Method for calibrating a liquid dispensing device and liquid dispensing device calibration system

Abstract

In a method for measuring the volume of dispensed liquid droplets, the aim is to provide a method that is convenient, quick, and easy to use even with small amounts of liquid. [Solution] A method for determining the volume of a liquid droplet dispensed from a liquid dispensing device, comprising the steps of: (a) depositing a liquid of an assumed volume measured on a calibration reference surface from the liquid dispensing device as a droplet, the calibration reference surface providing a known contact angle with the droplet under the deposition conditions used; (b) establishing a known angle with the droplet selected from the group consisting of an advancing contact angle, a receding contact angle, and an intermediate contact angle; (c) measuring the dimensions of the droplet, the measured dimensions being selected from the group consisting of the maximum height of the droplet, the diameter of the contact patch, the radius of curvature, and the cross-sectional area; and (d) calculating the actual volume of the droplet from the relationship between the measured dimensions and the known contact angle, wherein the advancing contact angle, receding contact angle, and intermediate contact angle are established by changing the kinetic energy given to the deposited droplet.

Description

Technical Field

[0001] (Cross - reference to Related Applications) This application claims the benefit of priority of U.S. Provisional Patent Application No. 62 / 502,024, filed on May 5, 2017, under the title "Methods and Devices for Measuring Microvolumes of Liquids", the content of which is incorporated herein by reference in its entirety for all purposes, based on 35 U.S.C. § 119(e).

[0002] The field disclosed herein generally relates to devices and methods for dispensing liquid droplets, and more particularly to the measurement of the dispensed droplet volume.

Background Art

[0003] Liquid volume can be measured in several ways. The liquid volume may be directly measured using a graduated cylinder or a pipette. Alternatively, the volume may be calculated by dividing the mass of the liquid amount by the density. These methods are inconvenient for small amounts of liquid. The precision of a graduated container is limited by the subjectivity of the measurement process. A sensitive and expensive balance is required to perform mass measurements of small volumes. These methods are not suitable for rapid and convenient use.

Summary of the Invention

[0004] In one aspect, the present disclosure provides a method and a device for dispensing liquid droplets, and more particularly a device and a method for measuring the volume of the dispensed droplets.

[0005] In one embodiment, the present invention provides a method and a test device for determining the volume of a liquid droplet. In one embodiment, the test device establishes any one of (i) the advancing, (ii) the receding, and (iii) the intermediate contact angles by depositing a droplet measured on a surface that provides a known contact angle with the liquid under the dispensing conditions used.

[0006] In another embodiment, the test apparatus images the droplet. In another embodiment, the test apparatus determines the height or diameter of the droplet, or both. In another embodiment, the test apparatus determines the volume of the droplet in relation to the contact angle and one or more parameters selected from the group consisting of maximum height, diameter of the contact patch, radius of curvature, and cross-sectional area of ​​the droplet.

[0007] These and other features are better described in the embodiments illustrated below. In general, features of one embodiment may be used in combination with features of another embodiment, and it should be understood that the embodiments are not intended to limit the scope of the present invention.

[0008] Various exemplary embodiments of the present invention, which will become clearer as the explanation progresses, are described in the following detailed description in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0009] [Figure 1] This figure shows the contact angle formed between a droplet and a surface, which is the angle between the surface and the tangent of the droplet at the point of contact with the surface, according to one or more embodiments. [Figure 2] This is a flowchart of a method for obtaining the volume of a droplet on a surface according to one or more embodiments. [Figure 3] This is a block diagram of a test apparatus for determining the contact angle of a liquid on a test object, according to one or more embodiments. [Modes for carrying out the invention]

[0010] When a droplet accumulates on a surface and reaches equilibrium, it forms a symmetrical shape determined by the balance of several forces: the surface tension of the liquid, the surface energy of the solid, gravity acting on the liquid, and the strength of the attractive force between the liquid and the surface on which it accumulates. For small droplets, gravity is small compared to surface tension and interfacial tension and can be ignored. In this case, assuming the droplet is spherical, the shape of the droplet is defined by the contact angle θ, which is the angle between the surface and the tangent line of the droplet at the point of intersection with the surface. The contact angle is defined as the angle formed by the intersection of the liquid-solid interface and the liquid-vapor interface (geometrically obtained by applying a tangent line from the contact point along the liquid-vapor interface in the profile of a small droplet). The interface where solid, liquid, and vapor coexist is called a "three-phase contact line." A small contact angle is observed when the liquid spreads across a surface, while a large contact angle is observed when the liquid beades on the surface. More specifically, a contact angle less than 90° indicates good surface wetting, where the fluid spreads over a large area of ​​the surface. On the other hand, when the contact angle exceeds 90°, surface wetting is generally undesirable, so contact between the fluid and the surface is minimized, forming compact droplets.

[0011] Figure 1 shows droplets on a surface. The dashed lines represent circles with the same radius of curvature R as the spherical droplets. The angle θ is the contact angle, d is the diameter of the contact patch, h is the maximum height of the droplet from the surface, and A is the maximum cross-sectional area of ​​the droplet.

[0012] The relationship between the contact angle, the surface tension of the liquid, and the surface energy of the substrate is defined by Young's equation.

[0013]

number

[0014] In addition to depending on the surface energy of the substrate, the surface tension of the liquid, and the interfacial energy between the substrate and the liquid, the contact angle depends on the way the liquid is deposited. When the liquid slowly advances over a surface that has not been wetted until then, the advancing contact angle is established. This is the maximum contact angle that can exist between a given pair of liquid and substrate. When the liquid slowly leaves the surface after wetting, the receding contact angle is established. This is the minimum contact angle that can exist between a particular pair of liquid and substrate. Other contact angles, which are intermediate between the advancing and receding angles, are also possible and depend on the exact way the liquid is deposited. This means that the contact angle is constant if the surface energies of the liquid and the substrate are consistent and the way the liquid is brought into contact with the surface is consistent.

