel; the gas circuit control device comprises: the device comprises a gas circuit terminal with M gas circuit channels, a solenoid valve island with a high-precision pressure reducing valve, a gas circuit flowmeter and a gas source (the pipeline connection is shown by a thick solid line in figure 1) which are connected with a tested micro valve channel pipeline in sequence; the liquid path device comprises: a liquid path terminal with M liquid path channels and M electrodes, a liquid path pressure sensor LPM, a pulse damper LEP, a liquid supply pump SP with a pressure regulating valve and a solution tank which are sequentially connected with a detected micro valve channel pipeline; the gas circuit control device and the liquid circuit device are respectively and electrically connected with the acquisition card; the power supply of the signal amplifier is integrated in the system power supply together with the waveform generator.
The detection method of the embodiment is based on a conductivity detection method and is used for improving the detection precision of the thin film micro valve performance detection system. The system is composed of a multichannel high-speed data acquisition card, a multichannel electromagnetic valve island, a detected micro valve channel, a sample injection system (an injection pump and a peristaltic pump), a detection circuit (M input/output electrodes, M resistors and an amplifying circuit), a liquid path pressure sensor, a pulse damper, a gas path flowmeter, a power supply, a computer and the like. The electromagnetic valve island integrates facilities such as electromagnetic valve controllers, power supplies and the like besides the electromagnetic valve.
One end of each of the M detection resistors is connected with the output end of the amplifier respectively, one end of each of the M detection resistors is connected with one end of an external voltage source in parallel, the other end of the external voltage source is connected with the parallel end of the M detection resistors, one end of each of the M detection resistors is connected with one input end of the amplifier, the other input end of the amplifier is connected with the output end of the amplifier to form a following loop, the multichannel input ends of the data acquisition card are connected with each detection channel respectively, the data acquisition card uploads acquired data to a computer through a USB (universal serial bus), signal change conditions are displayed in real time, real-time storage can be saved, the number of channels of the data acquisition card is expandable, and the data acquisition card is determined by the number of sampling liquid channels and sampling logic.
The tested micro-valve channel in this embodiment is a thin film micro-valve microfluidic system composed of at least one thin film micro-valve and its corresponding gas pipeline channel and liquid pipeline channel. An example of a two-fluid detection cell microvalve layout with 10 thin film microvalves is shown in FIG. 2. The small circles with numbers In FIG. 2 represent thin film micro-valves, the thick solid line segments separated by the small circles with numbers represent liquid micro-channels 0.3mm wide and 0.1mm deep, in a/b are inlets of the micro-channels, and Out a/b is a sample outlet of the micro-channels. The film micro valve can control the on-off of the flow paths of different flow paths and realize different detection functions.
The structure of the thin film micro valve according to this embodiment is shown in fig. 3: the liquid-gas-liquid separator comprises a three-layer structure, wherein a first layer is provided with a gas layer 1, a second layer is provided with a film 2 serving as a micro valve, a third layer is provided with a fluid micro channel 3, a liquid channel terminal 4 is connected with the fluid micro channel, the liquid channel terminal is provided with a liquid inlet channel 5 and a liquid outlet channel 6, detection electrodes 7a and 7b are respectively arranged on the liquid inlet channel and the liquid outlet channel of the liquid channel terminal, and an input electrode Eie, an output electrode Eoe and a gas control channel are connected with a gas circuit control device through an air pipeline 8. When gas with certain pressure enters the gas layer, the second layer of film deforms under the action of gas pressure (the position of the film is indicated by a dotted line in fig. 3), the micro-channel is blocked, namely, the micro-valve shutoff solution cannot continuously advance in the micro-channel, otherwise, no gas enters the gas flow path, the film is not deformed, and the micro-channel is unobstructed for the solution to continuously advance.
