CN115121306A - Method for modifying PDMS chip based on microfluidic technology - Google Patents
Method for modifying PDMS chip based on microfluidic technology Download PDFInfo
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- CXQXSVUQTKDNFP-UHFFFAOYSA-N octamethyltrisiloxane Chemical compound C[Si](C)(C)O[Si](C)(C)O[Si](C)(C)C CXQXSVUQTKDNFP-UHFFFAOYSA-N 0.000 title claims abstract description 132
- 239000004205 dimethyl polysiloxane Substances 0.000 title claims abstract description 131
- 235000013870 dimethyl polysiloxane Nutrition 0.000 title claims abstract description 131
- 238000004987 plasma desorption mass spectroscopy Methods 0.000 title claims abstract description 131
- 229920000435 poly(dimethylsiloxane) Polymers 0.000 title claims abstract description 131
- 238000000034 method Methods 0.000 title claims abstract description 36
- 238000005516 engineering process Methods 0.000 title claims abstract description 18
- 239000007788 liquid Substances 0.000 claims abstract description 73
- 239000003607 modifier Substances 0.000 claims abstract description 60
- 239000011521 glass Substances 0.000 claims abstract description 26
- 239000000758 substrate Substances 0.000 claims abstract description 25
- 238000010438 heat treatment Methods 0.000 claims abstract description 23
- 238000004140 cleaning Methods 0.000 claims abstract description 18
- 238000004519 manufacturing process Methods 0.000 claims abstract description 12
- 239000000839 emulsion Substances 0.000 claims description 75
- 239000012071 phase Substances 0.000 claims description 67
- 238000012986 modification Methods 0.000 claims description 48
- 230000004048 modification Effects 0.000 claims description 48
- 239000008385 outer phase Substances 0.000 claims description 30
- 239000008384 inner phase Substances 0.000 claims description 22
- 238000004891 communication Methods 0.000 claims description 21
- 238000012545 processing Methods 0.000 claims description 10
- 238000007599 discharging Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 5
- 239000000243 solution Substances 0.000 description 41
- 239000007789 gas Substances 0.000 description 29
- 239000004372 Polyvinyl alcohol Substances 0.000 description 22
- 229920002451 polyvinyl alcohol Polymers 0.000 description 22
- 230000000694 effects Effects 0.000 description 19
- 230000002209 hydrophobic effect Effects 0.000 description 10
- 230000008569 process Effects 0.000 description 7
- 239000003795 chemical substances by application Substances 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000002715 modification method Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 238000007789 sealing Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 238000004381 surface treatment Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 238000005842 biochemical reaction Methods 0.000 description 1
- 238000004113 cell culture Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000003094 microcapsule Substances 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000035699 permeability Effects 0.000 description 1
- 238000009832 plasma treatment Methods 0.000 description 1
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01L—CHEMICAL OR PHYSICAL LABORATORY APPARATUS FOR GENERAL USE
- B01L3/00—Containers or dishes for laboratory use, e.g. laboratory glassware; Droppers
- B01L3/50—Containers for the purpose of retaining a material to be analysed, e.g. test tubes
- B01L3/502—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures
- B01L3/5027—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip
- B01L3/502769—Containers for the purpose of retaining a material to be analysed, e.g. test tubes with fluid transport, e.g. in multi-compartment structures by integrated microfluidic structures, i.e. dimensions of channels and chambers are such that surface tension forces are important, e.g. lab-on-a-chip characterised by multiphase flow arrangements
Abstract
The invention relates to a method for modifying a PDMS chip based on a microfluidic technology. The PDMS chip comprises a glass substrate and a PDMS micro-channel, wherein the PDMS micro-channel comprises an inner liquid drop generation region and an outer liquid drop generation region, and the cross section area of the inner liquid drop generation region is smaller than that of the outer liquid drop generation region. The method comprises the following steps: placing the PDMS microchannel in a plasma cleaning machine for treatment, bonding the treated PDMS microchannel and a glass substrate to form a PDMS chip, and heating the PDMS chip; the heated PDMS chip is stood and cooled, after the PDMS chip is recovered to the room temperature, gas is injected into one of the inner liquid drop generation area and the outer liquid drop generation area, and a modifier is injected into the other of the inner liquid drop generation area and the outer liquid drop generation area, so that the gas and the modifier form dynamic balance at an intersection between the outer liquid drop generation area and the inner liquid drop production area; after maintaining the dynamic balance for a period of time, the pressure of the modifier is closed, the pressure of the gas is increased, and the modifier in the PDMS chip is discharged.
