Improved microfluidic device for ejecting very small droplets

Abstract

Embodiments of the present disclosure generally relate to improved microfluidic devices for ejecting very small droplets. A microfluidic device has a chamber; a fluid entry channel fluidically connected to the chamber; a plurality of nozzle apertures fluidically connected to the chamber; and an actuator operably coupled to the fluid containing chamber and configured to cause ejection of droplets of fluid through the nozzle apertures under operating conditions of the microfluidic device. The chamber has an elongated shape with a length and a maximum width, wherein an aspect ratio between the length and the maximum width of the chamber is at least 3: 1. The nozzle apertures are configured to generate, in use, a plurality of droplets having a total droplet volume, wherein a ratio of the total droplet volume to a volume of the chamber is at least 15%.

Description

Technical Field

[0001] This disclosure relates to an improved microfluidic device for ejecting very small droplets. Background Technology

[0002] It is well known that small-sized microfluidic devices, which can be obtained through microelectronics manufacturing technology, have been proposed for use in spraying ink and / or perfume, as well as in electronic cigarettes or inhalation medical devices.

[0003] The delivery of fluids with known or unknown components is feasible through improved design of inkjet structures, such as those described in US 2015 / 367014, US 2014 / 14310633, US 2015 / 0367356 or US 2015 / 367641.

[0004] However, in some applications, such as atomizers, it is necessary to spray droplets of very small size, as small as 1 μm. However, current semiconductor technology allows for the manufacture of nozzles with diameters greater than 6 μm.

[0005] To address this issue, for example, US2018 / 0141074 discloses a microfluidic device formed in a body that contains a fluid-containing chamber. An exemplary embodiment is shown in... Figure 1 and Figure 2 In this configuration, a chamber 1 formed in the body 5 is coupled to a fluid inlet channel 2 and a droplet emission channel or nozzle 3 formed in a nozzle plate (invisible, covering the chamber 1). The droplet emission channel 3 covers the chamber 1 and is partially offset thereto to define an intersection region 4 smaller than the orifice region, thereby defining an effective outlet area. A heater 8 is formed in the body 5 below the chamber 1 and is configured to heat the fluid in the chamber 1 to generate droplets emitted through the droplet emission channel 3.

[0006] Therefore, small droplets can be obtained. Specifically, the droplet size (diameter / volume) is directly related to the nozzle diameter, such as... Figure 2 As shown, the volume of the ejected droplets is plotted as a function of the nozzle diameter. Figure 1 (effective export area in China).

[0007] This solution has successfully reduced the size of the ejected droplets, but it has created further challenges for the operation of the equipment, especially when it is necessary to eject a large number of very small droplets at a high frequency.

[0008] In particular, test structures involving multiple holes arranged on the outer periphery of the cavity have been investigated to obtain a sufficient volume of emission fluid. However, it has been shown that such an architecture may not be thermally efficient.

[0009] In fact, for example, microfluidic devices with peripherally biased nozzles of 6 μm in diameter have been studied, configured to acquire droplets of approximately 0.28 pL (picoli). This results in droplet volumes less than 1% of the chamber volume, and therefore smaller than the fluid contained in the chamber (e.g., 50 pL). Consequently, a much larger volume of fluid than is actually ejected is heated. As a result, it has been observed that heat accumulates very rapidly in the chamber and may lead to overheating of the dies containing multiple adjacent chambers.

[0010] In some cases, boiling of the fluid is observed even before it enters the chamber, resulting in complete depriming of the system. Therefore, in devices comprising multiple chambers, each connected to multiple nozzles for high-frequency (even above 1 kHz) ignition, there is a risk of the entire device failing due to global depriming. Furthermore, depriming can occur rapidly, damaging the device.

[0011] Various embodiments of this disclosure provide improved microfluidic devices that address the problems of the prior art. Summary of the Invention

[0012] According to the present invention, a microfluidic device and a method for manufacturing the same are provided. Attached Figure Description

[0013] To understand this disclosure, embodiments thereof are now described with reference to the accompanying drawings, which are purely non-limiting examples, in which:

[0014] Figure 1 It is a simplified top view of the chamber of a microfluidic device, with transparent sections;

[0015] Figure 2 It is a graph showing the dependence of droplet volume on nozzle diameter;

[0016] Figure 3 This is a simplified perspective cross-sectional view of one embodiment of the chamber of this microfluidic device;

[0017] Figure 4 yes Figure 3 A simplified top view of the unit, with transparent portions;

[0018] Figure 5 It is a graph showing the relationship between the outlet area and the droplet diameter obtained through experiments;

[0019] Figure 6 This is a simplified top view of a microfluidic device that includes multiple chambers;

[0020] Figures 7-10 This is a top view of a different embodiment of a microfluidic device, including transparent portions;

[0021] Figure 11 A top perspective view of this microfluidic device during an intermediate manufacturing step is shown;

[0022] Figure 12 yes Figure 11 A top view of a part of the equipment;

[0023] Figure 13 It is along Figure 12 The line XI-XI intercepted Figure 11 A cross-section of a portion of a microfluidic device;

[0024] Figure 14 It shows Figure 11 Top perspective view of the microfluidic device in subsequent manufacturing steps;

[0025] Figure 15 yes Figure 14 A magnified perspective view of a portion;

[0026] Figure 16 Shown in top view form Figure 15 Magnified details;

[0027] Figure 17 yes Figure 13 The same part is Figure 14 The cross-section during the manufacturing process;

[0028] Figure 18 It shows Figure 14 Top perspective view of the microfluidic device in subsequent manufacturing steps;

[0029] Figure 19 yes Figure 18 An enlarged top view of a portion of a microfluidic device;

[0030] Figure 20 yes Figure 17 The same part in Figure 18 Along the manufacturing steps Figure 19 A cross-sectional view taken from the cross-section line XX-XX;

[0031] Figure 21 yes Figure 18 A magnified top perspective view of a portion of a microfluidic device in a subsequent manufacturing step;

[0032] Figure 22 yes Figure 21 A bottom perspective view of a microfluidic device, showing the cut-off corner portions;

