WO2006017737A2

WO2006017737A2 - Microtiter plate scrubbing device

Info

Publication number: WO2006017737A2
Application number: PCT/US2005/027900
Authority: WO
Inventors: Herbert J. Hedberg; Matthew S. Little; Brian A. Kangas
Original assignee: Cetek Corporation
Priority date: 2004-08-06
Filing date: 2005-08-05
Publication date: 2006-02-16
Also published as: WO2006017737A3

Abstract

Au automated microtiter plate scrubber device includes vertical hoppers for dirty plates on the input side (12) and clean plates on the out side (16) of the scrubber head assembly (14). The scrubber head (14) has distinct pair of liquid and air ports on a plurality of nozzles corresponding to each sample well on the plate. A shuttle mechanism receives a used plate from the input hopper (12) and slides it from the input hopper assembly (12), across the nozzles of the scrubber head assembly (14) and to the output hopper assembly (16). An array of air nozzles inserted into every well of the cleaned plate blows excess water from the wells as it is stored in the output side hopper (16).

Description

TITLE OF THE INVENTION Microtiter Plate Scrubbing Device

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. § 119 (e) of U.S. Provisional Patent Application No. 60/599,387, filed

August 6, 2004, and U.S. Provisional Patent Application No.

60/637,613, filed December 20, 2004, the disclosures of both of which are incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR

DEVELOPMENT

N/A

BACKGROUND OF THE INVENTION

The demand in the biotechnology industry for efficient processing of large quantities of individual sample compounds has evolved a standard multiple container device widely referred to as a microtiter plate 302 (see Fig. 43) . Over time, the density and number of the containers (or wells) in the face of commercially available plates has increased from 96 to 384 to 1536. The spacing between adjacent wells in such plates is 9.00 mm, 4.50 mm and 2.25 mm, respectively. Although the length and width of the plate has been standardized to allow wide application among various laboratory robotic plate handling devices, the height of the plate varies widely to allow wells of different depths in order to provide the end user with a selection of well volumes.

Of primary interest to laboratory workers using microtiter plates is the reliability of test results without concern for the possible contamination of the plates. Although new plates could be used for every assay, such a protocol has both procurement and recycling costs. For many types of assays, a washed plate can be suitable if it is sufficiently free from contamination.

A device to clean microtiter plates and make them ready for reuse by a biotech or clinical laboratory must pass stringent evaluations to assure that recycled plates produce neither false positive nor false negative assay results. Where recycled plates are particularly economical is when the primary assay is relatively inexpensive and where any positive result is always confirmed. If the effect of a contaminated well is a false positive, then there is no chance of missing an important assay result; such a condition will only result in an unnecessary confirmation test being run. Only if contamination produces a false negative result is there cause for concern that a positive result will be missed. In these instances, there may be important reasons to use only new plates in the assays.

More aggressive cleaning liquids such as organic solvents like methanol can produce superior cleaning results. However, organic cleaning solvents generate hazardous waste that cannot be disposed of in a municipal sewer system. If such cleaning liquids are necessary, a closed loop system to collect and reuse or safely dispose of the cleaning materials is required. The costs of these ancillary procedures make plate recycling using aggressive cleaning liquids uneconomical.

SUMMARY OF THE INVENTION

The invention relates to an automated high throughput microtiter plate scrubber device that cleans used microtiter plates of previous sample material, allowing their economical reuse as an alternative to using new plates. Adopting this recycling practice not only saves the cost of a new plate for each new assay, but also eliminates the necessity of recycling large quantities of lightly contaminated molded or machined plastic plates. Operated by a suitable programmable controller, the scrubber uses timed and sequenced applications of hot water, detergent, de-ionized water and compressed air to reduce quantities of previous sample materials in plate wells to undetectable levels. An automated embodiment of the device includes vertical hoppers for used (dirty) plates on the input side and clean plates on the output side of a scrubber head assembly, which has a pair of liquid and air ports in an extended nozzle corresponding to each well in the plate. A sequence of wash liquids applied at public water supply pressures combined with a compressed air source produces significant scrubbing action within each well. A shuttle mechanism receives a used plate from the input hopper and slides it from the input hopper assembly, across the nozzles of the scrubber head assembly and to the output hopper assembly, where clean and dried plates are stacked.

