WO2023052904A1 - Ultrasonic dispensing device - Google Patents

Abstract

A dispensing device includes an ultrasonic horn arranged to provide ultrasound to a liquid. The ultrasonic horn includes a first housing portion comprising an inlet configured to receive the liquid. A second housing portion includes an outlet and is configured to discharge the liquid. A passageway through the first and second portions fluidically connects the inlet and the outlet. A coupling is configured to removeably couple the first portion to the second portion.

Description

ULTRASONIC DISPENSING DEVICE

BACKGROUND

Systems for dispensing liquids such as adhesives typically include an inlet and an output or tip through which liquid is dispensed to a surface. Any liquid handling device is subject to cavitation that involves formation of vapor phase in a liquid. Cavitation can occur because of the rapid or explosive growth of small bubbles or nuclei that have become unstable due to change in ambient pressure. These nuclei are either trapped in the flow or are formed due to small cracks, sharp geometry features or crevices at the bounding surfaces. The tension a fluid can sustain before cavitating depends upon the size of these nuclei.

Gases in a solution can play a role in cavitation. The size and the number of nuclei in the flow is related to the concentration of the dissolved gas. Under some conditions cavitation occurs when the lowest pressure in the flow is substantially higher than vapor pressure. In this case the bubble growth would be due to diffusion of dissolved gas across the bubble wall. Particularly in micro-dispensing applications, air bubbles are detrimental as they cause voids in the liquid and part quality issues.

SUMMARY OF THE DISCLOSURE

Embodiments described herein involve a dispensing device comprising an ultrasonic horn arranged to provide ultrasound to a liquid. The ultrasonic horn comprises a first housing portion comprising an inlet configured to receive the liquid and a second housing portion comprising an outlet configured to discharge the liquid. A passageway through the first and second portions fluidically connects the inlet and the outlet. A coupling is configured to removeably couple the first portion to the second portion.

Embodiments described herein involve a bubble mitigation device comprising a housing, an ultrasonic horn, and a longitudinal opening extending along a longitudinal axis of the housing. The opening is dimensioned to receive and removeably retain a liquid dispensing syringe within the opening.

Embodiments described herein involve a dispensing device comprising an inlet configured to receive a liquid and an outlet configured to discharge the liquid. A passageway is coupled to allow the liquid to flow between the inlet and the outlet. A bubble removal port is configured to allow bubbles in the liquid to exit the passageway. An ultrasonic horn is configured to direct ultrasound to the passageway. The ultrasound has a frequency and amplitude sufficient to displace the bubbles in the liquid to the port.

Embodiments described herein involve a system comprising an ultrasonic horn arranged to provide ultrasound to a liquid. The ultrasonic horn comprises a first housing portion comprising an inlet configured to receive the liquid and a second housing portion comprising an outlet configured to discharge the liquid. A passageway through the first and second portions fluidically connects the inlet and the outlet. A coupling is configured to removeably couple the first portion to the second portion. An ultrasonic controller is configured to control the ultrasonic horn to direct ultrasonic energy sufficient to mitigate bubbles in the liquid to passageway.

Embodiments described herein involve a method of dispensing a liquid from a dispensing device. The liquid is received into a passageway through an inlet of the dispensing device. Ultrasound is directed toward the liquid, the ultrasound having frequency and amplitude sufficient to mitigate bubbles in the liquid. The liquid is dispensed from the passageway through an outlet of the dispensing device.

Any of the elements that are positively recited in this specification as alternatives may be explicitly included in the claims or excluded from the claims, in any combination as desired. Although various theories and possible mechanisms may have been discussed herein, in no event should such discussions serve to limit the claimable subject matter.

BRIEF DESCRIPTION OF FIGURES

FIG. 1A is a perspective view of a dispensing device in accordance with some embodiments;

FIGS. IB and 1C are cross sectional views of the dispensing device of FIG. 1A;

FIG. ID illustrates an ultrasonic bubble mitigation device that may be used in conjunction with a system using a two-part adhesive in accordance with some embodiments;

FIG. 2 is a perspective view of the first portion of a dispensing device in accordance with some embodiments;

FIG. 3 is a perspective view of the second portion of a dispensing device in accordance with some embodiments;

FIG. 4A shows a side view of the first portion shown in FIG. 2;

FIG 4B shows a cross sectional view of the first portion shown in FIG. 2;

FIG. 5 A shows a side view of the second portion shown in FIG. 3;

FIG 5B shows a cross sectional view of the second portion shown in FIG. 3;

FIG. 6 depicts an ultrasonic dispensing device that can be used in retrofit applications in accordance with some embodiments;

FIG. 7 illustrates an ultrasonic dispensing device having a cylindrical housing in accordance with some embodiments;

FIG. 8 depicts an ultrasonic dispensing device comprising an ultrasonic horn proximate to the dispensing end of the housing in accordance with some embodiments;

FIG. 9 is a cross sectional side view of an ultrasonic dispensing device having wherein the housing and the ultrasonic horn are concentric cylinders in accordance with some embodiments;

FIG. 10 is a cross sectional side view of an ultrasonic dispensing device wherein the ultrasonic horn is disposed on only one side of the housing in accordance with some embodiments; FIGS. 11 and 12 are cross sectional side views of ultrasonic dispensing devices wherein the ultrasonic horn is located proximate the outlet of the dispensing device in accordance with some embodiments;

FIG. 13 is a block diagram of a liquid dispensing system in accordance with some embodiments;

FIG. 14 is a block diagram showing component of the ultrasonic controller of FIG. 13;

FIG. 15 illustrates a subsystem comprising components of the ultrasonic controller of FIG. 14 mechanically coupled together; and

FIG. 16 is a flow diagram illustrating an ultrasonic dispensing process in accordance with some embodiments.

The figures are not necessarily to scale. Like numbers used in the figures refer to like components. However, it will be understood that the use of a number to refer to a component in a given figure is not intended to limit the component in another figure labeled with the same number.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Embodiments described herein are directed to dispensing devices, dispensing systems, and dispensing methods. The devices, systems, and methods involve exposure of liquids to ultrasonic energy (ultrasound) before, during, and/or after the liquids are dispensed. Exposure of liquids to ultrasound can enhance the dispensing flowrate of the liquids and/or enhance mitigation of bubbles in the liquids.

Bubbles in the liquid are generally detrimental leading to part quality issues and/or production down time for cleaning and/or restarting the system. Exposure to ultrasound can lower the apparent viscosity of the liquid around the bubble facilitating movement of the bubble to a point of extraction, such as an extraction port. Using the ultrasonic bubble mitigation approaches described herein, bubbles can be broken, coalesced, and/or agglomerated and extracted from the system to enhance dispense quality. According to some implementations, the dispensing device includes a bubble extraction port.

Flowrate during dispensing of high viscosity liquids, such as adhesives, can be limited due to the small micro-needles that are conventionally used for laying down small beads for small parts bonding. Exposing the liquid in the passageway to ultrasound can decrease the apparent viscosity of the liquid resulting in an increase in liquid flowrate during dispensing. This process is referred to herein as ultrasonic perturbation dispensing (UPD). Various embodiments are directed to UPD employed to enhance dispensing viscous materials with or without concurrent bubble mitigation.

Many conventional dispensing devices are made of plastics that dampen ultrasound. In some embodiments discussed below, liquid dispensers are made of rigid materials such as metal, glass, and/or other materials that enhance transmission of ultrasound as through the walls of the dispensing device. The ultrasound can be directed to the liquid anywhere along the passageway of the dispensing device containing the liquid. In some embodiments, the liquid is exposed to ultrasound just before or just after the liquid exits the outlet of the dispensing device. For example, some embodiments are directed to a dispensing device configured to expose the liquid to ultrasound just after the liquid exits the outlet of the device and before the liquid wets out on the substrate upon which it is dispensed.

FIGS. 1 through 12 illustrate ultrasonic dispensing devices 100 - 1200 in accordance with various embodiments. Each of the example dispensing devices 100 - 1200 can be used with a manual or automatically activated dispense mechanism that forces the liquid out of the outlet as described in more detail below. Dispensing devices 100 - 1200 can be used to effect bubble mitigation and or UPD.

FIG. 1A is a perspective view and FIGS. IB and 1C are cross sectional views of a dispensing device 100 in accordance with some embodiments. Device 100 comprises a first housing portion 110 that includes an inlet 111 arranged to receive the liquid to be dispensed. The second housing portion 120 includes an outlet 121 configured for dispensing the liquid. A passageway 140 through the first and second portions 110, 120 fluidically connects the inlet 111 and the outlet 121. Liquid entering the inlet 111 travels through the passageway 140 to the outlet 121 and is dispensed onto a substrate. In the configuration shown in FIG. 1A and IB, the device 100 is an ultrasonic horn and is arranged to produce ultrasonic energy (ultrasound). In various embodiments, the ultrasound is directed toward passageway 140 while the liquid is within the passageway 140 and/or while the liquid is traversing the passageway 140. In some embodiments, the energy, frequency, and/or amplitude of the ultrasound can be selected to mitigate bubbles in the liquid. Alternatively or additionally, the energy, frequency, and/or amplitude of the ultrasound can be selected so that the ultrasound lowers the viscosity of the liquid to facilitate ultrasonic perturbation dispensing.

