Patent Grant
9174445
1. Technical Field
The present disclosure is directed to a microfluidic delivery system including a die having a plurality of heaters and a plurality of nozzles associated with the heaters, where an area of each heater is significantly larger than an area of each nozzle.
2. Description of the Related Art
Microfluidic die are utilized in printers for ejection of drops of ink onto paper. The die is positioned on an extended end of a cartridge that is separated from a main body that holds a reservoir of the ink. The extended end puts the die in close proximity to the paper to accurately expel the drop of ink to form a word or image on the paper.
The lower opening 19 covers a larger area than both the chamber 17 and the heater 23. The relationship between the heater's area and the upper nozzle area are such that drops of ink are consistently formed and dropped downward onto a printing material, such as paper.
The present disclosure is directed to a fluid delivery system that is configured to eject fluid vertically away from a thermal microfluidic die for use with scented oils or other fluids. The die includes a plurality of heaters formed in a substrate and a plurality of nozzles positioned above the heaters. Each heater is positioned below a chamber that is configured to hold, heat, and eject a fluid from the chamber through one of the nozzles. A ratio of an area of each heater to an area of an upper opening of each nozzle is significant, such as a greater than 5 to one ratio. This high ratio of each heater area to the upper opening of the nozzle is configured to eject the fluid vertically away from the system. In addition, this ratio aids in vaporizing the fluid sufficiently so that little or no fluid drips back down onto the die. This prevents the nozzles from being plugged by the fluid as it dries. In addition, this allows the die to deal with low vapor pressure fluids while maintaining consistent drop mass. This is achieved by increasing the energy, increasing the heater size and a ratio of the heater size to an exit area of the nozzle.
In the drawings, identical reference numbers identify similar elements. The sizes and relative positions of elements in the drawings are not necessarily drawn to scale.
In the following description, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the disclosure. However, one skilled in the art will understand that the disclosure may be practiced without these specific details. In other instances, well-known structures associated with electronic components and semiconductor fabrication have not been described in detail to avoid unnecessarily obscuring the descriptions of the embodiments of the present disclosure.
Unless the context requires otherwise, throughout the specification and claims that follow, the word “comprise” and variations thereof, such as “comprises” and “comprising,” are to be construed in an open, inclusive sense, that is, as “including, but not limited to.”
Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
As used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
As used in the specification and appended claims, the use of “correspond,” “corresponds,” and “corresponding” is intended to describe a ratio of or a similarity between referenced objects. The use of “correspond” or one of its forms should not be construed to mean the exact shape or size.
In the drawings, identical reference numbers identify similar elements or acts. The size and relative positions of elements in the drawings are not necessarily drawn to scale.
A dielectric layer separates the heater 1002 from the chamber 1004. As can be seen in
The heating system 1000 includes a funnel inlet path 1006 that is fed by a large inlet path 1008 through the die. Only an edge of the inlet path 1008 is shown because the figure includes only one heater and chamber. The relationship between the heaters, chambers, and the large inlet path will be described in more detail below. A plurality of columns 1010 are formed in the funnel inlet path 1006 and are configured to prevent large particles from blocking a neck portion 1012 of the inlet path. If a large particle blocks one side of the funnel inlet path, the other side of the inlet path will continue to allow fluid to pass, prolonging the life of this system. The fluid composition can change over time, such as if the fluid is a scented oil that includes ethanol for plume height. The ethanol may evaporate over time causing the fluid composition to change. The ethanol increases the vapor pressure, which in turn creates a more powerful ejection. These columns 1010 provide mechanical filtering to prolong the life of the system.
The heater 1002 is coupled to a power line 1014 and a ground line 1016. All of the heaters 1002 may share the same ground line, while each heater may have a separate power line. Alternatively, groups of heaters may be driven together with a single power line. Various methods of driving the heaters may be utilized.
