FIELD OF THE INVENTION

[0002] The present invention generally relates to non-contact liquid transfer systems and in particular to acoustic liquid transfer systems with multiple sources and targets that may be dynamically positioned for liquid transfer.

DESCRIPTION OF RELATED ART

[0003] Many methods for the precision transfer and handling of fluids are known and used in a variety of commercial and industrial applications. However, most of these methods require the direct contact of transfer device with the source fluid, thus increasing the risk of cross contamination between various fluid sources. The presently burgeoning industries of biotechnology and biopharmaceuticals are particularly relevant examples of industries requiring ultra-pure fluid handling and transfer techniques. Not only is purity a concern, current biotechnological screening and manufacturing methods also require high throughput to efficiently conduct screening of compound libraries, synthesis of screening components, and the like.

[0004] Fluid transfer methods that require contacting the fluid with a transfer device, e.g., a pipette, a pin, or the like, dramatically increase the likelihood of contamination. Many biotechnology procedures, e.g., polymerase chain reaction (PCR), have a sensitivity that results in essentially a zero tolerance for contamination. Accordingly, a non-contact method for fluid transfer would result in a drastic reduction in opportunities for sample contamination.

[0005] Furthermore, fluid transfer methods that require physical contact with source fluids also require elaborate mechanical controls and cleaning mechanisms, and do not conveniently and reliably produce the high efficiency, high-density arrays.

[0006] Biotechnology screening techniques may involve many thousands of separate screening operations, with the concomitant need for many thousands of fluid transfer operations in which small volumes of fluid are transferred from a fluid source (e.g., a multi-well plate comprising, for example, a library of test compounds) to a target (e.g., a site where a test compound is contacted with a defined set of components). Thus, not only the source, but also the target may comprise thousands of loci that need to be accessed in a rapid, contamination-free manner.

[0007] Similarly, biotechnology synthesis methods for the generation of tools useful for conducting molecular biology research often require many iterations of a procedure that must be conducted without contamination and with precision. For example, oligonucleotides of varying lengths are tools that are commonly employed in molecular biology research applications, as, for example, probes, primers, anti-sense strands, and the like. Traditional synthesis techniques comprise the stepwise addition of a single nucleotide at a time to a growing oligomer strand. Contamination of the strand with an erroneously placed nucleotide renders the oligonucleotide useless. Accordingly, a non-contact method for transferring nucleotides to the reaction site of a growing oligomer would reduce the opportunity for erroneous transfer of an unwanted nucleotide that might otherwise contaminate a pipette or other traditional contact-based transfer device.

[0008] In order to meet these needs, methods have been developed utilizing acoustic waves to eject fluids out of source reservoirs. The acoustic droplet ejection systems allow for a non-contact method for the precision-transfer of small amounts of fluid in a rapid manner that is easily automated to meet industry needs. An exemplary non contact system for ejecting liquid droplets to a target location is described in U.S. Patent Application, Publication No. 2002/0094582 A1, published Jul. 18, 2002, entitled “Acoustically Mediated Fluid Transfer Methods And Uses Thereof” and it is incorporated herein by reference in its entirety.

[0009] However, a major obstacle in developing a reliable and cost-effective fluid ejection system lies in the development of an appropriate coupling interface for the wave-guide. As seen in FIG. 2 of the US Patent Application Publication No. 2002/0094582, coupling medium 20 is distributed across the entire bottom surface of fluid containment structure 30. This may increase the difficulty in changing fluid containment structure and changing alignment of the acoustic liquid deposition emitter. Dispersion or wicking of coupling fluid from the edge of the source fluid containment structure may also be a problem in this design.

[0010] Another example of non contact system for ejecting liquid droplets to a target location is described in U.S. Patent Application, Publication No. 2002/0037359 A1, published Mar. 28, 2002, entitled “Focused Acoustic Energy In The Preparation of Peptide Arrays.” As seen in FIG. 1 of the 2002/0037359 publication, the coupling medium 41 extends beyond the edges of the reservoir or fluid containment structure. The structure described in this application makes it difficult to replace or change source fluid containment structure without inadvertently spilling or splattering the coupling liquid since the coupling medium is not isolated. In addition, since the coupling medium 41 expands across the base 25 of the reservoir, it is also difficult reposition the acoustic radiation generator 35 while maintaining the coupling interface provide by the coupling medium 41.

[0011] Yet another example of the droplet ejection systems which utilize acoustic energy is U.S. Pat. No. 4,751,530 issued Jun. 14, 1988 to Elrod et al. The '530 patent describes an acoustic print head 11 having an array of spherical lenses 12a-12i. The print head 11 is submerged in a pool of ink 16, as shown in FIG. 2. The lenses 12a-12i may be acoustically isolated from each other “such as by providing narrow slots 66 between them which are filled with air or some other medium having an acoustic impedance which differs significantly from the acoustic impedance of the substrate 22 such that an acoustic mismatch is created.” See col. 5, line 62 to col. 6, line 8 and FIGS. 7-8 of U.S. Pat. No. 4,751,530. The slots 66 however do not extend the full thickness of substrate 22 nor do the slots surround each side of the substrate 22. Thus, there is no full isolation of the wave-guide or acoustic propagation path. Because this design requires that the acoustic wave generation units be immersed in the source fluid, different fluids would require separate wave generation and propagation paths positioned in each pool of fluid. Another associated consequence of immersing the acoustic wave generation unit in the source fluid is that the same wave generation and propagation unit can not be used with separate fluid containment structures without the risk of cross contamination. In addition, since this particular design requires the source fluid to be distributed over an array of emitters, it does not need nor suggest the use of a coupling interface.

[0012] Existing non-contact liquid transfer systems are limited and do not provide for high-throughput transfer of liquids and their ability to generate high-density arrays in an efficient and reliable manner are also limited. A system that is capable of transferring a large number of liquids from their receptive locations in a high density array to target locations comprise of another high density array in a predetermined pattern with precision, not only may be used for generating high-density arrays for screening or synthesis of chemical compound, the system itself may be implemented as the platform for synthesis and/or screening.

[0013] Accordingly, there exists a need in the art for a non-contact method for the precision transfer of small amounts of fluid in a rapid manner that is easily automated to meet industry needs. A system that is capable of efficient transfer of liquids from any location in a first set of well plates to a second set of well plates in any order and pattern, may provide significant advantages in high-throughput liquid transfer, high-throughput biological/chemical/biochemical synthesis and/or high-throughput screening of biological/chemicals/biochemical compounds.