The dispensing device can be operated to expose the liquid to the ultrasound before, during, and/or after the liquid is dispensed. For example, in one embodiment, the liquid in the passageway is exposed to the ultrasound for several minutes before the liquid is dispensed through the outlet. In some embodiments, liquid in the passageway is exposed to the ultrasound continuously or intermittently while the liquid is exiting the device through the outlet. In some embodiments, liquid is exposed to the ultrasound just after the liquid exits the outlet and before it wets out on the substrate.

The ultrasound emitted by the device 100 may mitigate bubbles by breaking bubbles into smaller bubbles. Alternatively or additionally, the ultrasound mitigates bubbles in the liquid by moving the bubbles to one or more ports 112, 114 where the bubbles are extracted from the liquid. The ultrasound may cause bubbles to agglomerate into a mass of bubbles or coalesce into larger bubbles as they move to the port 112, 114. The ultrasound can lower the viscosity of the liquid near the bubbles which facilitates moving and/or extracting bubbles from the liquid. According to some implementations, the port(s) 112 may comprise a vacuum fitting 113 that can be coupled to a vacuum pump operated to facilitate extraction of the bubbles. To prevent liquid being pulled out while bubbles are extracted, an air permeable membrane can be utilized. The amount of pressure to extract bubbles can be minimal.

FIGS. IB and 1C illustrate different locations for the one or more ports 112, 114. The one or more ports 112, 114 may be disposed in the first portion 110, the second portion 120, or both the first 110 and the second 120 portions. In some cases, at least one port is disposed on a same side as the inlet 111.

In general, the liquid can be any type of liquid. In many implementations, the liquid being dispensed comprises a structural adhesive. Generally, structural adhesives may be divided into two broad categories: one-part adhesives and two-part adhesives. With a one-part adhesive, a single composition comprises all the materials necessary to obtain a final cured adhesive. Such adhesives are typically applied to the substrates to be bonded and exposed to elevated temperatures (e.g., temperatures greater than 50° C.) to cure the adhesive. In contrast, two-part adhesives comprise two components. The first component, typically referred to as the “base resin component,” comprises the curable resin. The second component, typically referred to as the “accelerator component,” comprises the curing agent(s) and catalysts. Various other additives may be included in one or both components.

According to various embodiments described herein, the ultrasonic bubble mitigation device may be used in conjunction with a system using a two-part adhesive as shown in the example of FIG. ID. The two-part adhesive system includes a dispensing plunger 190, an adhesive cartridge 180, and a static mixing nozzle 175 configured to mix the two-part adhesive upon the activation of the dispensing plunger 190. The static mixing nozzle 175 is coupled to the ultrasonic bubble mitigation device 100 by a threaded luer lock 170 that coupled to the inlet 111.

Adhesives

Adhesives that are suitable to be dispensed using the approaches discussed herein include but are not limited to hot melt adhesives, epoxy adhesives, methyl methacrylates (MMA) adhesives, silicone adhesives, pressure sensitive adhesives, and urethane adhesives

Other adhesives used herein can include hot melt adhesives, for example one -component, moisture-curing hot melt adhesives. This product group is characterized by a very high heat resistance compared to classic, thermoplastic PO hot melts. In some examples, polyurethane (PUR) hot melts that contain isocyanates for the chemical crosslinking process are used. In other examples, polyolefin (POR) hot melts that use silanes as the reactive component are used herein. Two component adhesives are 100% solids systems that obtain their storage stability by separating the reactive components. They are supplied as “resin” and “hardener” in separate containers. It is important to maintain the prescribed ratio of the resin and hardener to obtain the desired cure and physical properties of the adhesive. The two components are only mixed to form the adhesive a short time before application with cure occurring at room temperature. Since the reaction typically begins immediately upon mixing the two components, the viscosity of the mixed adhesive increases with time until the adhesive can no longer be applied to the substrate or bond strength is decreased due to diminished wetting of the substrate. Formulations are available with a variety of cure speeds providing various working times (work life) after mixing and rates of strength build-up after bonding. Final strength is reached in minutes to weeks after bonding depending on the formulation. Adhesive must be cleaned from mixing and application equipment before cure has progressed to the point where the adhesive is no longer soluble. Depending on work life, two component adhesives can be applied by trowel, bead or ribbon, spray, or roller. Assemblies are usually fixtured until sufficient strength is obtained to allow further processing. If faster rate of cure (strength build-up) is desired, heat can be used to accelerate the cure. This is particularly useful when parts need to be processed more quickly after bonding or additional work life is needed but a slower rate of strength build-up cannot be accommodated. When cured, two component adhesives are typically tough and rigid with good temperature and chemical resistance.

Two component adhesives can be mixed and applied by hand for small applications. However, this requires considerable care to ensure proper ratio of the components and sufficient mixing to insure proper cure and performance. There is usually considerable waste involved in hand mixing as well. As a result, adhesive suppliers have developed packaging that allows the components to remain separate for storage and provides a means for dispensing mixed adhesive, e.g., side-by-side syringes, concentric cartridges. The package is typically inserted into an applicator handle and the adhesive is dispensed through a disposable mixing nozzle. The proper ratio of components is maintained by virtue of the design of the package and proper mixing is insured by use of the mixing nozzle. Adhesive can be dispensed from these packages multiple times provided the time between uses does not exceed the work life of the adhesive. If the work life is exceeded, a new mixing nozzle must be used. For larger applications, meter-mix equipment is available to meter, mix, and dispense adhesive packaged in containers ranging from quarts to drums.

Two-part adhesives consist of a resin and a hardener component which cure once the two components are mixed. They remain stable in storage if the two components are separate from each other. Two-part adhesives are typically designed to be dispensed in a set ratio to gain the desired properties from the specifically formulated adhesive; common ratios include, 10: 1, 1: 1, 2: 1 and so on. The reaction between the two components normally begins immediately once they are mixed and the viscosity increases until they are no longer usable. This can be described as work life, open time, and pot life, as discussed above. Once cured, two component adhesives are tough and rigid with good temperature and chemical resistance.

Epoxy Adhesives

As described earlier herein, epoxy adhesives of example embodiments can include one-part and two-part adhesives. One-part epoxy adhesives can include a resin. Like their one-part cousins, two-part epoxies are also formulated from epoxy resins. Two-part epoxies are widely used in structural applications and are used to bond many materials including, for example: metal, plastic, fiber reinforced plastics (FRP), glass and some rubbers. They are generally fast to cure and provide a relatively rigid bond. Some compositions can often be brittle although toughening agents and elastomers can be utilized to reduce this tendency. Two-part structural epoxy adhesives are made up of a Resin (Part A or Part 1) and Hardener (Part B or Part 2). An accelerator or chemical catalyst can speed up the reaction between the resin and hardener.

A two-part epoxy can cure at room temperature, so heat is not necessarily required when using one. Two-part epoxies generally achieve handling strength anywhere between five minutes and eight hours after mixing, depending on the curing agents. A chemical catalyst or heat can be applied to speed the reaction between the resin and hardener.

The resin that is the basis for all epoxy is the diglycidyl ether of bisphenol A (DGEBA). Bisphenol A is produced by reacting phenol with acetone under suitable conditions. The "A" stands for acetone, "phenyl" means phenol groups and "bis" means two. Thus, bisphenol A is the product made from chemically combining two phenols with one acetone. Unreacted acetone and phenol are stripped from the bisphenol A, which is then reacted with a material called epichlorohydrin. This reaction sticks the two ("di") glycidyl groups on ends of the bisphenol A molecule. The resultant product is the diglycidyl ether of bisphenol A, or the basic epoxy resin. It is these glycidyl groups that react with the amine hydrogen atoms on hardeners to produce the cured epoxy resin. Unmodified liquid epoxy resin is very viscous and unsuitable for most uses except as a very thick glue.

Chemical raw materials used to manufacture curing agents, or hardeners, for room- temperature cured epoxy resins are most commonly polyamines. They are organic molecules containing two or more amine groups. Amine groups are not unlike ammonia in structure except that they are attached to organic molecules. Eike ammonia, amines are strongly alkaline. Because of this similarity, epoxy resin hardeners often have an ammonia-like odor, most notable in the air space in containers right after they are opened. Epoxy hardeners are commonly referred to as "Part B".

Reactive amine groups are nitrogen atoms with one or two hydrogen atoms attached to the nitrogen. These hydrogen atoms react with oxygen atoms from glycidyl groups on the epoxy to form the cured resin - a highly crosslinked thermoset plastic. Heat will soften, but not melt, a cured epoxy. The three-dimensional structure gives the cured resin excellent physical properties.