The working principle of the measuring film micro valve is as follows: when gas enters the gas flow path, the thin film is deformed, but the thin film deformation does not necessarily completely block the flow of liquid. The micro valve opening and closing performance can be detected through respectively measuring the voltages at two ends of the detection resistor, and the obtained voltage value difference is specifically described as follows:
the detection circuit can be equivalent to the form of fig. 4. In fig. 4, the equivalent resistance of the micro channel of the thin film micro valve is R flu, and as shown in fig. 4, the input electrode Eie, the micro channel, the output electrode Eoe, the measurement resistor R and the voltage source V i (waveform generator SG) form a closed circuit.
When the micro valve is opened, the solution flows through the micro channel; the microvalve is turned off and the solution is blocked by the microvalve. When the micro valve is opened and closed, the difference of voltage values obtained by respectively measuring the voltages at two ends of the detection resistor can be detected, and the performance of the micro valve for opening and closing can be detected as follows:
The power supply alternating current power supply value is V i, the resistance value of the measuring resistor is measured, and according to an equivalent circuit, the voltage value V 0 at two ends of the detecting resistor can be obtained:
Kappa is the conductivity of the solution, S is the cross-sectional area of the microchannel, and L is the length of the microfluidic channel to be measured. Under the condition of determining the detection sample, kappa is determined by the conductivity of the solution. When the film micro valve is opened, the cross section area S of the fluid channel is constant, and R flu is positively related to the length of the fluid channel; when the thin film microvalve is closed, the fluid channel length is determined, and thus R flu is inversely proportional to the fluid channel cross-sectional area. In summary, the resistance to be measured generates a change curve with the same trend in the opening or closing process of the thin film micro valve. After being processed by the amplifying circuit, the micro valve is output to the upper computer through the data acquisition card, and is analyzed through a data processing program in the upper computer, so that the performance of the micro valve can be judged through the change of voltage values at two ends of the resistor.
The gas path part of the embodiment comprises a gas cylinder, a solenoid valve island for controlling the on-off of the gas, a gas path joint, a gas pipe and the like. After the gas pressure is reduced by two stages, the on-off of the gas film micro valve is controlled by a high-precision pressure reducing valve, and the pressure of the input gas valve is in the range of 0-0.5 Mpa.
The embodiment adopts a higher-precision operational amplifier, designs and selects the matching resistor-capacitor part, and reduces the common mode rejection ratio. The amplifier should employ a high precision low noise amplifier AD9632 with a slew rate of 1300V/. Mu.s.
The signal generator is an AWG5200 arbitrary waveform generator, can output bandwidth of 10MHz to 2GHz and output voltage range of 20mV to 10.0V based on accurate noiseless signals and 5GS/s16 bit performance, and two ends of the detection resistor are respectively connected with copper electrodes of input and output ports of electrodes arranged in the detected microchannel with the valve, and the detection resistor is adjustable and has typical value of 1MΩ.
The data acquisition card multifunctional data acquisition card PICO6000 can give out any waveform at the same time and can realize multichannel signal acquisition.
The liquid path device in the embodiment comprises an injection pump or a peristaltic pump, and in the process of using the peristaltic pump, a pulse damper is required to be added in a matched mode, so that pulsation of the peristaltic pump with a liquid path is reduced. The liquid path terminals are all made of PEEK elements, the detection electrodes are connected into PEEK compression blocks, the distribution electrodes are platinum electrodes, and the conductivity is far better than that of copper electrodes. The liquid for measurement may be a salt mineral such as saline water.
The gas path channel enters the detection object to carry out gas flow detection control, so that the instantaneous change values of the closing states of the gas valves with different flow rates and pressures can be accessed to the liquid path pressure sensor, the pressure change of the liquid path is detected before and after the gas valve is opened or closed, the on-off characteristic of the gas valve can be more accurately reflected, the pulsation of a sample injection system is reduced, and the detection precision is improved. The liquid path device is connected with the damper, and the damper improves liquid inlet precision by adjusting tiny change of gas in the sample injection device.