[0015] The relationship between the contact angle and the volume of a spherical drop is obtained from the following equation derived from basic trigonometry. If the bottom diameter of the drop and the contact angle are known:

[0016] [Number] (2)

[0017] If the height of the drop and the contact angle are known:

[0018] [Number] (3)

[0019] These equations show that the drop volume can be accurately calculated if the contact angle of the drop on the surface is known and either the height or the bottom diameter can be measured simultaneously. Although equations 2 and 3 are preferred, it is also possible to determine the volume using other relationships between the drop shape, contact angle, and volume. One example would be the determination of the drop volume from the radius of curvature and the contact angle.

[0020] [Number] (4)

[0021] Alternatively, calculation from cross-sectional area and contact angle:

[0022]

number

[0023] This approach is not limited to droplets that are spherical due to their small size. If the droplet is too large and gravity causes deformation, causing it to lose its spherical shape, a reasonably accurate estimate of the droplet volume can be obtained from the contact angle, droplet dimensions, and liquid density using other formulas, rather than analytical formulas such as (2) to (5).

[0024] Figure 2 shows a method 200 for accurately measuring the volume of a droplet. In one or more embodiments, method 200 includes testing a surface with a liquid to determine the contact angle, which is a characteristic of the surface, and the method by which the liquid comes into contact with the surface (block 202). This contact angle may be an advancing angle, a receding angle, or an intermediate angle. Method 200 includes the step of depositing a droplet to be measured onto a surface that provides a known contact angle with the liquid under the deposition conditions used, thereby establishing an advancing, receding, or intermediate contact angle (block 204). Method 200 includes the step of measuring one of the following: (i) the maximum height of the droplet, (ii) the diameter of the contact patch, (iii) the cross-sectional area of ​​the droplet, and (iv) the radius of curvature (block 206). As an example, method 200 may include the step of measuring the height or radius of curvature of the droplet from an image taken, for example, from the side or by any other preferred method (block 208). Similarly, method 200 may include the step of taking an image of the droplet from above to determine the average diameter of the contact patch (block 210). If the droplet establishes a contact angle greater than 90° with the surface and the contact patch is obscured in the upper and lower fields of view, the radius of curvature can be determined from the maximum droplet diameter. Method 200 includes the step of calculating the volume of the droplet from the relationship between the volume and the contact angle, and the height, contact patch diameter, outer diameter of the droplet, radius of curvature, or cross-sectional area, using an appropriate formula (block 214). For example, it can be calculated from the expected contact angle and any of formulas 2, 3, 4, or 5.

[0025] In one or more embodiments, the present invention provides a method for determining the volume of a liquid droplet dispensed from a test apparatus, the method comprising: (a) depositing a liquid of an assumed volume to be measured as a droplet on a calibration reference surface from the test apparatus, the calibration reference surface providing a known contact angle with the droplet under the deposit conditions used; (b) establishing a known contact angle with the droplet, selected from the group consisting of (i) an advancing contact angle, (ii) a receding contact angle, and (iii) an intermediate contact angle; (c) measuring the dimensions of the droplet, the dimensions to be measured being selected from the group consisting of (i) the maximum height of the droplet, (ii) the diameter of the contact patch, (iii) the radius of curvature, and (iv) the cross-sectional area; and (d) calculating the actual volume of the droplet from the relationship between the dimensions to be measured and the known contact angle. In one or more embodiments, the method further comprises (e) determining the difference between the assumed volume and the calculated volume of the droplet.

[0026] In one or more embodiments, the method further includes step (f) of correcting the difference between the volume of liquid dispensed by the test apparatus and the assumed volume. In one or more embodiments, the step of correcting the difference between the volume of liquid dispensed by the test apparatus and the assumed volume can be done by calculating the error factors of the test results obtained from the test apparatus onto the test surface. In one or more embodiments, the correction of the difference between the volume of liquid dispensed by the test apparatus and the assumed volume can be done by adjusting the volume of liquid dispensed by the test apparatus to correct the difference.

[0027] In one or more embodiments, the droplet volume is adjusted by adjusting the time interval between the opening of each valve, the degree to which each valve is opened, and / or the pressure applied by the liquid pressurization system (e.g., a specified pressure of pressurized gas applied by the compressed gas system).

[0028] In one or more embodiments, the test apparatus comprises a processor 353 and a nozzle valve orifice 334, which are calibrated to dispense liquid 316 to a calibrated droplet volume to a assumed volume by adjusting the time intervals in which each valve is open, the opening degree of each valve, and / or the pressure applied by a liquid pressurization system (e.g., a specified pressure of pressurized gas applied by a compressed gas system) according to the droplet volume deposited and calculated on a calibration reference surface.

[0029] In one or more embodiments, a calibration reference surface with a known and consistent contact angle is prepared for use as a volume determination device. In one or more embodiments, the calibration reference surface includes a material coated with an ink, polymer, or other coating having a consistent predetermined contact angle. In one or more embodiments, the calibration reference surface includes a polymer-coated substrate.

[0030] In one or more embodiments, the test apparatus is a device for depositing a known volume of liquid. In one or more embodiments, the test apparatus is a device for measuring the wettability of a liquid on the surface of a material, comprising a liquid dispensing component, a dimensional determination component, and a data generation component, wherein the liquid dispensing component is configured to deposit a certain amount of liquid on the surface of the material, the dimensional determination component is configured to determine one or more dimensions of the liquid deposited on the surface, and the data generation component is configured to analyze information regarding one or more geometric features of the volume of liquid on the surface of the material based on the dimensional determination component.