The ratio of the glycidyl oxygens to the amine hydrogens, considering the various molecular weights and densities involved, determines the final resin to hardener ratio. The proper ratio produces a "fully-crosslinked" thermoset plastic. Varying the recommended ratio will leave either unreacted oxygen or hydrogen atoms depending upon which is in excess. The resultant cured resin will have lower strength, as it is not as completely crosslinked. Excess Part B results in an increase in moisture sensitivity in the cured epoxy and generally should be avoided.

Amine hardeners are not "catalysts". Catalysts promote reactions but do not chemically become a part of the finished product. Amine hardeners mate with the epoxy resin, greatly contributing to the ultimate properties of the cured system. Cure time of an epoxy system is dependent upon the reactivity of the amine hydrogen atoms. While the attached organic molecule takes no direct part in the chemical reaction, it does influence how readily the amine hydrogen atoms leave the nitrogen and react with the glycidyl oxygen atom. Thus, cure time is set by the kinetics of the particular amine used in the hardener. Cure time for any given epoxy system can only be altered by adding an accelerator in systems that can accommodate one, or by changing the temperature and mass of the resin/hardener mix. Adding more hardener will not "speed things up" and adding less will not "slow things down.”

The epoxy curing reaction is exothermic. The rate at which an epoxy resin cures is dependent upon the curing temperature. The warmer it is the faster it goes. The cure rate will vary by about half or double with each 18°F (10°C) change in temperature. For example, if an epoxy system takes 3 hours to become tack free at 70°F (about 21.1 °C), it will be tack free in 1.5 hours at 88°F (about 31.1°C) or tack free in 6 hours at 52°F (about 11. 1°C). Everything to do with the speed of the reaction follows this general rule. Pot life and working time are greatly influenced by the initial temperature of the mixed resin and hardener. On a hot day for example, the two materials can be cooled before mixing to increase the working time.

The gel time of the resin is the time it takes for a given mass held in a compact volume to solidify. Gel time depends on the initial temperature of the mass and follows the above rule. One hundred grams (about three fluid ounces) of Silver Tip Laminating Epoxy with Fast Hardener (as an illustrative example) will solidify in 25 minutes starting at 77°F (about 25°C); at 60°F (about 15.6°C) the gel time is about 50 minutes. If the same mass were spread over 4 square feet at 77°F (about 25°C) the gel time would be a little over three hours. Cure time is surface area/mass sensitive in addition to being temperature sensitive.

As the reaction proceeds it gives off heat. If the heat generated is immediately dissipated to the environment (as occurs in thin fdms) the temperature of the curing resin does not rise and the reaction speed proceeds at a uniform pace. If the resin is confined (as in a mixing pot) the exothermic reaction raises the temperature of the mixture, accelerating the reaction.

Working time or work life (WL) of an epoxy formulation is about 75% of the gel time for the geometry of the pot. It can be lengthened by increasing the surface area, working with a smaller mass, or cooling the resin and hardener prior to mixing. Material left in the pot will increase in absolute viscosity (measured at 75°F, or about 23.9°C, for example) due to polymerization but initially decrease in apparent viscosity due to heating. Material left in the pot to 75% of gel time may appear quite thin (due to heating) but will be quite thick when cooled to room temperature. Experienced users either mix batches that will be applied almost immediately or increase the surface area to slow the reaction.

Although the cure rate of an epoxy is dependent upon temperature, the curing mechanism is independent of temperature. The reaction proceeds most quickly in the liquid state. As the cure proceeds, the system changes from a liquid to a sticky, viscous, soft gel. After gelation the reaction speed slows down as hardness increases. Chemical reactions proceed more slowly in the solid state. From the soft sticky gel the system gets harder, slowly losing its stickiness. It becomes tack free and continues to become harder and stronger as time passes. At normal temperatures, the system will reach about 60 to 80% of ultimate strength after 24 hours. Curing then proceeds slowly over the next several weeks, finally reaching a point where no further curing will occur without a significant increase in temperature. However, for most purposes room temperature cured systems can be considered fully cured after 72 hours at 77°F (about 25°C). High modulus systems like Phase Two epoxy, for example, must be post-cured at elevated temperatures to reach full cure.

It is usually more efficient to work with as fast a cure time as practical for the application at hand if the particular system being used offers this choice. This allows the user to move along to the next phase without wasting time waiting for the epoxy to cure. Faster curing films with shorter tack times will have less chance to pick up fly tracks, bugs, and other airborne contaminants.

Epoxy resin compositions generally comprise a first liquid part comprising an epoxy resin and a second liquid part comprising a curing agent. Although the first and second part are liquids at ambient temperature, the liquid parts can comprise solid components dissolved or dispersed within the liquid.

The first part of the two-part composition comprises at least one epoxy resin. Epoxy resins are low molecular weight monomers or higher molecular weight polymers which typically contain at least two epoxide groups. An epoxide group is a cyclic ether with three ring atoms, also sometimes referred to as a glycidyl or oxirane group. Epoxy resins are typically liquids at ambient temperature.

Various epoxy resins are known including for example a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a bisphenol S type epoxy resin, a phenol novolac type epoxy resin, an alkyl phenol novolac type epoxy resin, a cresol novolac type epoxy resin, a biphenyl type epoxy resin, an aralkyl type epoxy resin, a cyclopentadiene type epoxy resin, a naphthalene type epoxy resin, a naphthol type epoxy resin, an epoxy resin of condensate of phenol and aromatic aldehyde having a phenolic hydroxy group, a biphenyl aralkyl type epoxy resin, a fluorene type epoxy resin, a Xanthene type epoxy resin, a triglycidyl isocianurate, a rubber modified epoxy resin, a phosphorous based epoxy resin, and the like.

Blends of various epoxy-containing materials can also be utilized. Suitable blends can include two or more weight average molecular weight distributions of epoxy-containing compounds such as low molecular weight epoxides (e.g., having a weight average molecular weight below 200 g/mole), intermediate molecular weight epoxides (e.g., having a weight average molecular weight in the range of about 200 to 1000 g/mole), and higher molecular weight epoxides (e.g., having a weight average molecular weight above about 1000 g/mole). Alternatively, or additionally, the epoxy resin can contain a blend of epoxy-containing materials having different chemical natures such as aliphatic and aromatic or different functionalities such as polar and nonpolar.

In one embodiment, the first part of the two-part composition comprises at least one bisphenol (e.g., A) epoxy resin. Bisphenol (e.g., A) epoxy resins are formed from reacting epichlorohydrin with bisphenol A to form diglycidyl ethers of bisphenol A. The simplest resin of this class is formed from reacting two moles of epichlorohydrin with one mole of bisphenol A to form the bisphenol A diglycidyl ether (commonly abbreviated to DGEBA or BADGE). DGEBA resins are transparent colorless-to-pale- yellow liquids at ambient temperature, with viscosity typically in the range of 5-15 Pa s at 25° C. Industrial grades normally contain some distribution of molecular weight, since pure DGEBA shows a strong tendency to form a crystalline solid upon storage at ambient temperature. This same reaction can be conducted with other bisphenols, such as bisphenol F. The choice of the epoxy resin used depends upon the end use for which it is intended. Epoxides with flexibilized backbones may be desired where a greater amount of ductility is needed in the bond line. Materials such as diglycidyl ethers of bisphenol A and diglycidyl ethers of bisphenol F can provide desirable structural adhesive properties that these materials attain upon curing, while hydrogenated versions of these epoxies may be useful for compatibility with substrates having oily surfaces.

Aromatic epoxy resins can also be prepared by reaction of aromatic alcohols such as biphenyl diols and triphenyl diols and triols with epichlorohydrin. Such aromatic biphenyl and triphenyl epoxy resins are not bisphenol epoxy resins.

There are two primary types of aliphatic epoxy resins, i.e., glycidyl epoxy resins and cycloaliphatic epoxides. Glycidyl epoxy resins are typically formed by the reaction of epichlorohydrin with aliphatic alcohols or polyols to give glycidyl ethers or aliphatic carboxylic acids to give glycidyl esters. The resulting resins may be monofunctional (e.g., dodecanol glycidyl ether), difunctional (diglycidyl ester of hexahydrophthalic acid), or higher functionality (e.g., trimethylolpropane triglycidyl ether). Cycloaliphatic epoxides contain one or more cycloaliphatic rings in the molecule to which the oxirane ring is fused (e.g., 3, 4-epoxycyclohexylmethyl-3,4-epoxy cyclohexane carboxylate). They are formed by the reaction of cyclo-olefins with a peracid, such as peracetic acid. These aliphatic epoxy resins typically display low viscosity at ambient temperature (10-200 mPa s) and are often used as reactive diluents. As such, they are employed to modify (reduce) the viscosity of other epoxy resins. This has led to the term ‘modified epoxy resin’ to denote those containing viscosity-lowering reactive diluents. In some embodiments, the resin composition may further comprise a reactive diluent. Examples of reactive diluents include diglycidyl ether of 1, 4 butanediol, diglycidyl ether of cyclohexane dimethanol, diglycidyl ether of resorcinol, p-tert-butyl phenyl glycidyl ether, cresyl glycidyl ether, diglycidyl ether of neopentyl glycol, triglycidyl ether of trimethylolethane, triglycidyl ether of trimethylolpropane, triglycidyl p-amino phenol, N,N'-diglycidylaniline, N,N,N',N',-tetraglycidyl metaxylylene diamine, and vegetable oil polyglycidyl ether. The resin composition may comprise at least 1, 2, 3, 4, or 5 wt.-% and typically no greater than 15 or 20 wt-% of such reactive diluent(s).