SUMMARY OF THE INVENTION

[0014] Accordingly, the invention in one embodiment provides an acoustic wave source, which is capable of ejecting liquid from a pool of source liquid onto a target location. Another embodiment of the present invention provides for a mechanism to align any location in an array or arrays of source fluid pools with any location in an array or arrays of target locations, such that liquid may be transferred from any location in the source liquid array or arrays to any location in the target location array or arrays. Yet another embodiment of the present invention provides an image detection system for controlling and/or monitoring the fluid transfer between the source liquid array and the target location array. The image detection system may be implemented for aligning a source liquid array with a target location array, monitoring the transfer of liquid, or monitoring/recording reactions/condition within the target location after the completion of liquid transfer. Various other embodiments and advantages of the present invention will become apparent to those skilled in the art as more detailed description is set forth below.

[0015] In one aspect of the present invention, an integrated system is provided for non-contact transfer of small amounts of liquid materials from source vessels (or source fluid containment structures) to target vessels (or target devices, plates or surfaces). “Non-contact,” as used herein, means that a source liquid is transferred or removed from a source pool of liquid without contacting the source liquid with a transfer device. Because energy waves, such as acoustic waves, are used to force one or more drops of liquid out of the source pool and into a target region, no physical device needs to come into contact with the source pool to effectuate the transfer of the liquid.

[0016] In another aspect of the invention, an apparatus is provided for random-access liquid transfer. The random-access liquid transfer capability may allow transfer of a liquid from any location within a matrix of source fluid vessels to any location within a matrix of targets. For example, the source vessels may comprise a series of well plates, and the target vessels may comprise a separate series of well plates. Liquids from different wells (which may be from the same plate or a different plate) may be transferred to different or same target wells (which may be from the same plate or different plate) one after another in any sequence or pattern that is prescribed by the user. Unlike most system on the market, which require linear sequential access of source materials and has a predefined pattern of delivery to the target locations, this apparatus may allow non-linear and/or random access of both source liquid pools and target locations. That is to say, the user may eject fluid from any source liquid location in the source vessels into any target location in the target vessels, and the next source fluid location and target location may also be any source liquid location and any target location in their receptive arrays of vessels. The selection of the source liquid location and target location is completely independent of the previous source/target location selections.

[0017] In yet another aspect of the invention, the fluid transfer apparatus may allow transfer of predefined volume of liquids from a source vessel to a target vessel. The apparatus may be designed such that in a series of ejections, different volumes of liquid are transferred in each ejection. The user may also program the apparatus to deliver a series of liquid droplets of various sizes that are predefined by the user. As it will be apparent to one skilled in the art, various variations of the apparatus may be utilized for drug discovery or chemical synthesis.

[0018] In one variation, the non-contact, random-access liquid transfer apparatus is comprised of a) an acoustic emitter device, b) two X/Y linear stage assemblies, c) two handling devices, one each attached to the X/Y stage assemblies, d) two storage queues, one for source vessels and the other for target devices, e) a image detection system, f) machine controls, electronics and software, g) frame and support structure, and h) environment and safety enclosure. All of the system's sub-assemblies and components may be built upon an internal skeleton-like framework. Alternatively, the deferent sub-assemblies and components may be positioned by separate frame or supporting structure.

[0019] The acoustic emitter may provide the energy waves for ejecting liquid out of a source vessel and onto a target device. The X/Y linear stage assemblies along with their corresponding handling device may retrieve source vessel and target device from the storage queues and align the source vessel and the target device above the acoustic emitter. The storage queues may hold multiple source vessels and target device, and may be capable of delivery any of the source vessels or target devices to a predefined location where specific source vessel or target device may be accessed by the handling device attached to its X/Y linear stages. The image detection system may provide signal feedback to the machine controls so that appropriate alignment of source vessel and target vessel with the acoustic emitter may take place. The image system may be used for pre-ejection calibration, and it also may be implemented to monitor the ejection process. Furthermore, the image system may also be used for post ejection verification/measurements of physical and/or chemical parameters within each individual target location. Machine controls, electronic and software, may provide overall control of the various components within the liquid transfer apparatus. The machine controls may provide feedback control so that appropriate source vessel and target device are retrieved from the storage queue and positioned above the acoustic emitter appropriately. The machine controls may further define the amount of energy delivered by the acoustic emitter and the location of the focus of the acoustic wave been emitted. A software algorithm may be implemented along with machine controls such that specific source/target alignment and ejection sequence is followed in a high-throughput liquid transfer process. A frame and support structure may be provided for integrating the various components in the liquid transfer apparatus. Various moving mechanisms may be connected to a primary frame such that alignments and/or calibration may be easily carried out between various moving parts. An environment and safety enclosure may be provide to control/monitor various environment parameters and prevent unintended user intervention during system operation. Various design variations may be implemented in the liquid transfer apparatus.

[0020] [a] Acoustic Emitter Device

[0021] An acoustic emitter device is provided for generating and propagating an acoustic wave in a direction defined by a wave-guide. The wave-guide may comprise of a continuous piece of wave conducting medium for transferring an energy wave from the wave generation source to the coupling liquid. Alternatively, the wave-guide may comprise a plurality of interconnecting parts. The wave-guide may further comprise a focusing device (e.g. lens) at one end for focusing the energy wave as it exits the wave-guide. Materials may be selected for optimizing the transfer of a particular kind of wave. In one variation, the wave-guide is fabricated with materials for facilitating transfer of an acoustic wave. For example, the acoustic wave-guide may be constructed of aluminum, silicon, silicon nitride, silicon carbide, sapphire, fused quartz, glass, a combination there of, or the like. In one variation, a separate lens may be placed on the distal end of the wave-guide for forming a focused acoustic beam. Alternatively, the distal end of the wave-conducting medium may have a concave surface or other structural features for facilitating the focus of the wave as it exits the wave-conducting medium. Other wave conducting channels or medium that are well known to one skilled in the art may also be adapted for constructing the wave-guide.

