TW458896B - Apparatus and method for using bubble as virtual value in microinjector to eject fluid - Google Patents

Abstract

An apparatus and method for forming a bubble within a microchannel of a microinjector to function as a valve mechanism between the chamber and manifold, that provides for a high resistance to liquid exiting the chamber through the manifold during fluid ejection through an orifice and that also provides a low resistance to refilling of liquid into the chamber after ejection of fluid and collapse of the bubble. This effectively minimizes cross talk between adjacent chambers and increases injection frequency of the microinjector. The formation of a second bubble within the chamber coalesces with a first formed bubble between the chamber and manifold to abruptly terminate the ejection of fluid, thereby eliminating satellite droplets.

Description

V. Description of the invention (l) Background of the invention The invention relates to a liquid ejector, and more particularly to a device and method for ejecting fluid from a microdevice. Description of related techniques Liquid droplet ejectors are widely used for printing on inkjet printers. However, there are many other possible applications for bead ejectors, such as fuel injection systems, cell sorting, drug delivery systems, direct-print lithography, and micro-jet propulsion systems. All these applications have in common the need for a reliable and low cost liquid bead ejector that can provide high quality droplets with high frequency and high spatial resolution. Only a few devices can individually eject droplets of uniform shape. In the known and used liquid bead ejection systems, the method of using thermally driven bubbles to eject liquid beads is simple and relatively inexpensive, so it is the most successful design of these devices. The disadvantages of thermally driven bubble systems (also known as bubble jet systems) are cross talk and satellite drop 1 e t. The bubble jet system uses an electric current pulse to heat an electrode, thereby boiling the liquid in the fluid cavity. When the liquid boils, a bubble is formed in the liquid and expands outward. The function of the bubble is to eject the liquid in the fluid cavity from a sharp hole into a liquid column like a pump, and finally form liquid beads. When the current pulse ends, the bubble will shrink and the liquid will again fill the fluid cavity by capillary tension. The performance of these systems can be evaluated by the following performances: jet speed and direction, bead size, maximum jet frequency, adjacent page 5 458896 V. Description of the invention (2) Interphase between nearby fluid cavities + say BS XL- t- ten disturbances, overshoot during liquid backfilling, liquid surface vibration, and the phenomenon of satellite liquid droplets, and the generation of satellite liquid beads. During the printing process, the satellite liquid weight I @ will reduce the sharpness of the image. In addition, the accuracy of the liquid control will reduce the accuracy of the flow estimation f. When the bubble nozzle ejectors are arranged in an array with a narrow pitch, and the liquid beads are ejected from the adjacent nozzles, the interphase interference occurs in the radon. Beads Most hot-rolled bubble spray systems have a heater located at the bottom of the fluid cavity, and this design will cause most of the heat to be lost to the substrate material. Furthermore, joining is generally used to join the nozzle plate to its heater plate. This will limit the spatial resolution of the nozzle due to the necessary assembly tolerances. In addition, the bonding procedure may not be compatible with the [c] process. ♦ The micro-injector array and the control circuit need to be integrated into a single body to reduce wiring and ensure that the package is tight. This incompatibility will highlight its importance. In order to solve the problems of cross-phase interference and excessive backfilling, the long-term practice is to increase the length of the fluid cavity or the neck of the fluid cavity, so as to increase the fluid flow resistance between the body cavity and the storage tank. However, these practices will slow down The velocity of the body backfilling into the fluid cavity 'and greatly reduces the maximum ejection rate of the device. The most troublesome problem of the existing inkjet system is the satellite liquid beads, because satellites and beads can cause blurry images. The satellite liquid beads are trailing behind the main liquid beads ^ When the print head and the paper are in relative motion, the position of the 'satellite liquid beads on the ML' position will be slightly different from the position of the main liquid beads. There is no known effective, easy and economical method or method to solve the problem of satellite liquid beads. > And therefore, 'a liquid bead ejection system is currently highly needed, which can interfere with cross-phase interference

