Patent Application
20220080411
This application claims priority to Korean Patent Application No. 10-2020-0118881, filed on 16 Sep. 2020. The entire disclosure of the application identified in this paragraph is incorporated herein by reference.
The present disclosure relates to a photothermal adhesive composition containing a graphene-copper sulfide composite, a manufacturing method therefor, and a method for fabrication of a microfluidic chip using the same. More specifically, to a technique in which an ultrasonicated graphene oxide (GO) is conjugated with polyethylene glycol (PEG) and mixed with copper sulfide to fabricate composite which is used to induce a photothermal effect, thereby bonding substrates of microfluidic chips to each other.
Generally, the fabrication of microfluidic chips is achieved using a method in which a micrometer-scale structure is formed on a hard ceramic substrate such as a silicon wafer or a glass substrate through an etching process, followed by covering the hard ceramic substrate with a planar substrate and bonding the same, or a method in which a structure is fabricated on an elastomeric polymer material, most notably polydimethylene siloxane (PDMS), by soft-lithography.
Among of them, the method for fabricating thin film chip replicas or microfluidic chips using glass substrates is suggested by Korean Patent Number 10-0788458. With respect to the microfluidic chips fabricated using hard materials such as silicon wafers, glass substrates, etc., however, not only is the adhesion between the microstructure formed substrate and the planar substrate difficult, but also fine gaps are generated during fabrication processes or use, leading to water leakage therefrom. Furthermore, the ceramic material is vulnerable to an external impact.
There has recently been an increase in a need for research for microfluidic chips of composite plastics that are suitable for mass production and commercialization. Conventional bonding methods are carried out in a viscosity-based adhesive manner in which interfaces in the plastic materials for microfluidic chips are attached with high heat under a high pressure or by an adhesive agent or an adhesive film.
However, such conventional processes suffer from the disadvantages that the microstructures are prone to deformation due to heat and pressure; the microfluidic channels may be blocked with the fluidization of the adhesive agent or with the collapse thereof by the pressure-caused deformation of the plastic material; and high costs are required for the initial facility as well as the maintenance of the process.
In order to solve the problems encountered with the conventional techniques, the present inventors developed a technique for bonding chips of plastic materials using the photothermal effect of a graphene-copper sulfide composite. A technique for bonding chips plays a critical role in preventing a sample from leaking from the channel and in connecting chips to each other.
The graphene-copper sulfide composite according to the present disclosure allows chips made of plastics to be bonded within a short period of time upon exposure to a near infrared (NIR) laser. Existing as a liquid phase low in viscosity and density, the bonding material does not permit the occurrence of gaps between the plastic chips.
In addition, the present inventors confirmed that the chips did not leak fluids without deformation, as analyzed for physical and mechanical characteristics. Therefore, the technique for bonding microfluidic chips made of plastics using a photothermal effect of the graphene-copper sulfide composite can not only be used in research in which bonding needs to be maintained, like PCR, etc. where temperatures inside chips are high or experiments are performed for a long time, but also applied to the interface of a chip and a chip in research where modules of various chips are assembled.
Accordingly, a purpose of the present disclosure is to provide a photothermal adhesive composition containing a graphene-transition metal compound composite.
Another purpose of the present disclosure is to provide a method for manufacturing a photothermal adhesive composition containing a graphene-transition metal compound composite, the method comprising the steps of:
reacting graphene with a hydrophilic polymer and then reducing the graphene; and
mixing the graphene with transition metal compound nanoparticles to form a composite.
A further purpose of the present disclosure is to provide a method for fabrication of a microfluidic chip using a photothermal adhesive composition containing a graphene-transition metal compound composite, the method comprising:
a loading step of loading the photothermal adhesive composition to a target site on a microfluidic chip lower substrate;
a first laser irradiation step of irradiating a laser to the target site; and
a second laser irradiation step of contacting a microfluidic chip upper substrate with the target site on the lower substrate, followed by irradiating a laser thereto.
A still further purpose of the present disclosure is to provide a use of a graphene-transition metal compound composite in bonding microfluidic chips through a photothermal effect.
The present disclosure relates to a photothermal adhesive composition containing a graphene-copper sulfide composite, a manufacturing method therefor, and a method for fabrication of a microfluidic chip using same. The photothermal adhesive composition according to the present disclosure can be used to bond chips made of plastics through a photothermal effect, without applying a pressure thereto.