In one embodiment, the heater 1002 is formed first and the power and ground lines are formed on top of the heater, making direct contact with a top surface of the heater. Alternatively, the heater may be formed after the power and ground lines are formed.
A relationship between a size of the nozzle to a size of the heater is configured to provide the versatility of ejecting any number of fluids from this heating system. In particular, a high ratio of a diameter 1018 of each nozzle 1005 to a length 1020 of each heater 1002 is particularly beneficial.
In this embodiment, the nozzle is a cylinder such that a first end that is closest to the heater and a second end that is further from the heater than the first end have the same diameter 1018. As will be described below, the first end may have a larger diameter than the second end.
Forming a high ratio of an area of the heater to the second end of the nozzle is also particularly beneficial. Various embodiments and ratios will be described below.
The heating system may be utilized in a thermal inkjet printing system that ejects ink downward and includes active circuitry in the same die as the heating system, or the heating system may be included in a vertically ejecting system, such as the system described with respect to
The heating system is configured to heat a very small amount of fluid that is contained in the chamber. The heater causes the fluid to boil, which generates a bubble. As the bubble collapses and explodes, the fluid is ejected from the nozzle. In order to achieve a variety of ejection techniques for a variety of fluids, the shape of the nozzle with respect to the heater can be selected to increase the ejection velocity. For example, higher heater to nozzle ratios allow the system to eject a plume of scented oils vertically. In prior art thermal inkjet systems one end of the nozzle is wider than the heater. These previous techniques did not allow for vertical ejection or ejection of different types of fluids, even compounds unknown by the manufacturer.
These high ratios of heater to nozzle area increase the pressure in the chamber, which allow for ejection of a variety of fluids. In particular, this ratio is particularly beneficial to ejection of oils mixed with ethanol or some other volatile fluid. This arrangement can eject drops of the oil, ethanol mixture upward in a manner that allows the ethanol to vaporize and allows the oil to move through the air. The fluid may be 90% oil and 10% ethanol. Using oil as the fluid to eject utilizes more heat because of the low vapor pressure of the oil in the chambers. Prior art systems are not able to eject oil effectively and may not even be able to form a bubble because of the low vapor pressure. By increasing a size of the heater and utilizing small nozzle exits, the present disclosure provides a successful ejection and consistent bubble formation in oil.
Access to the interior portion 22 of the housing is provided by an opening 28 in the body portion 18. The opening 28 is accessible by a cover or door 30 of the housing 12.
The holder 24 includes an upper surface 32 and a lower surface 34 that are coupled together by one or more sidewalls 36 and has an open side 38 through which the microfluidic refill cartridge 26 can slide in and out. The upper surface 32 of the holder 24 includes an opening 40 that is aligned with the first hole 20 of the housing 12.
The housing 12 may include external electrical connection elements for coupling with an external power source. The external electrical connection elements may be a plug configured to be plugged into an electrical outlet or battery terminals. Internal electrical connections couple the external electrical connection elements to the holder 24 to provide power to the microfluidic refill cartridge. The housing 12 may include a power switch 42 on a front of the housing 12.
The microfluidic refill cartridge 26 includes a reservoir 50 for holding a fluid 52, see
A microfluidic delivery member 64 is secured to an upper surface 66 of the lid 54 of the microfluidic refill cartridge 26. The microfluidic delivery member 64 includes an upper surface 68 and a lower surface 70 (see
The end 84 of the fluid transport member 80 is surrounded by a transport cover 86 that extends from the inner surface of the lid 54. The end 84 of the fluid transport member 80 and the transport cover 86 form a chamber 88. The chamber 88 may be substantially sealed between the transport cover 86 and the fluid transport member 80 to prevent air from the reservoir 50 from entering the chamber 88.
Above the chamber 88 is a first through hole 90 in the lid 54 that fluidly couples the chamber 88 above the end 84 of the fluid transport member 80 to the fluid path through the opening 78 of the microfluidic delivery member 64. The microfluidic delivery member 64 is secured to the lid 54 above the first through hole 90 of the lid, and receives fluid.