A manual embodiment of the device allows the operator to feed a single microtiter plate onto the scrubber head assembly and initiate a sequence of valve actuations programmed within the unit's microprocessor-based controller. A wide variety of microtiter plates may be processed through the scrubber device without having to change the hardware setup or the program. Shallow, medium, and deep-well plates may be loaded into the input hopper assembly indiscriminately. The plates are loaded into the input hopper in an inverted orientation, with the well openings facing downward. An inverted plate is then released into the shuttle mechanism by an escapement mechanism, which grasps the bottom flange of the plate (the top edge in the inverted orientation of dimensionally standardized microtiter plates) . The plate is released into the shuttle mechanism upside down and travels through the device sliding on its inverted top surface. This feature results in the maintenance of a consistent spacing between the well openings of the plate and the wash nozzles of the scrubber device regardless of sample well depth, which determines plate height.

DESCRIPTION OF THE DRAWINGS The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings in which:

Fig. 1 is an isometric view of a microtiter plate scrubbing device according to the present invention; Fig. 2 is a front view of the microtiter plate scrubbing device of Fig. 1;

Fig. 3 is a right side view of the microtiter plate scrubbing device of Fig. 1;

Fig. 4 is a left side view of the microtiter plate scrubbing device of Fig. 1;

Fig. 5 is a schematic block diagram of the control system of the device of present invention;

Fig. 6 is an isometric view of the scrubber head assembly of the device of Fig. 1; Fig. 7 is an isometric view of the manifold plate of the scrubber head assembly of Fig. 6;

Fig. 8 is a top plan view of the manifold plate of Fig. 7 showing fluid passages therein;

Fig. 9 is an isometric view of the plenum base of the scrubber head assembly of Fig. 6;

Fig. 10 is an example of a timing diagram of a cleaning sequence applied by the scrubbing device of Fig. 1;

Fig. 11 is an isometric view of the input hopper assembly and shuttle mechanism of the device of Fig. 1; Fig. 12 is a left side view of the input hopper assembly and shuttle mechanism of Fig. 11;

Fig. 13 is a right side view of the input hopper assembly and shuttle mechanism of Fig. 11; Fig. 14 is a front view of the input hopper assembly and shuttle mechanism of Fig. 11;

Fig. 15 is a top plan view of the input hopper assembly and shuttle mechanism of Fig. 11; Fig. 16 is an isometric view of a primary pivot bar of the escapement mechanism of the input hopper assembly of Fig. 11;

Fig. 17 is an isometric view of a secondary pivot bar of the escapement mechanism of Fig. 11;

Fig. 18 is a plan view of a pivot bracket of the escapement mechanism of Fig. 11;

Fig. 19 is an isometric view of the shuttle mechanism of Fig. 11;

Fig. 20 is a side view of a guide plate at the scrubber head assembly of the device of Fig. 1; Fig. 21 is an isometric view of the output hopper assembly of the device of Fig. 1;

Fig. 22 is an isometric view of the elevator mechanism and carrier plate of the device of Fig. 1;

Fig. 23 is an isometric view of a retaining block of the output hopper assembly of Fig. 21;

Figs. 24A-24K illustrate a sequence of operations of the device of Fig. 1;

Fig. 25 is an isometric view of a further embodiment of a scrubber head assembly; Fig. 26 is a front view of an alternate embodiment of the device of Fig. 1, showing a weighting mechanism in the rest position, without a microtiter plate;

Fig. 27 is a front view of the alternate embodiment of Fig. 26, showing the weighting mechanism in the engaged position over a microtiter plate;

Fig. 28 is an isometric view of the weighting mechanism of Figs. 26 and 27; Fig. 29 is an isometric view of an alternate embodiment at the output hopper assembly in which air drying nozzles are oriented so as to deliver compressed air to the bottom of wells of an inverted, clean microtiter plate; Fig. 30 is a side view of a further embodiment of Fig. 29, including spacer plates between certain rows of drying nozzles and a microtiter plate support platform;

Fig. 31 is a side view of the embodiment of Fig. 30 showing a microtiter plate in position on the support platform; Fig. 32 is a side view of the embodiment of Fig. 31 showing the elevator mechanism in extended position;

Fig. 33 is an isometric view of the spacer plate of Figs. 30-32;

Fig. 34 is an isometric view of a weight in the output hopper stack for use with the air drying nozzles of Fig. 29;

Fig. 35 is a side view of a further embodiment of Fig. 29, including spacer plates having longitudinal holes disposed between certain rows of drying nozzles and a microtiter plate support platform; Fig. 36 is a side view of the embodiment of Fig. 35 showing a microtiter plate in position on the support platform;

Fig. 37 is a side view of the embodiment of Fig. 35 showing the elevator mechanism in extended position;

Fig. 38 is an isometric view of the spacer plate of Figs. 35-37;