[0031] The surface energy of a material may vary slightly from sample to sample or point to point due to the presence of small amounts of contamination or slight differences in surface composition and microstructure. Some materials and surface treatment methods provide more consistent surface energy than others. Using a standard material with a surface that has a consistent and precisely known contact angle as a calibration reference improves the accuracy of the method. In one embodiment, the calibration reference includes a polymer film such as polypropylene or polyester. In one embodiment, the polymer film is inexpensive and disposable. In one embodiment, the polymer film is available in roll or sheet form, which helps protect the surface being measured from contamination by contact or exposure. The calibration reference polymer film can be oxidized or otherwise treated using techniques such as flame, corona, or plasma processes to produce a surface that imparts a consistent contact angle with a desirable value. When carefully prepared, a polymer film typically exhibits a repeatable contact angle within a range of several degrees. In one embodiment, a pre-prepared polymer sheet exhibits a repeatable contact angle within the range of 5, 4, 3, 2, 1, 0.75, or 0.5 degrees or less. Other surfaces that have been demonstrated to be suitable include polymer films and sheets, corona-treated polymer films and sheets, paper, textiles or cardstock (coated or exposed), printing paper or cardstock, surfaces covered with coatings such as films or paints, vapor-deposited coatings, or self-assembled single-layer or multi-layer surfaces. In one or more embodiments, the coating having known surface properties may be used on a substrate, which is selected from the group including paper, cardboard, corrugated cardboard, plastic, cellophane, textiles, wood, metal, glass, mica sheets, nitrocellulose, or concrete, preferably paper, cardboard, corrugated cardboard, or plastic. In one or more embodiments, the coating may be one or more compositions selected from the group consisting of polymers or metals.

[0032] In one or more embodiments, the coating is applied by spray coating, inkjet printing, offset printing, flexographic printing, screen printing, plotting, contact stamping, rotary gravure printing, spin coating, reverse gravure coating, slot coating, curtain coating, slide bed coating, film press, weighing film press, blade coating, brush coating, and / or pencil, preferably by inkjet printing or spray coating.

[0033] Other suitable surfaces exhibiting a consistent contact angle can be prepared by the user immediately before use by cleaning the surface, for example with a solvent, detergent, or abrasive, or a combination thereof, or by stripping the protective layer or removing the release layer from the composite material immediately before use. An important characteristic is that such a surface has a known and repeatable contact angle. Any surface with a known and repeatable contact angle can be used, but for several reasons, surfaces with higher contact angles are advantageous. As shown in Equation 1, the larger the contact angle, the lower the surface energy. Surfaces with lower surface energy are more stable and resistant to contamination and reactions with the environment, making them more practical for use as volumetric measuring devices.

[0034] In one embodiment, the technological innovation of the present invention demonstrates a particularly preferred approach to providing a surface having a water contact angle of about 75° with a standard deviation of about 1° using cardstock prepared by a printing process. Once a batch of such cards is printed, the average contact angle obtained by the surface of that particular batch is preferably established by calibrating a reference test. Each batch test takes into account lot-to-lot variations in materials or processes that may affect the contact angle.

[0035] Surfaces with a reproducible contact angle are particularly suitable for measuring the volume of liquid deposited by devices such as inkjet printers or surface energy measuring devices. In one application, the volume of liquid deposited from a small valve is determined for the purpose of measuring surface wettability. This device deposits a droplet, images the droplet from above to determine the average diameter or area of ​​the contact patch, and uses this information along with the assumed volume of liquid to calculate the contact angle. However, if the volume of deposited liquid changes over time, for example due to drift in the characteristics of the mechanism, an error will occur in the calculated contact angle. It is beneficial to be able to periodically check and verify the amount of deposited droplets. This is preferably done by depositing droplets on a surface with a known contact angle, such as the surface of a composite calibration reference material that has been recently exposed by removing a release layer or some other cleaning method, or a single cardstock that is printed with ink to produce a surface with a consistent contact angle, and calculating the accurate volume using Equation 2 above. In this way, the accuracy and precision of the deposited volume can be checked and adjusted as needed.

[0036] The reference wettability measurement of a reference surface can be measured by any means well known to those skilled in the art. Wettability can be determined by contact angle goniometry. In one embodiment, wettability is determined using the drop method (or static drop method). In another embodiment, wettability is determined using forward and / or backward contact angle measurements, optionally using a Wilhelmie balance. In one embodiment, the forward and backward contact angles of a calibration reference material can be verified using the following two instruments and procedures.

[0037] (a) Test method using a tensiometer. The tensiometer measurement method used herein is a set of methods used to measure the contact angle and wettability of a surface, and includes gravimetric measurement of the interaction forces when a solid comes into contact with the test liquid (Wilhelmy method). These interaction forces are dynamic measurements and reflect the interaction of the entire immersed article (wetting length). The forces are measured as the article moves into and out of the test liquid. From these measurements, both the advancing contact angle and the receding contact angle can be indirectly calculated, respectively (Wilhelmy formula). In one embodiment, the Wilhelmy method may utilize a dynamic contact angle analyzer (DCA).

[0038] (b) Test method using a goniometer. The goniometer measurement method used herein involves optical observation of a droplet of test liquid on a solid substrate. The tangential angle of each test liquid is measured in order to directly measure the contact angle. Depending on the method of droplet deposition, the goniometer can establish forward, backward, or intermediate contact angles. These angles reflect only the average force applied from the area below the periphery (contact line) of the droplet, rather than the majority of the article. Using these angle calculations, the surface energy and corresponding components can be determined. In one embodiment, the goniometer measurement method includes a backlit droplet that is optically imaged, and the angle determined by the droplet at the solid-liquid contact point is determined using a machine vision algorithm.

