Multi-array ejection head and method of use

This is a reissue of the patent application No. 16/875,232, now U.S. Pat. No. 11,090,938.

The disclosure is directed to devices and methods that are used to accurately dispense one or more fluids onto or into precise areas of a substrate for performing analysis of samples confined to the precise areas of the substrate or for building up layers of material in predetermined areas on the substrate.

A device such as an inkjet device, can dispense very small droplets of ink, usually measured in picoliters onto a substrate. For inkjet printing applications, the volume of ink that is deposited is a relatively low amount, and the volume is not as important as other factors such as color matching and print quality. A typical inkjet printer is limited to the deposition of about 2 to about 3 μL/cm. A typical inkjet printhead may have one or more fluid supply vias each associated with a different color ejection head wherein the ejection heads may be provided on a single substrate as shown inor on multiple substrates. Locating the ejection heads on a single substrate has an advantage of reducing the cost of the ejection head. A typical printheadfor an inkjet printer has arrays of fluid ejectorsa-d that are oriented in a y direction perpendicular to a direction of travel of the printheadin the x direction as indicated by arrow.

However, for other applications that require accurate amounts of liquid to be dispensed onto or into a medium, fluid volume is an extremely important and/or a critical factor. For some application, it may be advantageous to specify that a volume of fluid is deposited into or over a specific area. An example may be the dispensing of a single drop of fluid containing a single cell into a well of a micro-well plate. Another example may be dispensing a large number of fluid droplets into a small areas such as filling each of 384 wells in a micro-well plate. Accordingly, the density of fluid deposited into the wells of a well plate may require the dispensing of more than 250 μL/cmof fluid. Likewise, depositing fluid onto a glass slide for analyzing a sample on the glass slide requires that a closely controlled amount of fluid is deposited over a specific area of the glass slide.

In the medical field, in particular, there is a need for automated sample preparation and analysis. The analysis may be colorimetric analysis or require the staining of samples to better observe the samples under a microscope. Such analysis may include drug sample analysis, blood sample analysis and the like. In the analysis of blood, for example, blood is analyzed to provide a number of different factors that are used to determine the health of an individual. When there are a large number of patients that require blood sample analysis, the procedures may be extremely time consuming. Also, there is a need for accurate preparation of the samples so that the results can be relied on. There are many other situations that require sample analysis in the medical field and in other fields that can benefit from the use of analytical instruments that provide accurate and reproduceable results, such as micro-titration of multiple samples.

Well plates, slides and other substrates are used for many experiments and laboratory procedures. The process of filling the wells or spotting is often performed manually or using expensive lab equipment. In some cases, the wells are filled with hand operated pipettes. In other cases, high-end automated devices based on pipette technology are used to fill the well plates. Such automated devices accommodate an open well dispense head only. The open well dispense head is a dispense head where a small amount of fluid must be deposited into an opening in the dispense head before use. The fluid is typically deposited manually using a pipette or similar means. The dispense head is held stationary while moving the micro-well plate in both X and Y directions. These high end devices are extremely expensive.

In the areas of micro-circuit manufacture, fluids are required to be dispensed in precise locations to provide circuit devices on a substrate. The volume of fluid dispensed per unit area is typically much greater than can be provided by conventional ink jet printing technology. In some cases, different fluids are combined together on the substrate to provide a chemical or physical change to the fluids so that the resulting material performs a desired circuit function.

Other areas of micro-manufacturing may also require the precise deposit of fluids into or onto a substrate. There is thus the need for a method and device that can be used to dispense a predetermine volume of one or more fluids per unit area of a substrate.

represents a single wellof a micro-well plate() that is used with a digital dispense device(). When an array of fluid ejectorsa of the printheadis oriented perpendicular to the direction of travel of the printhead, a portion of the fluid ejectorsa will be outside of a target areaof the welland thus will not be used to eject fluid into the well. Fluid ejectors in the ejector arraya that are idle may misfire due to fluid drying out on the printheadadjacent to the idle fluid ejectors. Also, fluid ejectors in the ejector arraya that are too close to the sidewalls of the wellmay cause fluid splashing out of the target area if used during a pass of the ejector arraya over the well.