As is shown in
The upper and lower surfaces of the board may be coated with a solder mask 124a, 124b (collectively 124). Openings in the solder mask 124 may be provided where contact pads 112 of the die 92 are positioned on the circuit board 106 or at the first end 72 where the contacts 74 are formed. The solder mask 124 may be used as a protective layer to cover electrical connections (not shown) carried by the board 106 that couple the contact pads 112 of the die 92 to the electrical contacts 74, which couple the contact pads 112 to the external power source.
The printed circuit board 106 (PCB) is a rigid planar circuit board, having the upper and lower surfaces 68, 70. The circuit board 106 includes one or more layers of insulative and conductive materials. In one embodiment, the substrate 107 includes a FR4 PCB 106, a composite material composed of woven fiberglass with an epoxy resin binder that is flame resistant. In other embodiments, the substrate 107 includes ceramic, glass or plastic.
The circuit board 106 includes all electrical connections on the upper surface 68 of the board 106. For example, a top surface 144 of the electrical contacts 74 that couple to the housing are parallel to an x-y plane. The upper surface 68 of the board 106 is also parallel to the x-y plane. In addition, a top surface 146 of a nozzle plate 132 of the die 92 is also parallel to the x-y plane. The contact pads 112 also have a top surface that is parallel to the x-y plane. By forming each of these features to be in parallel planes, the complexity of the board 106 is reduced and is easier to manufacture. In addition, this allows nozzles 130 to eject the fluid vertically (directly up or at an angle) away from the housing, such as could be used for spraying scented oils into a room as air freshener. This arrangement could create a scented plume 5-10 cm high.
The board 106 includes the electrical contacts at the first end and contact pads 112 at the end proximate the die 92. Electrical traces from the contact pads 112 to the electrical contacts are formed on the board and may be covered by the solder mask or another dielectric.
On the lower surface of the board, the filter 96 may be provided to separate the opening 78 of the board 106 from the chamber 88 at the lower surface of the PCB. The filter 96 is configured to prevent at least some of the particles from passing through the opening to prevent clogging of the nozzles 130 of the die 92. In some embodiments, the filter 96 is configured to block particles that are greater than one third of the diameter of the nozzles 130. It is to be appreciated that in some embodiments, the fluid transport member 80 can act as a suitable filter 96, so that a separate filter 96 is not needed. The filter 96 is attached to the bottom surface with adhesive material 98. The adhesive material 98 may be an adhesive material that does not readily dissolve by the fluid in the reservoir 50.
The opening 78 may be formed as an oval, as is illustrated in 7C; however, other shapes are contemplated depending on the application. The opening 78 exposes sidewalls 102 of the board 106. If the board 106 is an FR4 PCB, the bundles of fibers would be exposed by the opening. These sidewalls are susceptible to fluid and thus a liner 100 is included to cover and protect these sidewalls. If fluid enters the sidewalls, the board could begin to deteriorate, cutting short the life span of this product.
The liner 100 is configured to protect the board from all fluids that an end user may select to eject through the die 92. For example, if the die 92 is used to eject scented oils from the housing, the liner 100 is configured to protect the sidewalls of the board 106 from any damage that could be caused by the scented oils. The liner 100 prolongs the life of the board 106 so that an end user can reuse the housing and the die 92 again and again with refillable or replaceable fluid cartridges.
These oils have different chemical properties than typical ink used with inkjet printers. Accordingly, the prior inkjet print heads used very expensive, very specific materials to prevent the ink from damaging the components that support the ink ejection process, such as the reservoir 50. In the present disclosure, common materials, such as an FR4 board, can be utilized to create a sophisticated, but cost effective system. The liner 100 provides a protective coating to allow the cost effective FR4 board to be utilized in this system. In one embodiment, the liner is gold, however, in other embodiments the liner may be silicon nitride, other oxides, silicon carbide, other metals, such as tantalum or aluminum, or a plastic, such as PET.