Description
Technical Field
The invention relates to the technical field of PDMS chips, in particular to a PDMS chip modification method based on a microfluidic technology.
Background
PDMS is an elastic high molecular polymer, and is usually prepared by thermally polymerizing a PDMS matrix and a certain proportion of a curing agent. The thermal stability is good, and the method is suitable for manufacturing various biochemical reaction chips; has high biocompatibility and obvious air permeability, and can be used for cell culture. In addition, PDMS has low raw material cost, short material processing period and good material durability, and can form good sealing with various materials, such as silicon, silicon oxide, glass and the like. Manufacturing devices using PDMS soft lithography techniques is simpler, cheaper, and more time efficient than other techniques such as silicon and plastic microfabrication.
To successfully produce droplets, the continuous phase needs to effectively wet the tube walls. PDMS is a hydrophobic material that is very suitable for the generation of w/o rather than o/w droplets. Furthermore, unmodified PDMS chips are not suitable for the generation of double or even multiple emulsions. The incompatibility of PDMS has limited many applications.
Therefore, Chinese patent No. CN112371065B discloses a method for generating magnetic core-shell microcapsules based on a surface acoustic wave microfluidic device, and the method provides a local hydrophilic and hydrophobic treatment mode. Specifically, the first-stage T-shaped flow channel is hydrophobic, and the second-stage cross-shaped flow channel is hydrophilic; connecting nitrogen to an inner phase inlet and a middle phase inlet by using an air pump, adjusting the pressure to 50mbar, connecting a PVA aqueous solution with the mass fraction of 1% to an outer phase inlet, increasing the pressure of the outer phase inlet to slowly introduce the PVA solution, controlling the pressure of the air pump, and keeping the PVA solution to only pass through the second-stage cross-shaped flow channel and stop at a connecting port of the second-stage cross-shaped flow channel; keeping the state stable for 10 minutes, closing the pressure of the external phase inlet, pulling out the PVA solution pipeline, increasing the nitrogen pressure, discharging the residual PVA solution in the secondary cross-shaped flow channel through the external phase inlet and the outlet 203, heating and drying at 95 ℃ for 10 minutes, and finishing the hydrophilic and hydrophobic treatment process for 1 time; the hydrophilic-hydrophobic treatment process was repeated 3 times, and finally heated at 110 ℃ for 1 hour.
The inventor conducts local hydrophilic and hydrophobic treatment experiments similar to the Chinese patent CN112371065B, and finds that the treatment method has some problems, so that the modification success rate of the microfluidic chip is low. Specifically, in the step of "controlling the pressure of the air pump, keeping the PVA solution to only pass through the second-stage cross-shaped flow channel and stop at the communication port of the second-stage cross-shaped flow channel", because the channel of the microfluidic chip is smaller and the cross sections of the channel are the same, the pressure difference between the first-stage T-shaped flow channel and the second-stage cross-shaped flow channel is extremely small, and the pressure control accuracy of the air pump is limited, in actual operation, three situations can occur at the communication port of the second-stage cross-shaped flow channel: 1. the PVA solution stops just at the communication port of the secondary cross-shaped flow passage (as shown in figure 1); 2. gas enters the secondary cross-shaped flow passage from the communication port of the secondary cross-shaped flow passage (as shown in figure 2); 3. the PVA solution enters the primary T-shaped flow passage from the communication port of the secondary cross-shaped flow passage (as shown in figure 3). Therefore, if a local hydrophilic and hydrophobic treatment mode similar to that of CN112371065B is adopted, it is difficult to keep the PVA solution only passing through the second-level cross flow channel and ending at the communication port of the second-level cross flow channel, which results in a low modification success rate of the microfluidic chip, the modification success rate is generally 20% to 30%, and the modification effect is also general.
Therefore, the inventors considered that the above-mentioned manner of the partial hydrophilizing-hydrophobizing treatment still leaves room for further improvement.
Disclosure of Invention
Based on this, the present invention provides a method for modifying a PDMS chip based on a microfluidic technology, which can control a modification solution in a certain area more precisely under the condition of limited pressure control accuracy of an air pump, thereby ensuring the modification effect of the PDMS chip.