In some embodiments, the resin composition comprises (e.g., bisphenol A) epoxy resin in an amount of at least about 50 wt.-% of the total resin composition including the mixture of boron nitride particles and cellulose nanocrystals. In some embodiments, the amount of (e.g., bisphenol A) epoxy resin is no greater than 95, 90, 80, 85, 80, 75, 70, or 65 wt.-% of the total resin composition.

Epoxies are typically cured with stoichiometric or near-stoichiometric quantities of curative. In the case of two-part epoxy compositions, the second part comprises the curative, also referred to herein as the curing agent. The equivalent weight or epoxide number is used to calculate the amount of coreactant (hardener) to use when curing epoxy resins. The epoxide number is the number of epoxide equivalents in 1 kg of resin (eq/kg); whereas the equivalent weight is the weight in grams of resin containing 1 mole equivalent of epoxide (g/mol). Equivalent weight (g/mol)=1000 /epoxide number (eq/kg).

Common classes of curatives for epoxy resins include amines, amides, ureas, imidazoles, and thiols. In typical embodiments, the curing agent comprises reactive — NH groups or reactive — NR¹ R² groups wherein R’and R² are independently H or Ci to C4 alkyl, and most typically H or methyl.

The curing agent is typically highly reactive with the epoxide groups at ambient temperature. Such curing agents are typically a liquid at ambient temperature. However, the first curing agent can also be a solid provided it has an activation temperature at or below ambient temperature.

One class of curing agents are primary, secondary, and tertiary polyamines. The polyamine curing agent may be straight-chain, branched, or cyclic. In some favored embodiments, the polyamine crosslinker is aliphatic. Alternatively, aromatic polyamines can be utilized.

Useful polyamines are of the general formula R⁵ — (NR¹ R²)_x wherein R¹ and R² are independently H or alkyl, R⁵ is a polyvalent alkylene or arylene, and x is at least two. The alkyl groups of R¹ and R² are typically Ci to Cis alkyl, more typically Ci to C4 alkyl, and most typically methyl. R¹ and R² may be taken together to form a cyclic amine. In some embodiment x is two (i.e., diamine). In other embodiments, x is 3 (i.e., triamine). In yet other embodiments, x is 4.

Examples include hexamethylene diamine; 1,10-diaminodecane; 1,12-diaminododecane; 2-(4- aminophenyl)ethylamine; isophorone diamine; 4,4'-diaminodicyclohexyhnethane; and 1,3- bis(aminomethyl)cyclohexane. Illustrative six-member ring diamines include for example piperzine and 1 ,4-diazabicyclo [2.2.2] octane (“DABCO”) .

Other useful polyamines include polyamines having at least three amino groups, wherein the three amino groups are primary, secondary, or a combination thereof. Examples include 3,3'- diaminobenzidine, hexamethylene triamine, and triethylene tetramine.

The specific composition of the epoxy resin can be selected based on its intended end use. For example, in one embodiment, the resin composition can be for insulation, as described in US 2014/0080940, the disclosure of which is incorporated herein by reference thereto.

The resin composition may optionally further comprise additives including (e.g., silane-treated, or untreated) fillers, anti-sag additives, thixotropes, processing aids, waxes, and UV stabilizers. Examples of typical fillers include glass bubbles, fumed silica, mica, feldspar, and wollastonite. In some embodiments, the resin composition further comprises other thermally conductive fillers such as aluminum oxide, aluminum hydroxide, fused silica, zinc oxide, aluminum nitride, silicon nitride, magnesium oxide, beryllium oxide, diamond, and copper.

Methyl Methacrylates (MMA) Adhesives Methyl methacrylate (MMA) adhesives of example embodiments can include one-part and two- part MMA adhesives. One-part MMA adhesives can include a resin. Two-part methyl methacrylates (MMA) adhesives have a faster strength build up than epoxies. MMA adhesives are commonly used for bonding plastics and bonding metals to plastics. They are also extremely effective in joining solid surface materials together, and as they can be colored, they are used extensively in worktop manufacture and installation.

Methyl methacrylate adhesives are structural acrylic adhesives that are made of a Part A (Part 1) resin and Part B (Part 2) hardener. Most MMAs also contain rubber and additional strengthening agents. MMAs cure quickly at room temperature and have full bond strength soon after application. The adhesive is resistant to shear, peel, and impact stress. Looking at the bonding process more technically, these adhesives work by creating an exothermic polymerization reaction. Polymerization is the process of reacting monomer molecules together, in a chemical reaction, to form polymer chains. What this means is that the adhesives create a strong bond while still being flexible. These adhesives can form bonds between dissimilar materials with different flexibility, like metal and plastic. Unlike some other structural adhesives like two-part epoxies, MMAs do not require heat to cure. There are MMAs available with a range of working times to suit your specific needs.

MMAs have higher peel strength and are more temperature resistant. They develop strength faster allowing parts to be used sooner. It is also worth noting the different processing conditions used for MMAs. For example, the two components of MMAs can each be applied separately to one of the materials being bonded together, and the MMA will not begin to cure until the joints are brought together, combining the components. This means that you do not have to deal with precise mixing ratios to get a good bond. It is important to remember that MMAs do tend to have a strong smell, meaning you should have good ventilation when applying them and they are flammable, so some care is needed.

MMAs are formulated to have a Work Life between 5 minutes and 20 minutes.

All these acrylic structural adhesive types provide exceptional bond strength and durability - nearly that of epoxy adhesives - but with the advantages of having faster cure speed, being less sensitive to surface preparation, and bonding more types of materials.

Silicone Adhesives

Silicone adhesives of example embodiments can include one-part and two-part silicone adhesives. Two-part silicone adhesives are generally used when there is a large bond area or when there is not enough relative humidity to complete the cure. Common applications for these are electronics applications including the manufacture of household appliances, in automotive and window manufacture.

Suitable silicone resins include moisture-cured silicones, condensation-cured silicones, and addition-cured silicones, such as hydroxyl-terminated silicones, silicone rubber, and fluoro-silicone. Examples of suitable commercially available silicone PSA compositions comprising silicone resin include Dow Coming's 280A, 282, 7355, 7358, 7502, 7657, Q2-7406, Q2-7566 and Q2-7735; General Electric's PSA 590, PSA 600, PSA 595, PSA 610, PSA 518 (medium phenyl content), PSA 6574 (high phenyl content), PSA 529, PSA 750-D1, PSA 825-D1, and PSA 800-C. An example of two-part silicone resin commercially available is that sold under the trade designation “SILASTIC J” from Dow Chemical Company, Midland, Mich.

Pressure sensitive adhesives (PSAs) can include natural or synthetic rubbers such as styrene block copolymers (styrene-butadiene; styrene-isoprene; styrene-ethylene/butylene block copolymers); nitrile rubbers, synthetic polyisoprene, ethylene -propylene rubber, ethylene-propylene-diene monomer rubber (EPDM), polybutadiene, polyisobutylene, butyl rubber, styrene-butadiene random copolymers, and combinations thereof.

Additional pressure sensitive adhesives include poly(alpha-olefms), polychloroprene, and silicone elastomers. In some embodiments, poly chloroprene and silicone elastomers may be preferred since polychloroprene contains a halogen, which can contribute towards flame resistance, and silicone elastomers are resistant to thermal degradation.

Urethane Adhesives

Example urethane adhesives as used in embodiments can include both one-part and two-part urethane adhesives. Two-part urethane adhesives can be formulated to have a wide range of properties and characteristics when cured. They are often used when bonding dissimilar materials such as glass to metal or aluminum to steel, for example.

Most polyurethane adhesives are either polyester or polyether based. They are present in the isocyanate prepolymers and in the active hydrogen containing hardener component (polyol). They form the soft segments of the urethane, whereas the isocyanate groups form the hard segments. The soft segments usually comprise the larger portion of the elastomeric urethane adhesive and, therefore, determine its physical properties. For example, polyester-based urethane adhesives have better oxidative and high temperature stability than polyether-based urethane adhesives, but they have lower hydrolytic stability and low-temperature flexibility. However, polyethers are usually more expensive than polyesters.

Many urethane adhesives are sold as two-component urethane adhesives. The first component contains the diisocyanates and/or the isocyanate prepolymers (Part 1), and the second consists of polyols (and amine / hydroxyl chain extenders) (Part 2). A catalyst is often added, usually a tin salt or a tertiary amine, to speed up cure. The reactive ingredients are often blended with additives, and plasticizers to achieve the desired processing and/or final properties, and to reduce cost.