[0039] In one or more embodiments, the present invention can establish an advancing, receding, or intermediate contact angle by varying the kinetic energy imparted to the deposited droplet. Droplets deposited with a large amount of kinetic energy per unit volume establish a contact angle close to the receding angle. Droplets deposited with little to no kinetic energy per unit volume establish a contact angle close to the advancing angle. The amount of accumulated kinetic energy can be adjusted anywhere between the advancing and receding contact angles. Thus, the parameters of the liquid deposition device can be adjusted so that droplets are deposited with a moderate amount of kinetic energy per unit volume, establishing a contact angle midway between the receding and advancing contact angles or near there. Such an approach is useful for deposition on materials with a wider range of surface properties.

[0040] In one or more embodiments, the test droplets need to be deposited under substantially the same deposition conditions as the kinetic energy used to determine the characteristic contact angle of the calibration reference surface.

[0041] Both goniometer and tensiometer testing methods achieve similar results with goniometers, which are static measurements over small areas. In another embodiment, Dyne solutions or pens containing these solutions can be used. Dyne solutions are chemical blends of various surface tensions that wet a surface if the surface energy is sufficiently high, or form beads if the surface energy falls below a predetermined threshold. The value determined using Dyne solutions is called the wetting tension of the surface. In some cases, the wetting tension can be used to calculate the characteristic contact angle of the surface.

[0042] In one or more embodiments, the present invention provides an automatic or semi-automatic method for precisely adjusting the volume of liquid deposited by a device. If the diameter, height, radius of curvature, or cross-sectional area of ​​a droplet placed on a surface with a known contact angle differs from an expected value based on the assumed volume of the liquid, the amount of liquid deposited can be increased or decreased until the desired diameter or height of the droplet matches the expected value.

[0043] A suitable level of kinetic energy is in the range of approximately 0.1 to 10 μJ for droplets with a total volume in the range of 0.1 to 5 μl. In one embodiment, these impart a total kinetic energy in the range of approximately 0.5 to 2 μJ to the droplet.

[0044] Volumetric flow rate in liquid processing systems is a critical parameter that can be difficult to measure and control, especially when the flow rate is low or intermittent. Examples where controlling low or intermittent flow rates is critical include inkjet, i.e., "drop-on-demand" technology, printing systems, automated compound chemical devices, automated cell culture systems, and titration devices. The methods and devices of the present invention can be used in the medical and biotechnology industries, as well as other industries. Examples of use for precisely adjusting the volume of liquid deposited by the device include hematology equipment, bioassays, chemical synthesis, gene analysis, drug screening, antigen-antibody reaction sequencing, and combinatorial chemistry, drug testing, medical and biological diagnostics, and combinatorial chemistry. The methods and devices are also used in electrochromatography, surface micromachining, laser ablation, inkjet printers, and mechanical micromilling. In these systems, the liquid flow rate and dispensing volume may change due to factors such as changes in the amount of contaminated air or temperature changes. Conventional mass flowmeters, which rely on the thermal conductivity of the liquid or other properties that change with flow rate, are not useful in these situations. In such situations, the flow rate or dispensing volume can be intermittently checked and adjusted as needed by dispensing droplets onto a surface with a known contact angle and measuring the geometric characteristics of the droplets, such as the diameter or height of the contact patch.

[0045] As an example, U.S. Patent No. 8,272,254, which is incorporated in its entirety by reference herein, describes a device for measuring the contact angle of a liquid on a surface. This device uses a valve to supply liquid from a pressurized reservoir to deposit a droplet on a surface. The device then takes an image of the droplet and determines the diameter of the contact patch from the image. The contact angle is then calculated from the area or diameter of the droplet, which is determined in advance by directly measuring the mass of the liquid, and the assumed volume of the liquid. If the actual liquid volume differs from the assumed volume, an error will occur in the calculated contact angle. This can occur if air bubbles are unintentionally introduced into the system during a replenishment operation, or if dissolved air leaks from the solution.

[0046] Accuracy can be verified by depositing droplets onto a surface where a known contact angle is obtained under given deposition conditions, such as a single cardstock printed with ink that provides a consistent, known contact angle. The contact angle is calculated by the instrument, assuming the original droplet mass. To improve accuracy, multiple measurements can be averaged on the test surface. If the calculated contact angle differs from the expected contact angle on the printed cardstock surface, the instrument can adjust the volume of the deposited droplet by changing the droplet volume value used in the contact angle calculation or by adjusting the droplet deposition parameters. This process can be repeated as needed to achieve any level of reliability in the accuracy of the deposited volume.

[0047] Figure 3 shows a test apparatus 300 for rapidly determining the volume of a droplet 302 on a surface 304 of a test article 306 based on a known contact angle. In particular, the test apparatus 300 detects one or more geometric features of the droplet 302, such as height, cross-sectional area, radius of curvature, and diameter. While the dimensions of droplets of any volume can be measured, it has been found to be advantageous to use droplets with dimensions of approximately 0.1 to 10 millimeters. In one embodiment, the dimensions of the droplets are approximately 0.5 to 5 millimeters. In one embodiment, the test apparatus 300 is incorporated into a portable housing 308 to form a test device 310. In one embodiment, a single portable device may be highly suitable for use in manufacturing environments with various surfaces and structures of various orientations.

[0048] The test device 310 positions an imaging sensor 312, such as a video camera with an optical telescope, at a known point of good visibility to the surface 304. The test device 310 may include a positioning component 314 that provides a physical reference or detection reference to the surface 304. The liquid dispenser 316 dispenses liquid 318 as droplets 320 along a trajectory toward the surface 304, forming a controllable amount of energy that is transferred to the droplets 302. For example, the liquid 318 can be contained in a liquid reservoir 322, which is propelled by a peristaltic pump 324 through an orifice 326 of the liquid dispenser 316, which is sized to produce droplets 320 at a selected volume and rate.