[0022] A fluid basin may be provided for supplying coupling liquid to the distal end of the wave-guide and/or removing excess coupling liquid from the area surrounding the wave-guide. The fluid basin may comprise a structure that surrounds the wave-guide and has a channel for supplying coupling liquid and a separate channel for providing suction to remove excess coupling liquid. The “suction channel” is a channel through which liquid can be removed or withdrawn. A pressure gradient may be maintained across the two ends of the suction channel to facilitate removal of the liquid. A vacuum generator or a suction source may be connected to one end of the suction channel. In another variation, a suction generator, for generating a pressure pocket having a pressure lower than the pressure in the ambient or surrounding environment, may be attached to one end of the suction channel to facilitate the removal of the liquid from the other end of the suction channel.

[0023] In another variation, the wave-guide may be supported within a housing. The wave-guide housing and the wave-guide may move as a unit, independent of a fluid basin that provides the coupling liquid and fluid suction.

[0024] In yet another variation, a coupling liquid outlet surrounds the wave-guide, and a constant negative pressure is maintained around the immediate area surrounding the coupling liquid outlet. This may be achieved with a vacuum generator to create the negative pressure and routing the negative pressure source to a cavity that surrounds the coupling liquid outlet. The negative pressure area surrounding the wave-guide may create a suction, which facilitates removal of excess coupling liquid from the area surrounding the wave-guide.

[0025] Alternatively, the wave-guide may be positioned within a lumen. The lumen may be flooded with coupling liquid so that the tip of the wave-guide is covered with coupling liquid. A constant negative pressure may then be maintained around the lumen. The constant negative pressure may also be delivered through a channel surrounding the lumen or through a cavity surrounding the lumen. The channel or lumen may be connected to a negative pressure source. In another variation, two coaxial channels are implemented for providing the coupling liquid and the suction. The wave-guide may be positioned within the inner lumen and enough space may be provided between the walls of the inner lumen and the wave-guide for coupling liquid to flow. The outer lumen may be connected to a negative pressure source. In the above variations, the wave-guide may be fixedly positioned within the inner lumen or moveably positioned within the inner lumen.

[0026] A fluid pump may be used to supply fluid to the inner lumen or the coupling liquid outlet. A fluid reservoir may be connected to a fluid pump for supplying the coupling liquid. The fluid pump may be a peristaltic pump, a diaphragm pump, a centrifugal pump, a piston pump, a positive displacement pump or other active fluid transfer mechanisms well known to one skilled in the art. Alternatively, other fluid supply sources, including passive fluid supply sources, may also be implemented to supply fluid to the inner lumen. For example, the coupling liquid may be provided through gravitational force by displacement of a fluid container at an appropriate height. Connections may be provided for the fluid to flow from the liquid container to the inner lumen or the coupling liquid outlet. In this variation, the fluid container may be a separate container from the container for capturing returning coupling liquid from the negative pressure suction.

[0027] The negative pressure source may comprise a mechanical fluid pump, a diaphragm pump, a centrifugal pump, a vacuum generator or other flow generator well known to one skilled in the art. The negative pressure source may also be created by a siphon, which compresses air through a venturi whose throat has an opening to create a low-pressure source at the throat without the use of any moving mechanical parts.

[0028] It is understood that in this disclosure and related amendments the term “connect” and “connecting,” when used in the context of establishing a connection with a fluid source, a vacuum source or a pump, may include providing additional medium such as a tubing or a channel to achieve the connection between one element and another element. For example, a fluid pump connected to a channel may include a fluid pump that is connected to the channel through tubing to allow fluid transfer between the fluid pump and the channel, or the fluid pump may be directly connected to the channel.

[0029] In another variation, the coupling liquid may be supplied to the tip of the wave-guide through one or more channels positioned next to the wave-guide, and the negative pressure may be provided through one or more channels positioned next to the coupling liquid supply channels. For example, a coupling liquid outlet may surround the wave-guide, and a plurality of channels may surround the coupling liquid outlet for removing excess fluid from the distal end of the wave-guide assembly.

[0030] The wave-guide may have a cross-sectional area of 1 square mm to 10000 square mm. Preferably, the cross sectional area of the wave-guide is between 2 square mm to 800 square mm. More preferably, the cross sectional area of the wave-guide is between 3 square mm to 150 square mm. Most preferably, the cross sectional area of the wave-guide is between 20 square mm to 25 square mm.

[0031] The coupling liquid cross sectional area above the wave guide is preferably isolated to an area less than twenty times the cross-sectional area of the wave-guide, more preferably less than ten times the cross-sectional area of the wave-guide, even more preferably less than 3 time the cross-sectional area of the wave-guide. The coupling liquid area above the wave-guide may be isolated to an area about the same as the cross-sectional area of the wave-guide.

[0032] In the variation where a negative pressure surrounds the wave-guide, the area surrounded by the negative pressure region (including the wave guide and negative pressure region itself) is preferably between 3 square mm to 30000 square mm, more preferably between 3 square mm to 150 square mm, even more preferably between 60 square mm to 70 square mm. In one variation, the area surrounded by the negative pressure region is design to be about three times the cross-sectional area of the wave-guide. For example, the wave-guide may have a cross-sectional area of 21 square mm and the corresponding area surrounded by the negative pressure region (including the wave-guide and the negative pressure region itself) may be 64 square mm. In another variation, the area surrounded by the negative pressure region is 1.62 times the cross-sectional area of the wave-guide.

[0033] In another aspect of the invention, the wave-guide may be moveably disposed within the wave-guide assembly such that the wave-guide focus may be adjusted along a linear axis. The wave-guide assembly may comprise of a wave-guide positioned within a fluid basin, and the fluid basin may be configured to supply coupling liquid to the distal end of the wave-guide. In one variation, a fluid basin surrounding the wave-guide may be isolated from the wave-guide such that the wave-guide may move on a linear path independent of the fluid basin. This may allow the source fluid containment structure to maintain a constant gap from the fluid basin while the wave-guide focus is being adjusted. This constant gap may aid in maintaining the fluid coupling while the focus of the wave-guide is being adjusted. In addition, this design may also allow higher speed of movements of the source fluid containment structure in the X-Y plane, while allowing the source fluid containment structure to maintain contact with the coupling liquid.