Polyurethanes may be prepared, for example, by the reaction of one or more polyols and/or polyamines and/or aminoalcohols with one or more polyisocyanates, optionally in the presence of non- reactive component(s). For applications where weathering is likely, it is typically desirable for the polyols, polyamines, and/or aminoalcohols and the polyisocyanates to be free of aromatic groups.

Suitable polyols include, for example, materials commercially available under the trade designation DESMOPHEN from Bayer Corporation, Pittsburgh, Pa. The polyols can be polyester polyols (for example, Desmophen 631A, 650A, 651A, 670A, 680, 110, and 1150); polyether polyols (for example, Desmophen 550U, 1600U, 1900U, and 1950U); or acrylic polyols (for example, Demophen A160SN, A575, and A450BA/A).

Suitable polyamines include, for example: aliphatic polyamines such as, for example, ethylene diamine, 1,2-diaminopropane, 2,5-diamino-2,5-dimethylhexane, 1,11 -diaminoundecane, 1,12- diaminododecane, 2,4- and/or 2,6-hexahydrotoluylenediamine, and 2,4'-diamino-dicyclohexylmethane; and aromatic polyamines such as, for example, 2,4- and/or 2,6-diaminotoluene and 2,4'- and/or 4,4'- diaminodiphenylmethane; amine-terminated polymers such as, for example, those available from Huntsman Chemical (Salt Lake City, Utah), under the trade designation JEFFAMINE polypropylene glycol diamines (for example, Jeffamine XTJ-510) and those available from Noveon Corp., Cleveland, Ohio, under the trade designation Hycar ATBN (amine-terminated acrylonitrile butadiene copolymers), and those disclosed in U.S. Pat. No. 3,436,359 (Hubin et al.) and U.S. Pat. No. 4,833,213 (Leir et al.) (amine-terminated polyethers, and polytetrahydrofuran diamines); and combinations thereof.

Suitable aminoalcohols include, for example, 2-aminoethanol, 3 -aminopropan- l-ol, alkylsubstituted versions of the foregoing, and combinations thereof.

Suitable polyisocyanate compounds include, for example: aromatic diisocyanates (for example, 2,6-toluene diisocyanate; 2,5-toluene diisocyanate; 2,4-toluene diisocyanate; m-phenylene diisocyanate; p-phenylene diisocyanate; methylene bis(o-chlorophenyl diisocyanate); methylenediphenylene-4,4'- diisocyanate; polycarbodiimide-modified methylenediphenylene diisocyanate; (4,4'-diisocyanato- 3,3',5,5'-tetraethyl) diphenylmethane; 4,4'-diisocyanato-3,3'-dimethoxybiphenyl (o-dianisidine diisocyanate); 5-chloro-2,4-toluene diisocyanate; and 1 -chloromethyl -2, 4-diisocyanato benzene), aromatic-aliphatic diisocyanates (for example, m-xylylene diisocyanate and tetramethyl-m-xylylene diisocyanate); aliphatic diisocyanates (for example, 1,4-diisocyanatobutane; 1,6-diisocyanatohexane; 1,12-diisocyanatododecane; and 2-methyl-l,5-diisocyanatopentane); cycloaliphatic diisocyanates (for example, methylenedicyclohexylene-4,4'-diisocyanate; 3 -isocyanatomethyl-3, 5, 5 -trimethylcyclohexyl isocyanate (isophorone diisocyanate); 2,2,4-trimethylhexyl diisocyanate; and cyclohexylene- 1,4- diisocyanate), polymeric or oligomeric compounds (for example, polyoxyalkylene, polyester, polybutadienyl, and the like) terminated by two isocyanate functional groups (for example, the diurethane oftoluene-2,4-diisocyanate-terminated polypropylene oxide glycol); polyisocyanates commercially available under the trade designation MONDUR or DESMODUR (for example, Desmodur XP7100 and Desmodur N 3300A) from Bayer Corporation (Pittsburgh, Pa.); and combinations thereof. In some embodiments, the polyurethane comprises a reaction product of components comprising at least one polyisocyanate and at least one polyol. In some embodiments, the polyurethane comprises a reaction product of components comprising at least one polyisocyanate and at least one polyol. In some embodiments, the at least one polyisocyanate comprises an aliphatic polyisocyanate. In some embodiments, the at least one polyol comprises an aliphatic polyol. In some embodiments, the at least one polyol comprises a polyester polyol or a polycarbonate polyol.

Typically, the polyurethane (s) is/are extensible and/or pliable. For example, the polyurethane(s), or any layer containing polyurethane, may have a percent elongation at break (at ambient conditions) of at least 10, 20, 40, 60, 80, 100, 125, 150, 175, 200, 225, 250, 275, 300, 350, or even at least 400 percent, or more.

In certain embodiments, the polyurethane has hard segments, typically segments corresponding to one or more polyisocyanates, in any combination, in an amount of from 35, 40, or 45 percent by weight up to, 50, 55, 60, or even 65 percent by weight.

As used herein: wt % means percent by weight based on the total weight of material, and

Hard Segment wt % = (weight of short chain diol and polyol+weight of short chain di- or polyisocyanate )/total weight of resin wherein: short chain diols and polyols have an equivalent weight ^ 185 g/eq, and a functionality ^2; and short chain isocyanates have an equivalent weight =3 20 g/eq and a functionality = 2.

One or more catalysts are typically included with two-part urethanes. Catalysts for two-part urethanes are well known and include, for example, aluminum-, bismuth-, tin-, vanadium-, zinc-, tin-, and zirconium-based catalysts. Tin-based catalysts have been found to significantly reduce the amount of outgassing during formation of the polyurethane. Examples of tin-based catalysts include dibutyltin compounds such as dibutyltin diacetate, dibutyltin dilaurate, dibutyltin diacetylacetonate, dibutyltin dimercaptide, dibutyltin dioctoate, dibutyltin dimaleate, dibutyltin acetonylacetonate, and dibutyltin oxide. If present, any catalyst is typically included at levels of at least 200 parts per million by weight (ppm), 300 ppm, or more; however, this is not a requirement.

Additional suitable two-part urethanes are described in U.S. Pat. No. 6,258,918 Bl (Ho et al.) and U.S. Pat. No. 5,798,409 (Ho), the disclosures of which are incorporated herein by reference.

In general, the amounts of polyisocyanate to polyol, polyamine, and/or aminoalcohol in a two- part urethane are selected in approximately stoichiometrically equivalent amounts, although in some cases it may be desirable to adjust the relative amounts to other ratios. For example, a slight stoichiometric excess of the polyisocyanate may be useful to ensure a high degree of incorporation of the polyol, polyamine, and/or aminoalcohol, although any excess isocyanate groups present after polymerization will typically react with materials having reactive hydrogens (for example, adventitious moisture, alcohols, amines, etc.). According to some embodiments, a dispensing device supporting ultrasonic bubble mitigation and/or UPD comprises first and second portions that are separate parts which can be coupled and decoupled. FIG. 2 is a perspective view of a first portion 210 of a dispensing device 200 including an ultrasonic horn, wherein the first portion 210 includes at least an inlet port 211. FIG. 4A shows a side view and FIG 4B shows a cross sectional view of the first portion 210 through line A - A.

The length of the two-part dispensing device as shown can range from about 5 cm (2 inches) to about 25 cm (10 inches) in some embodiments. FIG. 3 is a perspective view of a second portion 220 of the dispensing device 200 wherein the second portion 220 at least includes the outlet port 221. FIG. 5 A shows a side view and FIG 5B shows a cross sectional view of the second portion 220. An internal passageway 240 fluidically connects the inlet 211 and the outlet 221.

The separable two-part configuration of the dispensing device 200 enables the use of different size dispensing tips without having to change the ultrasonic horn. The second portion 220 comprising the outlet 221 can be separated from the first portion 210 comprising the inlet 211. As depicted in FIGS. 4 - 5, the second portion 220 may have flat sections that facilitate the use of a tool for installing or removing the second portion 220 from the first portion 210.

As best seen in FIGS. 4 through 5, the first and second portions 210, 220 include coupling features 231, 232 configured to couple and decouple the first and second portions 210, 220. For example, the coupling features 231, 232 can include a threaded hole in the first portion and a compatible threaded peg on the second portion. In some cases, the device is configured to be used as a stand-alone ultrasonic unit that may be configured to be coupled to one or more of an additional dispensing system and/or external tubing.

The length of the dispensing device may be dependent upon the frequency and material selection. Typically for a frequency of 40 Khz and titanium material the length is about 6.4 cm (2.5 inches )for a half wavelength horn. The outer diameter of the dispensing device can range from about 2.5 cm (1 inch) to about 7.6 cm (3 inches) and the inner diameter of the passageway can range from about 0.13 cm (0.05 inches) to about 1.3 cm (0.5 inches).