A method for modifying a PDMS chip based on a microfluidic technology comprises the steps that the PDMS chip comprises a glass substrate and a PDMS micro-channel bonded on the glass substrate, the PDMS micro-channel comprises an inner liquid drop generating area and an outer liquid drop generating area, and the cross section area of the inner liquid drop generating area is smaller than that of the outer liquid drop generating area; the method comprises the following steps: placing the PDMS microchannel in a plasma cleaning machine for treatment, bonding the PDMS microchannel and the glass substrate after the treatment is finished to form the PDMS chip, and heating the PDMS chip; the heated PDMS chip is stood and cooled, after the PDMS chip is returned to the room temperature, gas is injected into one of the inner liquid drop generating area and the outer liquid drop generating area, and a modifier is injected into the other of the inner liquid drop generating area and the outer liquid drop generating area, so that the gas and the modifier form dynamic balance at an intersection between the outer liquid drop generating area and the inner liquid drop generating area; and after maintaining the dynamic balance for a period of time, closing the pressure of the modifier, increasing the pressure of the gas, and discharging the modifier in the PDMS chip.
Compared with the prior art, the cross-sectional area of the original outer droplet generation area is increased to increase the whole space of the outer droplet generation area, so that the pressure of the outer droplet generation area is reduced, namely under the condition of the same pressure source, the pressure of the outer droplet generation area is lower than that of the existing outer droplet generation area. Meanwhile, under the condition that the pressure of the inner liquid drop generating area is not changed, the pressure difference between the inner liquid drop generating area and the outer liquid drop generating area is larger than the pressure difference between the inner liquid drop generating area and the outer liquid drop generating area, and a sufficient space is provided for pressure regulation of the air pump. Through the design, the modifier can be well controlled at the intersection between the outer liquid drop generation area and the inner liquid drop production area, the modification success rate can reach more than 90 percent, and the modification success rate and the modification effect are greatly improved.
In addition, the method firstly carries out plasma cleaning on the PDMS microchannel to realize primary modification, changes the surface groups of the PDMS microchannel from hydrophobic to hydrophilic, then introduces PVA (polyvinyl alcohol) modification solution into the PDMS microchannel to carry out secondary modification, further improves the hydrophilic effect of the surface groups of the PDMS microchannel, and is beneficial to improving the success rate of modification and the effect of modification through double modification. And because the PDMS microchannel and the glass substrate are fixed together and then the modified solution can be introduced, the conventional bonding mode is to stick the PDMS microchannel and the glass substrate together and then stand for a period of time, the standing time is at least 6 hours, the primary modification effect after plasma cleaning can only be maintained for several hours, and the conventional bonding mode cannot meet the requirement of double modification, so that the PDMS chip is heated in the bonding process of the PDMS microchannel and the glass substrate, bonding is promoted, the bonding time is shortened, and the modification of the modified solution can be ensured before the primary modification effect is invalid, so that the aim of double modification is fulfilled. And the bonding process is carried out while heating treatment is carried out, so that the bonding strength and the sealing property between the PDMS microchannel and the glass substrate can be greatly improved, and the problem of leakage of the modified solution is avoided.
Further, the cross-sectional height of the inner drop generating region is less than the cross-sectional height of the outer drop generating region.
Furthermore, the height of the cross section of the inner liquid drop generating area is 30-70 mu m, and the height of the cross section of the outer liquid drop generating area is 70-120 mu m.
Further, the cross-sectional width of the inner drop generating region is smaller than the cross-sectional width of the outer drop generating region.
Further, the cross-sectional width of the inner droplet generation region is 30-70 μm, and the cross-sectional width of the outer droplet generation region is 70-120 μm.
Further, the inner droplet generation region comprises an inner phase flow channel, an intermediate phase flow channel and a single emulsion flow channel, wherein an inlet of the inner phase flow channel is used for injecting an inner phase solution, an inlet of the intermediate phase flow channel is used for injecting an intermediate phase solution, an outlet of the inner phase flow channel, an outlet of the intermediate phase flow channel and an inlet of the single emulsion flow channel are connected through a first flow channel communication port, and an outlet of the single emulsion flow channel is used for outputting a single emulsion generated at the first flow channel communication port; the outer liquid drop generating area comprises an outer phase flow channel and a double emulsion flow channel, an inlet of the outer phase flow channel is used for injecting an outer phase solution, an outlet of the single emulsion flow channel, an outlet of the outer phase flow channel and an inlet of the double emulsion flow channel are connected through a second circulation communicating port, and the double emulsion flow channel is used for outputting double emulsion generated at the second circulation communicating port.