[0033] Figure 23 yes Figure 21 Top perspective view of the microfluidic device in subsequent manufacturing steps;

[0034] Figure 24 Shown at magnified scale Figure 23 Details of the equipment;

[0035] Figure 25 yes Figure 20 The same part is Figure 23 Cross-sectional view during the manufacturing process;

[0036] Figure 26 yes Figure 23 A magnified perspective cross-sectional view of a portion of a microfluidic device, with the cut-off portion shown;

[0037] Figure 27 Shown at a further magnified scale Figure 26 Details of the parts, and the flow of the jet fluid in use are shown;

[0038] Figure 28 yes Figure 23 The bottom perspective view of the device shows the inlet flow of the fluid to be ejected in use;

[0039] Figure 29 This is a cross-sectional view of another embodiment of the microfluidic device;

[0040] Figures 30-31 yes Figure 29 The cross-section of a semiconductor material wafer used in subsequent manufacturing steps of a microfluidic device;

[0041] Figure 32 yes Figure 31 A bottom view of the chip;

[0042] Figures 33-34 It is similar to the subsequent manufacturing steps. Figures 30-31 The cross-section;

[0043] Figure 35 It shows Figure 34 A partial perspective cross-sectional view of a portion of a wafer;

[0044] Figure 36 It is used to form a basis Figure 29 A cross-section of a portion of another semiconductor material wafer in an embodiment of the microfluidic device;

[0045] Figures 37-38 It is from the subsequent manufacturing steps Figure 34 and Figure 36 A cross-section of a portion of the combined wafer obtained from the wafer;

[0046] Figure 39 yes Figures 37-38 A top perspective view of the combined wafer, showing the cut-off portion; and

[0047] Figure 40 Shown in an enlarged top perspective view Figure 39 Details of the combined chip. Detailed Implementation

[0048] Embodiments of the microfluidic device will be described in detail below. In the following description, spatial designations such as “upper,” “lower,” “above,” “below,” “top,” “bottom,” etc., will be interpreted in light of the figures discussed, rather than as limiting.

[0049] Figures 3-4 A microfluidic device 10 fabricated using microfabrication steps is shown, as discussed in more detail below.

[0050] Microfluidic device 10 has Figure 3 The general structure shown is formed in the body 11, which includes a substrate 12, an insulating layer 13, a chamber layer 14, and a nozzle layer 15.

[0051] The substrate 12, insulating layer 13, chamber layer 14 and nozzle layer 15 extend from one another in a height direction parallel to the vertical axis (the first axis Z of the Cartesian coordinate system XYZ).

[0052] The substrate 12 is, for example, a semiconductor material, such as monocrystalline silicon. The insulating layer 13 is, for example, a multilayer comprising silicon oxide, silicon nitride, and other insulating layers. The substrate 12 and the insulating layer form the substrate portion 22. The chamber layer 14 is, for example, a polymeric material such as a dry film. As described below, the nozzle layer 15 may be formed of a semiconductor material such as monocrystalline silicon or a polymeric material such as a dry film.

[0053] The chamber layer 14 forms multiple chambers 17. Figure 3 and Figure 4 A chamber 17 is shown. The chamber 17 is laterally defined by a sidewall 16 formed by a chamber layer 14; furthermore, the chamber 17 is defined by a bottom base 17A formed by an insulating layer 13 and an upper base 17B formed by a nozzle layer 15.

[0054] The insulating layer 13 houses multiple actuators, including heaters 18 (one shown). The heaters 18 are arranged below chambers 17, with one heater 18 for each chamber 17. However, in an alternative arrangement, more heater sections 18 may be arranged below each chamber 17.

[0055] Each heater 18 is coupled to an ignition circuit (not shown) via a connecting line 19.

[0056] Inlet 20 extends from the opposite side of chamber 17 through chamber layer 14. Inlet 20 connects chamber 17 to a fluid supply channel not shown here.

[0057] Multiple nozzle openings 23 extend along the periphery of each chamber 17 through the nozzle layer 17. Specifically, as Figure 4 As clearly visible, the nozzle opening 23 partially covers the chamber 17 and fluidly connects the chamber 17 to the external fluid of the microfluidic device 10 for droplet ejection.

[0058] To reduce the exit area of ​​the droplet, such as Figure 4 As shown in the magnified details, the nozzle openings 23 are each formed with Figure 1 The intersection region 4 is similar to the intersection region 34.

[0059] exist Figure 4 In the illustrated embodiment, the sidewalls 16 of chamber 17 extend in a rectangular shape, and chamber 17 has a parallelepiped shape with a rectangular base 17A extending parallel to the plane XY of the Cartesian reference frame XYZ. Figure 4 In the top view, the long side of the bottom base 17A of chamber 17 is much longer than the short side.

[0060] Specifically, the length of the longer side of the base 17C is greater than twice the length of the shorter side; in Figure 4 In the embodiment shown, the longer side of the bottom base 17C of the rectangle is four times the length of the shorter side.

[0061] exist Figure 4 In one embodiment, inlet 20 opens in chamber 17 at the short side of chamber 17. Nozzle opening 23 extends adjacent to the long side and partially intersects (e.g., overlaps) the long side.

[0062] The nozzle opening 23 is designed to have a smaller intersection region 34, in which the nozzle opening 23 and the chamber 17 overlap. Therefore, the droplet volume is reduced, such as... Figure 5 The graph shown illustrates the relationship between droplet diameter and effective outlet area (i.e., intersection area). Here, the region of interest is at 0.2 μm. 2 up to 0.5μm 2 The area between.

[0063] In the example shown, the nozzle opening 23 has a triangular, almost isosceles shape, with an acute-angled corner that intersects with the chamber 17 and forms an intersection region 34. Therefore, for a triangle height Ht of 6 μm... Figure 4 With current technology, approximately 0.32 μm can be obtained. 2 The intersection region 34, therefore, the droplet volume is approximately 0.02 pl.