[0049] In one or more embodiments, the liquid is supplied from a pressurized reservoir that can propel the liquid out of a valve with a desired energy.

[0050] In one or more embodiments, the test apparatus 300 includes a nozzle valve orifice 334 having a valve adapted to selectively block and allow the flow of liquid through the orifice. In one or more embodiments, the processor 353 and nozzle valve orifice 334 are adapted so that a liquid dispenser 316 dispenses liquid 318 as droplets onto the test surface at flow rates of less than approximately 50, 45, 40, 35, 30, 25, 20, 15, or 10 μl / second. In another embodiment, the processor 353 and nozzle valve orifice 334 are adapted so that the liquid dispenser 316 dispenses liquid 318 as droplets onto the test surface at flow rates greater than approximately 0.1, 0.5, 1, 1.5, 2, 2.5, 3, 4, or 5 μl / second.

[0051] In one or more embodiments, the flow rate may be controlled by the processor 353 by controlling and adjusting, for example, the valve opening and / or the pressure applied by the liquid pressurization system (e.g., a specified pressure of pressurized gas applied by the compressed gas system). In one or more embodiments, the processor 353 is adapted to adjust the droplet volume for each test apparatus by adjusting the time interval at which each valve is opened, the valve opening, and / or the pressure applied by the liquid pressurization system (e.g., a specified pressure of pressurized gas applied by the compressed gas system). In one or more embodiments, the processor 353 is adapted to automatically calibrate the droplet volume for each liquid dispenser by adjusting the time interval at which each valve is opened, the valve opening, and / or the pressure applied by the liquid pressurization system (e.g., a specified pressure of pressurized gas applied by the compressed gas system) according to the droplet volume deposited and calculated on the calibration reference surface.

[0052] The liquid dispenser 316 can control the energy of the droplet 320. High kinetic energy generates a receding contact angle, while low kinetic energy generates an advancing contact angle. A minimum amount of kinetic energy is required to give sufficient energy to the droplet 302 and achieve the desired contact angle, compensating for air drag and gravity effects along the trajectory. For example, the kinetic energy can be controlled by the size of the nozzle valve orifice 334. In another example, the kinetic energy can be controlled by a variable amount of pressure applied by the peristaltic pump 324. Pressures ranging from 0.1 pounds / square inch (psi) to 10 psi or more have been shown to be suitable. In one exemplary embodiment, the nozzle has a sapphire orifice with a diameter of 0.003 to 0.007 inches. This nozzle achieves a higher velocity at the same pressure as a stainless steel nozzle with a 0.015-inch stainless steel orifice.

[0053] In one or more embodiments, the test apparatus also includes one, two or more liquid dispensers, each of which is in fluid communication with a liquid reservoir arrangement, more specifically with at least one liquid reservoir of the liquid reservoir arrangement. Each of these liquid dispensers is adapted and positioned to apply a drop stored in the liquid reservoir arrangement to the surface of the test surface. If two or more liquid dispensers are provided, they may be coupled to the liquid reservoir arrangement to apply the same liquid to different locations on the surface, for example, to determine variations in surface properties, or they may be coupled to different liquid reservoirs of the liquid reservoir arrangement to store different liquids.

[0054] Exemplary liquids that can be used in the devices and methods described herein are water, dimethyl sulfoxide (DMSO), a mixture of formamide and glycol monoethyl ether, a mixture of water and ethanol, and other liquids having the desired wettability. In one embodiment, deionized ultrafiltered water is used for test purposes.

[0055] In one or more exemplary embodiments, the ambient temperature, sample temperature, and test solution temperature, as well as the relative humidity, are controlled. In one embodiment, the test is conducted within a maximum range of 15°C (59°F) and 35°C (95°F), and within a relative humidity of 35% to 70%. In another embodiment, the test is conducted within a maximum range of 20°C to 25°C and within a maximum range of 40% to 60% RH.

[0056] The image sensor 312 can be positioned to measure one or more parameters of the droplet 302, including its volume, height, base diameter, and curvature. The data generator 340 analyzes images 345a and 345b of the droplet 302 to measure one or more parameters selected from the group consisting of the height, base diameter, and curvature of the droplet 302. Based on the analysis, the data generator 340 calculates the volume of the droplet 302 based on a known contact angle and the measured dimensions. In one embodiment, the test device 310 further includes an illuminator 346, such as a laser. The data generator 340 detects the geometric characteristics of the droplet 302 via the image sensor 312 by illuminating the droplet 302 with the illuminator 346.

[0057] The test device 314 may also include additional illumination sources, such as light-emitting diodes (LEDs), lasers, fluorescent lamps, incandescent lamps, strobe lights, camera flashes, or other suitable light sources for illuminating the volume of liquid on the surface of the material. The illumination sources may be incorporated into the housing 320 or separated from the housing 320.

[0058] The test device 314 can be operated by a single actuator, or, if desired, by adding additional actuators including a visual display 351 and an auditory signaling device 352, or a user interface 350, to control the device or input data such as sample information or test parameters. The user interface 350 may include a touchscreen, keypad, toggle, button, rollerball, wheel, dial, mouse, etc. The test device 314 may include a processor 353 and may optionally be completely housed within the housing 320. The test device 314 may utilize a memory 354 in which data collected and generated by the test device 314 can be stored in a storage device 356. The data generator 340 may include a surface material detection utility 358 stored in the storage device 356 and executed by the processor 353. The stored data can be retrieved from the device by known methods, such as wireless transmission to a remote device, transmission to storage on removable media such as a thumb drive or memory chip (not shown), or transmission via an electrical cable or docking station (not shown). The stored data could have various uses, such as quality control and compliance with manufacturing standards and regulations.

