Micro-nano electrospray printing method based on electric field focusing and deflection control

Abstract

The application belongs to the field of advanced manufacturing technology, and proposes a micro-nano electro-fluid jet printing method based on electric field focusing and deflection control. The method uses double circular rings as induction electrodes to induce the printing of charged droplets with micro-nano scale resolution at the metal micro-tip of the ink, and then uses the time-varying pulse voltage signal generated by the jet deflection electrode to control the flight trajectory of the droplets, so as to print high-precision micron patterns on the stationary receiving plate. Combined with the movement of the work platform, macro-scale structures can be further manufactured. The method breaks through the limitation that the trajectory movement of the work platform is necessary for the electro-fluid jet printing of micron patterned structures, and can realize the deposition of any pattern on a stationary platform, and has the characteristics of high printing resolution, high precision and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of advanced manufacturing technology, and in particular to a micro / nano electrojet printing method based on electric field focusing and deflection control. Background Technology

[0002] Electrojet printing, based on the principles of electrohydrodynamics, provides a direct and efficient process for fabricating high-resolution micro / nano structures. This technology utilizes the stretching of a fluid in an electrostatic field to form a large-diameter, scaled-down jet, combined with the motion of a mechanical platform along a specific trajectory to achieve the positioning, deposition, and patterning of functional material droplets. The working principle involves applying an appropriate voltage between the capillary nozzle and the receiving substrate on the moving platform. When liquid is delivered to the micro-nozzle, the surface of the meniscus-shaped droplet formed at the nozzle exit forms a jet in the electric field. During this process, the electric field force acting on the liquid film tip is dynamically balanced with gravity, surface tension, and viscosity to maintain jet stability. By adjusting the ink flow rate, print height, and applied voltage, three printing types can be achieved: droplet electrojet printing, direct electrojet writing, and electrospray printing. Droplet electrojet printing is typically driven by DC voltage or pulsed voltage. Both technologies can produce uniform droplets from the printhead, and the droplet size is at least an order of magnitude smaller than the nozzle size.

[0003] However, during direct deposition of free-form patterns and trajectories, the irregular droplet gravity during the start-stop phase of the pulse voltage makes it difficult to ensure jet stability, reducing the controllability of the printing process. Furthermore, since the patterned printed structure is obtained through platform trajectory movement, under the premise of a fixed droplet emission frequency, the mechanical inertia and linear hysteresis (low acceleration) of the moving platform will inevitably cause localized droplet accumulation on the printed structure (such as at trajectory corners, curvature radius changes, and other transitional sections). Therefore, it is difficult to rapidly position and accurately deposit continuous droplets into patterned regions with micron-sized features using only two-dimensional mechanical platform motion.

[0004] To overcome the aforementioned fundamental limitations, current technologies achieve high-precision patterning of charged jets by controlling external electric or magnetic field parameters. References such as "Soldate P, Fan J. Controlled deposition of electrospun nanofibers by electrohydrodynamic deflection. Journal of Applied Physics, 2019, 125(5), 54901; Liashenko I, Rosell-Llompart J, Cabot A. Ultrafast 3D printing with submicrometer features using electrostatic jet deflection. Nature Communication. 2020;11(1):753" demonstrate how adding additional deflection electrodes to deposit oriented fibers can effectively improve the printing speed and resolution of fiber structures and achieve fiber deposition of complex patterns. However, precise control of the jet droplets remains unrealized, significantly limiting the geometric accuracy and application range of the print. Summary of the Invention

[0005] The technical problem this invention aims to solve is to overcome the shortcomings of existing technologies and to develop a micro / nano electrojet printing method based on electric field focusing and deflection control. This method combines electrostatic focusing and electrostatic deflection techniques. A double-ring structure is used as an inducing electrode to generate an electrostatic focusing electric field, thereby inducing ink aggregation at the tip of a metal microneedle and ejecting droplets with micro / nano scale resolution. Simultaneously, two additional jet deflection electrodes are introduced between the double-ring structure and the receiving plate to generate a deflection electric field that continuously adjusts the flight trajectory of the jet droplets. This allows for the creation of microstructures with any predefined pattern on a stationary receiving plate. This method offers advantages such as high printing resolution, high structural accuracy, and low cost.