Using the conventional printheadmay be an effective way to fill a wellof a micro-well plate, however many passes of the printheadmay be required to achieve a large dispense volume of fluid. For example, anozzle array of a conventional printhead printing at a resolution of 1200×1200 drops per inch (dpi) can generate a square with 10,000 drops, or a circle with around 7,853 drops. If a drop size of 10 picoliters (pL) is used, then the square will contain 100,000 pL (0.1 microliters) and the circle will contain 0.079 microliters. In order to achieve a volume of 1 microliter, 10 repeat passes of the printheadwill be required for the square, and more passes than that will be required for the circular example. What is needed therefore is a system and method for depositing relatively large volumes of fluids in a target area with greater accuracy and speed.

Accordingly, an embodiment of the disclosure provides a digital dispense device for ejecting one or more fluids into a target area of a substrate. The digital dispense device includes (A) a fluid ejection head for the digital dispense device having one or more arrays of fluid ejectors thereon; (B) a fluid ejection head translation device for moving the ejection head over the target area of the substrate in a first direction, wherein the one or more arrays of fluid ejectors on the fluid ejection head are oriented parallel to the first direction; and (C) a control device for activating one or more fluid ejectors in the one or more arrays of fluid ejectors as the one or more fluid ejectors intersect the target area of the substrate.

Another embodiment of the disclosure provides a method for dispensing a predetermined amount of fluid into a target area of a substrate. The method includes providing a digital dispense device. The digital dispense device contains (A) a fluid ejection head for the digital dispense device having one or more arrays of fluid ejectors thereon; (B) a fluid ejection head translation device for moving the ejection head over the target area of the substrate in a first direction, wherein the one or more arrays of fluid ejectors on the fluid ejection head are oriented parallel to the first direction; and (C) a control device for activating one or more fluid ejectors in the one or more arrays of fluid ejectors as the one or more fluid ejectors intersect the target area of the substrate. The fluid ejection head is moved over the target area of the substrate while activating one or more fluid ejectors to eject fluid into the target area until a predetermined amount of fluid is deposited in the target area.

In some embodiments, the fluid ejection head contains two arrays of fluid ejectors thereon. In other embodiments, the fluid ejection head contains three arrays of fluid ejectors thereon. In still other embodiments, the fluid ejection head contains four arrays of fluid ejectors thereon.

In some embodiments, the fluid ejection head contains four arrays of fluid ejectors thereon and the four arrays of fluid ejectors are arranged in a two-dimensional matrix.

In some embodiments, the target area of a well of a micro-well plate is 5 to 50% less than a total open area of the well of the micro-well plate.

In some embodiments, the each array of the one or more arrays of fluid ejectors spans more than one well of a micro-well plate. In other embodiments, each array of the one or more arrays of fluid ejectors has a span greater than the target area.

In some embodiments, the fluid dispense system includes a substrate translation mechanism for moving the substrate in a second direction perpendicular to the first direction. In other embodiments, the substrate is indexed in the second direction after the fluid ejector head has traversed the substrate a predetermined number of times.

In some embodiments, fluid is ejected only along a centerline of the target area. In other embodiments, the fluid ejectors are activated only in a portion of the target area that results in reduced fluid splattering outside of the target area.

In some embodiments, all of the fluid ejectors in the one or more arrays of fluid ejectors are activated at least once as the one or more arrays of fluid ejectors pass over the target area.

In some embodiments, a minimum velocity for movement of the ejection head over the target area is used and maximum frequency for activating the one or more fluid ejectors is used to thereby eject a maximum amount of fluid in the target area.

The device and method described herein improve the speed by which a precise amount of the one or more fluids is dispensed in a predetermined area of a substrate. Thus, the system and method may be used for performing analysis of samples and for micro-manufacturing of electrical and other devices.

In contrast to convention inkjet printing devices, the disclosed embodiments provide a unique fluid ejection head for dispensing a predetermined amount of fluid into a target area as described in more detail below. One application of the fluid ejection head is the deposition of fluids onto a substrate such as into wellsof the micro-well plate() using a digital dispense device. For purposes of this disclosure, the substrate described herein is the micro-well plate. However, the devices and methods described herein may be applied to the deposition of fluids onto any suitable substrate including, but not limited to, glass slides, circuit boards, and the like.