[0059] The processor 353 controls the operation of the liquid pressurization system, particularly the pressure applied to or from the liquid, and is adapted to preferentially automatically control the opening and closing of each nozzle valve orifice 334 for each droplet dispensing device, to advantageously apply each droplet having a specified droplet volume to the surface of the pressurized liquid jet from the outlet of each liquid line. Driven by pressure applied by a liquid pressurization system, such as pressurized gas from a compressed gas system, this jet may be supplied as a continuous flow or as a series of droplets, depending on the properties and flow parameters of the liquid in question.

[0060] The processor 353 may be an electronic component, such as a microcontroller, which can be advantageously integrated into a common housing with some or all of the remaining components of the device. However, it is also possible to have the processor 353 as a separate computing device, such as a properly programmed computer or PC, which is connected to the rest of the device and is not integrated into a common housing with the other components of the device.

[0061] The test device 314 enables the measurement of minute volumes of fluid samples and reagents, resulting in a portable biometric and diagnostic tool with faster processing speeds. The test device 314 is used in medical, pharmaceutical, chemical, biological diagnostics, environmental testing, food testing, water quality testing, and other fields. It can be used in a range of antigen-antibody reactions, drug testing, medical and biological diagnostics, and combinatorial chemistry. Other applications of the system 30 include inkjet printers, hematology equipment, bioassays, chemical synthesis, gene analysis, drug screening, electrochromatography, surface micromachining, laser ablation, and mechanical micromilling. The test device 314 is easy to manufacture and integrate. It is used in many fields, particularly in the medical and biotechnology industries.

[0062] The device includes a housing, a liquid dispensing component, a positioning component, and a data generation component. The liquid dispensing component, also referred to herein as a liquid dispenser, is configured to deposit a fixed amount of liquid onto the surface of a substrate material. The positioning component is configured to obtain information about the device's position relative to the volume of liquid on the surface. The data generation component, also referred to herein as a data generator, is configured to obtain information about the shape of the liquid volume on the surface of the material.

[0063] In one embodiment of the present invention, a liquid dispenser involves the ballistic deposition of one or more smaller volumes of liquid onto the surface of a material to construct a droplet to be measured. This embodiment includes a nozzle in fluid communication with a liquid reservoir. The liquid is pressurized before leaving the nozzle and may be pressurized in the reservoir, nozzle, or at an intermediate stage such as a peristaltic pump. Pressurization of the reservoir can be achieved by a piston or by other pressurizing techniques such as a pump or gas filling. The nozzle may be electrically operated between an open and closed state so that in the open state pressurized liquid is dispensed through the nozzle onto the surface of the material, and in the closed state no liquid is dispensed. This embodiment dispenses multiple smaller volumes of liquid pulses directed at the same location on the surface of the material to construct a liquid volume. The amount of energy applied to the droplet affects the final contact angle established. Exemplary droplet velocities are in the range of 0.4 to 5.0 meters / second. In one embodiment, the droplet velocity is in the range of 0.8 to 3.0 meters / second. These impart a total kinetic energy to the droplet in the range of approximately 0.1 to 10 μJ. In one embodiment, they impart a total kinetic energy to the droplet in the range of approximately 0.5 to 2 μJ.

[0064] Smaller volumes of liquid may be about 10 nl, 50 nl, 100 nl, 200 nl, 300 nl, or 400 nl. Smaller volumes are supplied in pulses to reach the final volume of liquid, and in one embodiment, may be in the range of about 0.5 μl to about 10 μl. In another embodiment, the final volume of liquid may be in the range of about 1 μl to about 5 μl. In another embodiment, the final volume of liquid is about 2 μl. The volume of liquid may be deposited over relatively short time intervals in the range of about 0.01 seconds to about 1.0 seconds. In one embodiment, the volume of liquid is deposited in about 0.5 seconds or less. Other smaller volumes and final volumes of liquid, as well as deposit times, may also be used in the apparatus and methods described herein.

[0065] In another embodiment, the liquid dispensing component is an elongated hollow projection having an opening distal to the housing, and a fluid reservoir in fluid communication with the hollow projection. Possible examples of elongated hollow projections include injection needles and pipette tips. The liquid volume passes from the fluid reservoir through the hollow projection and exits the hollow projection at the distal opening where it deposits on the surface of the material. The elongated hollow projection may optionally be doubled as a component that imparts kinetic energy. For example, the hollow projection can be coupled to a device that can impart kinetic energy to the hollow projection in the form of vibration, which in turn imparts kinetic energy to the liquid volume. Examples of suitable kinetic energy imparting devices include electromagnetic transducers, piezoelectric transducers, electric motors with eccentric masses, acoustic devices, and combinations of these devices.

[0066] The positioning component determines the position of the device relative to the volume of liquid on the surface by measuring at least one of the distance of the data generation component from the surface of the material or the angle of the data generation component relative to the surface of the material. The positioning component may be as simple as a mechanical probe having a fixed length that maintains a fixed distance between the data acquisition component and the volume of liquid on the surface. In this embodiment, the mechanical probe is in contact with the surface of the material to maintain the relative position of the data generation component. The positioning component may also include a point light source, a laser (not shown), and an acoustic measurement device (not shown).

[0067] The use of point sources, lasers, or acoustic measurement devices as positioning components can enable accurate measurement or calculation of contact angles without the device actually touching the material surface. A point source illuminates a region on the material surface. The shape of the illuminated region is a conical cross-section. By analyzing the shape of the illuminated region along with the liquid volume, the distance from the surface and the angle (α) between the surface plane and the data acquisition component can be calculated. Point sources, lasers, and acoustic measurement devices enable the construction of devices that can be pointed at the surface from anywhere within a distance range such as approximately 0.25 inches to approximately 2 inches, or approximately 0.5 inches to approximately 1.5 inches. The range of distances in which the device can operate is determined by various factors, including, for example, the effective operating range of the liquid dispensing component and / or data generation component.