The present inventors developed a technique of using the photothermal effect of a graphene-copper sulfide composite in bonding chips made of plastic materials and succeeded in bonding plastic chips by applying a laser to the graphene-copper sulfide composite within a short period of time. Also, the present inventors identified that the bonding material, which exists as a liquid phase low in viscosity and density, did not allow the generation of gaps between plastic chips.
Below, a detailed description will be given of the present disclosure.
A purpose of the present disclosure is to provide a photothermal adhesive composition containing a graphene-transition metal compound composite.
In an embodiment of the present disclosure, the graphene may be graphene oxide (GO) that is reduced after a reaction with a hydrophilic polymer.
In an embodiment of the present disclosure, the hydrophilic polymer may be at least one selected from the group consisting of polyethyleneglycol (PEG), polyvinylalcohol (PVA), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), polyurethane (PU), and polytetrafluoroethylene (PTFE), but is not limited thereto. For example, the hydrophilic polymer may be PEG.
In an embodiment of the present disclosure, the photothermal adhesive composition may contain graphene:transition metal compound at a weight ratio of from 1:1 to 1:4 or from 1:2 to 1:4, for example, from 1:3 to 1:4, but without limitations thereto. The graphene and the transition metal compound form a composite by physical mixing.
The transition metal compound may comprise at least one transition metal selected from the group consisting of coper (Cu), molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr), hafnium (Hf), rhenium (Re), vanadium (V), lead (Pd), niobium (Nb), platinum (Pt), tantalum (Ta), and iron (Fe) and may include copper, but without limitations thereto.
The transition metal compound may comprise at least one chalcogen element selected from the group consisting of sulfur (S), selenium (Se), and tellurium (Te) and may comprise, for example, sulfur, but without limitations thereto.
Another purpose of the present disclosure is to provide a method for manufacturing a photothermal adhesive composition containing a graphene-transition metal compound composite, the method comprising the steps of:
reacting graphene with a hydrophilic polymer and then reducing the graphene; and
mixing the graphene with transition metal compound nanoparticles to form a composite.
In an embodiment of the present disclosure, the graphene may be graphene oxide.
In an embodiment of the present disclosure, the hydrophilic polymer may be at least one selected from the group consisting of polyethyleneglycol (PEG), polyvinylalcohol (PVA), polyacrylic acid (PAA), polyvinylpyrrolidone (PVP), polyurethane (PU), and polytetrafluoroethylene (PTFE), but is not limited thereto. For example, the hydrophilic polymer may be PEG.
In an embodiment of the p, the hydrophilic polymer may be PEG.resent disclosure, the photothermal adhesive composition may contain a mixture of graphene:transition metal compound at a weight ratio of from 1:1 to 1:4 or from 1:2 to 1:4, for example, from 1:3 to 1:4, but without limitations thereto.
The transition metal compound may comprise at least one transition metal selected from the group consisting of coper (Cu), molybdenum (Mo), tungsten (W), titanium (Ti), zirconium (Zr), hafnium (Hf), rhenium (Re), vanadium (V), lead (Pd), niobium (Nb), platinum (Pt), tantalum (Ta), and iron (Fe) and may include copper, but without limitations thereto.
The transition metal compound may comprise at least one chalcogen element selected from the group consisting of sulfur (S), selenium (Se), and tellurium (Te) and may comprise, for example, sulfur, but without limitations thereto.
A further purpose of the present disclosure is to provide a method for fabrication of a microfluidic chip using a photothermal adhesive composition containing a graphene-transition metal compound composite, the method comprising:
a loading step of loading the photothermal adhesive composition to a target site on a lower substrate for microfluidic chips;
a first laser irradiation step of irradiating a laser to the target site; and
a second laser irradiation step of contacting an upper substrate for the microfluidic chips with the target site on the lower substrate, followed by irradiating a laser thereto.
In an embodiment of the present disclosure, the loading step may comprise dropwise loading the photothermal adhesive composition in a volume of from 1 to 20 μL, from 1 to 15 μL, or from 1 to 10 μL, for example, from 1 to 5 μL, but without limitations thereto.
