Method for high-efficiency preparation of terahertz micro-ring array by coffee ring effect assisted graphene micro-droplet printing
By using the coffee ring effect-assisted graphene microdroplet printing method, the problems of low printing efficiency and resolution of terahertz microring arrays in existing technologies have been solved, realizing efficient and low-cost microring array preparation, which is suitable for rapid and accurate preparation of multiple sizes and substrates.
Patent Information
- Application Number
- CN202310735313.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-06-20
- Publication Date
- 2026-02-10
- Estimated Expiration
- 2043-06-20
AI Technical Summary
Existing droplet printing methods struggle to achieve efficient and high-resolution fabrication of terahertz microring arrays, especially inkjet printing which has low resolution, low aerosol printing efficiency, and the presence of bump defects.
A coffee ring effect-assisted graphene microdroplet printing method was adopted. Stable dispersed graphene ink was prepared by ultrasonic dispersion process. Single graphene microdroplets were ejected on the substrate using a piezoelectric nozzle to form a high-resolution microring structure. The substrate temperature and coffee ring effect promoted the aggregation of solute at the edge of the microdroplet to form a microring array. The surfactant was removed by heat treatment.
It enables the fabrication of high-resolution (ring width 5–15 μm) and high-efficiency terahertz microring arrays, simplifies the process, reduces costs, and supports maskless, rapid, and precise fabrication of multi-size microring arrays.
Smart Images
Figure CN116604814B_ABST
Abstract
Description
Technical Field
[0001] This invention pertains to the preparation method of terahertz microstructure arrays, specifically a method for efficiently preparing terahertz microring arrays using graphene microdroplet printing assisted by the coffee ring effect. Background Technology
[0002] Terahertz technology is hailed as one of the "Top Ten Technologies That Will Change the Future World," holding immense application potential in fields such as terahertz radar, ultra-high-speed wireless communication, and non-destructive testing. Developing small, low-cost, and wideband tunable terahertz wave absorption and modulation devices is crucial for advancing terahertz technology. Terahertz devices based on subwavelength graphene microstructure arrays combine the unique advantages of graphene electro-optic modulation and microstructure plasmon resonances, making them excellent dynamic terahertz wave control devices. In particular, among numerous microstructures, microring structures, due to their high symmetry, exhibit polarization-independent terahertz responses, attracting significant research attention.
[0003] The fabrication technology for terahertz, especially graphene terahertz microstructure devices, is still under exploration and development. Current fabrication methods mainly include traditional photolithography, electron beam etching, and other etching methods, as well as microdroplet methods such as inkjet printing and aerosol printing. Among them, etching methods can achieve high-precision fabrication of terahertz microstructures, but they have limitations such as reliance on masks, complex process flow, and high cost. Microdroplet methods can achieve digital printing of microstructures, but due to their point-by-point, line-by-line, and layer-by-layer trajectory scanning method for structural units, the printing efficiency is limited, making it difficult to meet the rapid fabrication requirements of large-area arrays. In addition, inkjet printing resolution is usually low.
[0004] The literature “Flexible subterahertz metamaterial absorber fabrication using inkjet printing technology. Applied Physics B, 2016, 122(7): 1-8” describes the fabrication of a cross-shaped square ring Ag terahertz microstructure and its array with a minimum linewidth of ~50μm by inkjet printing silver nanoparticle ink on a polyimide substrate. The literature “Digital Aerosol Jet Printing for the Fabrication of Terahertz Metamaterials. Advanced Materials Technologies, 2018, 3(2): 1700236” proposes a method for preparing terahertz microstructures by aerosol printing silver nanoparticle ink, obtaining Ag terahertz closed resonant rings and their arrays with a ring width of ~14μm, but forming convex defects due to the same starting point of the closed-loop deposition path. The aforementioned droplet methods can all achieve maskless printing of terahertz microstructures. However, due to limitations in nozzle aperture and droplet size, conventional droplet printing methods such as inkjet printing have low resolution (~50 μm), making it difficult to meet the high-resolution forming requirements of terahertz microstructures. Aerosol printing has higher resolution (~14 μm), but its closed-loop trajectory scanning method reduces printing efficiency and results in significant bump defects at the printing start point. The limitations of existing methods in fabricating terahertz microstructure arrays severely restrict the development of terahertz devices, necessitating the exploration of maskless, rapid, and accurate methods for constructing terahertz microstructures and their large-area arrays. Summary of the Invention
[0005] Technical problems to be solved
[0006] To overcome the shortcomings of existing technologies, this invention proposes a method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with the coffee ring effect, which overcomes the low printing efficiency and resolution of existing microdroplet printing methods for terahertz microstructures and their arrays.