Fig. 39 is a side view of a further embodiment of Fig. 29, including spacer plates having longitudinal holes disposed between certain rows of drying nozzles, the spacer plates serving the purpose of a microtiter plate support platform; Fig. 40 is a side view of the embodiment of Fig. 39 showing a microtiter plate in position on the supporting spacer plates;

Fig. 41 is a side view of the embodiment of Fig. 39 showing the elevator mechanism in extended position; Fig. 42 is an isometric view of the spacer plate of Figs. 39-41; and

Fig. 43 is an isometric view of a prior art microtiter plate for use in the microtiter plate scrubbing device of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

A microtiter plate scrubbing device of the present invention is illustrated in Figs. 1-4. The device 10 includes an input hopper assembly 12, a scrubber head or washer assembly 14 and an output hopper assembly 16, supported by a suitable frame 18. Used microtiter plates to be washed are stacked in the input hopper assembly in the inverted position, so that their wells open downwardly (see Figs. 24A-24K, described further below) . A shuttle or plate indexing mechanism 22 moves one plate at a time into the scrubber head assembly 14, where cleaning fluids such as detergent, water, and air are supplied to each well to wash the plate. After the plate is washed, the shuttle mechanism moves the cleaned plate to the output hopper assembly 16 and the next used plate into the scrubber head assembly. Operation of the device can be automated under the control of a suitable controller 20 (see Fig. 5) , as described further below. The frame 18 can include a base plate 24, which may be in the form of a basin to collect used cleaning liquids and can include one or more suitable openings to direct the collected liquids to a drain or for recycling. Splash guards (not shown) can also be provided to prevent the fluids from splashing outside the region of the frame. Any suitable frame configuration can be employed.

The scrubber head assembly 14 is illustrated more particularly in Figs. 6-9. The scrubber head assembly includes a manifold plate 32 and a plenum base 34 mounted at a suitable height above the base plate 24. The manifold plate includes a number of upstanding nozzles 36, each of which includes an air port 38 and a liquid port 42. In the embodiment shown, the number and spacing of the nozzles is designed to correspond to the number and spacing of wells in a standardized 96-well microtiter plate.

When a used microtiter plate is moved by the shuttle mechanism 22 into position to be cleaned, each of the nozzles is aligned with a corresponding well on the microtiter plate. To accommodate plates having differing well densities, several replaceable manifold plates, each having appropriately spaced nozzles, can be provided. In another embodiment, for example, a 384-well microtiter plate can be adapted to the plate scrubbing device by using an existing 96-well manifold plate and jogging the microtiter plate, or the scrubber head, laterally by a suitable mechanism 2.25 mm about the existing centerlines of the 96-well cleaning head pattern such that the sequence of cleaning fluids and agitation air are applied to each sample well of the microtiter plate.

The nozzles 36 are each spaced immediately below the wells, so that fluid flow is directed into the wells. The currently preferred embodiment maintains a spacing of about 0.25 inches between the nozzle openings and the inverted well opening surface of the plate. After the microtiter plate is released into the shuttle mechanism 22, it travels by sliding on its inverted well opening surface. Thus, the height of the plate (determined by the depth of the wells) does not affect the nozzle-to-plate spacing as the plate slides through the device. Accordingly, the present device provides maximum flexibility in feeding plates of different heights into the input hopper assembly indiscriminately, because the spacing between the nozzles and the surface of the plate containing the well openings is maintained by referencing the well opening surface, not the flange around the (here inverted) bottom surface of the plate.

The air ports 38 are in fluid communication with the plenum base 34 below the manifold plate 32. The manifold plate and the plenum base are fastened together with a suitable air-resistant seal, such as an 0-ring (not shown) situated in a channel 44 formed in the plenum base. A fitting 46 for connection to a compressed air source, for example, at 85 psi, is provided in one side of the plenum base. A passage 48 from the fitting extends through the lower wall 52 to the center of the plenum base, where the passage terminates in an opening 54 into a plenum chamber 56. The air ports in the nozzles of the manifold plate open to the plenum chamber for fluid communication therewith. In this manner, air can be supplied simultaneously to all of the air ports. Air flow can be controlled via suitable upstream valving, for example, a solenoid valve 50 under control of the controller 20 (see Fig. 5) .