[0064] In the microfluidic device 10, the chamber 17 and the nozzle opening 23 are designed such that the volume ratio between the droplet volume and the chamber volume is greater than 15%.

[0065] According to the applicant's research, it has been observed that less overheating can be achieved by designing chamber 17 to maximize its circumference (thus having a greater number of smaller nozzle openings 23) while reducing the volume of chamber 17.

[0066] In particular, it has been demonstrated that a constant high liquid flow rate from inlet 20 to nozzle opening 23 can be obtained when the volume ratio is higher than 15%, thereby eliminating stagnant liquid in chamber 17 and thus eliminating contamination of the chamber.

[0067] For example, a width W = 6 μm, a length L = 12 μm, and therefore a volume of 1008 μm. 3 This can be achieved with a chamber 17 containing eight nozzle openings 23 (the total volume of the emitted droplets is 0.16 pL). The same ratio can be achieved with chamber 17 having an area that is an integer multiple n of the area of ​​the basic chamber and a number of nozzle openings 23 equal to 4n.

[0068]

[0069] Figure 6 The device 10 is shown, comprising three sets of emitting sections 25, each set of emitting sections 25 being formed by a plurality of chambers 17 (here, five) adjacent to each other.

[0070] Here, each chamber 17 is formed by four basic units (as shown by the dashed lines) and thus has sixteen nozzle openings 23.

[0071] The heaters 18 of the chambers 17 of the same set of launching sections 25 are connected together, such as Figure 6 Line 26 is shown in the figure. In particular, as shown, the heater 18 of the same set of transmitting sections 25 is coupled between the transmitting circuit that provides the transmitting pulse Vo (e.g., 10V) and ground.

[0072] According to embodiments of this microfluidic device, a smaller cross-section can be obtained by forming small-sized features in the sidewall 16 of the chamber 17 instead of in the nozzle layer 15. Indeed, the applicant's testing has shown that aligning the nozzle opening 23 relative to the chamber 17 can sometimes be difficult. Furthermore, in some cases, such as by drilling very small nozzle openings 23 in the nozzle layer 15 using a laser, it has proven challenging and does not always result in the formation of openings of constant size; in rare cases, partially closed nozzles have been observed, leading to uneven cross-sections and suboptimal behavior.

[0073] Specifically, according to this embodiment, the sidewall 16 is not smooth and straight, but has a plurality of very small protrusions. Each nozzle opening here has an area equivalent to the chamber area (in the top view) and extends almost entirely offset relative to the adjacent chamber 17 except for the chamber protrusions, thereby defining a plurality of very small nozzle orifices.

[0074] For example, Figures 7-9 Three different shapes of chambers and nozzle orifices are shown, which allow for the simple acquisition of very small cross regions using current macromachining techniques.

[0075] Figure 7 and Figure 8 A microfluidic device 100 including a chamber layer 114 is shown.

[0076] The chamber layer 114 forms a plurality of chambers 117 (four visible), which have a generally rectangular region (parallel to the plane XY) in the top view. The chambers 117 are defined by sidewalls 116 formed by the chamber layer 114. Each chamber 17's sidewall 116 forms a plurality of protrusions 130 adjacent to each other. Figure 8 The protrusion 130 extends within the chamber 117 and separates the corresponding indentations 131.

[0077] The heater 118 extends below the chamber 117 and is indicated by a dashed line.

[0078] The protrusion 130 here has a roughly square shape with sides of, for example, about 2.5 μm to 2.6 μm.

[0079] The nozzle layer 115 (indicated by the shaded line) extends over the chamber layer 114 and closes the chamber 117 upward. The nozzle layer 115 has an opening 132 that is offset from the chamber 117 but intersects (e.g., overlaps) with the notch 131.

[0080] Specifically, the opening 132 is vertically aligned with a portion 119 of the chamber layer 114 extending between pairs of adjacent chambers 117.

[0081] Here, opening 132 is also rectangular in the top view.

[0082] Therefore, the opening 132 and the notch 131 form a very small intersection region 134. Figure 8 (especially those in the few μm) 2 .

[0083] For example, if the opening 132 extends almost the entire length of the notch 131 (along the second axis Y, parallel to the width dimension of the chamber 117), then 1.5 × 2.6 μm can be obtained for each chamber 131. 2 Export area.

[0084] Under the operating conditions of the microfluidic device 100, the cross region 134 is the outlet area of ​​the fluid contained in the chamber 117. Therefore, the microfluidic device 100 is capable of generating very small droplets in each chamber 117, and after a voltage pulse V is applied to the heater 118 (similar to...). Figure 6 As shown in the figure, many very small droplets of aerosol are obtained.

[0085] Due to the elongated shape of chamber 117 (here, the length along the third axis X is approximately four times the width along the second axis Y), a volume ratio greater than 15% can be achieved, thereby providing reliable operation of the microfluidic device 100 without causing the microfluidic device 100 to overheat or detach.

[0086] Figure 7 The inlet 120 and the column 133 formed in the inlet 120 to block any impurities that may be dragged by the liquid that may enter are also shown.

[0087] Figure 9 Different shapes of the chambers (here indicated by 217) and openings (here indicated by 232) in the nozzle layer 215 are shown.

[0088] Here, chamber 217 has a generally oval or elliptical bottom region. Also here, chamber 217 is defined by sidewalls 216 forming a plurality of adjacent protrusions 230 and corresponding notches 231. Furthermore, the larger dimension (length, measured along the third axis X) of each chamber 217 is twice the smaller dimension (width, measured along the second axis Y).

[0089] For example, chamber 217 may have an elliptical shape with a first semi-axis length of 60 μm and a second semi-axis length of approximately 20 μm.

[0090] The heater represented here by 218 can also have a rectangular shape.

[0091] The protrusion 230 and the notch 231 have sharp points here.

[0092] The nozzle layer 215 (also indicated by the shaded line) extends over the chamber layer 214 and has an opening 232, which, in the top view, is generally opposite in shape to the chamber 217. Specifically, the opening 232 extends in a direction parallel to the third axis X and has an arcuate concave shape. Therefore, in different cross-sections taken along the third axis X, the width of the opening 232 decreases from one end (near one inlet 220 of the chamber 217) toward the central portion of each opening 232, and then increases again toward the other end. The opening 232 also extends here at least partially over the protrusion 230 and the notch 231.