[0007] Technical solution
[0008] A method for efficiently preparing terahertz microring arrays using graphene microdroplet printing assisted by the coffee ring effect, characterized by the following steps:
[0009] Step 1: Ultrasonic dispersion of graphene powder and surfactant PVP powder is used. The graphene sheet size is controlled to be 100-1000 nm by changing the ultrasonic power and time. The ink concentration is adjusted to 0.2-3 mg / mL by adjusting the mass ratio of graphene powder. Stable dispersion, suitable for spraying and exhibiting coffee ring effect of graphene ink are obtained.
[0010] Step 2: Use a signal driving device to generate a pulse voltage to make the piezoelectric nozzle eject single graphene microdroplets and deposit them on the designed position of the printing substrate. Maintain the substrate temperature at 20-80℃ during the printing process to enhance the coffee ring effect of the microdroplets, and promote the solute to accumulate in large quantities at the edge of the microdroplets under the drive of evaporation capillary flow, so that the single microdroplet forms a high-resolution microring structure unit.
[0011] Step 3: According to the printing path set by the computer, control the movement of the three-dimensional motion platform to make graphene microdroplets periodically deposit on the substrate surface at a set step distance to form a graphene lattice. After the lattice is completely dried under the action of the coffee ring effect, a graphene microring array containing PVP is obtained.
[0012] Step 4: Heat-treat the printed graphene microring array containing PVP to finally obtain a graphene microring array without PVP, which is the graphene terahertz microring array.
[0013] The mass ratio of graphene to PVP powder in step 1 is 1:1 to 1:5.
[0014] Step 1 uses a probe-type ultrasonic disperser with an ultrasonic power of 240–720W and an ultrasonic time of 0.5–4h.
[0015] The nozzle diameter of the piezoelectric nozzle in step 2 is 50–200 μm.
[0016] The graphene microdroplets in step 2 have a diameter of 50–150 μm, and the spreading diameter after deposition on the substrate surface is 100–300 μm. Both can be adjusted by the nozzle diameter and pulse voltage parameters.
[0017] The printing substrate in step 2 includes, but is not limited to, any one of the following: glass slide, single-crystal silicon wafer, Si / SiO2 substrate, etc.
[0018] The edge width of the microring in step 2 is 5–15 μm.
[0019] The micro-ring array period, i.e., the droplet step size, in step 3 is 120–600 μm.
[0020] The graphene microring unit size in step 3, i.e. the droplet spreading diameter, is 100-300 μm, which can be adjusted in real time by the pulse voltage parameter to achieve single-size or multi-size microring array printing.
[0021] The heat treatment temperature in step 4 is 450–500℃, and the heat treatment time is 1–3 hours.
[0022] Beneficial effects
[0023] This invention proposes a method for efficiently preparing terahertz microring arrays using graphene microdroplet printing assisted by the coffee ring effect. First, a stable and dispersed graphene ink with a significant coffee ring effect is prepared using an ultrasonic dispersion process. Then, single graphene microdroplets are ejected and deposited using a piezoelectric nozzle. By controlling the substrate material and temperature parameters, the coffee ring effect of the microdroplets is enhanced, causing the solute to accumulate in large quantities at the edges of the microdroplets, forming high-resolution microring structural units. The above deposition process is repeated to print a periodic graphene microdroplet lattice. After complete drying, a microring array is obtained. Finally, a graphene terahertz microring array is obtained through heat treatment.