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Minimizing without slowing down liquid backfill can still eliminate satellite droplets, and this has manufacturing complexity. The present invention is generally and capable of overcoming the speeds in the conventional technology and maintaining high frequency response. The achievement of these objectives will not increase the design to meet these and other requirements, in addition to the defects found. SUMMARY OF THE INVENTION The present invention relates to a device and method for generating a bubble in a micro-channel of a micro-injector to a micro-channel as a valve mechanism between a fluid cavity and a manifold. During the ejection of the sharp hole, a high resistance will be provided to the fluid to prevent the fluid from being lost from the fluid cavity to the manifold. In addition, after the fluid is ejected and the bubbles are contracted, the valve mechanism will provide a low resistance to the fluid backfilling into the fluid cavity. _. Generally, the device of the present invention includes a micro-injector, the micro-injector has a fluid cavity and a manifold communicating with the fluid cavity, an acute hole communicating with the fluid cavity, and at least one for communicating with the fluid. A bubble structure is generated between the cavity and the manifold, and a member for pressurizing the fluid cavity. When gas .. bubbles form at the inlet of the fluid cavity, it restricts fluid flow from the fluid cavity to the manifold. The pressure member pressurizes the fluid cavity after the bubble is formed, so that the pressure of the fluid cavity is increased to force the fluid to be ejected from the sharp hole. After the fluid is ejected from the sharp hole, the air bubbles will shrink and the fluid can quickly fill the fluid cavity again. At the same time that the fluid chamber is pressurized, the problem of cross-phase interference that the bubble will isolate the fluid chamber from the manifold and adjacent fluid chambers is minimized. In a preferred embodiment of the present invention, a component package for forming bubbles

45889a V. Description of the invention (4) Contains a first heater arranged near the fluid cavity. The pressurizing member includes a second heater capable of forming a second bubble in the fluid cavity. These heaters are located near the sharp hole and include an electrode connected in series, and their resistance varies with the width of the electrode. The electrode of the first heater is narrower than the electrode of the second heater. 'Even if the two heaters are applied with a common electrical signal', the first bubble will be formed before the second bubble. As the first and second bubbles expand, they approach each other until they are combined, thereby reliably cutting off the fluid flowing from the sharp holes, thereby eliminating or greatly reducing the satellite liquid beads. An object of the present invention is to provide a micro-injector device capable of eliminating satellite liquid beads. Another object of the present invention is to provide a micro-injector device capable of minimizing cross-phase interference. Yet another object of the present invention is to provide a micro-injector device, which can quickly fill the fluid back into the fluid cavity after the fluid is ejected. Another object of the present invention is to provide a method for ejecting fluid from a fluid cavity of a micro-injector, which can minimize satellite liquid beads. Another object of the present invention is to provide a method for ejecting fluid from a fluid cavity of a micro-injector, which can minimize cross-phase interference. Another object of the present invention is to provide a method for ejecting fluid from a microprojectile 5 | fluid cavity, which can quickly backfill the fluid into the fluid cavity after the fluid is ejected. Other objects and advantages of the present invention will be described in the following parts of the description, wherein the detailed description is only to fully disclose the preferred embodiments of the present invention,

Page 8 V. Description of the invention (5) Instead of narrowly limiting the invention to this embodiment. To put it simply, the present invention can be more fully understood by referring to the following drawings. These diagrams are for clarification only, in which: Figure 1 is a perspective view of a part of a micro-injector array device according to the present invention. FIG. 2A is a cross-sectional view of a fluid cavity and a manifold of the micro-injector array shown in FIG. 1. FIG. Fig. 2B is a cross-sectional view of a fluid cavity and a manifold shown in Fig. 2A, which is used to indicate that after a first bubble is formed ', a second bubble is subsequently formed to eject the fluid from an acute hole. Fig. 2C is a cross-sectional view of a fluid cavity and a manifold shown in Fig. 2A, which is used to represent the combination of a first bubble and a second bubble, thereby stopping the ejection of liquid from an acute hole. Fig. 2D is a cross-sectional view of a fluid cavity and a manifold shown in Fig. 2A, which shows that after a first bubble has contracted, a second bubble then receives the fluid and backfills the fluid cavity. Figure 3 is a view of a micro-injector array used to make the present invention. The top view of the Japanese Yen 4 is a composition of the line segment 4 _ 4 along the stone evening wafer shown in FIG. 5 is a top view showing the sand wafer shown in FIG. Illustration. ^ y said that the circle follower surface is etched to FIG. 6 is a cross-sectional view taken along line 6 _ 6 of the Shixi wafer shown in FIG. 5.