[0093] Figure 10 Another shape of the chamber (represented here by 317) and opening (represented here by 332) in the nozzle layer 315 is shown.

[0094] Here, chamber 317 has a generally rectangular shape in top view (parallel to plane XY) and has pointed protrusions 330 separated by notches 331 of similar shape.

[0095] The opening 332 has a substantially constant width (in a direction parallel to the second axis Y), has an enlarged end, and has an aspect ratio of at least 3:1.

[0096] Typically, in other embodiments, the shapes of the chambers, openings, protrusions, and gaps between them can vary widely, as long as the openings have a micron-sized intersection area with the gaps.

[0097] Figures 7-10 The microfluidic device 100 can be referenced as follows: Figures 11-28 Manufactured as discussed.

[0098] These figures depict the fabrication of a single microfluidic device 100; however, in general, many microfluidic devices are fabricated in a single wafer and separated in intermediate or final steps in a manner known in the art, even if not discussed in detail.

[0099] Figure 11 A portion of a wafer 400 that has been processed to form a heater and electrical connection structure is shown.

[0100] In detail, such as Figure 13 As shown, the wafer 400 includes, for example, a single-crystal silicon substrate 401, which is covered with an insulating layer 413 that houses the heater 418. The substrate 401 and the insulating layer 413 form a substrate portion 422.

[0101] Here, the insulating layer 413 is multilayered, including, for example, an oxide layer 450, such as a thermal oxide layer; a first intermediate dielectric layer 451, such as BPSG (borophosphosilicate glass); a second intermediate dielectric layer 452, such as silicon nitride; and a protective layer 454, such as USG (undoped silicon glass).

[0102] For example, a heater 418 of TaSiN or TaAlN extends between a first intermediate dielectric layer 451 and a second intermediate dielectric layer 452.

[0103] For example, a tantalum metal layer 453 extends here on the second intermediate dielectric layer 452 and forms a heat distribution layer. However, in some applications, the metal layer 453 may be omitted.

[0104] The protective layer 454 covers the metal layer 453 and houses the electrical connection lines 419 of conductive material (e.g., Al). Figure 12 Electrical connection 419 connects to heater 418 in an opening (not visible) in protective layer 454 and metal layer 453 and couples heater 418 to pads (not shown) arranged around the microfluidic device.

[0105] The protective layer 454 is shaped to form a chamber body 455 at the location where the chamber will be formed. Specifically, each chamber body 455 covers a corresponding heater 418. The shape of the chamber body 455 may be the same as the desired shape of the chamber, or may have any shape, such as rectangular; generally, the area of ​​each first chamber body 455 is smaller than the area of ​​the chamber.

[0106] In addition, the protective layer 454 forms a groove connecting the cavity 456 ( Figure 11 Each cavity 456 extends near the group of first chamber cavities 455, as explained better later, and the pad cavity 457 ( Figure 11 Cover pads (not shown).

[0107] Then, as Figures 14-17 As shown, a lower chamber layer 460 is deposited and defined. The lower chamber layer 460 is, for example, a photosensitive drying material, which is spun and defined to define a lower chamber opening 461, which is vertically arranged above and communicates with the chamber body 455, but is slightly larger, such as... Figure 17 As shown.

[0108] The shape of the lower chamber opening 461 is, for example, as shown in the figure. Figure 9 As shown and in Figure 16 This can be seen in the magnified details. Specifically, the lower chamber opening 461 is defined by a wall forming a lower notch 466, which is obscured by a lower protrusion 467. Figure 16 Separate them.

[0109] Furthermore, the lower chamber layer 460 is shaped to form the lower pillar portion 464 ( Figure 15 and Figure 16 ).

[0110] The lower chamber layer 460 was also removed in order to... Figure 11 A lower groove connection opening 462 is formed on the groove connection cavity 456, and a lower pad opening 463 is formed on the pad cavity 457, such as Figure 14 As shown.

[0111] Then, the lower chamber layer 460 is baked and hardened.

[0112] exist Figures 18-21 In the middle, an upper chamber layer 470 is deposited and defined. The upper chamber layer 470 is, for example, a photosensitive drying material, and may be the same as or different from the lower chamber layer 460. The upper chamber layer 470 is, for example, spinned and defined to define an upper chamber opening 471, which is vertically arranged above and communicates with the lower chamber opening 461 (e.g., fluidly connected to the lower chamber opening 461). The lower chamber layer 460 and the upper chamber layer 470 form a chamber layer 414.

[0113] Therefore, sidewall 416 is formed. Figure 20 ).

[0114] like Figure 19 As can be seen in the top view, the upper chamber opening 471 has a similar shape to the lower chamber opening 461, but is slightly larger. Specifically, the upper chamber opening 471 has an upper notch 476 that extends deeper in the sidewall 416 than the lower notch 266, and an upper protrusion 477 that is substantially aligned with the lower protrusion 467, as shown... Figure 20 The dashed line portion is shown in the image.

[0115] Furthermore, the upper chamber layer 470 is shaped to form the upper pillar portion 474 ( Figure 19 The upper column 474 and the lower column 464 are vertically aligned.

[0116] like Figure 20 As shown, the upper chamber opening 471 and the lower chamber opening 461 form chamber 417; the upper protrusion 477 and the lower protrusion 467 form chamber protrusion 430; the upper notch 476 and the lower notch 466 form chamber notch 431; the upper column portion 474 and the lower column portion 464 form column 433. Figure 19 ).

[0117] like Figure 19 As can be seen in the middle, the lower chamber layer 460 and the upper chamber layer 470 also form the entrance 420.

[0118] like Figure 18 As shown, the upper chamber layer 470 is still... Figure 15An upper groove connection opening 472 is formed above the lower groove connection opening 462 and in Figure 14 An upper pad opening 473 is formed above the lower pad opening 463.