[0024] The specific beneficial effects of this invention are:
[0025] 1. This invention addresses the low printing efficiency and resolution of current microdroplet printing methods for preparing terahertz microstructure arrays. Combining the solute distribution law of the coffee ring effect in microdroplets and the requirements for the preparation of terahertz microring arrays, this invention proposes a method for efficient preparation of terahertz microring arrays using graphene microdroplet printing assisted by the coffee ring effect. The principle is that under the condition of contact line pinning microdroplets during evaporation, due to the difference in evaporation rate between the center and the edge of the microdroplet, there is an outward capillary flow from the center to the edge inside the microdroplet, which drives solute migration and ultimately forms a ring-shaped deposition pattern that is thick at the edges and thin in the middle.
[0026] 2. This invention can directly print high-resolution microrings and their arrays (ring width 5-15 μm) using a large-aperture nozzle (50-200 μm), which can effectively improve the forming resolution compared with conventional microdroplet printing methods (~50 μm). It also has the advantages of microdroplet method, such as simple process, low cost and direct forming on various substrates. By enhancing the microdroplet coffee ring effect, microring structural units can be formed using a single microdroplet, which can significantly improve printing efficiency compared with trajectory scanning printing. Moreover, the size of the microrings and their array arrangement and period can be directly controlled by changing the printing parameters. The method is simple and easy to implement, and can realize the maskless rapid and accurate preparation of multi-size graphene terahertz microring arrays.
[0027] 3. In step 1, a probe ultrasonic dispersion method was used, with ultrasonic power set to 240–720 W and ultrasonic time to 0.5–4 h. Based on the principle of ultrasonic cavitation and a suitable mass ratio of graphene to PVP powder (1:1–1:5), stable graphene ink with small sheet size (100–1000 nm) was obtained. Since the small graphene sheet size can accelerate edge solute pinning and promote the tight accumulation of solute at the edge of microdroplets, the combination of ultrasonic process parameters in step 1 and the resulting small sheet size graphene ink can enhance the coffee ring effect of microdroplets, which is beneficial to the formation of graphene microrings in this invention.
[0028] 4. In step 2, the use of hydrophilic substrates such as glass slides, single-crystal silicon wafers, and Si / SiO2, along with a substrate temperature of 20–80°C, allows the contact lines of graphene microdroplets to rapidly pinnify on the substrate surface. This promotes the accumulation of graphene sheets at the edges of the microdroplets under the drive of evaporative capillary flow. Combined with the small-sized graphene sheets from step 1, this achieves the beneficial effect of forming microring structural units from a single microdroplet. The principle is that a suitable substrate temperature range (20–80°C) ensures stable microdroplet ejection and deposition, and a higher substrate temperature can reduce the solute deposition characteristic time, promote edge solute pinning, and accelerate the solute migration process inside the microdroplet, thereby forming continuous and dense graphene microrings with solute at the edges. Attached Figure Description
[0029] Figure 1 This is a flowchart illustrating the efficient fabrication of terahertz microring arrays using graphene microdroplet printing assisted by the coffee ring effect. As shown in the figure, the basic process of this invention includes four steps: graphene ink preparation and sheet size control, single graphene microdroplet printing and evaporation, graphene dot matrix printing and evaporation, and heat treatment of the graphene microrings.
[0030] In the figure, 1-graphene powder, 2-PVP powder, 3-deionized water, 4-probe-type ultrasonic disperser, 5-graphene ink, 6-piezoelectric nozzle, 7-printing substrate, 8-signal driving device, 9-pulse voltage, 10-graphene microdroplets, 11-three-dimensional motion platform, 12-graphene lattice, 13-graphene microring array containing PVP, 14-graphene microring array without PVP.
[0031] Figure 2 This is an optical micrograph of a graphene terahertz microring array. The image shows a graphene microring array with a uniform and stable spreading diameter (~175 μm) arranged on the substrate with a constant period (~300 μm), demonstrating high forming accuracy and printing quality.
[0032] Figure 3 This is a SEM image of a single graphene microring. The image shows a single graphene microring with a width of only ~8 μm. The solute at the microring edges is continuous and dense, indicating that the coffee ring effect-assisted printing method can utilize single microdroplets to form dense microrings and effectively improve printing resolution.