As a trayholding the well plateis moved by a translation mechanismthrough the digital dispense devicein a y direction as indicated by arrow, a fluid ejection head(), according to an embodiment of the disclosure, moves in the x direction as indicated by arrowwhich is orthogonal to y direction so that fluid can be dispensed into the wellsin each rowof the micro-well plate. Unlike the conventional printhead of, the fluid ejection headaccording to the disclosure has ejector arraysa-d disposed parallel to the x direction of travel of the fluid ejection head. Also, ejector arraysa-c andb-d are spaced-apart a distance Y ranging from about 4 to about 5 mm that corresponds to the centerline of each well. Likewise, each ejector arraya-b andc-d is spaced-apart a distance X that may range from about 1000 to about 1100 μm and each ejector arraya-d has a length L ranging from about 1800 to about 2000 μm. In other embodiment, the length L of each ejector arraya-d may be greater than the diameter of each well.is a close-up view off an ejector arraya containing two columns of fluid ejection nozzlesa andb disposed on opposite sides of a fluid supply via.

When the ejector array of the fluid ejection headis larger than the diameter of the wellsor a predetermined target area for fluid deposition, only select portions of the ejector arraysa-d will be activated to deposit fluid into the well.illustrates a sequence for activating groups of fluid ejectors defined by primitives P-Pin the ejector arraya as the fluid ejection headmoves in the direction of arrowacross a single well. In the first stepof the sequence only the fluid ejectors in primitive Pare activated to deposit fluid into well, In the second stepof the sequence, the fluid ejectors in primitives Pand Pare activated. In the third stepof the sequence, the fluid ejectors in primitives P, Pand Pare activated. As the fluid ejection headcontinues to move in the direction of arrow, as shown in step, only the fluid ejectors in primitives Pand Pare activated. In stepof the sequence, the fluid ejectors in primitives P, Pand Pare activated, and in step, the fluid ejectors in primitives Pand Pare activated. The fluid ejectors in each of the primitives P, P, and Pmay be activated sequentially or randomly as fluid ejection headmoves over the target area.

In order to improve the accuracy and speed of depositing fluid in the predetermined target area or receptacle of a substrate, the following assumptions for a single array of fluid ejectors is provided:

Once the fluid ejection headis in motion, each fluid ejector in the array will transverse the target area or receptacle. For a single ejector array dispensing fluid, the array is positioned so that it crosses the full diameter of the wellin the case of a circular well. If the receptacleis rectangular (), then positioning of the ejector array is less critical, but targeting the central areaof the rectangular receptacleis still the best practice. However, due to positioning accuracy of the ejector array as well as fluid jetting misdirection and potential satellite deposition of fluid, the target areaof the receptaclewill be smaller than the actual receptacle. The target area depends on the device accuracy as well as the ejector array's accuracy. Likewise, for a circular receptacle, the target areawill be smaller than the receptacle.

As the ejector array moves relative to the receptacleor, fluid ejectors according to the primitives described above will enter the target areaorone by one, and later leave the target area one by one, in a “first in first out” manner. Considering just one fluid ejector in the nozzle array, the number of fluid droplets the fluid ejector can dispense at a specific frequency can be calculated. In order to calculate the number of fluid droplets per fluid ejector, the velocity of the fluid ejection headis set to Sbecause the minimum velocity of the fluid ejection headwill produce the greatest volume output of fluid. The jetting frequency is set to the maximum frequency Fsince this also produces the greatest volume output of fluid. The number of fluid droplets per fluid ejector is calculated by the formula:DropletsPerFluidEjector=F*D/S.

For example, if the target diameter is 4 mm, the maximum jetting frequency is 18 Khz, and the minimum speed of the fluid ejection headis 25.4 mm/sec, one fluid ejector in the ejector array will dispense 18,000*4/25.4=2835 fluid droplets.

Since each fluid ejector in our ejector array will take the same path across the receptacle, the total fluid droplets over the entire ejector array can be calculated by the formula:TotalFluidDroplets=DropletsPerFluidEjector*N.

For example, if there are 100 fluid ejectors in each ejector array, then the total droplets per ejector array will be 2835*100=283,500 droplets of fluid.

Each droplet will contain a certain volume of fluid, so the dispensed volume of fluid can be calculated by the formula:VolumeDispensed=Droplets Total*V.