[0119] Then, the upper chamber layer 470 is baked and hardened.

[0120] Then, as Figures 21-22 As shown, substrate 401 is dry-etched to remove semiconductor material from substrate 401 below trench connection openings 472, 462. This forms a fluid supply channel 480. The fluid supply channel 480 extends through the entire thickness of substrate 401, transverse to chamber 417, and is fluidly connected to inlet 420.

[0121] exist Figures 23-26 In the middle, a nozzle layer 415 is deposited and defined. The nozzle layer 415 is, for example, a photosensitive dry film, which may be the same as or different from the lower chamber layer 460 and the upper chamber layer 470. The nozzle layer 415 is laminated and defined according to standard photolithography techniques to form an opening 432, shaped as follows: Figure 9 and Figure 24 As shown.

[0122] Opening 432 is offset relative to chamber 417, as shown in the reference. Figure 9 The explanation and Figures 26-27 As can be seen, the nozzle layer 415 thus covers most of the area of ​​the chamber 417, except for at least a portion of the chamber notch 431, to form the intersection region 434. Figure 27 ).

[0123] Nozzle layer 415 also covers upward inlet 420 and fluid supply channel 480, and has lower pad opening 463 and upper pad opening 473 (pad opening 483, Figure 23 The section above was removed to allow electrical connection to electrical connection line 419. Figure 12 ).

[0124] Therefore, as Figures 26-28 As can be seen and indicated by arrow L, fluid entering the fluid supply channel 480 from the lower surface 482 of the substrate 401 can reach the inlet 420 and the chamber 417, be heated by the heater 418, causing the formation of bubbles, and be sprayed through the cross region 434, similar to the operation described in the aforementioned patent application US 2018 / 0141074.

[0125] In particular, such as Figure 27 As indicated by arrow S, due to the smaller size of the intersection region 434, many small droplets are ejected, ensuring a high total volume of the ejected liquid with very small diameter droplets.

[0126] Since the smaller features that define the size of the jet droplets are formed in the lower chamber layer 460 and the upper chamber layer 470, especially in the upper chamber layer 470, this can be defined in a simple manner using standard, reliable and well-known photolithography techniques, making the fabrication of the microfluidic device 100 simple and reliable.

[0127] The acquired geometry is thus well controlled, and the microfluidic device 100 is able to operate in the desired manner.

[0128] Better injection conditions can be obtained by shaping the chamber 417 such that the area at the lower chamber opening 461 is smaller than the area at the upper chamber opening 471; in addition, the resulting chamber 417 is more likely to meet the aforementioned 15% volume ratio, with all other geometric aspects being the same.

[0129] According to different implementations Figure 3 The nozzle layer 15 is formed from a separate wafer, which is bonded to the wafer housing the chamber 17, as shown in the following reference. Figures 29-40 The subject of discussion.

[0130] refer to Figure 29 The microfluidic device 500 includes a lower wafer 600 and an upper wafer 650.

[0131] The next chip 600 basically includes and Figures 21-22 The same structure as the wafer 400. Therefore, the same components are made relative to... Figures 21-22 The corresponding elements are marked with a reference numeral 200 to identify them, and are no longer described in detail.

[0132] Specifically, the chamber layer identified by the number 614 here can be formed from a single layer of, for example, polymeric material, as shown in the figure, or from multiple layers, similar to... Figure 20 The lower chamber layer 460 and the upper chamber layer 470. The chamber layer 614 forms a chamber 617 defined by the sidewall 616.

[0133] The upper wafer 650 is a semiconductor wafer formed to form a plurality of nozzle openings 623, extending the entire thickness of the upper wafer 650.

[0134] Specifically, each nozzle opening 623 includes a smaller cross-sectional portion 655 and a larger cross-sectional portion 656.

[0135] Specifically, the upper wafer 650 has a lower main surface 660 facing the lower wafer 600 and an upper main surface 661 opposite to the lower main surface 660. A smaller cross-sectional portion 655 of the nozzle opening 623 extends from the upper main surface 661; a larger cross-sectional portion 656 extends from the lower main surface 660 and faces directly towards the lower wafer 600.

[0136] The smaller cross-sectional portion 655 of the nozzle opening 623 may have a circular cross-section with a diameter of approximately 2 μm; the larger cross-sectional portion 656 may also have a circular cross-section with a diameter of approximately 3 μm and be concentric with the smaller cross-sectional portion 655.

[0137] Figure 29 Microfluidic Devices 500 Reference Figures 30-40 Manufactured as described below.

[0138] Initially, such as Figure 30 As shown, a starting substrate 700 is used. The starting substrate 700 includes a first semiconductor layer 701, an intermediate layer of insulating material 702, and a second semiconductor layer 703. For example, the first semiconductor layer 701 may be silicon with a thickness of about 400 μm, the intermediate layer 702 may be silicon oxide with a thickness of about 1 μm, and the second semiconductor layer 703 may be silicon with a thickness of about 5-10 μm.

[0139] exist Figure 31 In this process, a second semiconductor layer 703 is etched using known photolithography techniques to form a smaller cross-sectional portion 655 of the nozzle opening 623.

[0140] The smaller cross-sectional portion 655 of the nozzle opening 623 can have Figures 7-10 The shapes shown. In alternative configurations, they can be arranged according to what is known as a nozzle arrangement, such as... Figure 32 As shown, or arranged in any other arrangement.

[0141] Then, as Figure 33 As shown, thermal oxidation is performed; therefore, the etch stop layer 705 covers the surface of the second semiconductor layer 703, including the interior of the smaller cross-sectional portion 655 of the nozzle opening 623. The etch stop layer 705 may be, for example, 0.4 μm thick.

[0142] exist Figure 34 In this process, a silicon structure layer 706 is epitaxially grown on an etch stop layer 705 and then planarized, for example, by CMP (chemical mechanical polishing). The structure layer 706 is grown on a thin capping layer 705 and can extend in a smaller cross-sectional portion 655 of the nozzle opening 623. The final thickness of the structure layer 706 can be 10 μm.