[0033] Figure 4 This is the terahertz transmission spectrum of the graphene microring array measured by a terahertz time-domain spectrometer. The image shows that the microring array has a resonant frequency of 0.125 THz, at which the relative transmittance is lowest, approximately 0.331. This indicates that the microring array can resonate with the incident terahertz wave, achieving a significant reduction in the transmittance of the terahertz wave at the resonant frequency. Detailed Implementation
[0034] The present invention will now be further described in conjunction with the embodiments and accompanying drawings:
[0035] The technical solution adopted by this invention to solve its technical problem is: a method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with coffee ring effect assistance, characterized by the following steps:
[0036] Step 1: Add graphene powder and surfactant PVP powder in a certain mass ratio, use a probe-type ultrasonic disperser to disperse them stably, control the size of graphene sheets by changing the ultrasonic power and time, and adjust the ink concentration by adjusting the mass ratio of graphene powder to obtain a graphene ink that is stably dispersed, suitable for spraying, and has a significant coffee ring effect.
[0037] Step 2: A pulse voltage is generated using a signal driving device to stably eject single graphene microdroplets from the piezoelectric nozzle and deposit them at specific locations on the printing substrate. By selecting different substrate materials and changing the substrate temperature, the coffee ring effect of the microdroplets is enhanced, causing the solute to accumulate in large quantities at the edge of the microdroplets under the drive of evaporation capillary flow, and single microdroplets form high-resolution microring structure units.
[0038] Step 3: According to the printing path set by the computer, control the movement of the three-dimensional motion platform so that graphene microdroplets are periodically deposited on the substrate surface at a specific step distance to form a graphene lattice. After the lattice is completely dried under the action of the coffee ring effect, a graphene microring array containing PVP is obtained.
[0039] Step 4: Heat-treat the printed graphene microring array containing PVP to finally obtain a graphene microring array without PVP, which is the graphene terahertz microring array.
[0040] The mass ratio of graphene to PVP powder in step 1 is 1:1 to 1:5.
[0041] The ultrasonic power in step 1 is 240–720W, and the ultrasonic time is 0.5–4h.
[0042] The graphene sheet size in step 1 is 100–1000 nm.
[0043] The concentration of the graphene ink in step 1 is 0.2–3 mg / mL.
[0044] The nozzle diameter of the piezoelectric nozzle in step 2 is 50–200 μm.
[0045] The graphene microdroplets in step 2 have a diameter of 50–150 μm, and the spreading diameter after deposition on the substrate surface is 100–300 μm. Both can be adjusted by the nozzle diameter and pulse voltage parameters.
[0046] The printing substrate in step 2 includes, but is not limited to, any one of the following: glass slide, single-crystal silicon wafer, Si / SiO2 substrate, etc.
[0047] The base temperature in step 2 is 20–80°C.
[0048] The edge width of the microring in step 2 is 5–15 μm.
[0049] The micro-ring array period, i.e., the droplet step size, in step 3 is 120–600 μm.
[0050] The graphene microring unit size in step 3, i.e. the droplet spreading diameter, is 100-300 μm, which can be adjusted in real time by the pulse voltage parameter to achieve single-size or multi-size microring array printing.
[0051] The heat treatment temperature in step 4 is 450–500℃, and the heat treatment time is 1–3 hours.
[0052] Example 1:
[0053] Reference Figure 1-4 The specific steps of the method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with the coffee ring effect assisted by the present invention are as follows:
[0054] (1) Step 1: Add 15mg of graphene powder 1 and 30mg of surfactant PVP powder 2 to 30mL of deionized water 3 in a mass ratio of 1:2. Use a probe-type ultrasonic disperser 4 to stably disperse the solution and break up the graphene sheets. During the ultrasonic process, the ultrasonic power is set to 540W and the ultrasonic time is 2h to obtain a stably dispersed graphene ink 5 that is suitable for spraying and has a significant coffee ring effect. The graphene ink concentration is 0.5mg / mL and the average graphene sheet size is about 300nm.