45δ89β 5. Description of the invention (6) FIG. 7 is a top view showing that the silicon wafer shown in FIG. 5 is etched to enlarge the depth of a fluid cavity. FIG. 8 is a cross-sectional view along the line segment 8-8 of the Shixi wafer shown in FIG. 7. Fig. 9 is a plan view showing the Shi Xi wafer shown in Fig. 7 on which a heater having a pattern is deposited. FIG. 10 is a cross-sectional view taken along the line segment 10-10 of the silicon wafer shown in FIG. FIG. 11 is a top view showing that the Shi Xi wafer shown in FIG. 9 has a sharp hole formed. FIG. 12 is a cross-sectional view along the line segments 1 2-1 2 of the silicon wafer shown in FIG. 11. DESCRIPTION OF SYMBOLS 1 0 micro-injector array 1 2 micro-injector 1 4 fluid cavity 16 manifold 1 8 sharp hole 2 0 first heater 2 2 second heater 2 4 common electrode 26 fluid 28 liquid level height 3 0 first bubble

Page 10 45889β 5. Description of the invention (7) 32 Second bubble 34 Tail of liquid column 36 3 Liquid column 3 8 Silicon wafer 4 0 Fluid cavity sacrificial layer 4 2 Low-stress tritium silicon 4 4 Metal wiring 4 6 Oxidation layer 4 7 The convex corner 4 8 of the fluid cavity 14 The detailed description of the preferred embodiment of the interconnecting layer refers to the illustrations in detail. The embodiment of the present invention is the device shown in FIGS. 1 to 12. Reference is first made to FIG. 1, which shows an array 1 0 of a microinjector device 12. As shown in FIG. The array 10 includes a plurality of adjacent micro-injectors 12. Each micro-injector includes a fluid cavity 14, a manifold 16, an acute hole 18, a first heater 20 and a second heater 22. The first heater 20 and the second heater 2 2 are generally electrodes connected in series to a common electrode 24. Referring to FIG. 2A, the fluid cavity 14 is adapted to be filled with a fluid 26. The fluid 26 may include, but is not limited to, the following fluids: ink, gasoline, oil, chemicals, biomedical solutions, water, and the like, and which flow system is selected depends on the particular application. In general, the liquid level 28 of the fluid 26 will be stable at the sharp holes 18. The manifold 16 is adjacent to the fluid cavity 1 4 and is connected to the fluid cavity

Page 11 4 ^ B89Θ V. Description of the Invention (8) --- 14 are connected. Liquid from a storage tank (not shown) flows through the manifold 16 and is supplied to the fluid chamber 14. The first to second heaters 20 and 22 are disposed adjacent to the sharp holes 18 and above the fluid cavity 14 to prevent heat from being lost to the substrate. The first heater 20 is disposed adjacent to the manifold 6 and the second heater 22 is disposed adjacent to the fluid chamber 4. As shown in FIG. 2A, the cross section of the first heater 20 is narrower than that of the second heater 22. Referring to FIG. 2B, since the first heater 20 and the second heater 22 are connected in series, a common electrical pulse can be used to start the first heater 20 and the second heater 22 at the same time. Because the cross section of the first heater 20 is narrow, the power consumption of the current pulse is relatively high on the first heater 20, and in response to the common electrical pulse, the heating of the first heater 20 is heated. The speed is thus faster than the first heater 22 having a wider cross section. This method is relatively simple in design because it is not necessary to continuously activate the first heater 20 and the second heater 22. Activation of the first heater 20 will result in the formation of a first bubble 30 between the manifold 16 and the fluid chamber 14. When the first bubble 30 expands in the direction of the arrow p, the first bubble 30 will begin to restrict the flow of fluid to the manifold 6 and thus form an imaginary valve, which can isolate the fluid cavity 14 and protect it. Adjacent fluid chambers are protected from cross-phase interference. After the first bubble 30 is formed, a second bubble 32 is also formed under the second heater 22. As the second bubble 32 expands in the direction of the arrow p, the pressure of the fluid chamber 14 also increases, so that the fluid 2 6 can be ejected from the acute hole 18 in a direction F into a liquid column 3 β. Referring to FIG. 2C, as the first bubble 30 and the second bubble 32 continue to expand, the first bubble 30 and the second bubble 32 will approach each other, thereby stopping the ejection of the fluid from the sharp hole 18. When the first bubble 30 and the second bubble 32 are combined,