[0034] The fluid basin surrounding the wave-guide may additionally include a trough for collection of excess coupling liquid that is not captured by the outer lumen or suction channel. The trough may be a formed by a lip surrounding the fluid basin. Alternatively, the trough may comprise a groove surrounding the negative pressure area. A channel for draining fluids from the trough may be provided. In addition, this draining channel may be connected to a negative pressure source for facilitating removal of fluids in the trough.

[0035] In another aspect of the invention, a fluid compensation mechanism is provided to offset the displacement of the wave-guide during focus adjustment so that fluid coupling between the tip of the wave-guide and the bottom of the source fluid containment structure may be maintained. In one variation, the coupling liquid is transferred back and forth through a flow line to a fluid displacement device (e.g., piston pump). The fluid displacement device may be coupled to the displacement mechanism moving the wave-guide to achieve synchronization. For example, the same motor that positions the wave-guide may actuate the fluid displacement device, so that coupling liquid displacement may be synchronized with the movement of the wave-guide. In another variation, a mechanically separate mechanism may provide the coupling liquid displacement. In addition, an electronic control mechanism may be provided to control the coupling liquid displacement and the wave-guide displacement. For example, a computer may be used to provide control and synchronization.

[0036] The source fluid containment structures may be well plates or microtiter plates that are commonly used in the biotech field, for example well plates having 384 wells or 1536 wells may be utilized. Other fluid containers such as capillaries (e.g., capillary arrays), a flat plate with isolated regions of liquids, and the like may also be used. Furthermore, the source fluid containment structure may also have channels or micro-channels embedded in the structure for supplying the wells with source fluids as needed. In addition, gates or valves may be integrated with these fluid supply paths for controlling the flow and/or the level of fluids in the wells. Sensors and electronic control mechanisms may also be implemented for managing the source fluid and maintaining the fluid levels in the wells.

[0037] A moveable stage may be provided for positioning the source fluid containment structure. Actuators, motors, or other displacement devices may be implemented with electronic control mechanisms (e.g. a computer or a feed back control circuitry) for positioning and aligning the desirable well in the source fluid containment structure over the wave-guide after each ejection.

[0038] A frame may be provided for positioning the fluid basin around the wave-guide. The frame may be connected to an independent stage or an existing structure (e.g., a skeleton framework built into the fluid ejection system) in the fluid ejection system. The fluid basin may be coupled to the frame in such a way as to allow some degree of X-Y movement but no movement in the Z direction. In one variation, bearings are provided to remove any side loads that could be imparted on the wave-guide due to the fluid basin and wave-guide misalignment, as one skilled in the art would appreciate.

[0039] A computer or electronic controller may be adapted for synchronizing different mechanisms in the fluid ejection system and/or controlling the size and direction of the ejection. The computer may be programmed to eject fluids out of selected wells on the source fluid containment structure in a particular sequence. Feedback mechanisms, such as sensors or other detectors, may be implemented in the computer controlled fluid ejection system to improve the performance and capability of the system.

[0040] A method for utilizing a negative pressure area or suction surrounding a wave-guide for isolating the coupling liquid is also contemplated in this disclosure. In one variation, the method includes the process of providing a wave-guide, supplying a coupling liquid to the distal end of the wave-guide, maintaining a negative pressure in an area surrounding the wave-guide to remove excess coupling liquid, directing an acoustic wave through the wave-guide toward the distal end of the wave-guide, and allowing the acoustic wave to pass through the coupling liquid, the source containment structure and into the source fluid. In another variation, the method further includes repositioning of a source fluid containment structure (e.g., a well plate) above the wave-guide to allow ejection of a different source fluid from a different reservoir in the source fluid containment structure. In yet, another variation, the position of the wave-guide may be adjusted to reposition the focus point of the acoustic wave, and may further include fluid displacement device for making appropriate compensation to the volume of the coupling liquid on top of the wave-guide in order to maintain the coupling between the wave-guide and the source fluid containment structure. The method may also include the step of maintaining a constant distance between the fluid basin and the bottom surface of the source fluid containment structure as the source fluid containment structure is re-positioned between individual reservoirs containing source fluids.

[0041] [b] Droplet Steering Mechanism

[0042] In another aspect of the invention, a droplet steering mechanism may be integrated within the non-contact liquid transfer apparatus to maintain, correct or adjust the trajectory of liquid ejected out of the source liquid container. The steering mechanism may be placed between the source liquid container and the target device to assist the ejected liquid to reach its intended target. The steering mechanism may also be aligned with the acoustic ejector to maintain or adjust the flight path of the ejected droplet so that the ejected droplet may stay on the Z-axis of the system.

[0043] In one variation, gas or air flow is directed through a throated structure to steer the trajectory of the ejected liquid droplet. For example, the throated structure may comprise a nozzle defining a throat, which may have an inlet or entrance port and a preferably smaller outlet or exit port. A venturi structure may also be used, in which case the inlet or entrance port may open into a nozzle which converges to a narrower throat and reopens or diverges into a larger outlet or exit port.

[0044] In the case of a nozzle defining a throat having an inlet or entrance port and a smaller outlet or exit port, the throat preferably converges from a larger diameter inlet to a smaller diameter outlet. Through this throat, a vectored or directed gas or air stream may be directed into the inlet to be drawn through the structure. The gas or air stream is preferably driven through the system via a pump, either a positive or negative displacement pump, such as a vacuum pump. The gas or air stream may also pass through a heat exchanger that is connected to the nozzle. The heat exchanger may be used to maintain or change the temperature of the gas or air stream. This in turn may be used to control the temperature of the droplets through convective heating or cooling as the droplets traverse through the nozzle. As the gas or air stream approaches the outlet, the gas or air may increase in velocity and is preferably drawn away from the centerline of the nozzle through a connecting deviated air flow channel. The gas or air stream may be drawn away from the throat at a right angle from the centerline of the nozzle or at an acute angle relative to the nozzle centerline. The gas or air stream may then continue to be drawn away from the throat and either vented or recycled through or near the inlet again. The gas used may comprise of various gases well known to on skilled in the art that are suitable for displacing liquids (e.g. nitrogen, carbon-dioxide, helium, etc. or a combination thereof). The gas may comprise any number of preferably inert gases, i.e., gases that will not react with the droplet or with the liquid from which the droplet is ejected. The gas may also comprised of several gases, a single gas, or a mixture of gas or air with other micro-particles or liquid mist. However, a gas that is highly reactive with the ejected liquid droplet may also be used. This reactive gas may comprise of several compounds, a single compound, or a mixture of gas or air with other micro-particles or fine liquid mist.