[0055] (2) Step 2: Graphene ink 5 is loaded into a piezoelectric nozzle 6 with a nozzle diameter of about 120 μm and clamped above a single-crystal silicon wafer printing substrate 7. The substrate temperature is set to 20°C. A pulse voltage 9 is generated by a signal driving device 8. The pulse voltage parameters are adjusted: amplitude 150-300V, pulse width 10-50μs, until the piezoelectric nozzle 6 can stably spray uniform graphene microdroplets 10 with a diameter of about 90 μm. Single graphene microdroplets are deposited on the surface of the single-crystal silicon wafer printing substrate 7. After deposition, the microdroplets spread to a diameter of about 175 μm. By setting the above materials and printing parameters, the coffee ring effect of the microdroplets is enhanced, which promotes the solute to accumulate in large quantities at the edge of the microdroplets under the drive of evaporation capillary flow. After the microdroplets are dried, a high-resolution micro-ring structure unit with an edge width of about 8 μm is formed.
[0056] (3) Step 3: According to the arrangement rules and period size requirements of the micro-ring array to be formed, the computer generates the printing path and controls the movement of the three-dimensional motion platform 11 so that the graphene microdroplets 10 are periodically deposited on the surface of the single crystal silicon wafer printing substrate 7 at a step of 300μm and form a graphene lattice 12. Under the action of the coffee ring effect, the lattice is completely dried to obtain a graphene micro-ring array 13 containing PVP, and its array period is 300μm.
[0057] (4) Step 4: The graphene microring array 13 containing PVP after printing is placed in a vacuum tube furnace for heat treatment to remove the surfactant PVP. The heat treatment temperature is set to 450℃ and the heat treatment time is 2h. Argon gas is kept in the air throughout the heat treatment to prevent graphene oxidation. Finally, a graphene microring array 14 with a period of 300μm and no PVP is obtained, which is the graphene terahertz microring array.
[0058] Example 2:
[0059] Reference Figure 1-4 The specific steps of the method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with the coffee ring effect assisted by the present invention are as follows:
[0060] (1) Step 1: Add 20mg of graphene powder 1 and 30mg of surfactant PVP powder 2 to 20mL of deionized water 3 in a mass ratio of 1:1.5. Use a probe-type ultrasonic disperser 4 to stably disperse the solution and break up the graphene sheets. During the ultrasonic process, the ultrasonic power is set to 360W and the ultrasonic time is 2.5h to obtain a stably dispersed graphene ink 5 that is suitable for spraying and has a significant coffee ring effect. The graphene ink concentration is 1mg / mL and the average graphene sheet size is about 600nm.
[0061] (2) Step 2: Load graphene ink 5 into a piezoelectric nozzle 6 with a nozzle diameter of about 100 μm and clamp it above the glass slide printing substrate 7. Set the substrate temperature to 50°C. Generate pulse voltage 9 through signal driving device 8 and adjust the pulse voltage parameters: amplitude 150~250V, pulse width 10~50μs until the piezoelectric nozzle 6 can stably spray uniform graphene microdroplets 10 with a diameter of about 80μm. Deposit single graphene microdroplets on the surface of glass slide printing substrate 7. After deposition, the microdroplets spread to a diameter of about 180μm. By setting the above materials and printing parameters, enhance the coffee ring effect of microdroplets and promote the solute to accumulate in large quantities at the edge of the microdroplets under the drive of evaporation capillary flow. After the microdroplets are dried, they form high-resolution micro-ring structure units with an edge width of about 12μm.
[0062] (3) Step 3: According to the arrangement rules and period size requirements of the micro-ring array to be formed, the printing path is generated by computer and the movement of the three-dimensional motion platform 11 is controlled so that the graphene microdroplets 10 are periodically deposited on the surface of the glass slide printing substrate 7. During the deposition process, a row of dots is first deposited with a spreading diameter of 180μm and a step size of 320μm. Then, the pulse voltage parameters are adjusted: amplitude 250~350V, pulse width 10~50μs, so that the piezoelectric nozzle 6 can stably spray uniform graphene microdroplets 10 with a diameter of about 100μm. Then, a row of dots is deposited at a distance of 280μm from the previous row with a spreading diameter of 230μm and a step size of 320μm. The above deposition process is repeated to form a graphene dot array 12. Under the action of the coffee ring effect, after the dot array is completely dried, a graphene micro-ring array 13 containing PVP is obtained. The array period is 320×560μm and the array contains two micro-ring structures with different spreading diameters.