As depicted in FIGS. 1 - 5, the first portion 110, 210 may be substantially cylindrical. In some cases, the first portion 110, 210 may be a different shape. For example, the first portion may be substantially cuboid. The overall length of the two-part dispensing device 100, 200 can range from about 5 cm (2 inches) to about 25 cm (10 inches) in some embodiments. For example, the first portion 110, 210 may have length of about 5 cm (2 inches) to about 6.4 cm (2.5 inches) and an outer diameter of about 2.5 cm (1 inch) to about 3.8 cm (1.5 inches), for example. The second portion 120, 220 may have length of about 1.3 cm (0.5 inches) to about 3.8 cm (1.5 inches) and an outer diameter of about 0.13 cm (0.05 inches) to about 3.8 cm (1.5 inches). The inner diameter of the passageway 140, 240 may range from about 0.13 cm (0.05 inches) to about 1.3 cm (0.5 inches). The diameter of the inlet 111, 211 may be about 0.13 cm (0.05 inches) to about 1.3 cm (0.5 inches). The inlet 111, 211 may be in line with the longitudinal axis 199, 299 of the cylindrical first portion 110, 210 or may be angled at an angle, 0, wherein 0 may be between about 0 to about 90 degrees with respect to a longitudinal axis 199, 299 of the first portion 110, 210.

The inner diameter of the bubble port 112 may be about 0.025 cm (0.01 inches) to about 1.3 cm (0.5 inches). The bubble port 112 could be in line with the longitudinal axis 199, 299 of the cylindrical first portion 110, 210 or can be angled by about 0 to about 90 degrees with respect to a longitudinal axis 199, 299 of the first portion 210. The inner diameter of the tip portion 122, 222 of the passageway 140, 240 can range from about 0.01 cm (0.004 inches) to about 0.26 cm (0.102 inches) corresponding to needle gauges between about 32 and 10 in various embodiments.

The first 110, 210 and/or second portions 120, 220 typically made of metals. In some embodiments, the first 110, 210 and/or second portions 120, 220 are also typically made of a material that does not substantially dampen the transmission of ultrasound to the liquid. In some implementations, the material of the dispensing device may facilitate direct ultrasound applied to the liquid.

Some embodiments involve an ultrasonic dispensing device that can be retrofitted to a standard dispensing syringe. The device can be used to mitigate bubbles and/or to facilitate UPD enhancing the dispense flowrate through application of ultrasonic energy to the liquid in the syringe. FIGS. 6 - 8 illustrate various examples of an ultrasonic dispensing device that can be used with a standard dispensing syringe in accordance with some embodiments.

FIG. 6 shows an ultrasonic dispensing device in accordance with some embodiments. Ultrasonic dispensing device 600 comprises a housing 610 and an ultrasonic horn 620 disposed in, on or near the housing 610. An opening 630 extends through the housing 610, the opening 630 dimensioned to receive and removeably retain a liquid dispensing syringe 650 within the opening 630. In some embodiments, the device 600 may include features that removeably retain the syringe within the opening. For example, the retaining features may comprise a tapered opening that retains the syringe 650 by a friction fit. After the syringe 650 is used to dispense the liquid, it can be removed from the device 600 so that the device 600 can be re-used with another syringe.

In some embodiments, the housing 610 includes a cavity 665 configured to contain an ultrasonic coupling medium 660 within the cavity 665 such that the ultrasonic coupling medium 660 is disposed between the ultrasonic horn 620 and the opening 630. The cavity 665 and the medium 660 may be disposed only one side of the opening 630 or on both sides of the opening 630 as shown in FIG. 6. In some implementations, the syringe may be modified to include a bubble extraction port 612.

FIG. 7 depicts an ultrasonic dispensing device 700 having a cylindrical housing 710. An opening 730 extends along the longitudinal axis 799 of the cylindrical housing 710. As previously discussed, the opening 730 is dimensioned to receive and removeably retain a dispensing syringe (not shown in FIG. 7). The device 700 includes an ultrasonic horn 720 disposed in, on, or near the housing 710. As depicted in FIG. 7, the ultrasonic horn 720 may be a cylinder attached to the housing that partially or fully encircles the opening 730. In some embodiments, the housing 710 includes a cavity configured to contain an ultrasonic coupling medium within the cavity and between the ultrasonic horn 720 and the opening 730. As previously discussed in connection with FIG. 6, the syringe may be modified to include a bubble port for bubble extraction. The bubble port may be connected to a vacuum pump to facilitate bubble extraction. In some implementations, a channel extends through the housing fluidically connecting the bubble port in the syringe to the vacuum pump.

FIG. 8 depicts an ultrasonic dispensing device 800 comprising an ultrasonic horn 820 proximate to the dispensing end 815 of the housing 810. The housing 810 includes an opening 830 dimensioned to receive and removeably retain a dispensing syringe 850. The device 800 includes an ultrasonic horn 820 disposed in, on, or near the dispensing end 815 of the housing 810. Placement of the ultrasonic horn 820 at the dispensing end 815 facilitates exposure of the liquid to the ultrasound after the liquid exits through the outlet 821 of the syringe 850 and before the liquid wets out to the substrate upon which the liquid is dispensed. In some embodiments, a bubble port 812 can be formed in the syringe 850. In some implementations, the bubble port 812 can be coupled to a vacuum pump so as to facilitate extraction of the bubbles.

FIGS. 9 - 12 show cross sectional diagrams of ultrasonic dispensing devices 900, 1000, 1100, 1200 illustrating placement of the ultrasonic horn 950, 1050, 1150, 1250 and/or optional ultrasonic coupling medium 960, in accordance with various embodiments. In these embodiments, the ultrasonic dispensing devices 900, 1000, 1100, 1200 include a housing 905, 1005, 1105, 1205 illustrated as being cylindrical although the housings of the devices may be formed in any suitable shape depending on the implementation. The ultrasonic dispensing devices 900, 1000, 1100, 1200 include an inlet 910, 1010, 1110, 1210 and an outlet 920, 1020, 1120, 1220 with a passageway 930, 1030, 1130, 1230 through the housing 905, 1005, 1105, 1205 that fluidically connects the inlet 910, 1010, 1110, 1210 to the outlet 920, 1020, 1120, 1220. The passageway 930, 1030, 1130, 1230 is suitable to transport the liquid to be dispensed between the inlet 910, 1010, 1110, 1210 and the outlet 920, 1020, 1120, 1220. As shown in FIGS. 9 - 12, the inlet 910, 1010, 1110, 1210, outlet 920, 1020, 1120, 1220, and passageway 930, 1030, 1130, 1230 are arranged along a line parallel to the longitudinal axis 999, 1099, 1199, 1299 of the housing 905, 1005, 1105, 1205 in these embodiments.

Each of the ultrasonic dispensing devices 900, 1000, 1100, 1200 includes a bubble extraction port 912, 1012, 1112, 1212 with a channel 913, 1013, 1113, 1213 connecting the port 912, 1012, 1112, 1212 to the passageway 930, 1030, 1130, 1230. The bubble extraction port 912, 1012, 1112, 1212 and bubble extraction channel 913, 1013, 1113, 1213 may be positioned at any suitable location along the passageway 930, 1030, 1130, 1230. The bubble extraction channel 913, 1013, 1113, 1213 may be disposed at any suitable angle with respect to the longitudinal axis 999, 1099, 1199, 1299 of the device 900, 1000, 1100, 1200.

In the device 900 shown in FIG. 9, the housing, 905, the ultrasonic horn 950, and the cavity 965 that contains the ultrasonic coupling medium 960 are concentric cylinders. When a fully cylindrical “donut” ultrasonic horn 950 is used, the liquid may be exposed to the ultrasound any angle (360 degrees) around the longitudinal axis 999. Note that the cavity 965 and coupling medium 960 are optional features. The ultrasonic horn and/or cavity can extend a majority of the distance between the inlet 910 and the outlet 920 in some embodiments. In alternative implementations, the ultrasonic horn and/or cavity extend less than a majority of the distance between the inlet 910 and the outlet 920. The horn 950 and the 965 cavity need not be the same length and may extend different distances or substantially equal distances along the longitudinal axis 999.

In the device 1000 shown in FIG. 10, the ultrasonic horn 1050 is disposed on only one side of the housing 1005. The device 1000 may optionally include a cavity containing an ultrasonic coupling medium although these features are not shown in FIG. 10. When present, the cavity and ultrasonic coupling medium may be disposed between the ultrasonic horn 1050 and the passageway 1030 connecting the inlet 1010 and outlet 1020.

In the implementation depicted in FIG. 10, the ultrasonic horn 950 extends a majority of the distance between the inlet 1010 and the outlet 1020. In alternative implementations, the ultrasonic horn may less than a majority of the distance between the inlet 1011 and the outlet 1021.

Devices 1100 and 1200 shown in FIGS. 11 and 12 include ultrasonic horns 1150, 1250 located near the outlet 1120, 1220 of the device 1100, 1200. Device 1100 includes an ultrasonic horn 1150 positioned such that the liquid in the passageway 1130 is exposed to the ultrasound prior to being dispensed. Device 1200 includes an ultrasonic horn 1250 is positioned such that the liquid is exposed to the ultrasound just after exiting the outlet 1220. For example, the liquid may be exposed after it exits the outlet 1220 and before the liquid wets out on the surface of the substrate 1298.