[0143] Then, the structural layer 706 is etched using a mask to form a larger portion of the cross section 656 of the nozzle opening 623.

[0144] Since the larger portion of the cross section 656 is vertically centered with the smaller portion of the cross section 655 of the nozzle opening 623, the etching stops on the etch stop layer 705 and removes the silicon within the smaller portion of the cross section 655.

[0145] Figure 35The resulting starting substrate 700 is shown in a partially cut-out perspective view, in which the intermediate layer 702 and the etch stop layer 705 are not visible.

[0146] Simultaneously, before or after processing the starting wafer 700, the first wafer 600 is processed to obtain... Figure 36 The structure. The fluid supply channels are invisible. Figure 40 The 680 in the middle has also been formed.

[0147] Then, in Figure 37 In this process, the starting wafer 700 is inverted and bonded to the lower wafer 600. Here, the chamber layer 614 serves as an adhesion layer for direct bonding to the structural layer 706, and the first semiconductor layer 701 is disposed on top.

[0148] Subsequently, the starting wafer 700 is thinned, for example, by grinding the first semiconductor layer 701, as shown by the dashed line. For example, the thickness of the first semiconductor layer 701 can be reduced to approximately 40 μm.

[0149] exist Figure 38 In the process, the first semiconductor layer 701 is completely removed, for example by dry etching; in addition, the exposed portions of the intermediate layer 702 and the etch stop layer 705 are also removed by dry etching. Thus, the upper wafer 650 is obtained.

[0150] Therefore, it was obtained Figure 29 and Figure 38 500 microfluidic devices.

[0151] Figure 39 and Figure 40 A perspective view of the microfluidic device 500 is shown, illustrating the relative positions of the chamber 617 and the nozzle orifice 623, as well as the relative positions of the fluid supply channel 680, the inlet 420, and the column 633.

[0152] pass Figures 29-40 The process allows for easy definition of smaller features. In particular, when the nozzle openings 623 form a nozzle pattern, each chamber 617 has multiple nozzle openings 623, and a smaller size can be obtained by dry etching the starting wafer 700 in an easily defined manner.

[0153] However, the same steps can be used to form a larger nozzle opening 623, wherein smaller features are formed in the chamber layer 614 as an alternative for the deposition of a photosensitive dry film, as referenced. Figures 11-28 The subject of discussion.

[0154] Finally, it is obvious that various changes and modifications can be made to the microfluidic devices and manufacturing steps described and illustrated herein, all of which fall within the scope of this disclosure.

[0155] For example, the various embodiments described above can be combined to provide other embodiments.

[0156] In particular, heaters 18, 418, and 618 can be replaced with actuators that operate according to different principles; for example, actuators made of piezoelectric materials, such as PZT (Pb, Zr, TiO3), can be used, for example, as disclosed in US2019 / 0358955.

[0157] The shapes of chambers 17, 417 and 617 can vary greatly, as can the shapes of protrusions 130, 230, 430 and notches 131, 231 and 431.

[0158] A microfluidic device (1; 100; 500) can be generally described as including a chamber (17; 117; 217; 317; 417; 617); a fluid inlet channel (20; 120; 420, 480; 620, 680) fluidly connected to the chamber; a plurality of nozzle orifices (34; 134; 434; 623) fluidly connected to the chamber; and an actuator (18; 418; 618) operatively coupled to the fluid-containing chamber and configured to eject droplets of fluid through the nozzle orifices under operating conditions of the microfluidic device, wherein the chamber (17; 117; 217; 317; 417; 617) has an elongated shape having a length and a maximum width, wherein the aspect ratio between the length and the maximum width of the chamber is at least 3:1.

[0159] The chambers (17; 117; 217; 317; 417; 617) may have a rectangular or elliptical base shape.

[0160] The chamber (17; 117; 217; 317; 417; 617) can be defined by a first base (17A), a second base (17B) and a sidewall (16; 116; 216; 416), the first base and the second base extending along a first direction and a second direction, the second direction being transverse to the first direction, the first direction and the second direction defining the length of the chamber and the maximum width of the chamber, respectively, and the sidewall extending along a third direction transverse to the first direction and defining the height of the chamber.

[0161] The chambers (17; 117; 217; 317; 417; 617) may have chamber volumes, and the nozzle orifices (34; 134; 434; 623) may be configured to generate multiple droplet volumes with a total droplet volume in use, wherein the ratio of the total droplet volume to the chamber volume is at least 15%.

[0162] The microfluidic device may include a substrate portion (22; 422), a chamber layer (14; 114; 414; 614), and a nozzle layer (15; 115; 215; 315; 415; 650), the substrate portion forming a first base (17A) and housing an actuator (18; 418; 618), the chamber layer forming a sidewall (16; 116; 216; 416; 616), and the nozzle layer forming a second base (17B) of the chamber (17; 117; 217; 317; 417; 617).

[0163] The sidewalls (16; 116; 216; 416) may form multiple notches (131; 231; 331; 431) and protrusions (130; 230; 330; 430), and the nozzle layer (15; 115; 215; 315; 415) may include at least one nozzle opening (132; 232; 332; 432) which is offset relative to the chamber (17; 117; 217; 317; 417) and intersects with the notches at the intersection area forming the nozzle orifice (34; 134; 434).

[0164] The chamber layer (414) may include a first layer (460) extending on the substrate (422) portion and a second layer (470) extending on the first layer, the first layer defining a lower chamber orifice (461) and the second layer defining an upper chamber orifice (471), the area of ​​the lower chamber orifice being smaller than the area of ​​the upper chamber orifice.

[0165] The chamber layer (14; 114; 214; 314; 414) and the nozzle layer (15; 115; 215; 315; 415) can be polymer layers.

[0166] The nozzle layer (650) can be a silicon wafer.

[0167] Each nozzle orifice (623) may include a larger cross-sectional portion (656) facing the chamber (617) and a smaller cross-sectional portion (655) extending and connecting the larger cross-sectional portion and extending from the outer surface (661) of the nozzle plate (661).