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A 5 8 8 P S V. Description of the Invention (9) The tail 34 of the 36 will be cut off suddenly to prevent the formation of satellite liquid beads. Referring to FIG. 2D, the termination of the electrical pulse will cause the first bubble 30 to begin to contract in the direction P. The first bubble 30 shrinks, and there is no longer any obstruction between the manifold 16 and the fluid cavity 14. The fluid 26 can quickly fill the fluid cavity 14 again in the direction r. As can be seen from the above, the method for ejecting the fluid 26 from a micro-injector device 12 according to the present invention generally includes the following steps: (a) generated in the fluid-filled fluid cavity 14 of the micro-injection device 12 The first bubble 3 0; (b) pressurize the fluid cavity 14 to eject the fluid 26 from the fluid cavity 14, wherein this pressurizing step includes generating a second bubble 32 in the fluid cavity 14; (c) increase The first bubble 30 in the fluid cavity 14 serves as a simulative valve, thereby restricting fluid flow between the fluid cavity 14 and the manifold 16; (d) increasing the second bubble 32 in the fluid cavity 14, Thereby, the first bubble 30 and the second bubble 32 will approach each other, and then the fluid ejection from the fluid cavity 14 is suddenly stopped; and (e) the first bubble 30 is contracted to accelerate the backfilling of the fluid into the fluid cavity 14. Referring to FIG. 3 and FIG. 4, the present invention combines a surface micromachining technology and a body micromachining technology ′ without a wafer bonding process to fabricate a micro-injector array 丨 0 on a broken wafer 38. In this manufacturing process, a silicon-silicon (PSG) layer is first deposited as a fluid cavity sacrificial layer 40 'and a fluid cavity sacrificial layer 40 is subjected to a case transfer', and then a low-stress silicon nitride 42 is deposited as a fluid cavity. upper layer. Next, as shown in FIG. 5 and FIG. 6, potassium hydroxide (koh) is used to remove silicon crystals.

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The back of the circle 38 is etched to form the manifold 16. The sacrificial psG layer 40 is removed with hydrofluoric acid (HF). Referring to FIG. 7 and FIG. 8, another etching is performed under a precisely controlled time to increase the depth of the fluid cavity 14. Pay special attention during this step, as the convex corners of the fluid cavity 4 will also be attacked and etched into a circle.

Referring to FIG. 9 and FIG. 10, the first heater 20 and the second heater 22 'are deposited for pattern transfer. For the first heater 20 and the second heater 22, 5 'is preferably platinum. Next, a metal wiring 44 'is formed, and an oxide layer 46 is deposited on the metal wiring 乜 as a protective layer. An interconnect layer 48 between the first heater 20 and the common electrode 24 is disposed under the oxidation layer 46. Finally, referring to FIG. 12 and FIG. 12, a sharp hole 18 is formed here. If the lithography can accommodate a line width of 3 μra, the sharp holes 丨 8 can be as small as 2 " m, and the distance between the sharp holes ^ (P i7Ch) can be as small as 1 5 # m. It can also be seen from the figure that the lobes 47 of the fluid cavity 14 have shown a clear shape after being etched. Therefore, from the above, it can be known that the present invention provides a novel micro-injector. The micro-injector uses a bubble to restrict the fluid from flowing into a fluid cavity, and thereby prevents the fluid from being lost to the fluid cavity during the ejection of the fluid from the sharp hole. ^. 3 ί ί Ming uses a second bubble in combination with a first bubble to suddenly cut off the liquid column ejected from the hole to eliminate satellite liquid beads. The specific second embodiment I proposed in the detailed description of the preferred embodiment is easy to explain the technical content of the present invention, but not narrow the invention to the embodiment 'without exceeding the spirit of the present invention and the scope of the following applications * The situation can be implemented in various changes. Kidney

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Claims (1)