The key of this embodiment is to add a liquid path pressure sensor to react to the pressure change of the flow path in real time. The instantaneous change single-point numerical value can be detected through the liquid path pressure sensor. The combination of the voltage parameter and the liquid path pressure parameter can further judge the change of the turn-off and turn-on time of the film micro valve, namely: and the characteristic index of opening or closing the micro valve. Compared with the prior art that only the envelope of the voltage signal change can be seen, the method is more accurate and has higher precision.
Embodiment two:
The present embodiment is an improvement of the first embodiment, and is a refinement of the first embodiment with respect to the liquid path terminal, wherein the electrode in the liquid path terminal is a platinum electrode.
The size and shape of the electrode can be adjusted according to the actual sample injection requirement. Flexible electrodes may be used. The flexible electrode is soft and non-rigid. Flexible electrodes are fabricated on flexible or ductile plastic or thin metal substrates.
Embodiment III:
This embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the waveform generator. The waveform generator in this embodiment is a square wave generator; the output bandwidth is 10MHz to 2GHz, and the output voltage range is 20mV to 10.0V based on the accurate noise-free signal and the 5GS/s16 bit performance.
Embodiment four:
This embodiment is a modification of the above embodiment and is a refinement of the above embodiment with respect to the air source. The gas source in this embodiment is a nitrogen cylinder with a flow regulating valve.
The flow regulating valve is a micro-flow regulating valve with high precision.
Fifth embodiment:
This example is a modification of the above example and is a refinement of the above example with respect to the solution. The solution in the solution tank described in this embodiment is sodium chloride solution NaCl.
The concentration of NaCl in the sodium chloride solution can be controlled between 0.1 and 1mol.
Example six:
This embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the liquid supply pump. The liquid supply pump in this embodiment is a peristaltic pump or a syringe pump.
The sample feeding flow rate of the liquid feeding pump ranges from 10um/min to 500ul/min.
Embodiment seven:
This embodiment is a modification of the above embodiment, and is a refinement of the above embodiment with respect to the solenoid valve island. The electromagnetic valve island is provided with a micro pneumatic sample injection pump, a two-stage high-precision pressure reducing valve and a pump valve electric controller.
The sample injection amount of the micro sample injection pump can be controlled to be less than 5 ul/min.
Example eight:
The embodiment is a method for improving the detection precision of the on-off performance of the film micro valve by using the system. The method judges whether the micro valve is completely closed by using the voltage value change of the amplifying circuit, if the micro valve is completely closed, the voltage value is from a certain fixed value to zero, and if the micro valve is not completely closed, the micro valve is not completely closed.
The detection process is roughly as follows: firstly, a micro-fluid system to be detected is connected to a detection device, a micro-valve to be detected is determined, an input electrode is connected to a liquid inlet of a micro-channel where the micro-valve is located and is in contact with liquid, a plurality of output end electrodes which do not affect the flow of the liquid in the micro-channel are respectively connected to a plurality of liquid outlet of the micro-channel and are in contact with the liquid, the flow communication gas circuit and the liquid circuit of the liquid in the micro-channel are not affected, and a computer is turned on.
And then, the micro valve is turned off, voltage data on a measuring resistor connected with a plurality of liquid outlet ports are detected at the same time, a collecting card collects voltage signals on the resistor connected between the ports in real time and sends the voltage signals to a computer for data processing, voltage signal change curves on the resistor on each micro channel are obtained, and the characteristics of the thin film micro valve are judged through analysis of the voltage signal change curves.
The method comprises the following specific steps:
Step 1, a connection system: the detected micro-flow channel is connected to the detection device, each micro-valve to be detected is determined, an input electrode is connected to the liquid inlet of the micro-channel where the micro-valve is located to be in contact with liquid, the flow of the liquid in the micro-channel is not affected, each output electrode is connected to each liquid outlet of the micro-channel and in contact with the liquid, the flow of the liquid in the micro-channel is not affected, the gas circuit control device and the liquid circuit device are communicated, each electrode is connected with the amplifying device, and the acquisition card and the computer are connected.