[0168] The nozzle orifice (623) can be arranged above the chamber (617) in a nozzle arrangement.

[0169] A method for manufacturing a microfluidic device can be summarized as comprising forming a chamber (17; 117; 217; 317; 417; 617); forming a fluid inlet channel (20; 120; 420, 480; 620, 680) fluidly connected to the chamber; forming a plurality of nozzle orifices (34; 134; 434; 623) fluidly connected to the chamber; and forming an actuator (18; 418; 618), the actuator being operatively coupled to the fluid-containing chamber and configured to eject droplets of fluid through the nozzle orifices under operating conditions of the microfluidic device, wherein the chamber (17; 117; 217; 317; 417; 617) has an elongated shape having a length and a maximum width, wherein the aspect ratio between the length and the maximum width of the chamber is at least 3:1.

[0170] Forming an actuator (18; 418; 618) may include forming the actuator in a base portion (22; 422); forming a chamber (17; 117; 217; 317; 417; 617) may include forming a chamber layer (14; 114; 414; 614) on the base portion, wherein the chamber covers the actuator, the base portion forms a first base (17A) of the chamber, and the chamber layer forms a sidewall of the chamber; and forming a plurality of nozzle holes (34; 134; 434; 623) may include forming a nozzle layer (15; 115; 215; 315; 415; 650) on the chamber layer and forming at least one opening that at least partially covers the chamber, the nozzle layer covering the chamber and forming a second base (17B) of the chamber.

[0171] Forming the chamber layer (114; 214; 314; 414) may include shaping the sidewalls (116; 216; 316; 416) to form a plurality of notches (131; 231; 331; 431) and protrusions (130; 230; 330; 430), and forming at least one opening includes forming a nozzle opening (132; 232; 332; 432) offset relative to the chamber and intersecting with the notches at the intersection region to form a nozzle orifice (34; 134; 434)).

[0172] Forming the chamber layers (414, 614) may include forming a first layer (460) on the substrate portion (422), the first layer defining a first chamber aperture (461); and forming a second layer (470) on the first layer, the second layer defining a second chamber aperture (471), the area of ​​the first chamber aperture being smaller than the area of ​​the second chamber aperture.

[0173] The chamber layer (14; 114; 214; 314; 414) and the nozzle layer (15; 115; 215; 315; 415) can be polymer layers.

[0174] Forming the nozzle layer may include forming a first opening (655) in a semiconductor wafer (700); forming a second opening (656) in the semiconductor wafer above the first opening, the second opening having an area larger than the first opening and extending to communicate with the first opening; bonding the semiconductor wafer (700) to a chamber layer (614), the second opening facing the chamber; and thinning the semiconductor wafer to expose the first opening.

[0175] The first opening portion (655) extends a portion of the thickness of the starting wafer (700) of the semiconductor material; after the first opening portion is formed, an etch stop layer (702) may be grown on the starting wafer, and a semiconductor layer (706) may be grown on the etch stop layer to form a semiconductor wafer (700), and a second opening portion is formed in the semiconductor layer; and thinning the semiconductor wafer may include removing the starting wafer up to the first opening portion.

[0176] The various embodiments described above can be combined to provide other embodiments. These and other changes can be made to the embodiments based on the detailed description above. Generally, the terminology used in the following claims should not be construed as limiting the claims to the specific embodiments disclosed in the specification and claims, but should be construed as including all possible embodiments and the full scope of equivalents to which such claims are entitled. Therefore, the claims are not limited by this disclosure.

Claims

1. A microfluidic device, comprising: Multiple chambers, each chamber having an elongated shape, having a length and a maximum width, wherein the aspect ratio between the length and the maximum width of the chamber is at least 3:1; The fluid inlet channel for each chamber is fluidly connected to the corresponding chamber. Multiple nozzle orifices for each chamber, fluidly connected to the corresponding chamber; as well as An actuator for each chamber is operatively coupled to the respective chamber and configured to eject droplets of fluid through the nozzle orifice under the operating conditions of the microfluidic device. A chamber layer, wherein the chamber layer forms the plurality of chambers; The nozzle layer includes at least one nozzle opening. Each chamber is defined by sidewalls with multiple notches and protrusions; and The nozzle opening is offset relative to the chamber, each nozzle opening extends between two adjacent chambers and intersects with the notches of the two adjacent chambers; The plurality of nozzle holes are formed in the region where the plurality of nozzle openings intersect with the plurality of notches.

2. The microfluidic device according to claim 1, wherein the chamber has a rectangular or elliptical base shape.

3. The microfluidic device of claim 1, wherein the chamber is defined by a first base, a second base, and a sidewall. The first base and the second base extend along a first direction and a second direction, respectively. The second direction is transverse to the first direction. The length and width of the chamber extend in the first direction and the second direction, respectively. The sidewall extends along a third direction, which is transverse to both the first and second directions. The height of the chamber extends upward from the third party.

4. The microfluidic device according to claim 3, wherein The chamber has a chamber volume, and The nozzle orifice is configured to generate multiple droplets with a total droplet volume during use, and The ratio of the total droplet volume to the chamber volume is at least 15%.

5. The microfluidic device according to claim 3, further comprising: Matrix portion; The nozzle layer, the substrate portion forming the first base and housing the actuator, the chamber layer forming the sidewall, and the nozzle layer forming the second base of the chamber.

6. The microfluidic device of claim 5, wherein the sidewall is formed with a plurality of notches and protrusions, and the at least one nozzle opening is offset relative to the chamber and overlaps with the notch at the intersection region forming the nozzle orifice.

7. The microfluidic device of claim 5, wherein the chamber layer comprises a first layer extending over the substrate portion and a second layer extending over the first layer, the first layer defining a lower chamber orifice, the second layer defining an upper chamber orifice, the area of ​​the lower chamber orifice being smaller than the area of ​​the upper chamber orifice.

8. The microfluidic device of claim 5, wherein the chamber layer and the nozzle layer are polymer layers.

9. The microfluidic device of claim 5, wherein the nozzle layer is a silicon wafer.

10. The microfluidic device of claim 8, wherein each nozzle orifice includes a larger cross-sectional portion facing the chamber and a smaller cross-sectional portion communicating with the larger cross-sectional portion and extending from the outer surface of the nozzle layer.