[0068] A data generation component is a device capable of acquiring information about the geometric shape of the liquid volume on the surface of a material. This geometric information includes the shape of the liquid volume on the material surface, the tip contact angle, the average contact angle, the diameter (d), the average diameter, and / or curvature. Exemplary data generation components include cameras, lasers, scanners, and / or acoustic devices. The exemplary data generation component shown in the figure is a camera. In some embodiments, the data generation component and the positioning component can be included in the same element. For example, a laser or acoustic device can function as both a data generation component and a positioning component.

[0069] The device may also include additional lighting sources such as light-emitting diodes, fluorescent, incandescent, strobe, camera flash, or other suitable light sources for illuminating the liquid volume on the surface of the material. The light source may be integrated into the housing or may be separate from the housing (not shown).

[0070] The device can be operated by a single actuator, or, if desired, additional actuators or user interfaces can be added to control the device or to input data such as sample information or test parameters. The user interface may include a touchscreen, keypad, toggle, button, rollerball, wheel, dial, mouse, etc. The electronic circuitry may include a processor and may optionally be completely housed within the housing. The electronic circuitry may also store data collected and generated by the device. Stored data can be retrieved from the device by known methods such as wireless transmission to a remote device, wireless transmission to storage on removable media such as a thumb drive or memory chip (not shown), or communication via electrical cables or a docking station (not shown). Stored data may have various applications, such as quality control and compliance with manufacturing standards and regulations.

[0071] The device may further include a display coupled to electronic circuitry for displaying information including data and / or images. The display may include light-emitting diodes (including both individual light-emitting diodes and screens), liquid crystal displays, and / or gauges. The display may be located within or on the housing, or within or on the secondary housing of a remote device, and may be coupled to at least part of the electronic circuitry by at least one of electrical contacts (not shown), electrical cables, and wireless connections. The display can convey any information that may be relevant to the use of the device, such as the surface energy of a surface, a display of the volume of liquid on the surface, an image of the volume of liquid on the surface, a path indicator, a fail indicator, an error message, the diameter of the volume of liquid on the surface, the average diameter of the volume of liquid on the surface, the contact angle formed by the volume of liquid on the surface, the surface wetting characteristics, the battery charge, and the reservoir volume.

[0072] The device may optionally include an auditory signaling device (not shown). The auditory signaling device may be a simple tone or mixture of tones, or a complex one such as a voice. The auditory signaling device may indicate, for example, that the device is in use, that the test has been completed successfully or unsuccessfully, a pass or fail indicator, an error, that the device is in the correct relative position to the surface, battery life, and the remaining liquid volume in the reservoir.

[0073] Examples of liquids that can be used in the devices and methods described herein include deionized water, dimethyl sulfoxide (DMSO), a mixture of formamide and glycol monoethyl ether, a mixture of water and ethanol, and other liquids with the desired wettability.

[0074] In one embodiment, surface energy is evaluated as a multi-component vector quantity, and contact angle measurements are determined for multiple liquids in order to obtain a more accurate surface energy calculation value.

[0075] In one embodiment, energy is imparted to the droplet by a microburst of air or another gas, rather than another droplet, in order to obtain a contact angle lower than the advance angle. Once the droplet is energized, a contact angle lower than the advance angle is established. Once the droplet is sufficiently energized, a receding contact angle is established.

[0076] The test display may include light-emitting diodes (including both individual light-emitting diodes and screens for light-emitting diodes), liquid crystal displays, and / or gauges. The display may be located in or on a housing, or in or on a secondary housing or remote device, and may be coupled to at least part of the test device by at least one of electrical contacts, electrical cables, and wireless connections. The display may convey any information that may be relevant to the use of the device, such as the surface energy of a surface, a display of the volume of liquid on a surface, an image of the volume of liquid on a surface, a pass indicator, a fail indicator, an error message, the diameter of the volume of liquid on a surface, the average diameter of the volume of liquid on a surface, the contact angle formed by the volume of liquid on a surface, the shape of the liquid volume on the surface, the wetting characteristics of the surface, the charge of a battery, and the capacity of a reservoir.

[0077] The device may optionally include an auditory signaling device. The auditory signaling device may be a simple tone or mixture of tones, or a complex one such as a voice. The auditory signaling device may indicate, for example, that the device is in use, that the test has been completed successfully or unsuccessfully, a pass or fail indicator, an error, that the test device is in the correct relative position to the surface, battery life, and the remaining liquid volume in the reservoir.

[0078] All publications, patents, and patent applications referenced herein are incorporated by reference as a whole, notwithstanding the foregoing or otherwise, as if each individual publication, patent, or patent application were specifically and individually incorporated by reference.

[0079] As used herein and in the appended claims, it should be noted that the singular forms “a,” “an,” and “the” refer to multiple objects unless the content explicitly indicates otherwise. Therefore, for example, a reference to “coloring agents” includes two or more such agents.

[0080] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art to which the present invention relates. Many methods and materials similar or equivalent to those described herein can be used in carrying out the present invention, but preferred materials and methods are described herein.

[0081] As will be understood by those skilled in the art, the methods and compositions of the present invention substantially reduce or eliminate the disadvantages and drawbacks associated with prior art methods and compositions.

[0082] When used in this disclosure, the terms “contains,” “includes,” and other derivatives of the etymological term “contains” are intended to be non-restrictive terms that identify the presence of the described features, elements, integers, steps, or components, and not intended to exclude the presence or addition of one or more other features, elements, integers, steps, components, or groups thereof.