The connection system includes a plumbing connection and an electrical connection. The pipeline connection connects the paths of gas or liquid flow together by micro-channels, including the connection of micro-gas channels: connecting the tested micro valve channel, the air circuit terminal, the electromagnetic valve island, the air circuit flowmeter, the air source and the like together; and (3) connection of micro liquid paths: the tested micro valve channel, the liquid path terminal, the liquid path pressure sensor pulse damper, the liquid supply pump with the pressure regulating valve, the solution tank and the like are connected. The electric connection refers to connection of the acquisition card and each amplifying chip and connection of the detection electrode and the amplifying chip. The electrical connection also includes each power unit being connected to a power source. The electricity utilization unit mainly comprises an air path control device, a liquid path device, a signal amplifying device, an acquisition card, a computer and the like.
Step 2, starting the system: powering up the system and opening the computer, and setting the computer as a data acquisition interface; the nitrogen cylinder is opened, all micro-valve gas paths are closed through the electromagnetic valve island, the gas path linking tightness is detected, after no gas leakage is determined, the air pressure input into each film micro-valve is adjusted through the electromagnetic valve island, and after the air pressure passes through the secondary pressure reducing valve, the input air pressure value is determined; injecting standard sodium chloride solution into the solution tank, starting a liquid supply pump, adjusting the liquid pressure, and monitoring the pressure change through a liquid path pressure sensor; the pulse damper is adjusted to enable the liquid output to be stable; the waveform generator is turned on to provide the input signal to the amplifier.
Whether the air leakage can be through opening the gas circuit when closing all film micro valves, observe whether the gas circuit flowmeter is zero to when the gas circuit flow is not zero, the size of opening of film micro valve part is judged indirectly, thereby know the characteristic of micro valve. The monitoring liquid path pressure is used for indirectly monitoring whether the film micro valve is opened or closed.
Step 3, collecting data: according to experimental requirements, the solenoid valve island adjusts the gas circuit to drive each micro valve, voltage data V 0 on a detection resistor connected with a detection electrode of each micro valve on a detection liquid circuit terminal is acquired by the acquisition card in real time, voltage signals on the resistor connected between the ports are sent to a computer for data processing, and a voltage signal change curve on the detection resistor on each thin film microchannel is obtained; the air pressure value and the liquid flow value were changed, the change of each voltage data V 0 was observed, and the change curve of the voltage data V 0 at the different air pressure value and liquid flow value was plotted and recorded in the computer.
The data acquisition mainly acquires the change curve of the voltage data V 0, which is a main means for knowing the performance of the micro valve, and in addition, the motion characteristics of the micro valve can be indirectly obtained through monitoring the gas circuit flowmeter and the monitoring liquid circuit pressure. The characteristics of the micro valve and the related micro valve channel can be more accurately known and judged by corresponding and comparing the monitoring data of the gas circuit and the liquid circuit with the monitoring data of the signal amplifying device.
Step 4, data analysis: judging whether the micro valve is completely closed or not through the voltage value change of the amplifying circuit, if the micro valve is completely closed, the voltage value is from a certain fixed value to zero, and if the micro valve is not completely closed, the micro valve is not completely closed; when the micro valve is opened, the solution flows through the micro channel; the micro valve is turned off, and the solution is blocked by the micro valve; when the micro valve is opened and closed, voltage value differences obtained by measuring voltages at two ends of the detection resistor are respectively measured, so that the opening and closing performances of the micro valve are detected:
The alternating voltage value output by the waveform generator is V i, the resistance value of the measuring resistor is R, and the equivalent resistance of the thin film micro valve liquid flow passage is R flu:
The voltage value V 0 at two ends of the detection resistor is as follows:
wherein: kappa is the conductivity of the solution, S is the cross-sectional area of the microchannel; l is the length of the microfluidic channel to be tested.