Further, the cross sections of the internal phase flow channel, the intermediate phase flow channel and the single emulsion flow channel are consistent in height; the widths of the cross sections of the internal phase flow channel, the intermediate phase flow channel and the single emulsion flow channel are consistent; the height of the cross section of the outer phase flow channel is greater than that of the cross section of the single emulsion flow channel; the width of the cross section of the outer phase flow channel is larger than that of the single emulsion flow channel; the height of the cross section of the double emulsion flow channel is greater than that of the cross section of the single emulsion flow channel; the width of the cross section of the double emulsion flow channel is larger than that of the cross section of the single emulsion flow channel; the height of the cross section of the double emulsion flow channel is equal to that of the cross section of the external phase flow channel; the width of the cross section of the double emulsion flow channel is equal to that of the cross section of the external phase flow channel; the height of the cross sections of the internal phase flow channel, the intermediate phase flow channel and the single emulsion flow channel is designed to be 30-70 mu m; the widths of the cross sections of the internal phase flow channel, the intermediate phase flow channel and the single emulsion flow channel are designed to be 30-70 mu m; the height of the cross sections of the external phase flow channel and the double emulsion flow channel is designed to be 70-120 mu m; the width of the cross section of the external phase flow channel and the double emulsion flow channel is designed to be 70-120 mu m.
Further, the working power of the plasma cleaning machine is 220W, and the processing time of the plasma cleaning machine is 20-50 s.
Further, the heating temperature is 60-70 ℃, and the heating time is 10-20 min.
Further, the modifier is a hydrophilic modifier, and the modifier is 1-10 wt% of PVA solution.
Further, the initial gas pressure value is set to be 3Psi, the initial pressure value of the modifying agent is set to be 2Psi, and the time for keeping the dynamic balance between the gas and the modifying agent is 5-10 min.
Further, after the modifier is discharged, the PDMS chip is heated and dried.
Further, if the PDMS chip is a W/O/W type chip, gas is firstly introduced into the inlet of the internal phase flow channel and the inlet of the intermediate phase flow channel; then introducing a modifier to an inlet of the external phase flow channel; then, the pressure of the solution is slowly and continuously increased, so that the gas and the modifier form dynamic balance at the intersection of the outer liquid drop generation area and the inner liquid drop production area; and after maintaining the dynamic balance for a period of time, stopping introducing the modifier, then increasing the gas pressure, and discharging the modifier from the inlet of the external phase flow channel and the outlet of the PDMS chip.
Further, if the PDMS chip is an O/W/O type chip, firstly introducing gas into an inlet of the outer phase flow channel and an outlet of the PDMS chip; then introducing a modifier to the inlet of the intermediate phase flow channel; then, the pressure of the solution is slowly and continuously increased, so that the gas and the modifier form dynamic balance at the intersection of the outer liquid drop generation area and the inner liquid drop production area; after maintaining the dynamic equilibrium for a period of time, the introduction of the modifier is stopped, the gas pressure is then increased, and the modifier is discharged from the inlets of the internal phase flow channels and the intermediate phase flow channels.
For a better understanding and practice, the invention is described in detail below with reference to the accompanying drawings.
Drawings
FIG. 1 is a schematic view showing a PVA solution stopping just at a communicating port of a secondary cross-shaped flow passage;
FIG. 2 is a schematic view of gas entering the secondary cross-shaped flow passage from the secondary cross-shaped flow passage communication port;
FIG. 3 is a schematic view of a PVA solution entering a primary T-shaped flow passage from a secondary cross-shaped flow passage communicating port;
FIG. 4 is a schematic diagram of a PDMS chip;
FIG. 5 is a schematic view of a PDMS chip at a second flow communication port;
FIG. 6 is an optical microscope photograph of a hydrophilic agent and a gas in a dynamic equilibrium state;
FIG. 7 is a schematic diagram comparing the contact angle of liquid and PDMS chip;
reference numerals:
1. an inner phase flow channel; 2. an intermediate phase flow channel; 3. a single emulsion flow channel; 4. an outer phase flow channel; 5. a double emulsion flow channel; 6. a first flow passage communication port; 7. the second flow communication port.
Detailed Description
The invention provides a method for modifying a PDMS chip based on a microfluidic technology, which is mainly used for carrying out hydrophilic and hydrophobic modification treatment on part of flow channels of the PDMS chip.
Referring to fig. 4 and 5, the PDMS chip includes a glass substrate and a PDMS micro channel, the PDMS micro channel is attached to the top surface of the glass substrate, and the PDMS micro channel and the glass substrate form a closed channel. Specifically, PDMS microchannels were used to inject internal, intermediate, and external phase solutions to create multiple emulsions. The PDMS micro flow channel comprises an inner liquid drop generating area and an outer liquid drop generating area. Wherein the inner droplet generation zone is used for injecting the inner phase solution and the intermediate phase solution to generate the inner droplets. The outer droplet generation area is communicated with the inner droplet generation area, and the outer droplet generation area is used for injecting the inner droplet and the outer phase solution to generate double droplets. Wherein the cross-sectional area of the inner drop generating region is smaller than the cross-sectional area of the outer drop generating region.