[0045] A droplet ejected from the surface of a liquid will typically have a first trajectory or path. The liquid is preferably contained in a well or reservoir disposed below the nozzle. To prevent overheating of the liquid within the reservoir during droplet ejection, the temperature of the well plate may be controlled actively, e.g., through conductive thermal heating or cooling, or the droplet generator may be used indirectly to control the temperature of each of the wells during droplet ejection. If the trajectory angle of the droplet relative to a centerline of the inlet nozzle is relatively small, i.e., less than a few tenths of a degree off normal, the droplet may pass through the outlet and on towards a target with an acceptable degree of accuracy. If the trajectory angle of the droplet is relatively large, i.e., greater than a few degrees and up to about ±22.5°, the droplet may be considered as being off target.

[0046] As the droplet enters the inlet off-angle and as it advances further up into the structure, the droplet is introduced to the high velocity gas or air stream at the perimeter of the interior walls of the nozzle. The gas or air stream accordingly steers or redirects the momentum of the droplet such that it obtains a second or corrected trajectory which is closer to about 0° off-axis. The gas or air stream at the connecting deviated air flow channel is preferably drawn away from the centerline of the nozzle and although the droplet may be subjected to the gas or air flow from the connecting deviated air flow channel, the droplet has mass and velocity properties that constrain its ability to turn at right or acute angles when traveling at a velocity, thus the droplet is allowed to emerge cleanly from the outlet with high positional accuracy. Throated structure may correct for droplet angles of up to about ±22.50, but more accurate trajectory or correction results may be obtained when the droplet angles are between about 0°-15° off-axis.

[0047] To facilitate efficient gas or air flow through the throated structure, the throat is preferably surrounded by a wall having a cross-sectional elliptical shape. That is, the cross-sectional profile of the wall taken in a plane that is parallel to or includes the axis of the nozzle preferably follows a partial elliptical shape. The exit channels which draw the gas or air away from the centerline of the throat may also have elliptically shaped paths to help maintain smooth laminar flow throughout the structure. It also helps to bring the gas or air flow parallel to the centerline as well as maintaining a smooth transition for the exit flow as well as maintaining an equal exit flow on the throat diameter. This in turn may help to efficiently and effectively eject droplets through the structure.

[0048] In addition to the throated structure, alternative variations of the device may include a variety of additional methods and/or components to aid in the gas/air flow or droplet steering. For instance, the nozzle may be mounted or attached to a platform which is translatable in a plane independent from the well plate over which the nozzle is located. As the well plate translates from well to well and settles into position, the nozzle may be independently translated such that as the well plate settles into position, the nozzle tracks the position of a well from which droplets are to be ejected and aligns itself accordingly. The nozzle may be tracked against the well plate and aligned by use of a tracking system such as an optical system, e.g., a video camera or digital camera, which may track the wells by a tracking algorithm on a computer.

[0049] Additionally, an electrically chargeable member, e.g., a pin, may be positioned in apposition to the outlet to polarize the droplets during their travel towards the target. Polarizing the droplets helps to influence the droplet trajectory as the droplets are drawn towards the chargeable member for more accurate droplet deposition. Additionally, well inserts for controlling the ejection surface of the pool of source liquid from which the droplets are ejected may also be used in conjunction with the throated structure. Furthermore, various manifold devices may be used to efficiently channel the gas or air through the mechanism.

[0050] [c] X/Y Linear Stage Assemblies

[0051] The X/Y linear stages may be used to manipulate the source vessels and the target device above the acoustic emitter device. This may allow the liquid transfer apparatus to transport a liquid from any source location to any target location. In one variation, the X/Y linear stages, along with the elevator storage queue, provide the mechanism to position any well on any source vessel or target device above the acoustic emitter.

[0052] The X/Y linear stages may be sized accordingly to various stroke/travel specifications, as one skilled in the art would appreciate. The X/Y stage may be designed to complement the storage queues, the source vessels and/or the target device.

[0053] In one variation, the acoustic emitter device is in a fixed location, and with the assistance of the X/Y linear stage the source vessel and the target device are movable in the X/Y plane to selectively align a source well on the source vessel with the target well on a target device with the acoustic emitter. However, one skilled in the art would appreciate that other variations are also possible. For example, the position of the target device may be fixed, and the source vessel and the acoustic emitter device are allowed to move in the X/Y plane. Alternatively, the source vessel may be in a fixed position and the target device and the acoustic emitter are given freedom of movement in the X/Y plane. It is also within the contemplation of this invention that all three elements (the source vessel, the target device and the acoustic emitter) may move in the X/Y plan independent of each other. The X/Y plane movements may allow any source location to be aligned with any target location and the acoustic emitter. Only two of the three elements need to move to allow this dynamic alignment to take place.

[0054] In another variation, mechanisms may be provided to allow vertical movement of the source vessel, the target device and/or the acoustic emitter. An actuator may be provided to physically move the acoustic emitter. However, mechanisms may also be provided for adjusting the location of the focus for the acoustic beam without physically moving the position of the complete acoustic emitter unit.

[0055] The X/Y linear stage provides the mechanism to retrieve source vessels and target devices from their receptive storage queue and position them over the acoustic emitter. Other mechanisms for transferring objects (e.g. robotic arms) which can serve similar purpose may also be adapted in the liquid transfer apparatus. Although the object transfer mechanism describe herein only has two-dimensional degrees of freedom, one skilled in the art would appreciate that the object transfer mechanism may be modified to have additional degrees of freedom. For example, the linear stage may be adapted on an elevator to provide motion in the Z direction.

[0056] In another variation, two X/Y linear stages are provided, one for handling the source vessel and the other for handling the target device. The two linear stages may be arranged in a stacked configuration, one positioned above the other. The linear stages may be located behind the acoustic emitter device. In another variation, the X/Y stages may be arrange opposite to one another, one on each side of the transporter device. In this configuration, the X/Y linear stage may be able to transport the well plates from the front of the system to the back of the system. The X/Y linear stages may be positioned in various configurations, including implementing them as an interface with other external devices to facilitate automation. For example, the X/Y linear stages may extend beyond the main compartment holding the acoustic emitter, so that well plates may be retrieved from a separate storage system holding various well plates.