There are a number of dispensing methods available for dispensing viscous materials such as adhesives. These dispensing methods range from manual application of the adhesive to pneumatic dispensing to tabletop robots. In any of these methods, liquids can be dispensed to a substrate by timepressure or volumetric dispensing.

FIG. 13 is a block diagram illustrating various optional components of a dispensing system 1300 that can be used in conjunction with an ultrasonic dispensing device 1310 such as ultrasonic dispensing devices 100 - 1200 shown in FIGS. 1 through 12. According to various embodiments, the system 1300 includes a dispense mechanism 1320 that can be operated to push the liquid in the passageway of the dispensing device out through the device outlet. The dispensing mechanism 1320 can include a machine screw as illustrated within the dispensing syringes shown in FIGS. 6 and 8 (see element 651 of FIG. 6 and element 851 of FIG. 8, for example). Alternatively or additionally, the dispense mechanism 1320 can comprise a piston that fits within the passageway, such as the piston 931 shown in FIG. 9.

In some embodiments, the dispensing mechanism can be manually operated, e.g., by manually depressing a plunger attached to the piston or by manually operating the auger screw. Alternatively, the dispense mechanism can include a mechanical subsystem that automatically operates the dispense mechanism, e.g., a pneumatically or hydraulically operated plunger or motor-driven screw. In these embodiments, the automatic dispense mechanism can be controlled by a dispense controller 1330, e.g., electrical circuitry designed to automatically control the rate, volume, and/or other parameters associated with dispensing the liquid.

In some embodiments, the dispense device 1310 is coupled to a movement mechanism 1360 that operates to move the dispense device in one or more dimensions as the dispensing device 1310 is dispensing the liquid to form various predetermined patterns of dispensed liquid on a substrate. The movement mechanism 1360 can cause movement of the dispensing device by pneumatic, hydraulic, electrical and/or electromagnetic forces, for example. The movement mechanism 1360 may include one or more mechanical supports, gantries, linkages, belts, pulleys, hydraulic pumps, pneumatic pumps, solenoids, and/or motors that can be activated to move the dispense device 1310 before, after, and/or during dispensing the liquid. The movement mechanism 1360 may be automatically controlled by a movement controller 1370, e.g., a computer processor-based controller.

The system 1300 can include an ultrasonic controller 1340 that controls various parameters associated with the ultrasonic energy radiated by the ultrasonic horn. For example, the ultrasonic controller 1340 may generate ultrasonic energy, controlling parameters of the ultrasonic energy such as frequency and amplitude.

As previously discussed, in some embodiments, the dispensing device 1310 includes a port that allows bubbles to exit the passageway. In embodiments that include a bubble port, the system 1300 may include a vacuum pump 1350 operated to facilitate extraction of the bubbles from the port.

FIG. 14 is a block diagram that shows in more detail a representative ultrasonic controller 1340. The controller 1340 comprises an electrical signal generator 1410 that produces an electrical signal, e.g., a sine wave having frequency ranging from 10 to 60 kHz. In some embodiments, the electrical signal generated by the signal generator 1410 has a frequency of about 20 kHz. An ultrasonic converter 1420 converts the electrical signal produced by the signal generator 1410 to mechanical vibrations at the frequency of the electrical signal. The ultrasonic controller 1340 may include an ultrasonic booster 1430 that boosts the amplitude of the vibrations produced by the converter 1420. The mechanical vibrations from the booster 1430 drive the ultrasonic horn 1450.

A subsystem 1500 comprising components of the ultrasonic controller shown in FIG. 14 can be mechanically coupled together as depicted in FIG. 15. The illustrated subsystem 1500 includes the ultrasonic converter 1420, the ultrasonic booster 1430, and the dispensing device ultrasonic horn 1450 of the dispensing device 1310 arranged in a configuration that can be mounted on a robotic stage for liquid dispensing.

There are a number of dispensing methods available for dispensing liquids, such as viscous liquids including structural adhesives. As set forth above, dispensing methods for liquids range from manual applications to pneumatic dispensing to tabletop robots. In any of these methods, liquids can be dispensed to the surface of a substrate by a time/pressure system which ideally dispenses a predetermined volume repeatably each time. Control of the process depends on the applied pressure, the time the pressure is applied, and the diameter of the dispensing passageway.

In many applications it is desirable to dispense adhesives at high flowrates to increase the speed of manufacturing. In general, the higher the pressure being applied, the greater the flowrate. However, when conventional thermoplastic dispensing syringes are used as the dispensing device, there is a limit to the amount of pressure that can be applied before the syringe deforms or fails.

Dispensing devices discussed in accordance with some embodiments outlined above can be made of relatively rigid materials when compared to thermoplastic syringes, allowing increased dispense pressures and flowrates during the dispense process. For example, the dispense devices may be made of metal, glass, and/or plastics loaded with carbon, metal or other particles to enhance structural rigidity. Enhanced structural rigidity of the dispense device decreases the occurrence of deformation and/or failure due to higher pressures used for dispensing.

Flowrates for highly viscosity adhesives can be limited due to the small micro-needles that have been conventionally used for laying down small beads for small parts bonding. Exposing the adhesive (or other liquid) in the passageway to ultrasound can decrease the viscosity of the liquid resulting in an increase in flowrate during dispensing. Ultrasonic perturbation dispensing (UPD) can be employed to enhance dispensing viscous materials with or without bubble mitigation. Dispensing systems that incorporate UPD can provide increased flowrates when compared to substantially similar systems without UPD.

The higher flowrate achievable with a UPD dispensing system can enhance efficiency for dispensing viscous materials such as adhesives resulting in a higher number of dispense cycles per unit weight to be repeatably dispensed. Furthermore, a liquid dispensing system could include a feedback loop for the ultrasonic controller to control the ultrasound. Such a feedback system may include a sensor to measure viscosity of the liquid and control the ultrasound based on the sensor feedback. Such a feedback system could be used to achieve predetermined viscosities of the liquid being dispensed during the dispense cycle. The applied pressure to push adhesive through the UPD dispensing system will depend on the overall viscosity of the adhesive but generally pressure between 135-690 kPa (20-100 psi) can be utilized for syringe and cartridge-based systems. However, higher pressure (> 690 kPa (100 psi) but < 6900 kPa (1000 psi) )could also be utilized if the adhesive delivery is from a pressurized meter mix tank. The higher applied pressure can lead to higher flowrate as the material are sheared through the cavity of the UPD dispensing system.

The UPD technology may be employed for both general industrial macro-dispensing applications and micro-dispensing applications so long as the tip diameter can be machined. For example, tip diameters ranging from 10 gauge to 32 gauge can be machined and used depending on the application. The UPD c technology an also be utilized as an inline bubble mitigation device where adhesive could be pumped through via the inlet port and connected directly to another dispensing system. FIG. 16 is a flow diagram illustrating a method of dispensing liquids in accordance with some embodiments. The method includes receiving 1610 the liquid to be dispensed into a passageway through an inlet of a dispensing device. Ultrasonic energy is directed 1620 toward the liquid while it is in the passageway and/or just after the liquid exits the passageway through the dispensing device outlet. The ultrasonic energy may vibrate along the direction of the longitudinal axis of the dispensing device, having a frequency between about 10 and 60 kHz and an amplitude between about 2 and 100 microns. The frequency, amplitude, direction and/or other parameters of the ultrasonic energy may be selected to mitigate bubbles 1632 and/or to facilitate UPD 1634 in which the viscosity of the liquid is decreased to enhance the dispensing flowrate. The above processes could be used in conjunction with additional vibrations, e.g., vibrations lower than 15 kHz to further facilitate dispensing the liquid and/or bubble mitigation. Additionally, these processes could be used in conjunction with a centrifugal bubble mitigation system. Centrifugal bubble mitigation system may involve using adhesive syringe that is spun using a centrifuge to remove all trapped air bubbles within the adhesives. Once the air bubbles are removed, the syringe can be connected to the UPD valve for further dispensing. The combination of using centrifugal and ultrasonic can further enhance air bubble reduction or elimination.

Examples:

In example 1, the volumetric flowrates for all three systems are: 1) syringe with a 21 -gauge Nordson EFD dispensing metal tip, 2) UPD with ultrasonic turned off, and 3) UPD with ultrasonic turned on. The liquid was 3M™ Scotch-Weld™ One-Part Epoxy Adhesive 6101 Off-White (“6161 OW”) from 3M Company, St. Paul, Minnesota. To measure the flowrate of system 1, the 6101 OW syringe was connected via a tube to a Nordson EFD E3 dispenser with time-pressure capability. The 21- gauge EFD dispensing straight metal tip was leur locked to the 6101 OW adhesive syringe and the system was subject to an air purge (pressure set at 517 kPa (75 psi)) to ensure there is adequate adhesive at the tip of the dispensing metal tip. To measure adhesive flowrate, an aluminum weighing pan was tared on a Mettler Toledo analytical balance and set aside for materials to be purged into. To initiate flow measurements, adhesive materials were dispensed continuously for about 1 minute into the aluminum weighing pan while using a stopwatch to time the material flow. The aluminum pan was re-weighed with the adhesive materials in it. The entire process was repeated three times for repeatability and accuracy. The volumetric flowrate was calculated by taking the mass in gram of the adhesive material and dividing by the recorded time in minutes and in this case, it is flowrate = grams/min.