Compared with the prior art, the cross-sectional area of the original outer droplet generation region is increased to increase the whole space of the outer droplet generation region, so that the pressure of the outer droplet generation region is reduced, namely, the pressure of the outer droplet generation region is lower than that of the existing outer droplet generation region under the condition of the same pressure source. Meanwhile, under the condition that the pressure of the inner liquid drop generating area is not changed, the pressure difference between the inner liquid drop generating area and the outer liquid drop generating area is larger than the pressure difference between the inner liquid drop generating area and the outer liquid drop generating area, and a sufficient space is provided for pressure regulation of the air pump. Through the design, the modifier can be well controlled at the intersection between the outer liquid drop generation area and the inner liquid drop production area, the modification success rate can reach more than 90 percent, and the modification success rate and the modification effect are greatly improved.
In particular, the cross-sectional height of the outer drop generating region is greater than the cross-sectional height of the inner drop generating region. By adopting the design, the PDMS material is softer, and if the cross section is at the same height and at different widths, the larger the width is, the higher the possibility of collapse of the outer liquid drop generation area is, so that the PDMS material is not beneficial to liquid drop generation and local modification. And under the condition that the cross sections are the same in width and different in height, the situation that the outer liquid drop generating area collapses can be effectively avoided. On this basis, the cross section width of the outer liquid drop generation area is designed to be larger than that of the inner liquid drop generation area, so that the cross section neps of the outer liquid drop generation area can be increased, the strength of the overall outline of the outer liquid drop generation area can be improved, and the collapse situation of the outer liquid drop generation area is further avoided. In the embodiment, the height of the cross section of the inner liquid drop generating area is 30-70 μm, and the height of the cross section of the outer liquid drop generating area is 70-120 μm; the cross-sectional width of the inner droplet generation region is 30 to 70 μm, and the cross-sectional width of the outer droplet generation region is 70 to 120 μm.
More specifically, the inner droplet generation region includes an inner phase flow channel 1, an intermediate phase flow channel 2, and a single emulsion flow channel 3, wherein an inlet of the inner phase flow channel 1 is used for injecting an inner phase solution, an inlet of the intermediate phase flow channel 2 is used for injecting an intermediate phase solution, an outlet of the inner phase flow channel 1, an outlet of the intermediate phase flow channel 2, and an inlet of the single emulsion flow channel 3 are connected through a first flow channel communication port 6, and an outlet of the single emulsion flow channel 3 is used for outputting a single emulsion generated at the first flow channel communication port 6. The outer droplet generation area comprises an outer phase flow passage 4 and a double emulsion flow passage 5, wherein an inlet of the outer phase flow passage 4 is used for injecting an outer phase solution, an outlet of the single emulsion flow passage 3, an outlet of the outer phase flow passage 4 and an inlet of the double emulsion flow passage 5 are connected through a second circulation communication port 7, and the double emulsion flow passage 5 is used for outputting double emulsion generated at the second circulation communication port 7.
Wherein, the cross sections of the inner phase flow channel 1, the intermediate phase flow channel 2 and the single emulsion flow channel 3 are consistent in height. The widths of the cross sections of the inner phase flow channel 1, the intermediate phase flow channel 2 and the single emulsion flow channel 3 are consistent. The height of the cross section of the outer phase flow passage 4 is larger than that of the single emulsion flow passage 3, and the width of the cross section of the outer phase flow passage 4 is larger than that of the single emulsion flow passage 3. The height of the cross section of the double emulsion flow channel 5 is greater than the height of the cross section of the single emulsion flow channel 3, the width of the cross section of the double emulsion flow channel 5 is greater than the width of the cross section of the single emulsion flow channel 3, in the embodiment, the height of the cross section of the double emulsion flow channel 5 is equal to the height of the cross section of the external phase flow channel 4, and the width of the cross section of the double emulsion flow channel 5 is equal to the width of the cross section of the external phase flow channel 4. In this embodiment, the cross-sectional heights of the internal phase flow channel 1, the intermediate phase flow channel 2, and the single emulsion flow channel 3 are designed to be 30 to 70 μm, and the cross-sectional widths of the internal phase flow channel 1, the intermediate phase flow channel 2, and the single emulsion flow channel 3 are designed to be 30 to 70 μm. The height of the cross sections of the external phase flow passage 4 and the double emulsion flow passage 5 is designed to be 70-120 mu m, and the width of the cross sections of the external phase flow passage 4 and the double emulsion flow passage 5 is designed to be 70-120 mu m.