[0057] In addition to the two X/Y linear stages described above, additional X/Y linear stages may be added along with other transport assemblies such that multiple source and target well plates or substrate may be processed simultaneously. In one variation, separate sets of X/Y linear stage assemblies may be implemented to retrieve well plates from different storage queues containing different sets of chemical libraries. For example, the liquid transfer apparatus may be supported by three sets of X/Y linear stages interacting with three sets of elevator storage queues, each holding a different set of chemical library. Alternatively, one main storage queue may support multiple liquid transfer apparatus. For example, one storage queue containing a large chemical library may support three liquid transfer units that surround it. Each liquid transfer unit may have a X/Y linear stage that extends to the main storage queue for retrieving source well plates contain the chemical library. In addition, each liquid transfer unit may have its own target storage queue for storing its own sets of target wells, which may hold a predefined set of chemicals to be tested against the main chemical library. A system configured in this fashion may allow three sets of chemicals to be tested against one primary chemical library simultaneously. Various other configuration that are well known to one skilled in the art may be implemented to design scalable systems for large scale, high throughput production lines for chemical synthesis and/or lead compound screening.

[0058] [d] Handling Device—Attached to the X/Y Stage Assembly

[0059] The handling device may be an integral part of the X/Y linear stage assembly or it may be separate mechanisms that may be easily detached from the X/Y linear stage, depending on the design need of the overall system as one skilled in the art would appreciate. For example, the handling device may be a gripper assembly that may be easily detached from its X/Y linear stages. Single and/or dual axis mechanism may be utilized to manipulate a wide variety of well plates, substrates (e.g. glass plate, glass slides, polymeric plate), or liquid containment devices for holding source liquids or serving as target devices. Automated grippers that are commonly used in the industry to move well plates tend to lack precision repeatability in their ability to hold the well plates within the grippers in the same position every time. In applications where the handling devices are used to hold and align well plates in a precise manner, a device capable of holding and securing well plates in a consistent manner may provide significant advantages.

[0060] In one variation, the system aligns (or calibrate the amount of misalignment with a reference axis defined by the system) the well plate each time a well plate is picked up. This alignment process may be achieved through detecting and measuring two or more fiduciary points on a well plate to determine the amount of misalignment of the well plate. Base on this misalignment determination the system may then compensate with appropriate amount of displacement when moving the well plate so specific location, such as a well, may be lined up with a reference point on the system. With this approach, the system may also compensate for variation in well plate size since each well plate is aligned each time it is picked up by a handling device. In another variation, the alignment of each handling device is aligned once when it picks up the first well plate. This variation may be feasible if al the well plate are the same size and variation between well plate is minimal relative to the amount of precision of alignment required. In this approach, the ability for the gripper assembly to hold the well plates in a repeatable and consistent manner may be important to overall system performance.

[0061] In another variation, the handling device may apply forces in three separate axes such that an object held by the handling device may be forced into the same corner (or wedge) in a consistent manner. Other force/pressure distribution systems well known to one skilled in the art may also be implemented to ensure that when the same well plate is held by the handling device the well plate is held at the same position relative to the gripping mechanisms of the handling device.

[0062] The handling device may also be designed in such a way that pressure is applied to the object being held in the default position. Thus, in order for the controller to release the object (e.g. a well plate) being held by the handling device, power or energy must be delivered to active mechanisms (e.g. motor or piston) to force the gripping mechanism to release pressure on the object being held. Such a design may prevent accidental dropping of well plate during power failure or emergency shutdown of the system.

[0063] The handling device may have removable/replaceable finger attachments or extensions, which have costume shapes adapted to handle a particular kind of well plate or fluid container. This design feature may allow the system to be quickly customized to handle well plates or microtiter plates of various dimensions.

[0064] [e] Storage Queues

[0065] The storage queue may be a rack or other holding structures for storing a plurality of well plates, liquid containment structures, or target devices. In one variation, the storage queue comprises of one or more elevator assemblies. In each elevator assembly, there may be multiple source vessels and/or target devices. In one variation, two elevators are provided with one elevator storing all the source vessels and the other stores all the target devices. The elevator may move vertically to position the appropriate source vessel or target device for retrieval by the handling device.

[0066] The source vessel and target device may be well plates that are commonly used in the biotechnology industry. The source vessels and target device may also be any liquid containment structures, which is capable of holding a plurality of isolated pools of liquids, well known to one skilled in the art. The source vessels and target vessels may also be flat surfaces, which is capable of holding individual pools of liquids on its surface. Chemical coatings, such as hydrophobic or hydrophilic materials, may be implemented to improve liquid isolation on or in the vessels. The source vessel and target device may comprise of the same material. For example both the source vessels and the target devices may be well plates. Alternatively, the source and target vessels may be different materials. For example, the source vessels may be well plates and the target devices may be glass plates with coatings. It is also within the contemplation of this invention that source vessels may comprise of different liquid containment structures. For example, within the elevator holding the source vessels, some source vessels may be well plates and some vessels may be glass plates. The target vessels may also comprise of different liquid containment structures. Barcode or other markers may be provide on the source vessels and/or the target device so the liquid transfer system may track the well plates that are being handled by the system. By detecting the barcodes, the system may track the well plate in the storage queues. Sensors or other detectors may be positioned within the liquid transfer apparatus to read the markers or barcodes on the well plates and track the well plates while they are being handling by the liquid transfer system. The barcode or markers may also be used to track other source fluid containment structures or fluid receiving surface or containment structures that are implemented in the liquid transfer apparatus.

[0067] The storage queues (e.g. elevators) may be sized accordingly to meet various source vessel storage requirement. For example, the elevator may be sized to hold well plates of particular height/width/depth. The storage queues may also have a built-in mechanism for adjusting the vessel holder or slot for securing well plates of various sizes within the storage queues. Depending upon the type of source vessels used, an entire library of biological compounds may be stored in the storage queues. For example, an elevator with ten slots, each slot holding a well plate with 1536 wells, may hold a biochemical library with 15360 compounds.