To measure the flowrate of system 2, the 6101 OW syringe was luer locked to the UPD via inlet 111 port. The UPD was connected to the booster, converter, and power supply with power being turned OFF, applied pressure was set at 517 kPa (75 psi). To measure adhesive flowrate, an aluminum weighing pan was tared on a Mettler Toledo analytical balance and set aside for materials to be purged into. To initiate flow measurements, adhesive materials were dispensed continuously for about 1 minute into the aluminum weighing pan while using a stopwatch to time the material flow. The aluminum pan was reweighed with the adhesive materials in it. The entire process was repeated three times for repeatability and accuracy. The volumetric flowrate was calculated by taking the mass in gram of the adhesive material and dividing by the recorded time in minute and in this case, it is flowrate = grams/min.

For measurement of flowrate for system 3, the 6101 OW syringe was luer locked to the UPD via inlet 111 port. The UPD was connected to the booster, converter, and power supply with power turned ON and with applied pressure set at 517 kPa (75 psi). To measure adhesive flowrate, an aluminum weighing pan was tared on a Mettler Toledo analytical balance and set aside for materials to be purged into. To initiate flow measurements, adhesive materials were dispensed continuously for about 1 minute into the aluminum weighing pan while using a stopwatch to time the material flow. The aluminum pan was re-weighed with the adhesive materials in it. The entire process was repeated three times for repeatability and accuracy. The volumetric flowrate was calculated by taking the mass in gram of the adhesive material and dividing by the recorded time in minute and in this case, it is flowrate = grams/min.

The flowrate for all three systems is tabulated in Table 1.

Table 1

In example 2, 6101 OW was dispensed through the UPD valve and materials were collected to analyze for polymer defragmentation or degradation. Adhesive materials from systems 2 and 3 above were analyzed based on rheological properties. A shear sweep using a TA G2 Rheometer was conducted and based on rheological data there were no significant material changes to the polymer backbone which are shown by overlapping shear profiles for both systems 2 and 3. The shear sweeps for both overlaid nicely which indicates no degradation took place.

In example 3, 6101 OW was dispensed through the UPD valve and dispense patterns were analyzed for air bubble elimination and minimization. A serpentine dispense pattern was program on the Nordson EFD E3 dispenser. The experimental setup was carried out by connecting the 6101 OW syringe luer locked to the UPD via inlet 111 port. The UPD was connected to the booster, converter, and an applied pressure set at 517 kPa (75 psi). With ultrasonic power supply turned off, the UPD valve was able to dispense serpentine pattern on glass substrates as programmed above. Similarly, with ultrasonic power supply turned on, the same dispense pattern was also carried out. The dispense patterns were repeated multiple times and a comparison of UPD ultrasonic on and off dispense patterns were compared. The total number of lines on the patterns were recorded along with total numbers of observed air bubbles, voids, and gaps on each dispense line for both UPS ultrasonic on/off. The percent air bubble reduction was calculated by dividing the total number of bubbles when ultrasonic was turned off by the total number of bubbles taken on the combined ultrasonic on/off. In this example the total number of bubbles observe when ultrasonic is turned off is 15 while the total number of bubbles when ultrasonic is on is 4. Therefore, the percent bubble observed with ultrasonic on is 4 divided by 19 multiplied by 100 is 21%. This is about a 79% reduction of bubbles.

These examples are merely for illustrative purposes and are not meant to be overly limiting on the scope of the appended claims. Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed considering the number of reported significant digits and by applying ordinary rounding.

The recitation of numerical ranges by endpoints include all numbers subsumed within that range as well as the endpoints (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.) and any sub-ranges (e.g., 1 to 5 includes 1 to 4, 1 to 3, 2 to 4, etc.).

The term “in the range” or “within a range” or “between” (and similar statements) includes the endpoints of the stated range.

Reference throughout this specification to “one embodiment,” “an embodiment,” “certain embodiments,” or “some embodiments,” etc., means that a particular feature, configuration, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the disclosure. Thus, the appearances of such phrases in various places throughout this specification are not necessarily referring to the same embodiment of the disclosure. Furthermore, the features, configurations, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

Claims

What Is Claimed Is:

1. A dispensing device comprising: an ultrasonic horn arranged to provide ultrasound to a liquid, the ultrasonic horn comprising: a first housing portion comprising an inlet configured to receive the liquid; a second housing portion comprising an outlet configured to discharge the liquid; a passageway through the first and second portions fluidically connecting the inlet and the outlet; and a coupling configured to removeably couple the first housing portion to the second housing portion.

2. The device of claim 1, wherein frequency and amplitude of the ultrasound is sufficient to mitigate bubbles in the liquid.

3. The device of claim 1 or 2, wherein the first housing portion is cylindrical.

4. The device of any one of claims 1 to 3, wherein one or both of the first and second housing portions are metal.

5. The device of any one of claims 1 to 4, wherein the coupling is a threaded coupling configured to couple and decouple the first housing portion and the second housing portion.

6. The device of any one of claims 1 to 5, wherein: the ultrasonic horn is a cylinder; the passageway runs along a longitudinal axis of the cylinder; and the inlet is disposed at an angle to the longitudinal axis.

7. The device of claim 6, wherein the ultrasonic horn is oriented to produce vibrations along the longitudinal axis.

8. The device of any one of claims 1 to 7, further comprising at least one bubble removal port fluidically connected to the passageway.

9. The device of any one of claims 1 to 8, further comprising an ultrasonic controller configured to control the ultrasonic horn to direct ultrasonic energy sufficient to mitigate bubbles in the liquid to passageway.

25

10. The device of claim 9, wherein the ultrasonic controller comprises: a signal generator configured to generate oscillating electrical energy; an ultrasonic transducer coupled to the signal generator and configured to convert the electrical energy to ultrasonic energy; and an ultrasonic energy booster disposed between the ultrasonic transducer and the ultrasonic horn.

11. The device of claim 9, further comprising: a dispense mechanism configured to dispense the liquid through the outlet; and a dispense controller coupled to the dispense mechanism and configured to control one or both of rate and volume of the liquid dispensed.

12. The device of claim 9, further comprising: a movement mechanism configured to move the dispensing device in one or more dimensions; and a movement controller configured to control operation of the movement mechanism.

13. The device of claim 9, wherein: the dispensing device further comprises a vacuum port fluidically coupled to the passageway; and the system includes vacuum pump coupled to the vacuum port.

14. A device comprising: a housing; an ultrasonic horn; and a longitudinal opening extending along a longitudinal axis of the housing, the opening dimensioned to receive and removeably retain a liquid dispensing syringe within the opening.

15. The device of claim 14, wherein the ultrasonic horn is configured to emit ultrasound having frequency and amplitude sufficient to mitigate bubbles in a liquid contained within the dispensing syringe.

16. The device of claim 14 or 15, further comprising an ultrasonic medium disposed between the ultrasonic horn and the opening.

17. The device of any one of claims 14 to 16, wherein the ultrasonic horn is arranged to expose liquid dispensed by the liquid dispensing syringe to ultrasonic energy after the liquid exits the syringe.

18. A dispensing device comprising: an inlet configured to receive a liquid; an outlet configured to discharge the liquid; a passageway coupled to allow the liquid to flow between the inlet and the outlet; a bubble removal port configured to allow bubbles in the liquid to exit the passageway; and an ultrasonic horn configured to direct ultrasound to the passageway, the ultrasound having frequency and amplitude sufficient to displace the bubbles in the liquid to the port.

19. The device of claim 18, wherein the ultrasonic horn is a cylinder that encircles the passageway.

20. The device of claim 18, wherein the ultrasonic horn is disposed proximate to the outlet.

21. The device of claim 18, further comprising an ultrasonic coupling medium disposed between the ultrasonic horn and the passageway.

22. A method of dispensing a liquid from a dispensing device, the method comprising: receiving the liquid into a passageway through an inlet of the dispensing device; directing ultrasound toward the liquid, the ultrasound having frequency and amplitude sufficient to mitigate bubbles in the liquid; and dispensing the liquid from the passageway through an outlet of the dispensing device.

23. The method of claim 22, wherein mitigating the bubbles comprises: displacing the bubbles to a port in the passageway; and extracting the bubbles through the port.

24. The method of claim 23, wherein extracting the bubbles comprises applying a vacuum to the port.

25. The method of claim 22, wherein directing the ultrasound toward the liquid comprises directing the ultrasound toward the liquid after the liquid has passed through the outlet.

26. The method of any one of claims 22 to 25, wherein the ultrasound has one or more of a frequency between about 20 to about 60 kHz and an amplitude between about 2 to about 100 microns.

27. The method of any one of claims 22 to 26, wherein the liquid is an adhesive.