The method for modifying the PDMS chip based on the microfluidic technology comprises the following steps:
s1, placing the PDMS microchannel in a plasma cleaning machine for processing, bonding the PDMS microchannel and the glass substrate after the processing is finished so as to enable the PDMS microchannel and the glass substrate to be pasted into a PDMS chip, and then placing the PDMS chip on a heating plate for heating;
s2, standing and cooling the heated PDMS chip, after the PDMS chip returns to room temperature, injecting a gas into one of the inner droplet generation region and the outer droplet generation region, and injecting a modifier into the other of the inner droplet generation region and the outer droplet generation region, so that a dynamic balance is formed between the gas and the modifier at an intersection of the outer droplet generation region and the inner droplet generation region (as shown in fig. 6), that is, the gas and the modifier form a dynamic balance at the second flow communication port 7;
s3, after the gas and the modifier are kept in dynamic balance for a period of time, closing the pressure of the modifier, increasing the gas pressure, and discharging the modifier in the PDMS chip;
s4, placing the PDMS chip on a heating plate for heating and drying treatment.
Compared with the prior art, the embodiment firstly carries out plasma cleaning on the PDMS microchannel to realize primary modification, changes the surface group of the PDMS microchannel from hydrophobic to hydrophilic, then introduces PVA (polyvinyl alcohol) modification solution into the PDMS microchannel to carry out secondary modification, further improves the hydrophilic effect of the surface group of the PDMS microchannel, and is beneficial to improving the success rate of modification and the effect of modification through double modification. And because the PDMS microchannel and the glass substrate are fixed together and then the modified solution can be introduced, the conventional bonding mode is to stick the PDMS microchannel and the glass substrate together and then stand for a period of time, the standing time is at least 6 hours, the primary modification effect after plasma cleaning can only be maintained for several hours, and the conventional bonding mode cannot meet the requirement of double modification, so that the PDMS chip is heated in the bonding process of the PDMS microchannel and the glass substrate, bonding is promoted, the bonding time is shortened, and the modification of the modified solution can be ensured before the primary modification effect is invalid, so that the aim of double modification is fulfilled. And the bonding process is carried out while heating treatment is carried out, so that the bonding strength and the sealing property between the PDMS microchannel and the glass substrate can be greatly improved, and the problem of leakage of the modified solution is avoided.
After the treatment by the method, the contact angle between the PDMS chip and the hydrophilic liquid is much less than 90 degrees, and the hydrophilic modification effect is better than the modification effect of the untreated PDMS chip, the only plasma treatment of the PDMS chip, and the only PVA solution treatment of the PDMS chip (as shown in fig. 7). Moreover, the modification effect of the PDMS chip modified by the method can be maintained for at least one month, while the modification effect of the existing modification method can be maintained for only one week.
Specifically, in step S1, the working power of the plasma cleaning machine is set to 220W preferentially, and the processing time of the plasma cleaning machine is 20-50S. In research experiments, the inventor finds that when the plasma cleaning machine adopts 150W power, the PDMS chip needs to be placed for at least 6 hours before the modification solution is introduced, the modification effect is general, and the modification effect maintaining time is short. And after the plasma cleaning machine adopts 220W power, the plasma can better change the surface group of the PDMS microchannel, the effect of changing hydrophobic into hydrophilic and then introducing the modifier is better, meanwhile, the adhesiveness of the PDMS microchannel is increased, so that the PDMS microchannel and the glass substrate are combined more firmly, and the liquid leakage condition is prevented from occurring in the modification process.
Specifically, in step S1, the heating temperature of the heating plate is 60 to 70 ℃, and the heating time of the heating plate is 10 to 20 min.
Specifically, in step S2, the modifier is a hydrophilic modifier, and a 1-10 wt% PVA solution is used as the modifier.
Specifically, in step S2, the gas pressure value is set to 3Psi, the initial pressure value of the modifying agent is set to 2Psi, and the time for the gas and the modifying agent to keep dynamic equilibrium is 5-10 min.
Since the PDMS chip can generate W/O/W type double emulsion or O/W/O type double emulsion, the hydrophilic modification method of the O/W/O type PDMS chip is slightly different from that of the W/O/W type PDMS chip, and therefore, the hydrophilic modification method of the O/W/O type PDMS chip and the hydrophilic modification method of the W/O/W type PDMS chip will be described in detail below.