A second mechanical spacer 104 separates a bottom surface 108 of the die 92 from the upper surface 68 of the printed circuit board 106. An encapsulant 116 covers the contact pads 112 and leads 110, while leaving a central portion 114 of the die exposed.
The die 92 includes a plurality of electrical connection leads that extend from one of the intermediate dielectric layers 109 down to the contact pads 112 on the circuit board 106. Each lead couples to a single contact pad. Openings 150 on the left and right side of the die provide access to the intermediate layers 109 to which the leads are coupled. The openings 150 pass through the nozzle plate 132 and chamber layer 148 to expose contact pads 152 that are formed on the intermediate dielectric layers. In other embodiments that will be described below, there may be one opening 150 positioned on only one side of the die such that all of the leads that extend from the die extend from one side while the other side remains unencumbered by the leads.
In the illustrated embodiment, there are eighteen nozzles 130 through the nozzle plate 132—nine nozzles on each side of a center line.
The die 92 includes an inlet path 94 that passes completely through the substrate 107 and interacts with the chamber layer 148 and the nozzle plate 132. The inlet path 94 is a rectangular opening; however, other shapes may be utilized according to the flow path constraints. The inlet path 94 is in fluid communication with the fluid path that passes through the opening 78 of the board 106.
The inlet path 94 is coupled to a channel 126 (see
Proximate each nozzle chamber is a heater 134 (see
In one embodiment, it is preferable to have a resistance of each heater be significantly larger than a parasitic resistance of the first and second contacts. For example, the heater may have a resistance of 60 ohms and the parasitic resistance of the contacts will be 10 ohms. To achieve this, the contacts may be made wider. The traces, pads, and contacts can be made wider to reduce the resistance.
In use, when the fluid in each of the chambers 128 is heated by the heater 134, the fluid vaporizes to create a bubble. The expansion that creates the bubble causes fluid to eject from the nozzle 130 and to form a drop or droplet.
The chamber layer 148 defines angled funnel paths 160 that feed the fluid from the channel 126 into the chamber 128. The chamber layer 148 is positioned on top of the intermediate dielectric layers 109. The chamber layer defines the boundaries of the channels and the plurality of chambers associated with each nozzle. In one embodiment, the chamber layer is formed separately in a mold and then attached to the substrate. In other embodiments, the chamber layer is formed by depositing, masking, and etching layers on top of the substrate.
The intermediate layers 109 include a first dielectric layer 162 and a second dielectric layer 164. The first and second dielectric layers are between the nozzle plate and the substrate. The first dielectric layer 162 covers the plurality of first and second contacts 154, 156 formed on the substrate, and covers the heaters 134 associated with each chamber. The second dielectric layer 164 covers the conductive traces 155.
As mentioned above, it is beneficial to make sidewalls 135 of each chamber wider than edges 137 of each heater 134 to prevent delamination of the chamber layer 148 from the dielectric layer 164.
In this embodiment, the nozzles 130 are cylindrical in that a first end 141 and a second end 143 have a same diameter 145. The first end is the input end of the nozzle such that the second end is where a drop is ejected. A ratio of an area of the heater 134 to an area of the nozzle is significant, such as greater than seven to one. In one embodiment, the heater is square, with each side having a length 147. The length may be 47 microns, 51 microns, or 71 microns. This would have an area of 2209, 2601, or 5041 microns square, respectively. If the nozzle diameter is 20 microns, an area at the second end would be 314 microns square, giving an approximate ratio of 7 to 1, 8 to 1, or 16 to 1, respectively.