[0068] In another variation, the storage queue may be a device with fixed drop-off locations for individual well plates. In this design, individual well plates may be fed to the liquid transfer apparatus by placing the well plate at the drop-off location. A transfer device, such as a robotic arm or a mechanical gripper may transfer the well plate from the drop off location to the fluid ejection location or the target location on top of the acoustic emitter. Well plates may be loaded onto the drop-off location by manual transfer or via robotic automation. In another variation, a separate storage/sorting device holding well plates may interface with the liquid transfer apparatus through the drop-off location by feeding and retrieving well plates from the drop-off location.

[0069] In yet another variation, the storage queue may comprise of rotating carousel type mechanisms. The carousel may provide rapid interchange of well plates. For example, the carousel may hold 1 to 8 , or more, well plates and may be loaded/unloaded manually or with automation. In another design variation, the carousel may have multiple stack or levels. The carousel may also incorporate elevator mechanisms for facilitating access of well plates within the various levels in the carousel.

[0070] In one variation, when the storage queue are not being accessed by the gripper assembly, the storage queue may be lowered into a cavity or climate chamber, where environmental parameters (e.g., temperature, humidity) may be controlled. This climate chamber may also be filled a with specific gas to facilitate cell growth or initiate chemical reactions. The chamber may also be heated to increase the rate of chemical reactions taking place within the well plates.

[0071] [f] Image Detection System

[0072] The image detection system may comprise a vision system with variable focus capability. For example, in one variation, the image detection system may focus on three separate planes (e.g., the plane where the tip of the acoustic emitter is located, the plane where the source vessel is positioned, and the plane where the target device is located.). The image detection system may have various focal depths depending on the particular design need, as one skilled in the art would appreciate. In one variation, the image detection system may comprise of a CCD camera, lenses for focusing images on the CCD and motorized mechanisms for adjusting the focus. In another variation, the image detection system comprises a fixed-focus vision system. The fixed focused system may be adjusted vertically by an actuator so that the focus location of the camera may be adjusted by shifting the position of the camera/lens unit. Other electronic hardware and/or software may be implemented to enhance image detection and/or provide automatic focus adjustments, as one skilled in the art would appreciate.

[0073] The image detection system may provide the input signal for the control mechanism of the overall system to align the source vessels and the target device. The image detection system may also be used to monitor and verify the fluid transfer process. For example, the image detection system may be used for quality control. One of the limitations in most of the gene array fabrication devices in the market is the inability to verify the quality of each printed DNA spot after it is printed. The image detection system may allow the fluid transfer apparatus disclosed herein to verify whether a drop of liquid was successfully transfer on to the target device in real time. For this application, the target device may comprise of transparent or translucent materials. Furthermore, the image detection system may further allow size of the delivered droplet to be measured. The volume of the liquid delivered may be calculated based on the diameter of the droplet.

[0074] The image system may also be used to monitor post delivery changes within the target device. For example, a well on the target device may contain chemical compound A. A liquid containing chemical compound B may be ejected out of a well in the source vessel, into the well on the target device which contain chemical compound A. Chemical compound A may react with chemical compound B and give off a fluorescent light. This fluorescent light may be detected and measured by the image detection system. A computer may determine the chemical reaction base on the color of the fluorescent or the intensity of the fluorescent detected. Other chemical/biochemical reactions and associated method for detecting and measuring the reactions, which are well known to one skilled in the art, may also be implemented in this liquid transfer apparatus.

[0075] Target device may also be pulled from the storage queue for the sole purpose of monitoring and/or tracking chemical reactions or biological/biochemical indicators with the image detection system. For example, proteins placed in various wells in a target well plate may be treated with different chemicals from a chemical library by ejecting different chemicals into each well on the target well plate. The target well plate may be incubated within the storage cue for a period of time before it is pulled from the storage queue and examined under image detection system.

[0076] [g] Machine Controls, Electronics and Software

[0077] A computer with associated electronics may be implemented to provide overall control of the liquid transfer system. Various computation device, processors, controller, etc., which are well known to one skilled in the art, may be configured to provide processing control to various components in the liquid transfer apparatus. Software and/or graphic user interface may also be implemented to provide control and/or monitoring functions to the system.

[0078] For example, system software may be programmed to define selective amounts of liquid to be transferred in each individual ejection. A graphic user interface may provide a user-friendly environment where the user can easily enter the desired liquid amount to be transferred in each ejection. When the program executes, it may control the amount of acoustic wave energy and/or the location of the wave-guide focus of the acoustic emitter, thus defining the amount of liquid being ejected.

[0079] The system controller may also be programmed by the user with instructions defining where, when and/or what volume of liquid to transfer during each ejection. Specific sequence of liquid transfer protocol may be fed into the computer and executed by the liquid transfer system. The user may also define the selective location of source liquid to be transferred into each well in the target well plates, and allow the computer to determine the optimum sequence of transfer. Because of the random-access liquid transfer capability described above, the liquid transfer system described herein does not have to transfer/eject fluid in a linear fashion (one well after another on the same row or column). Since the system may allow the user to select any source location from any well plate in the storage queue, and transfer it to any target location on any target well plate/substrate in the storage queue, software may be provide to calculate the optimal transfer sequence based on the pattern of the target well plate to be created (the end product) and calculate the most efficient transfer sequence.

[0080] Software may also be implement in the control system to allow efficient reformatting of well plate type (e.g., 384, 1536, etc.) to the same or different type of plates. In one variation, four 384 type well plates may be reformatted into one 1536 type well plate. For example, a 1536 well plate man be divided into four (4) equal quadrants of 384 wells. Liquids from each well of the 384 well plates would be transferred directly into a corresponding well of the target 1536 well plate. For instance, well plate #1 may be transfer to quadrant #1 of the 1536 target and keep all of the source wells in the same row/column order. In other words, take the four plates and combined them into one. In another variation, the liquids in the wells of well plate #1 may be scattered in any fashion to any 384 wells of the target 1536 plate. The wells of plate #2 would go to any of the remaining 1,152 wells, and so on. Again, four plates go into one, but now they are not in an ordered sequence that corresponds to the sequences on the original 384 well plates.

[0081] In addition, the system may also be implemented to reformat array density. For example, liquid may be extracted from a 1536 well plate to create an array of liquid spots within a 1 square cm area that corresponds to the array in the 1536 well plate.