Example one
For the W/O/W type PDMS chip, firstly, the PDMS micro-channel which is cast and molded is placed in a plasma cleaning machine for processing (220W,40s) and then is bonded with a glass substrate, and then the bonding is promoted by heating for 15 min. After the chip was returned to room temperature, surface treatment was performed using a hydrophilic modifier 5% PVA solution. And introducing gas into the inlet of the internal phase flow channel 1 and the inlet of the intermediate phase flow channel 2 through a gas pump, wherein the gas pressure value is 3 Psi. Then 5% PVA solution is introduced into the inlet of the outer phase flow passage 4, the initial pressure is 2Psi, and then the pressure of the solution is slowly and continuously increased, so that the air and the modifier form dynamic balance at the intersection of the outer droplet generation area and the inner droplet production area. And after keeping for 5min, stopping introducing the modifier, pulling out the pipeline connected with the modifier, then increasing the gas pressure of the inner phase flow channel 1 and the middle phase flow channel 2, discharging the modifier in the PDMS chip from the inlet of the outer phase flow channel 4 and the outlet of the PDMS chip, and finally placing the PDMS chip on a heating plate for drying.
Example two
For an O/W/O type PDMS chip, firstly, a PDMS micro-channel which is cast and molded is placed in a plasma cleaning machine for processing (220W,40s) and then is bonded with a glass substrate, and then, the bonding is promoted by heating for 15 min. After the chip was returned to room temperature, surface treatment was performed using a hydrophilic modifier 5% PVA solution. And introducing gas into the inlet of the external phase flow channel 4 and the outlet of the PDMS chip through a gas pump, wherein the gas pressure value is 3 Psi. Then 5% PVA solution is introduced into the inlet of the intermediate phase flow channel 2, the initial pressure is 2Psi, and then the pressure of the solution is slowly and continuously increased, so that the air and the modifier form dynamic balance at the intersection of the outer droplet generation area and the inner droplet production area. Keeping for 5min, stopping introducing the modifier, pulling out the pipeline connected with the modifier, increasing the gas pressure at the inlet of the outer phase flow channel 4 and the outlet of the PDMS chip to 5Psi, discharging the modifier in the PDMS chip from the inlet of the inner phase flow channel 1 and the inlet of the intermediate phase flow channel 2, and finally placing the PDMS chip on a heating plate for drying.
The above-mentioned embodiments only express several embodiments of the present invention, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the inventive concept, which falls within the scope of the present invention.
Claims (10)
1. A method for modifying PDMS chip based on micro-fluidic technology is characterized in that,
the PDMS chip comprises a glass substrate and a PDMS micro-channel bonded on the glass substrate, wherein the PDMS micro-channel comprises an inner liquid drop generation region and an outer liquid drop generation region, and the cross-sectional area of the inner liquid drop generation region is smaller than that of the outer liquid drop generation region;
the method comprises the following steps:
placing the PDMS microchannel in a plasma cleaning machine for processing, bonding the PDMS microchannel and the glass substrate after the processing is finished so as to combine the PDMS microchannel and the glass substrate into a PDMS chip, and heating the PDMS chip;
the heated PDMS chip is kept still and cooled, after the PDMS chip is returned to the room temperature, gas is injected into one of the inner liquid drop generation area and the outer liquid drop generation area, and a modifier is injected into the other of the inner liquid drop generation area and the outer liquid drop generation area, so that the gas and the modifier form dynamic balance at an intersection between the outer liquid drop generation area and the inner liquid drop production area;
and after maintaining the dynamic balance for a period of time, closing the pressure of the modifier, increasing the pressure of the gas, and exhausting the modifier in the PDMS chip.
2. The method of modifying a PDMS chip based on microfluidic technology of claim 1, wherein: the inner drop generating region has a cross-sectional height less than the cross-sectional height of the outer drop generating region.
3. The method of modifying PDMS chip based on microfluidic technology of claim 2, wherein: the height of the cross section of the inner liquid drop generating area is 30-70 mu m, and the height of the cross section of the outer liquid drop generating area is 70-120 mu m.
4. The method of modifying PDMS chip based on microfluidic technology of claim 2, wherein: the inner drop generating region has a cross-sectional width less than a cross-sectional width of the outer drop generating region.
5. The method of PDMS chip modification based on microfluidic technology of claim 4, wherein: the cross section width of the inner droplet generation area is 30-70 mu m, and the cross section width of the outer droplet generation area is 70-120 mu m.