[0063] (4) Step 4: The graphene microring array 13 containing PVP after printing is placed in a vacuum tube furnace for heat treatment to remove the surfactant PVP. The heat treatment temperature is set to 500℃ and the heat treatment time is 1h. Argon gas is kept in the air throughout the heat treatment to prevent graphene oxidation. Finally, a graphene microring array 14 with a period of 320×560μm without PVP is obtained, which is the graphene terahertz microring array.
[0064] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any improvements or substitutions that can be easily conceived by those skilled in the art without departing from the principle of the present invention should be included within the scope of protection of the present invention.
Claims
1. A method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with coffee ring effect-assisted printing, characterized in that... The steps are as follows: Step 1: Ultrasonic dispersion of graphene powder and surfactant PVP powder is used. The graphene sheet size is controlled to be 100-1000 nm by changing the ultrasonic power and time. The ink concentration is adjusted to 0.2-3 mg / mL by adjusting the mass ratio of graphene powder. Stable dispersion, suitable for spraying and exhibiting coffee ring effect of graphene ink are obtained. Step 2: Use a signal driving device to generate a pulse voltage to make the piezoelectric nozzle eject single graphene microdroplets and deposit them on the designed position of the printing substrate. Maintain the substrate temperature at 20-80℃ during the printing process to enhance the coffee ring effect of the microdroplets, and promote the solute to accumulate in large quantities at the edge of the microdroplets under the drive of evaporation capillary flow, so that the single microdroplet forms a high-resolution microring structure unit. Step 3: According to the printing path set by the computer, control the movement of the three-dimensional motion platform to make graphene microdroplets periodically deposit on the substrate surface at a set step distance to form a graphene lattice. After the lattice is completely dried under the action of the coffee ring effect, a graphene microring array containing PVP is obtained. Step 4: Heat-treat the printed graphene microring array containing PVP to finally obtain a graphene microring array without PVP, which is the graphene terahertz microring array.
2. The method for efficiently preparing terahertz microring arrays using coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The mass ratio of graphene to PVP powder in step 1 is 1:1 to 1:
5.
3. The method for efficiently preparing terahertz microring arrays using coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: Step 1 uses a probe-type ultrasonic disperser with an ultrasonic power of 240–720W and an ultrasonic time of 0.5–4h.
4. The method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with the coffee ring effect as described in claim 1, characterized in that: The nozzle diameter of the piezoelectric nozzle in step 2 is 50–200 μm.
5. The method for efficiently preparing terahertz microring arrays by coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The graphene microdroplets in step 2 have a diameter of 50–150 μm, and the spreading diameter after deposition on the substrate surface is 100–300 μm. Both can be adjusted by the nozzle diameter and pulse voltage parameters.
6. The method for efficiently preparing terahertz microring arrays using coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The printing substrate in step 2 includes, but is not limited to, any one of the following: glass slide, single-crystal silicon wafer, Si / SiO2 substrate, etc.
7. The method for efficiently preparing terahertz microring arrays by printing graphene microdroplets with the coffee ring effect as described in claim 1, characterized in that: The edge width of the microring in step 2 is 5–15 μm.
8. The method for efficiently preparing terahertz microring arrays by coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The micro-ring array period, i.e., the droplet step size, in step 3 is 120–600 μm.
9. The method for efficiently preparing terahertz microring arrays by coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The graphene microring unit size in step 3, i.e. the droplet spreading diameter, is 100-300 μm, which can be adjusted in real time by the pulse voltage parameter to achieve single-size or multi-size microring array printing.
10. The method for efficiently preparing terahertz microring arrays by coffee ring effect-assisted graphene microdroplet printing according to claim 1, characterized in that: The heat treatment temperature in step 4 is 450–500℃, and the heat treatment time is 1–3 hours.