The loading step is adapted to load three or more drops of the photothermal adhesive composition per 1 cm of the length to be attached. More drops of the photothermal adhesive composition give higher tensile strength to the attachment site, but the drops are closer to each other and more likely to merge, resulting in one drop with a large volume. Thus, the division of drops is allowed within the extent that individual drops are not combined with each other.
In an embodiment of the present disclosure, the first laser irradiation step, which is a pre-heating step, is to irradiate a near infrared (NIR) laser beam at an intensity of 1.00 to 3.00, 1.25 to 3.00, 1.50 to 3.00, 1.75 to 3.00, 2.00 to 3.00, 2.25 to 3.00, 2.50 to 3.00, 1.00 to 2.75, 1.25 to 2.75, 1.50 to 2.75, 1.75 to 2.75, 2.00 to 2.75, or 2.25 to 2.75 W, for example, 2.50 to 2.75 W, but without limitations thereto.
The first laser irradiation step may be carried out for 4 to 15 seconds, for example, 8 to 12 seconds, but without limitations thereto.
In an embodiment of the present disclosure, the second laser irradiation step, which is a heating step, is to irradiate an NIR laser beam at an intensity of 1.00 to 3.00, 1.25 to 3.00, 1.50 to 3.00, 1.75 to 3.00, 2.00 to 3.00, 2.25 to 3.00, 2.50 to 3.00, 1.00 to 2.75, 1.25 to 2.75, 1.50 to 2.75, 1.75 to 2.75, 2.00 to 2.75, or 2.25 to 2.75 W, for example, 2.50 to 2.75 W, but without limitations thereto.
The second laser irradiation step may be carried out for 20 to 40 seconds, for example, 25 to 35 seconds, but without limitations thereto.
In an embodiment of the present disclosure, when a laser beam is irradiated at an intensity of 2.5 W or higher in the first or the second laser irradiation step, the photothermal adhesive composition rapidly and excessively increases in temperature so that the water splatters, and the excessive heat deforms the surface of the substrate. Thus, the intensity of the laser beam is limited to the value. In addition, the temperature increment is not large when the intensity of laser beams exceeds 2.50 W. For stabilization, the upper limit of the intensity of laser beams is set to be 2.50 W in the adhesion step.
In an embodiment of the present disclosure, the microfluidic chip may be made of poly(methyl methacrylate) (PMMA) or polycarbonate (PC), for example, PMMA, but without limitations thereto.
The present disclosure relates to a technique for bonding chips made of plastic materials by taking advantage of a photothermal effect of a graphene-copper sulfide composite. Using A photothermal adhesive composition containing the composite, microfluidic chips that pass fluids therethrough with neither leakage nor deformation can be effectively fabricated.
The above and other aspects, features and advantages of the present disclosure will be more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:
Hereinafter, the present invention will be described in detail with reference to examples. These examples are only for illustrating the present invention more specifically, and it will be apparent to those skilled in the art that the scope of the present invention is not limited by these examples.
Unless otherwise noted, “%” used to indicate concentrations of particular substances means represents (weight/weight) % for solid/solid, (weight/volume) % for solid/liquid, and (volume/volume) % for liquid/liquid through the specification.
To 20 mL of graphene oxide (GO, 1 mg/m L) was added 100 mg of each of EDC (N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide) and NHS (N-hydroxysuccimide), followed by exposure to ultrasonic waves for 1 hour. Then, the solution was stirred, together with mPEG-NH2 (methoxy polyethylene glycol amine), for 18 hours to react GO with mPEG. Afterwards, reduction was performed at 90° C. under the condition of 20 vol % (0.05%) diazene (N2H2).
CuS nanoparticles were synthesized by stirring 14 mg of CuCl2 and 20 mg of trisodium citrate and then reacting the same with 7.8 mg of Na2S at 90° C. for 15 minutes. As shown in
Dilution was made so as to mix rGO-PEG (0.25 mg/mL) and CuS nanoparticles (0.25 to 1.00 mg/mL) at various ratios. After application of 808 nm NIR laser beam at 1 W/cm2, temperature increments (ΔT, ° C.) were measured.
As shown in Table 1 and
The synthesized composites were assessed for morphology by FETEM (Field-Emission Transmission Electron Microscopy, 200 kV).