Under the condition of determining a detection sample, determining the conductivity kappa of the solution, wherein when the film micro valve is opened, the cross section area S of the fluid channel is constant, R flu is only related to the length of the fluid channel of the film micro valve, and when the film micro valve is closed, the length of the fluid channel is determined, so that R flu is inversely proportional to the cross section area of the fluid channel; the resistance to be measured generates a change curve with the same trend in the process of opening or closing the film micro valve; after being processed by the amplifying circuit, the signal is output to a computer through a data acquisition card, and is analyzed through the computer, namely the performance of the thin film micro valve is judged through the change of voltage values at two ends of the resistor.
The output voltage of the liquid path pressure sensor is an analog quantity, the voltage value of the liquid path pressure sensor can be converted into a pressure value, and the root mean square value V RMS of the voltage value of the liquid path pressure sensor can be directly calculated:
wherein: t is the measurement duration; v (t) is the instantaneous voltage of the pressure as a function of time but not necessarily with periodicity. The equation is squared on both sides to yield:
then, equation (2) is simplified to obtain:
VRMS 2＝Avg[V(t)2] (3)
the equation two-sided divided by V RMS yields:
This expression provides the basis for the implicit function solution of V RMS, note that the square root taken on both sides of equation (4) yields:
This is another way of expressing the root mean square value of the function. From a practical point of view, the implicit root mean square calculation method has excellent dynamic range, which is superior to the explicit calculation method (continuous square, average and square root of the input signal). Using the explicit method, the squarer output will vary within a dynamic range of 10,000:1 (1 mV to 10V) for an instantaneous input of 100:1 (0.1V to 10V). The input squarer error for the explicit method will be greater than 1mV, so the error is largely dependent on the signal level, making the overall dynamic range less than 100:1.
Finally, it should be noted that the above is only for illustrating the technical solution of the present invention and not for limiting the same, and although the present invention has been described in detail with reference to the preferred arrangement, it should be understood by those skilled in the art that the technical solution of the present invention (such as the form of the thin film micro valve, the selection of various measuring circuits and elements, the sequence of steps, etc.) may be modified or substituted for the same without departing from the spirit and scope of the technical solution of the present invention.
Claims (8)
1. A system for improving the detection accuracy of the on-off performance of a thin film micro valve, comprising: the liquid path device is connected with a tested micro valve channel with M thin film micro valves, the gas path control device, the amplifying device with M signal amplifiers and the waveform generator; the signal amplifier is connected with the data acquisition card and the computer in sequence, M is 1, 2,3 or more tested film micro valves, and the signal amplifier is characterized in that each signal amplifier comprises: the detection resistor MR is electrically connected with the detection electrode, the detection resistor MR is electrically connected with the negative input end of the operational amplification chip MOP, the positive input end of the operational amplification chip is electrically connected with the output end of the amplification chip and is electrically connected with one input end of the acquisition card, the voltage high end +Vcc of the operational amplification chip is electrically connected with the waveform generator SG and the other input end of the acquisition card, the other end of the waveform generator is electrically connected with the electrode of the liquid circuit terminal, the voltage low end-Vcc of the operational amplification chip is grounded, and a reference resistor MRef is connected between the negative input end and the output end of the operational amplification chip in parallel; the gas circuit control device comprises: the device comprises a gas circuit terminal with M gas circuit channels, a solenoid valve island with a high-precision pressure reducing valve, a gas circuit flowmeter and a gas source, wherein the gas circuit terminal is connected with a detected micro valve channel pipeline in sequence; the liquid path device comprises: a liquid path terminal with M liquid path channels and M electrodes, a liquid path pressure sensor LPM, a pulse damper LEP, a liquid supply pump SP with a pressure regulating valve and a solution tank which are sequentially connected with a detected micro valve channel pipeline; the gas circuit control device and the liquid circuit device are respectively and electrically connected with the acquisition card; the power supply of the signal amplifier is integrated in the system power supply together with the waveform generator.