[0006] The technical solution adopted in this invention is as follows: A micro / nano electrojet printing method based on electric field focusing and deflection control, wherein a double ring is set as an induction electrode to generate an electrostatic focusing electric field, which is used to induce ink droplets to be ejected from the tip of the metal microneedle 2; the droplets fly away from the upper conductive ring 5 by inertia and enter the jet deflection domain. Two jet deflection electrodes are set to generate time-varying pulse voltage signals to control the flight trajectory of the droplets to the stationary receiving plate 6, thereby realizing the fabrication of micro / nano devices; the specific steps are as follows:

[0007] The first step is to prepare and install the printing device;

[0008] The metal microneedle 2 is etched to create a roughened surface structure 4 on its tip, which allows the ink to fully wet its surface, providing a sufficient ink volume. The bottom of the etched metal microneedle 2 is fixed on the base 1, with its tip located between the upper conductive ring 5 and the lower conductive ring 3. A high-voltage DC power supply 12 is connected to the metal microneedle 2. A receiving plate 6 is located above the upper conductive ring 5 and grounded. The upper conductive ring 5 and the lower conductive ring 3 are grounded as ground electrodes, forming an electrostatic focusing electric field between them and the metal microneedle 2. An x-direction deflection electrode 7 and a y-direction deflection electrode 8 are located between the receiving plate 6 and the upper conductive ring 5. One channel of the pulse power supply 10 is connected to the y-direction deflection electrode 8 through the first high-voltage amplifier 9, applying the amplified pulse voltage to the y-direction deflection electrode 8. Another channel of the pulse power supply 10 is connected to the x-direction deflection electrode 7 through the second high-voltage amplifier 11, applying the amplified pulse voltage to the x-direction deflection electrode 7 to form a jet deflection electric field.

[0009] The second step is to induce micro / nano droplets;

[0010] Printing ink is prepared and adhered to the metal microneedles 2, so that the tip is completely immersed in the ink; the ink's wettability is improved by the roughening structure 4; a DC voltage is applied to the metal microneedles 2 by a high-voltage DC power supply 12, and the voltage value is adjusted so that some of the ink at the tip of the metal microneedles 2 overcomes the surface tension and viscosity of the ink under the action of the focusing electric field, further focusing and sharpening it and inducing the formation of micro-nano droplets for emission; the remaining ink on the surface of the metal microneedles 2 enters the next droplet emission cycle;

[0011] The third step is to deflect the micro / nano droplets;

[0012] The pulse power supply 10 channel one and the first high voltage amplifier 9 apply a pulse voltage signal in the y direction to the y-direction deflection electrode 8, and the pulse power supply 10 channel two and the second high voltage amplifier 11 apply a pulse voltage signal in the x direction to the x-direction deflection electrode 7 to form a jet deflection electric field. By adjusting the parameters of the focusing electric field and the deflection electric field, the emitted micro-nano droplets are continuously controlled and positioned for deposition, and finally a micro-nano patterned complex functional structure is obtained on the receiving plate 6.

[0013] The central axes of the lower conductive ring 3 and the upper conductive ring 5 are coaxial; the metal microneedle 2 is located on the central axis of the two conductive rings; the x-direction deflection electrode 7 and the y-direction deflection electrode 8 are placed orthogonally, and the distance from the central axis is greater than the inner radius of the two conductive rings; the distance between the deflection electrodes in the two directions and the upper conductive ring 5 is 0.1~1mm. The distance between the receiving plate 6 and the upper conductive ring 5 is 0.5~1.5mm.