ra 9 9 g-«· 〇 --- VI. T patent scope 1. A device that uses a bubble as a simulative valve of a micro-injector to eject fluid, including: (a) a fluid cavity, which Contains fluid; (b)-an acute hole communicating with the fluid cavity, the sharp hole is arranged above the fluid cavity; (c) a fluid cavity is created when the fluid cavity is filled with fluid- The first bubble is used as the first bubble generating member of an imaginary valve, and the first bubble generating member is arranged close to the sharp hole and located outside the fluid cavity; and (d)-used as the fluid When the cavity is filled with fluid, after the fluid cavity relays the first bubble generation, a second bubble is generated to generate a second bubble generation member for ejecting fluid from the fluid cavity, and the second bubble generation member is disposed near the The sharp hole is located outside the fluid cavity. 2. The device as claimed in claim 1, wherein the first bubble generating member includes a first heater. 3. If requested, the device in the second scope of the patent, wherein the second bubble generating member includes a second heater D 4. If the device in the third scope of the patent application, the first heater and the second heater The position of the device is such that the first bubble and the second bubble are close to each other when they expand, thereby abruptly stopping fluid from being ejected from the fluid cavity. ^ 5 The device of claim 3, wherein the first heater and the second heater are adapted to be driven by a common signal. 6. The device as claimed in claim 3, wherein the first heater and the second heater are connected in series. 45 889 β Six 'scope of patent application 7. For the device in the scope of application for patent item i ..., the generation of the first air bubble is used as an imaginary valve to restrict fluid from flowing out of the fluid cavity. 8 · A device that uses a bubble as a micro-injector to emulate a fluid to eject a fluid, including: (a)-a fluid cavity; (b)-a manifold communicating with the fluid cavity 'for supplying fluid to the Fluid cavity; (c) an acute hole communicating with the fluid cavity; (d)-used to generate a first bubble in the fluid cavity when the fluid cavity is filled with fluid as the first of an illusion valve A bubble generating member, the first bubble generating member is disposed close to the sharp hole and is located outside the fluid cavity; and i (e) —a first step for generating a second bubble after the first bubble is generated Two bubble generating members, the second bubble generating member is disposed near the sharp hole and located outside the fluid cavity, wherein the sharp hole is arranged between the first bubble generating member and the second bubble generating member And the formation of the second bubble will cause the fluid in the fluid cavity to be ejected from the sharp hole = one, nine pieces of the device of the above item, wherein the first bubble generating member includes a first heater. The device according to item 9 of the Danish Application / Profit Range 'wherein the second bubble generating member includes a second heater. Secluded. The device according to item 10 of Di Rushen's patent scope, wherein the first heater and the first heating system are adapted to be driven by a common signal. 1 2. The device according to the scope of the patent application, wherein the-heater and Page 17 458896 6. Scope of patent application The second heater is connected in series. 13. The device according to the scope of claims 1-0. Wherein the first heater and the second heater are arranged near the sharp hole, so that the first bubble and the second bubble can be combined, thereby Sudden termination of fluid ejection from this sharp hole. 1 4. The device according to item 8 of the scope of patent application, wherein the generation of the first air bubble is used as an imaginary valve to restrict fluid from flowing out of the fluid cavity. 15 — A method for ejecting fluid from a microchannel having an acute hole, comprising the following steps: (a) generating a first bubble at a sharp hole very close to a fluid-filled microchannel; ( b) A second bubble is generated near the sharp hole in the microchannel, and the fluid is ejected from the microchannel by pressurizing the microchannel. The second bubble generation step is after the first bubble generation step. Performing, wherein the first bubble and the second bubble are each juxtaposed with the sharp hole; (c) increasing the first bubble in the microchannel as a quasi-valve to restrict fluid from flowing into the microchannel; and (d) Enlarge the second bubble in the microchannel, so that the first bubble and the second bubble are close to each other, and then suddenly stop the fluid from being ejected from the sharp hole. The method further includes the following steps: shrinking the first bubble to accelerate fluid flow into the microchannel. 17. The method according to item 15 of the scope of patent application, wherein a common signal is used to continuously start generating the first bubble and the second bubble. 1 8. The method of claim 1 in which the first bubble is increased Page 18 45889s 6. The scope of patent application is larger than the speed at which the second bubble is enlarged. 19, A method for ejecting fluid from a micro-injector having a fluid cavity, a manifold communicating with the fluid cavity to supply fluid to the fluid cavity, and a sharp hole communicating with the fluid cavity, including the following Steps: (a) When the fluid cavity is filled with fluid, a first bubble is generated at the sharp hole in the fluid cavity as a quasi-valve; (b) A first bubble is generated in close proximity to the sharp hole. Two bubbles to eject fluid from the sharp hole, wherein the second bubble generating step is performed after the first bubble generating step; and (c) combining the first bubble and the second bubble to suddenly stop the fluid from the sharp hole Hole shot. 20. The method according to item 19 of the scope of patent application, further comprising the following steps: shrinking the first bubble to accelerate the flow of fluid into the fluid cavity. 21. The method of claim 19, wherein a common signal is used to continuously start generating the first bubble and the second bubble. 2 2. The method according to item 19 of the scope of patent application, wherein the speed at which the first bubble is enlarged is faster than the speed at which the second bubble is enlarged. Page 19