[0083] Where necessary, detailed embodiments of the present invention are disclosed herein. However, it should be understood that the disclosed embodiments are merely illustrative of the present invention and can be embodied in various forms. Accordingly, the specific structural and functional details disclosed herein should not be constrained, but rather should be interpreted merely as the basis for the claims and as a representative basis for teaching those skilled in the art to utilize the invention in various ways in substantially all appropriately detailed structures.

[0084] While it is clear that the exemplary embodiments of the present invention disclosed herein satisfy the above-described objectives, it will be understood that numerous modifications and other embodiments can be devised by those skilled in the art. Therefore, it should be understood that the attached claims encompass all such modifications and embodiments that fall within the spirit and scope of the present invention.

Claims

1. A method for determining the volume of a small liquid droplet dispensed from a liquid dispensing device, (a) The liquid dispenser deposits a liquid of an assumed volume measured on the calibration reference surface as droplets. The calibration reference surface provides a known contact angle with the droplet under the deposition conditions used, (b) A group consisting of (i) forward contact angle, (ii) backward contact angle, and (iii) intermediate contact angle A known angle is established with the selected droplet, (c) Measure the dimensions of the droplet, and the measured dimensions are (i) the maximum height of the droplet, (ii) the contact Selected from the group consisting of (iii) diameter of the contact patch, and (iv) cross-sectional area, (d) Calculate the actual volume of the droplet from the relationship between the measured dimensions and the known contact angle. The steps include, (i) forward contact angle, (ii) backward contact angle, and (iii) intermediate contact angle are determined by the deposited droplet. It is established by changing the kinetic energy that is given. method.

2. (e) The method according to claim 1, further comprising the step of determining the difference between the assumed volume and the calculated actual volume of the droplet.

3. (f) The method of claim 2, further comprising the step of correcting the difference between the calculated actual volume and the assumed volume of the liquid dispensed by the liquid dispensing device.

4. The method according to claim 3, wherein the correction of the difference between the calculated actual volume and the assumed volume of the liquid dispensed by the liquid dispensing device includes the step of adjusting the actual volume of the liquid dispensed by the test device to correct the difference.

5. The method according to claim 4, wherein the step of correcting the difference by adjusting the actual volume of the liquid dispensed by the liquid dispensing device is performed by adjusting the time interval in which one or more valves are open, the degree of opening of one or more valves and / or the pressure applied to the dispensed liquid by the liquid dispensing device.

6. The method according to claim 4, wherein the liquid dispensing device is a device for measuring the wettability of a liquid on the surface of a material, comprising a liquid dispensing component, a dimensioning component, and a processor component, the liquid dispensing component is configured to deposit a certain amount of liquid on the surface of the material, the dimensioning component is configured to determine one or more dimensions of the liquid deposited on the surface, and the processor component is configured to analyze information regarding one or more geometric features of the volume of liquid on the surface of the material based on the dimensioning component.

7. The method according to claim 5, further comprising the step of calculating the average value of the difference between the assumed volume and the calculated actual volume of the droplet measured from a plurality of regions of the calibration reference surface.

8. The method according to claim 1, wherein the calibration reference surface is a surface coated with an ink, polymer, metal, or other coating having a consistent predetermined contact angle.

9. The method according to claim 1, wherein the liquid dispensing device is a device for depositing a known volume of liquid.

10. A liquid dispensing device calibration system comprising a liquid dispensing component and a dimensional determination component. The liquid dispensing component comprises a to and a processor component, and the liquid dispensing component is located on the surface of the substrate. It is configured to deposit a certain amount of liquid on top, and the dimension-determining component is the dimension A method determination component is connected to determine the dimensions of one or more liquids deposited on the surface. The processor component is configured such that the dimensional determination component is based on the dimensional determination component. Therefore, information relating to one or more geometric features of the volume of the liquid on the surface of the substrate It is configured to analyze, The dimensions to be measured are: (i) maximum height of the drop, (ii) diameter of the contact patch, and (iii) half curvature. Selected from the group consisting of diameter and (iv) cross-sectional area, The processor component is determined by the relationship between the measured dimensions and the known contact angle. The volume of the aforementioned droplet is adapted to calculate (i) the advancing contact angle, (ii) the receding contact angle, (iii) The intermediate contact angle changes the kinetic energy given to the deposited droplet. To be more established, Liquid dispensing device calibration system

11. The liquid dispensing apparatus calibration system according to claim 10, wherein the processor component is adapted to determine the difference between the volume of the dispensed liquid and a predicted volume level.

12. The liquid dispensing apparatus calibration system according to claim 10, wherein the processor component is adapted to transmit an adjustment signal to a nozzle valve coupled to the liquid dispensing apparatus, the signal adjusting one or more parameters so that the nozzle dispenses a liquid volume approximating the predicted volume level.

13. A liquid dispensing device calibration system according to claim 10, wherein the processor component is adapted to controllably adjust the operation of the liquid dispensing component by adjusting one or more parameters of the system selected from the group consisting of the time interval in which one or more nozzle valves are open, the degree of opening of one or more nozzle valves, and / or the pressure applied to the dispensing fluid by the liquid dispensing device.

14. A liquid dispensing device calibration system according to claim 10, wherein the processor component is adapted to automatically calibrate the volume of the droplet for each of the liquid dispensing components by adjusting the time interval in which one or more nozzle valves are open, the degree of opening of one or more nozzle valves, and / or the pressure applied to the dispensing fluid by the liquid dispensing device, based on the calculated volume of the droplet deposited on a calibration reference surface.

15. The liquid dispensing apparatus calibration system according to claim 10, wherein the processor component is adapted to calculate the average value of liquid volumes measured over multiple regions of one or more substrates.

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