For example, if each fluid ejector in the ejector array ejects droplets of 10 picoliters (pL), then the total volume dispensed is 283,500*10 pL=2,835,000 pL or 2.835 (μL) of fluid.

If we assume that the optimal jetting frequency Fis also the maximum frequency (at least for the moment), then the calculation above represents the maximum fluid volume that can be dispensed in one pass of the fluid ejection headover the receptacleor. If the target volume is larger than the maximum volume, then multiple passes of the fluid ejection headover the receptacle will be required, since the fluid ejection head is already moving at the lowest speed the device can provide.

If the target volume is lower than the maximum volume output of the ejector array, then a maximum speed for the fluid ejection head using the first equation according to the formula is as follows:S=F*D/DropletsPerFluidEjector.

For a lower value for DropletsPerFluidEjector, the equation becomesDropletsPerFluidEjector=Target Volume(droplets)/NwhereTarget Volume(droplets)=V/V.

So, after substituting variables, the equation for the optimum fluid ejection head speed Sbecomes:S=F*D/((V/V)/N)

A simpler equation that only uses the ratio of Vto Vcan be used as follows:S=S*V/Vwhere Sis the calculated speed of the fluid ejection head.

Using the previous example values with a target volume of 1.0 uL (1000000 pL):S=18,000 hz4 mm/((1000000/10)/100)=72 mm/sec.Or with the simpler equation:S=25.4 mm/sec2.835 μL/1.0 μL=72 mm/sec.

Accordingly, the fluid ejection head or fluid ejector array can move at 72 mm/sec and still achieve the target volume.

However, if the calculated speed of the fluid ejection head exceeds S, then several things can be done to compensate for the slower speed of the fluid ejection head. First, the fluid ejection frequency can be reduced using Sas the speed of the fluid ejection head and recalculating the fluid ejection frequency to use in the equations rather than the maximum fluid ejection frequency. It is desirable, however, a fluid ejection frequency that will work with the device is determined by selecting a frequency from the closest match of fluid ejection frequencies to the calculated frequency and modifying the speed to compensate for the fluid ejection frequency.

A second option would be to reduce the target diameter or area. By reducing the target diameter or area, the same calculated speed and optimal fluid ejection frequency can be used thereby delivering the correct volume of fluid to the receptacle.

A third option would be to reduce the number of fluid ejectors in the nozzle array that are used. This third option would provide a similar outcome to second option without reducing the target diameter or area. The disadvantage of the third option is that some of the fluid ejectors would be idle and thus may require additional cleaning or maintenance before use for the next fluid ejection job.

The equation for reducing the fluid ejection frequency may be calculated using the Droplets Per Fluid Ejector equation above and solving for the new frequency as follows:F=DropletsPerFluidEjector*S/D.

As before Droplets Per Fluid Ejector is now a value associated with the target volume rather than a maximum volume according to the equation:DropletsPerFluidEjector=Target Volume(Droplets)/NwhereTargetVolume(Droplets)=V/Vso:F=((V/V/N)*(S/D).

Alternatively, the same answer can be obtained by using a ratio of the max speed to the calculated speed as follows:F=F*S/S,wherein Sis the uncapped calculated fluid ejection head speed from the previous fluid ejection head speed calculation.

A reduced target diameter can be calculated using the following formula:D=DropletsPerFluidEjector*S/Fwhereas before, DropsPerFluidEjector=(V/V)/N.

The known volumes can be used in the following equation:D=((V/V)/N)*S/F.

Or the ratio of max speed to calculated speed can be used as follows:D=D*S/Sto get the same result.

So far only one receptacle has been considered, however, there may be many receptacles in a row to fill with fluid, and based on the ejector array length L and receptacle diameter, there could be more than one receptaclea-c filling at the same time, as shown by the hashed circles in. In this scenario, the fluid ejection head speed is limited by the receptaclea that requires the lowest fluid ejection head speed for filling with fluid.

For the other receptacles, a method such as changing the frequency or target diameter to account for the difference in fluid ejection head speed may be used to compensate for the slower fluid ejection head speed. If the device can deliver different frequencies to each fluid ejector, modifying the frequency would be the best choice. However, if changing the fluid ejection frequency to individual fluid ejectors is not possible, reducing the target diameter of the receptaclesa-c as shown inmay be a suitable choice that will work in most cases.