11. The microfluidic device of claim 10, wherein the nozzle orifice is arranged above the chamber as a nozzle.

12. A method for manufacturing a microfluidic device, comprising: Multiple chambers are formed, each chamber having an elongated shape, having a length and a maximum width, wherein the aspect ratio between the length and the maximum width of the chamber is at least 3:1; Forming fluid inlet channels for each chamber that are fluidly connected to the corresponding chambers; Multiple nozzle orifices are formed for each chamber, which are fluidly connected to the corresponding chamber. as well as An actuator is formed for each chamber, the actuator being operatively coupled to the corresponding chamber and configured to eject droplets of fluid through the nozzle orifice under the operating conditions of the microfluidic device. The formation of multiple chambers includes forming chamber layers and forming sidewalls for each chamber, the sidewalls defining each corresponding chamber and having multiple notches and protrusions. Forming multiple nozzle orifices includes forming a nozzle layer on the chamber layer and forming multiple nozzle openings in the nozzle layer; The nozzle opening is offset relative to the chamber, each nozzle opening extends between two adjacent chambers and intersects with the notches of the two adjacent chambers; The plurality of nozzle holes are formed in the region where the plurality of nozzle openings intersect with the plurality of notches.

13. The method according to claim 12, wherein: Forming the actuator includes forming the actuator in a base portion; Forming the chamber includes forming a chamber layer on the base portion, the chamber covering the actuator, the base portion forming a first base of the chamber, and the chamber layer forming a sidewall of the chamber; as well as Forming the plurality of nozzle orifices includes forming a nozzle layer on the chamber layer and forming at least one opening that at least partially covers the chamber, the nozzle layer covering the chamber and forming a second base of the chamber.

14. The method of claim 13, wherein forming the chamber layer comprises shaping the sidewall to form a plurality of notches and protrusions, and forming at least one opening comprises forming a nozzle opening offset relative to the chamber and overlapping the notches at an intersection region, thereby forming the nozzle orifice.

15. The method of claim 13, wherein forming the chamber layer comprises: A first layer is formed on the substrate portion, the first layer defining a first chamber orifice; A second layer is formed on the first layer, the second layer defining a second chamber orifice, the area of ​​the first chamber orifice being smaller than the area of ​​the second chamber orifice.

16. The method of claim 15, wherein the first and second layers of the chamber layer and the nozzle layer are polymer layers.

17. The method of claim 13, wherein forming the nozzle layer comprises: A first opening is formed in the semiconductor wafer; A second opening is formed above the first opening in the semiconductor wafer, the second opening having an area larger than the first opening and extending to connect with the first opening; The semiconductor wafer is bonded to the chamber layer, with the second opening portion facing the chamber; as well as The semiconductor wafer is thinned to expose the first opening portion.

18. The method of claim 17, wherein: The first opening extends a portion of the thickness of the starting wafer of the semiconductor material; After forming the first opening portion, an etch stop layer is grown on the starting wafer, and a semiconductor layer is grown on the etch stop layer to form the semiconductor wafer, and the second opening portion is formed in the semiconductor layer; as well as Thinning the semiconductor wafer includes removing the starting wafer up to the first opening portion.

19. A microfluidic device, comprising: Multiple chambers, the chambers having an elongated shape; Multiple fluid inlet channels are respectively fluidly connected to the multiple chambers; Multiple nozzle orifices are respectively fluidly connected to the multiple chambers; as well as Multiple actuators are operatively coupled to the multiple chambers and configured to eject droplets of fluid through the multiple nozzle orifices under the operating conditions of the microfluidic device; A chamber layer, wherein the chamber layer forms the plurality of chambers; A nozzle layer is provided on the chamber layer, the nozzle layer forming a plurality of nozzle openings. Each of the plurality of chambers is defined by a sidewall having multiple notches and protrusions; as well as The plurality of nozzle openings are offset relative to the plurality of chambers, and each of the plurality of nozzle openings extends between two adjacent chambers and intersects with the notches of the two adjacent chambers; The plurality of nozzle holes are formed in the region where the plurality of nozzle openings intersect with the plurality of notches.

20. The microfluidic device of claim 19, wherein each of the plurality of chambers has a rectangular or elliptical base shape.

21. The microfluidic device of claim 19, wherein each of the plurality of chambers is defined by a first base, a second base, and a sidewall. The first base and the second base extend along a first direction and a second direction, respectively. The second direction is transverse to the first direction. The length and width of each of the plurality of chambers extend in the first direction and the second direction, respectively. The sidewall extends along a third direction, which is transverse to both the first and second directions. The height of each of the plurality of chambers extends upward from the third.

22. The microfluidic device according to claim 21, wherein... Each of the plurality of chambers has a chamber volume, and The plurality of nozzle orifices are configured to generate, during use, a plurality of droplets having a total droplet volume, and The ratio of the total droplet volume to the chamber volume is at least 15%.

23. The microfluidic device according to claim 21, further comprising: The base portion forms the first base and houses the plurality of actuators, and the nozzle layer forms the second base.

24. The microfluidic device of claim 23, wherein the chamber layer comprises a first layer and a second layer extending on the first layer, the first layer defining a lower chamber orifice, the second layer defining an upper chamber orifice, the lower chamber orifice having a smaller area than the upper chamber orifice.

25. The microfluidic device of claim 24, wherein the first layer extends over the substrate portion.

26. The microfluidic device of claim 23, wherein the chamber layer and the nozzle layer are polymer layers, or the chamber layer is a polymer layer and the nozzle layer is a silicon wafer.

27. The microfluidic device of claim 19, wherein the plurality of actuators are heaters.

28. The microfluidic device of claim 19, wherein the plurality of nozzle openings have a larger area than the plurality of chambers.

29. The microfluidic device of claim 19, wherein the aspect ratio between the length and width of each of the plurality of chambers is at least 3:1.

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