2. The system of claim 1, wherein the electrodes in the motor module are platinum electrodes.
3. The system of claim 2, wherein the waveform generator is a square wave generator; the output bandwidth is 10MHz to 2GHz, and the output voltage range is 20mV to 10.0V based on the accurate noise-free signal and the 5GS/s16 bit performance.
4. A system according to claim 3, wherein the gas source is a nitrogen cylinder with a flow regulating valve.
5. The system of claim 4, wherein the solution in the solution tank is a sodium chloride solution.
6. The system of claim 5, wherein the fluid supply pump is a peristaltic pump or a syringe pump.
7. The system of claim 5, wherein the solenoid valve island is provided with a micro pneumatic sample pump, a two-stage high-precision pressure reducing valve, and a pump valve electric controller.
8. A method for improving the detection precision of the on-off performance of a film micro valve by using the system of claim 7, which is characterized by comprising the following steps:
Step 1, a connection system: the method comprises the steps of connecting a detected micro-flow channel into a detection device, determining each micro-valve to be detected, connecting an input electrode to a liquid inlet of the micro-channel where the micro-valve is located to be in contact with liquid, wherein the liquid inlet of the micro-channel is not influenced by the flow of the liquid in the micro-channel, connecting an output end electrode to a liquid outlet of the micro-channel respectively and in contact with the liquid, and not influencing the flow of the liquid in the micro-channel, connecting a gas circuit control device and a liquid circuit device, connecting the electrodes to an amplifying device and connecting an acquisition card and a computer;
Step 2, starting the system: powering up the system and opening the computer, and setting the computer as a data acquisition interface; opening a nitrogen bottle, closing all micro-valve gas paths through an electromagnetic valve island, detecting the gas path linking tightness, adjusting the gas pressure input into each film micro-valve through the electromagnetic valve island after no gas leakage is determined, and determining that the input gas pressure value is 0.3Mpa after passing through a secondary pressure reducing valve; injecting standard sodium chloride solution into the solution tank, starting a liquid supply pump, adjusting the liquid pressure, and monitoring the pressure change through a liquid path pressure sensor; the pulse damper is adjusted to enable the liquid output to be stable; turning on a waveform generator to provide an input signal to an amplifier;
step 3, collecting data: according to experimental requirements, the solenoid valve island adjusts the gas circuit to drive each micro valve, voltage data V 0 on a detection resistor connected with a detection electrode of each micro valve on a detection liquid circuit terminal is acquired by the acquisition card in real time, voltage signals on the resistor connected between the ports are sent to a computer for data processing, and a voltage signal change curve on the detection resistor on each thin film microchannel is obtained; changing the air pressure value and the liquid flow value, observing the change of each voltage data V 0, drawing a change curve of the voltage data V 0 with different air pressure values and different liquid flow values, and recording the change curve in a computer;
Step 4, data analysis: judging whether the micro valve is completely closed or not through the voltage value change of the amplifying circuit, if the micro valve is completely closed, the voltage value is from a certain fixed value to zero, and if the micro valve is not completely closed, the micro valve is not completely closed; when the micro valve is opened, the solution flows through the micro channel; the micro valve is turned off, and the solution is blocked by the micro valve; when the micro valve is opened and closed, voltage value differences obtained by measuring voltages at two ends of the detection resistor are respectively measured, so that the opening and closing performances of the micro valve are detected:
The alternating voltage value output by the waveform generator is V i, the resistance value of the measuring resistor is R, and the equivalent resistance of the thin film micro valve liquid flow passage is R flu:
The voltage value V 0 at two ends of the detection resistor is as follows:
Wherein: kappa is the conductivity of the solution, S is the cross-sectional area of the microchannel; l is the length of the microfluidic channel to be tested;
Calculating a root mean square value V RMS of an output voltage value of the liquid path pressure sensor:
Or/>
Wherein: t is the measurement duration and V (T) is the instantaneous voltage.
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