In one embodiment, the heater is a 20-nanometer thick tantalum aluminum layer. In another embodiment, the heater may include chromium silicon films, each having different percentages of chromium and silicon and each being 10 nanometers thick. Other materials for the heaters may include tantalum silicon nitride and tungsten silicon nitride. The heaters may also include a 30-nanometer cap of silicon nitride. In an alternative embodiment, the heaters may be formed by depositing multiple thin film layers in succession. A stack of thin film layers combine the elementary properties of the individual layers. In a preferred embodiment, the heater may be 1000 Angstroms thick. A 2000 Angstrom layer of tantalum may be over the heater and a 3000 Angstrom layer of dielectric may be over the tantalum.
The first contact 154 provides power, while the second contact 156 is coupled to ground 158a, 158b. As noted above, each of the heaters 134 on one side of the die are coupled to the same ground line 158a, 158b. Alternatively, each of the heaters 134 on the die may be coupled to a single ground line to reduce the number of contact pads 152 on the die.
The first dielectric layer 162 covers the heaters and the contacts, and the second dielectric layer 164 covers the first dielectric layer 162. The second dielectric layer 164 forms a bottom surface of the chamber 128. The thickness of the second dielectric layer 164 may be quite small to reduce a distance between the heater 134 and the chamber. The second dielectric layer may be silicon nitride.
As can be seen in these figures, the die 92 is relatively simple and does not include complex integrated circuitry. This die 92 can be controlled and driven by an external microcontroller or microprocessor. The external microcontroller or microprocessor may be provided in the housing. This allows the board 64 and the die 92 to be simplified and cost effective.
In one embodiment, the die 92 includes active circuitry including transistors, resistors, capacitors, and other features that are configured to drive the heaters and eject fluid out of the nozzles. In other embodiments, the die 92 does not include any active circuitry and only includes electrical connections to the heaters. This other embodiment will be controlled and driven by a controller that is spaced from the die and is also spaced from the board 106.
In
In this embodiment, there is a ground line 158a, 158b associated with each side of the die 92. Although there are two separate contacts 74b, 74c coupled to each ground line 158a, 158b, respectively, these two contacts could be a single contact. The total number of contacts 74 could be reduced to seven. It is to be understood that any number of nozzles and heaters could be driven together based on the voltage limitations of the system. As will be discussed in more detail below, dimensions of the board can be significantly reduced by reducing the number of contacts 74 that are included.
In an alternative embodiment, the leads 110 extending from the die 92 may extend from a smaller side 93 of the die. The contact pads 112 would then be positioned between the opening 78 and the contacts 74. The traces that couple the contact pads 112 to the contacts 74 would then use less material and could allow the board to have a smaller width.
The microfluidic delivery system 64 can be utilized in a variety of new environments, such as for ejecting scented oils vertically from the die. They may also be used in the medical field to vaporize medicine for a patient to inhale. Using the proposed microfluidic delivery system as described herein can give the patient or physician precise control over the rate and time of the dosage. For example, the physician could program the system 300 to vaporize the medicine for 20-second bursts spaced by 60 seconds without medicine for a period of time. Further, two or more die can be mounted side-by-side to deliver two or more different types of vapors to a patient using the same electronic controls.
In one embodiment, each heater will use around 150-200 milliamps. The current for five heaters may be around 750 milliamps-1 amp. These groups of five heaters may be fired in sequence at 5 khz per group.
In an alternative embodiment, the controller may fire groups of three consecutively so that a maximum amount of current can be sent to each group. This also allows the chambers of a recently fired group to refill and be ready to eject when the pulse returns to that group of three nozzles. In one embodiment, the controller will output a two-microsecond pulse of 10 volts to a first one of the power delivering contacts. Then, the controller will output a two-microsecond pulse to a second one of the power delivering contacts, and so forth, until the controller returns to the first one of the power delivering contacts. This configuration will eject three drops for every two-microsecond pulse. The number of nozzles that can be driven in parallel can vary and is limited by the power supply of the system.
An edge 1080 of a chamber 1082 extends past a first side 1084 and a second side 1086 of the heater. A third side and a fourth side of the heater are coplanar with edges 1088 of the chamber.