[0014] The tip curvature radius of the metal microneedle 2 is 0.01~10μm; the inner diameter of the lower conductive ring 3 and the upper conductive ring 5 is 1~3mm; the thickness of the x-direction deflection electrode 7 and the y-direction deflection electrode 8 is 0.01~0.2mm.

[0015] The voltage of the high-voltage DC power supply 12 is 200~2000V, which controls the droplet volume and printing rate; the pulse amplitude of the y-direction deflection electrode 8 is -500~1500V, and the pulse amplitude of the x-direction deflection electrode 7 is 0~2000V, which controls the deflection distance of the droplet.

[0016] The metal microneedles 2 are etched using ferric chloride solution.

[0017] The beneficial effects of this invention are as follows: The micro / nano electrojets printing method based on electric field focusing and deflection control enables high-precision and high-resolution patterned electrojets to be printed on a stationary receiving plate. Furthermore, by combining the movement of the mechanical working platform, large-format arrays with micron-sized features and precise positioning can be manufactured. By changing the DC voltage parameters, the focusing state of the ink can be adjusted, further controlling the printing speed and droplet volume. By adjusting the pulse voltage amplitude, the deflection distance of the droplets can be controlled. Employing a double-ring structure for electrojets effectively avoids electric field crosstalk between the deflection and focusing domains, improving printing controllability. This method has broad application prospects in fields such as large-format LED displays and sensors. Attached Figure Description

[0018] Figure 1(a) is a schematic diagram of a micro-nano electrojet printing device based on electric field focusing and deflection control;

[0019] Figure 1(b) is a magnified view of the tip of the metal microneedle in Figure 1(a);

[0020] Figure 2 This is a schematic diagram of the metal microneedle tip being immersed in ink in a micro / nano electrojet printing device based on electric field focusing and deflection control.

[0021] Figure 3 This is a high-resolution photograph of the printing device in this invention;

[0022] Figures 4(a)-4(d) These are high-speed camera images of the droplet flight trajectory controlled by electric field focusing and deflection. In Figure 4(a), the liquid film covers the needle tip; in Figure 4(b), the liquid surface focuses a Taylor cone to drive the droplet emission; in Figure 4(c), the deflection controls the droplet flight; and in Figure 4(d), the droplet is deposited on the receiving plate.

[0023] Figure 5 It is a circular pattern array printed using the method proposed in this invention.

[0024] Wherein: 1-base, 2-metal microneedle, 3-lower conductive ring, 4-roughened structure, 5-upper conductive ring, 6-receiving plate, 7-x-direction deflection electrode, 8-y-direction deflection electrode, 9-first high-voltage amplifier, 10-pulse power supply, 11-second high-voltage amplifier, 12-high-voltage DC power supply. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in detail below with reference to the technical solutions and accompanying drawings.

[0026] Figures 1(a) and 1(b) are schematic diagrams of the micro / nano electrojet printing device based on electric field focusing and deflection control according to the present invention. As shown in Figures 1(a) and 1(b), the micro / nano electrojet printing method based on electric field focusing and deflection control first prepares and installs the printing device. The specific steps of the method are as follows:

[0027] The first step is to prepare and install the printing device;

[0028] First, metal microneedles 2 with a radius of curvature of 0.01~10μm are immersed in a 1~2mol / L ferric chloride solution for 1~5 minutes to etch them, giving their surface a roughened structure 4. This allows the ink to fully wet the surface, providing a sufficient amount of ink. Figure 2 As shown; the etched metal microneedles 2 are fixed to the base 1 by PDMS thermosetting, achieving the effect of isolation from the outside world; next, the upper conductive ring 5 and the lower conductive ring 3, with an inner diameter of 1~3mm, are simultaneously fixed on the micro-motion platform to facilitate real-time adjustment of the position of the conductive rings; then, the metal microneedles 2 are vertically placed between the upper conductive ring 5 and the lower conductive ring 3, ensuring that they coincide with the central axis of the two conductive rings; the x-direction deflection electrode 7 and the y-direction deflection electrode 8, with a thickness of 0.01~0.2mm, are orthogonally placed between the receiving plate 6 and the upper conductive ring 5, at a distance of 0.1~1mm from the upper conductive ring 5; the distance between the receiving plate 6 and the upper conductive ring 5 is 0.5~1.5mm. Figure 3 As shown; the high-voltage DC power supply 12 is connected to the metal microneedle 2; the upper conductive ring 5 and the lower conductive ring 3 are grounded as grounding electrodes, forming an electrostatic focusing electric field between them and the metal microneedle 2; the first channel of the pulse power supply 10 is connected to the first high-voltage amplifier 9, and applies the amplified pulse voltage to the y-direction deflection electrode 8; the second channel of the pulse power supply 10 is connected to the second high-voltage amplifier 11, and applies the amplified pulse voltage to the x-direction deflection electrode 7, thereby forming a jet deflection electric field.