In Example 1-1, the CuS nanoparticles having a diameter of 10 nm were synthesized and the rGO-PEG was observed to be in a sheet form with a width of 1 μm.
The rGO-PEG/CuS composite with a mass ratio of 1:3 was morphologically examined by transmission electron microscopy (TEM). As shown in the images of
GO-PEG and rGO-PEG were analyzed by FT-IR (Fourier-transform infrared spectroscopy). As can be seen in the spectra of
Evaluation was made of optical characteristics of the composites. To this end, rGO-PEG/CuS, CuS, rGO-PEG, and GO-PEG were each dispersed at a concentration of 0.1 mg/mL in distilled water and absorbance at the wavelength band of 400 to 900 nm was read using UV-Vis (ultraviolet-visible) spectroscopy.
As shown in
The CuS nanoparticles also absorbed light at the NIR band. A dilution of rGO-PEG and CuS nanoparticles (rGO-PEG/CuS) was measured to show stronger NIR absorption than conventional CuS nanoparticles.
Plastic microfluidic chips to which the present invention is applied were fabricated with PMMA (poly(methylmethacrylate)), which has a melting point of 150° C. As can be seen in
The attachment between the plastic chip upper substrate and the lower substrate for fabrication of microfluidic chips was performed according to the protocol illustrated in
If the graphene-copper sulfide composite is intactly disposed between the upper and the lower substrate, it is spread over the substrate because its surface tension decreases due to the wettability of water. This condition is insufficient to apply laser beams, with the consequent failure of exhibiting a sufficient bonding strength.
In order to prevent such a condition, pre-treatment with a laser was conducted. In this regard, temperatures of the graphene-copper sulfide composite loaded on the chip lower substrate were examined by a thermographic camera before the application of the laser to the lower substrate, after the lower substrate is pre-heated with the laser, and after the lower substrate covered with the upper substrate was heated subsequent to the pre-heating.
As can be seen in
Analysis was made of a relationship between the intensity of the laser and time to reach the melting point of PMMA, that is, 150° C., and between the intensity of the laser and heating rate.
As shown in
In order to solve the problem, selection was made of the range of 2.50 to 3.00 W in which the intervals between times to reach 150° C., based on the data of
In order to examine the bonding strength of the chip bonded in the optimal heating condition, the graphene-copper sulfide composite applied to the substrate was measured for tensile strength by volume and number.
Drops of the composite with respective volumes of 5 μL, 10 μL, and 15 μL were loaded on plastic lower substrates and pre-heated using an NIR laser at 2.50 W for 10 seconds. The lower substrates were covered with corresponding upper substrates and heated for 30 seconds to bond the lower and the upper substrates. Tensile strength was measured using a tension compression machine.
As shown in
2 Tensile strength was measured using a tension compression machine.
Among the substrates to which one, two, and three drops were loaded per 1 cm, the highest tensile strength was detected in the substrate having three drops loaded per 1 cm thereto. In light of the tendency toward the increase of tensile strength with the abundance of drops of the composite, as many drops of the composite as possible were loaded insofar as the drops were not overlapped with each other. As a result, the tensile strength was increased in proportion to the number of drops of the composite on the surface of the substrates.
In addition, the bonded surface was scrutinized. To this end, gap spacings between the bonded plastic surfaces were measured according to the number of drops of the composite. As shown in
As can be seen from the data of Table 2 and
The graphene-copper sulfide composite was analyzed for preventive effect on water leakage. To this end, 24 drops of the graphene-copper sulfide composite, each having a volume of 5 μL, were loaded around a channel on a plastic lower substrate, followed by bonding.
The microfluidic chip thus fabricated was examined for functional integrity. In this regard, leakage was monitored by passing various fluids including water, dimethyl sulfoxide (DMSO), and mineral oil through the channel.
The flow rate of each fluid was increased by 10 μL/min in every 10 seconds while the channel was monitored for internal collapse. As shown in
In light of the fact that flow analysis of conventional microchips for water is based on the measurements obtained at up to 200 μL/min in, the chips bonded by the graphene-copper sulfide composite were considered to be suitable for testing microfluidics of water.
As can be seen in
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2020-0118881 | Sep 2020 | KR | national |