[0082] In yet another variation, the system may randomly select source wells in a non-sequential fashion and dispense them into an array of target locations in a sequential or non-sequential format. For example, it may be used for “cherry picking” source well liquids and dispensing them in precise sequential locations within other assay well plates. In another example, it may be used for selecting source well liquids and dispensing them in precise sequential locations on porous or non-porous substrates.

[0083] [h] Database

[0084] In one aspect of the invention, a database is provided to manage user inputs and or instruction sets for transferring liquid from any source locations within a collection of source fluid containment structures to any target locations within a collection of target devices. “Database” as used herein means “a collection of data organized especially for search and retrieval by a computer.” The computer may collect and store data in the database during real time operation of the machine to facilitate resource distribution tracking and/or for further analysis. The database may contain information such as user defined liquid transfer map or sequence information, well plate IDs, well plate configurations, source liquid volumes, depth of liquids in each source well, source liquid type, source liquid surface tension, source liquid viscosity, source liquid location on the well plate, age of source liquid (e.g., when it was created), how often the source liquid has been accessed, first/last time source liquid was accessed, time-stamp and other information related to each liquid ejection (e.g., volume or size of liquid droplet transferred, amount of acoustic energy used for the transfer). Information in the database may be updated to track changes in the system. Furthermore, information may also be added to the database as needed.

[0085] In one variation, each source library, which is comprised of a series of well plates holding a library of chemicals or biochemical, has a corresponding database file describing the content of each source, its location and corresponding volume and/or fluid height. The user may provide information defining specific locations on the target plates and corresponding source liquid and the volume to be transferred onto each target location. Base on the information in these databases, the liquid transfer platform may generate a new liquid library on a series of target well plates (by selectively transferring liquids from the source well plates to the target well plates), and an output database containing corresponding information regarding liquids at each of the target locations (e.g., liquid source (identifying or destination information) and/or volume of liquid at each location). The output database may be stored on a removable data storage medium (e.g. floppy disk, removable hard disk, miniature USB disk, compact flash card, memory stick, etc.) so it may be transferred to a remote facility along with the new liquid library. Alternatively, the output database may be transferred to the remote facility through a computer network.

[0086] In another variation, an input data set or mapping profile is provided with information regarding specific source locations, volume of liquid to transfer from each location and corresponding target location where each defined volume of fluid is to be transferred. The data may be provided on a memory device or transferred onto the liquid transfer platform through network connections. Base on the information provided, the liquid transfer platform generates a set of target plates with the desired liquids in the predefined locations. An output database containing information regarding the liquids on the target plates and/or information tracking the transfer process (e.g. time-stamp, successfulness of the transfer, volume transferred, and/or volume remained in the source wells) may be provide for each set of output target plates.

[0087] The ability to track the volume of liquids transferred out of the source wells may allow the system to track the height of the liquid in each source well and thus allow efficient positioning of acoustic wave's focus. Furthermore, tracking the remaining volume of the liquid in the source wells as fluids are ejected from the source well may also allow more efficient utilization of resources.

[0088] The data base may also be utilized to track alignment and associated coordinate information. In addition, information regarding optimal focus location(s) for the acoustic waves and/or fluid depth (fluid height, fluid surface location, fluid volume) in each of the source fluid wells may also be maintained in the database. The information maintained in the database may be used to speed the process of well plate alignments and facilitate the positioning of the wave-guide during each fluid ejection cycle.

[0089] The database may also be implemented to provide feedback and/or verification of the transferred liquids, which may also include volume information. Error recovery algorithm or protocols may be implemented along with the database to improve or manage the output liquid arrays' quality. For example, error recovery mechanisms may be applied to verify the detection of source liquid level and/or droplet ejection. The error recovery mechanisms may implement necessary correction measures when liquid level detection failed or when droplet ejection did not reach its intended target.

[0090] As described earlier, the non-contact liquid transfer apparatus may be configured to function with multiple database. For example, the apparatus may utilize a source library database and a mapping database, and generates an output library database. However, it is also possible to configure the apparatus to retrieve and store all the information from a single database.

[0091] In addition, when multiple liquid transfer apparatuses are being operated at the same time. All the liquid transfer apparatuses may be linked to a central computer with a centralized database through a computer network. The network of liquid transfer apparatuses may be configured such that all the source and target information are managed by the central computer and information are passed to the local database, which reside on the computer in each liquid transfer apparatus, when it is needed. The local database on each apparatus may maintain additional information that are unique to that particular apparatus (e.g., calibration information, operation or functional parameters for the various mechanisms in the apparatus, data regarding specific well plates that are being stored in the storage queues in that particular apparatus, etc.). The local computer operating on each apparatus may also retrieve additional data from the central computer to facilitate the operation of the liquid transfer apparatus.

[0092] [i] Frame and Support Structure

[0093] The frame and support structure may be provide for integrating the liquid transfer apparatus and its related supporting devices into one stand alone unit. Various mechanical sub units may be attached to a primary frame so that the different moving parts may be aligned and/or calibrated for precision interactions. Various compartments may be provided within the frame and supporting structure for housing supporting electronics and peripheral support devices. For example, a compartment may be provided for housing the system control computer. A separate compartment may house an environmental temperature control unit. Another compartment may be provided for housing a carbon dioxide supply source for supplying the primary enclosure or chamber with carbon dioxide gas.

[0094] [j] Environment and Safety Enclosure

[0095] An enclosure or chamber may be provide to house the liquid transfer apparatus. Various devices and mechanisms, which are well known to one skilled in the art, may be implemented to control specific parameters within the enclosure. Some of the environmental factors that may be monitored and/or controlled include, but are not limited to, temperature, humidity, air pressure, air flow, air cleanliness, destiny of particles inside the chamber (e.g. air filtration), light exposure levels (e.g., ambient light to complete black-out), lighting environment (e.g., constant UV light), and gas atmosphere compositions (nitrogen, argon, carbon dioxide, etc.). One or more of the above parameters may be monitored and/or controlled at the same time.

[0096] The enclosure or chamber may also prevent unintended user access during system operation. The access doors to the enclosure may be automatically locked, while various mechanisms in the liquid transfer apparatus are moving to prevent accidental injury to users. This may also prevent the user from prematurely accessing the source vessels or target devices before the completion of a programmed fluid transfer protocol. Emergency shutdown interface (e.g., a button or valve) may also be provided for terminating system operation.