[0029] The second step is to induce micro / nano droplets;

[0030] Printing ink is prepared, and a small amount of ink is applied to the metal microneedle 2 in a manner similar to dipping a pen, so that the tip is completely immersed in the ink; the ink's wettability is improved by the roughening structure 4; a DC voltage is applied to the metal microneedle 2 by a high-voltage DC power supply 12, and the voltage value is adjusted (200~2000V), so that the small amount of ink at the tip of the metal microneedle 2 overcomes the surface tension and viscosity of the ink under the action of the focused electric field, further focusing and sharpening it and inducing the formation of micro-nano droplets for emission; then, the ink on the surface of the metal microneedle 2 enters the next droplet emission cycle.

[0031] The third step is to deflect the micro / nano droplets.

[0032] Channel 1 of the pulse power supply 10 and the first high-voltage amplifier 9 apply a pulsed voltage signal (-500~1500V) in the y-direction to the deflection electrode 8. Simultaneously, channel 2 of the pulse power supply 10 and the second high-voltage amplifier 11 apply a pulsed voltage signal (0~2000V) in the x-direction to the deflection electrode 7, forming a jet deflection electric field. By adjusting the electric field parameters of the focusing electric field domain and the deflection electric field domain, continuous control and positioning deposition of the jet droplets are achieved, ultimately obtaining a micro-nano patterned complex functional structure on the receiving plate 6. The printed droplets are as follows: Figure 5 As shown.

[0033] Figures 4(a)-4(d) This is a high-speed camera image of the droplet flight trajectory controlled by electric field focusing and deflection. First, a constant DC voltage is applied to the metal microneedle 2. Under the electrostatic focusing effect within the double ring, the surface of the liquid film is polarized with charge. Under the combined action of electric field force and surface tension, the focusing liquid cone is further sharpened by electrowetting and overcomes the surface tension, viscosity, and gravity of the liquid cone, ejecting micro- and nano-droplets. Subsequently, the jet droplets fly away from the double ring structure and enter the jet deflection domain by inertia. Under the action of the time-varying pulse voltage signal generated by the jet deflection electrode, the flight trajectory of the droplets can be further controlled and deposited on the predetermined pattern position.

[0034] The micro / nano electrojet printing method proposed in this invention, based on electric field focusing and deflection control, overcomes the limitation that electrojet printing of patterned structures must rely on the trajectory movement of a mechanical work platform. It utilizes an electrostatic focusing electric field generated by two circular rings to eject droplets, and further employs jet deflection electrodes to control the droplet's flight trajectory. This allows for high-precision micron-scale pattern printing on a stationary receiving plate, while simultaneously enabling the fabrication of macroscale structures through the movement of a mechanical work platform. This method has potential applications in fields such as light-emitting diodes and sensors.