6. The method of PDMS chip modification based on microfluidic technology of claim 4, wherein:
the inner droplet generation area comprises an inner phase flow channel (1), an intermediate phase flow channel (2) and a single emulsion flow channel (3), wherein an inlet of the inner phase flow channel (1) is used for injecting an inner phase solution, an inlet of the intermediate phase flow channel (2) is used for injecting an intermediate phase solution, an outlet of the inner phase flow channel (1), an outlet of the intermediate phase flow channel (2) and an inlet of the single emulsion flow channel (3) are connected through a first flow channel communication port (6), and an outlet of the single emulsion flow channel (3) is used for outputting a single emulsion generated at the first flow channel communication port (6);
the outer liquid drop generating area comprises an outer phase flow channel (4) and a double emulsion flow channel (5), an inlet of the outer phase flow channel (4) is used for injecting an outer phase solution, an outlet of the single emulsion flow channel (3), an outlet of the outer phase flow channel (4) and an inlet of the double emulsion flow channel (5) are connected through a second circulation communication port (7), and the double emulsion flow channel (5) is used for outputting double emulsion generated at the second circulation communication port (7).
7. The method of PDMS chip modification based on microfluidic technology of claim 6, wherein:
the cross sections of the inner phase flow channel (1), the intermediate phase flow channel (2) and the single emulsion flow channel (3) are consistent in height;
the widths of the cross sections of the inner phase flow channel (1), the intermediate phase flow channel (2) and the single emulsion flow channel (3) are consistent;
the height of the cross section of the outer phase flow channel (4) is greater than that of the cross section of the single emulsion flow channel (3);
the width of the cross section of the outer phase flow channel (4) is larger than that of the single emulsion flow channel (3);
the height of the cross section of the double emulsion flow channel (5) is greater than that of the cross section of the single emulsion flow channel (3);
the width of the cross section of the double emulsion flow channel (5) is larger than that of the cross section of the single emulsion flow channel (3);
the height of the cross section of the double emulsion flow channel (5) is equal to that of the cross section of the outer phase flow channel (4);
the width of the cross section of the double emulsion flow channel (5) is equal to that of the cross section of the outer phase flow channel (4);
the heights of the cross sections of the internal phase flow channel (1), the intermediate phase flow channel (2) and the single emulsion flow channel (3) are designed to be 30-70 mu m;
the widths of the cross sections of the internal phase flow channel (1), the intermediate phase flow channel (2) and the single emulsion flow channel (3) are designed to be 30-70 mu m;
the heights of the cross sections of the external phase flow channel (4) and the double emulsion flow channel (5) are designed to be 70-120 mu m;
the widths of the cross sections of the external phase flow channel (4) and the double emulsion flow channel (5) are designed to be 70-120 mu m.
8. The method of modifying a PDMS chip based on microfluidic technology of claim 1, wherein:
the working power of the plasma cleaning machine is 220W, and the processing time of the plasma cleaning machine is 20-50 s;
the heating temperature is 60-70 ℃, and the heating time is 10-20 min;
the modifier is a hydrophilic modifier, and the modifier is 1-10 wt% of PVA solution;
setting the initial gas pressure value to be 3Psi, setting the initial pressure value of the modifier to be 2Psi, and keeping the gas and the modifier in dynamic equilibrium for 5-10 min.
9. The method of modifying a PDMS chip based on microfluidic technology of claim 1, wherein: and after the modifier is discharged, heating and drying the PDMS chip.
10. The method of modifying a PDMS chip based on microfluidic technology of claim 1, wherein:
if the PDMS chip is a W/O/W type chip, firstly introducing gas into the inlet of the inner phase flow channel (1) and the inlet of the intermediate phase flow channel (2); then introducing a modifier into an inlet of the outer phase flow passage (4); then, the pressure of the solution is slowly and continuously increased, so that the gas and the modifier form dynamic balance at the intersection of the outer liquid drop generation area and the inner liquid drop production area; after maintaining the dynamic balance for a period of time, stopping introducing the modifier, then increasing the gas pressure, and discharging the modifier from the inlet of the external phase flow channel (4) and the outlet of the PDMS chip;
if the PDMS chip is an O/W/O type chip, firstly introducing gas into an inlet of the outer phase flow channel (4) and an outlet of the PDMS chip; then introducing a modifier into an inlet of the intermediate phase flow channel (2); then slowly and continuously increasing the pressure of the solution to ensure that the gas and the modifier form dynamic balance at the intersection of the outer liquid drop generation area and the inner liquid drop production area; after maintaining the dynamic equilibrium for a period of time, the introduction of the modifier is stopped, and then the gas pressure is increased, and the modifier is discharged from the inlet of the internal phase flow channel (1) and the inlet of the intermediate phase flow channel (2).
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