This embodiment has a long narrow neck 1090 that couples the chamber 1082 to an inlet path 1092 through the die. The inlet path 1092 feeds a channel 1094, which feeds fluid to the neck. A plurality of columns 1096 may be in the channel or the neck to filter out larger particles that may be in the fluid. A size and shape of the neck affects blowback caused by the bursting bubble. Blowback affects how quickly the chamber can refill. If there is significant blowback, it will take more time to push more fluid form the inlet path into the neck and back into the chamber.
Each of the heaters are configured to have a high ratio of area with respect to an area of an associated nozzle. The fluid moves through the inlet path 602 to a channel region 612, through a funnel region 614, into a narrow flow path 616, and then into the chamber 604. The flow path 616 is narrower in width than the chamber and narrower than a widest part of the funnel region 614.
Each of the heaters 606 are coupled to power lines 608 and a ground line 610. Each of the heaters 606 share the same ground line 610, which overlaps the narrow flow path 616 that leads to the chambers. In this embodiment, there is one contact 618 for ground. There are ten power contacts 620. There are twenty heaters 606, which are each associated with a nozzle (not shown). Each heater is paired with an adjacent heater and coupled to one of the power lines 608. This way pairs of heaters are driven at the same time by a single power contact 620. In an alternative embodiment, the uncoupled contact pad may be a second ground contact.
This die may be coupled to a circuit board, such as the boards described above. It is possible that two of the power contacts 620, and thus four heaters, may be coupled to a single contact pad of the board. Accordingly, four heaters would be driven at the same time and four drops would be ejected at the same time.
A thermal sense resistor 622 may be included around an edge of the die 600 and may be coupled to a pair of contact pads 624. The thermal sense resistor may be configured to calculate a temperature of the die during use. The thermal sense resistor may use a common ground with the rest of the die, however, that creates more noise on the signal that is sensed. The sense resistor is read between firing pulses so there is no overlap of signals. The sense resistor is generally run as a serpentine to increase the number of squares and therefore increase the sensitivity of the measurement.
The heating system 502 also includes a plurality of heaters 508. A nozzle 510 is shown positioned centrally with respect to the heater; however, the nozzle is simply a reference of the nozzle position. The actual nozzles are not shown because no nozzle plate is included in this view. The nozzle plate has been omitted so that the single metal level is visible without overlapping features from the chambers and nozzles.
Each heater 508 includes an input contact 512 and an output contact 514. All of the output contacts 514 are coupled together and are coupled to a single ground trace 516. The single ground trace 516 is positioned between the heaters 508 and the inlet path 506. The ground trace 516 extends along a first edge 518 of the die.
A ratio of an area of each heater to an area of each nozzle is sufficiently high to allow an end user to eject a fluid in a variety of configurations. The plurality of heaters are driven in groups of five such that there are four input traces 520a, 520b, 520c, 520d. The input traces 520c and 520d extend along a second edge 522 of the die.
In one embodiment, the ground trace 516 may be positioned directly under the funnel paths 160 that feed the chamber. There may be an extended flow path between the funnel path and the chamber. For example, in
In some embodiments, this system may be configured to eject a fluid that has been mixed with ethanol or some other volatile additive. The ethanol helps each drop to evaporate as it moves vertically away from the die once ejected. This also prevents the fluid from falling back onto a top surface of the die and clogging the nozzles. If the ethanol is mixed with a scented oil, the scented oil is released into the air when the ethanol evaporates. By ejecting multiple drops at the same time, the evaporation of the drops can extend a height of a plume formed from the drops. A single ejected drop will have a much smaller plume than a plurality of drops ejected together.
The various embodiments described above can be combined to provide further embodiments. All of the U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet are incorporated herein by reference, in their entirety. Aspects of the embodiments can be modified, if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.
These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.
| Number | Name | Date | Kind |
|---|---|---|---|
| 6209203 | Murthy et al. | Apr 2001 | B1 |
| 8096643 | Olbrich et al. | Jan 2012 | B2 |