Claims

1. A method of micro / nano electro-fluidic jet printing based on electric field focusing and deflection control, characterized in that, The double circular ring is set as an induction electrode to generate an electrostatic focusing electric field for inducing ink ejection from the tip of the metal microneedle (2); two jet deflection electrodes are set to generate time-varying pulse voltage signals respectively for controlling the flight trajectory of the liquid droplet to the stationary receiving plate (6); the specific steps are as follows: First, prepare and install the printing device; The metal microneedle (2) is corroded to have a roughened structure (4) on the tip surface for facilitating the ink to fully infiltrate the surface to provide sufficient amount of ink; the bottom of the corroded metal microneedle (2) is fixed on the base (1), and the tip is located between the upper conductive circular ring (5) and the lower conductive circular ring (3); the high-voltage direct-current power supply (12) is connected to the metal microneedle (2); the receiving plate (6) is located above the upper conductive circular ring (5) and grounded; the upper conductive circular ring (5) and the lower conductive circular ring (3) are grounded as the grounding electrode to form an electrostatic focusing electric field with the metal microneedle (2); the x-direction deflection electrode (7) and the y-direction deflection electrode (8) are located between the receiving plate (6) and the upper conductive circular ring (5); the channel one of the pulse power supply (10) passes through the first high-voltage amplifier (9) and is connected to the y-direction deflection electrode (8); the channel two of the pulse power supply (10) passes through the second high-voltage amplifier (11) and is connected to the x-direction deflection electrode (7) to form a jet deflection electric field; Second, induce micro-nano droplets; Configure the printing ink to attach the ink to the metal microneedle (2) so that the tip is fully immersed in the ink; The ink improves its wettability under the action of the roughened structure (4); the high-voltage direct-current power supply (12) applies a direct-current voltage on the metal microneedle (2) to adjust the voltage value, so that part of the ink at the tip of the metal microneedle (2) overcomes the surface tension and viscous force of the ink under the action of the focusing electric field, is further focused and sharpened, and induces the formation of micro-nano droplets to be emitted; the remaining ink on the surface of the metal microneedle (2) enters the next droplet emission cycle; Third, deflect the micro-nano droplets; The channel one of the pulse power supply (10) and the first high-voltage amplifier (9) apply a y-direction pulse voltage signal on the y-direction deflection electrode (8), and the channel two of the pulse power supply (10) and the second high-voltage amplifier (11) apply an x-direction pulse voltage signal on the x-direction deflection electrode (7) to form a jet deflection electric field; by adjusting the parameters of the focusing electric field and the deflection electric field, the emitted micro-nano droplets are continuously controlled and positioned to be deposited, and finally a micro-nano patterned complex functional structure is obtained on the receiving plate (6).

2. The method according to claim 1, wherein, The central axes of the lower conductive circular ring (3) and the upper conductive circular ring (5) are coaxial; the metal microneedle (2) is located on the central axes of the two conductive circular rings; the x-direction deflection electrode (7) and the y-direction deflection electrode (8) are placed orthogonally and the distance from the central axes is greater than the inner radius of the two conductive circular rings; the distance between the two deflection electrodes in the two directions and the upper conductive circular ring (5) is 0.1-1mm; the distance between the receiving plate (6) and the upper conductive circular ring (5) is 0.5-1.5mm.

3. The micro / nano electro-fluidic jet printing method based on electric field focusing and deflection control according to claim 1 or 2, characterized in that, The tip curvature radius of the metal microneedle (2) is 0.01-10 μm; the inner diameter of the lower conductive circular ring (3) and the upper conductive circular ring (5) is 1-3 mm; the thickness of the x-direction deflection electrode (7) and the y-direction deflection electrode (8) is 0.01-0.2 mm.

4. The method according to claim 3, wherein, The voltage value of the high-voltage direct-current power supply (12) is 200-2000 V, the pulse amplitude of the y-direction deflection electrode (8) is -500-1500 V, and the pulse amplitude of the x-direction deflection electrode (7) is 0-2000 V.

5. The micro / nano electro fluidic jet printing method based on electric field focusing and deflection control according to claim 1, 2 or 4, characterized in that, The corroded metal microneedle (2) is corroded by using a ferric chloride solution.

6. The method according to claim 3, wherein, The corroded metal microneedle (2) is corroded by using a ferric chloride solution.

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