The liquid nozzles 42 are in communication with any desired liquid sources, such as a detergent source, a hot water source, and a de-ionized water source. A central passage 58 extends through the manifold plate from a fitting 62 at one end. Side passages 64 extend from the central passage along each row to communicate with each of the liquid nozzles 42 in the manifold plate 32. In this manner, one or more liquids can be supplied simultaneously to each row and to each liquid nozzle along each row. Flow from the desired liquid sources can be controlled via suitable upstream valving, such as solenoid valves 60, 61, 63 under control of the controller 20. For ease of manufacture, the central passage and side passages may be machined entirely through the manifold plate from both ends and the ends later closed by suitable plugs 66.

When a microtiter plate to be washed is positioned over the manifold plate, air and liquids (typically detergent, hot water, and de-ionized water) can be sprayed through their individual ports in nozzles 36 into each well of the plate. Due to the adsorbant nature of many biological sample materials, aggressive agitation of each well in addition to the flow of detergent and

—Q— rinsing solutions produces superior cleaning results. The most aggressive agitation occurs when air is directed into the wells from a port immediately adjacent to the liquid port. Air and liquid can be introduced through a single port if desired; however, this generally produces inconsistent flow and/or agitation results across all wells on the plate. Thus, separate but closely spaced air and liquid ports are preferred.

Attempting to wash a plate right side up, especially a deep well plate, allows the wells to fill with wash liquid. The relatively deep well volume prevents the aggressive agitation of all inside surfaces of the well to remove contaminants. With inversion of the plate, as in the scrubber device according to the invention, liquid is not able to accumulate and the well surfaces remain exposed to the full force of the agitation generated by the pressure of the wash liquid and the compressed air jet. The additional agitation provided by the compressed air greatly enhances the ability of the present device to remove all previous sample from the wells.

An example of a wash sequence is illustrated with reference to the timing diagram in Fig. 10. A used, dirty plate is slid by the shuttle mechanism from the input hopper assembly to the scrubber head assembly. If a previous microtiter plate was washed and is at the scrubber head assembly, the shuttle mechanism simultaneously pushes the clean microtiter plate to the elevator assembly of the output hopper assembly. An elevator assembly 72 lifts the clean plate into the output hopper assembly. Next, the controller initiates a cleaning sequence for the used plate. For example, detergent is sprayed through the liquid nozzles into the wells of the used plate at the scrubber head assembly. Then, hot water is sprayed through the liquid nozzles into the wells. While the hot water is being sprayed, air is sprayed periodically through the air nozzles into the wells. For example, the hot water is sprayed continuously for 15 seconds, and the air is sprayed after an interval of three seconds for a duration of two seconds. Next, de-ionized water is sprayed into the wells, for example, continuously for ten seconds, while air is jetted at intervals of three seconds for a duration of two seconds. The de-ionized water and air rinse all traces of contaminants (soap or sample debris) from the wells. Compressed air alone can be used as a final cleaning step (not shown in Fig. 10) to remove most of the water from the plate before it is inserted into the output hopper assembly. Using this sequence, the wells of the microtiter plate can be adequately cleaned and rinsed. It will be appreciated by one of skill in the art that other wash sequences can be employed, as well as other wash reagents, depending on the plates to be cleaned. Moreover, the use of a programmable controller in this preferred embodiment anticipates the desire of a user of this device to apply a variety of wash protocols to plates, for example, protocols that are dependent upon the specific plate configuration and upon the degree of plate contamination.

Referring to Fig. 5, operation of the device is controlled by a suitable controller 20, for example, a microprocessor controlled programmable logic controller (PLC) . The controller is operative to respond to operator input commands 21 and signals from various sensors and safety interlocks on the device. The controller' s outputs are connected through time delay relays 25 to solenoid valves 50, 60, 61, 63 that control the flow of air and liquids to the scrubber head assembly 14. The time delay relays allow the operator to change the time of each liquid and air application without having to change the operating program in the controller. An LCD display and/or other means of displaying information to the operator in conjunction with a data entry keypad provide the operator with the ability to specify reagent sequences and dwell times that comprise the cleaning sequence meeting the particular requirements of the plates to be cleaned. The controller also controls via solenoid valve 51 compressed air to the shuttle mechanism 22, and an air knife 65 or other mechanism to supply drying air to a cleaned plate.

The device is fitted with various sensors to provide reliable and productive operation. The device includes a sensor 74 to detect when the input hopper stack is empty and a sensor 76 to detect when the output hopper stack is full. A sensor 78 is provided to communicate when a used plate is ready to be washed at the scrubber head assembly. Also, a sensor 82 is provided to detect when the detergent source is empty. Other sensors can include a sensor to detect that the nozzles are aligned with the wells of the inverted plate before the wash cycle is started, if the water temperature drops too low and if a plate is crooked on the outlet hopper elevator. Each sensor is operative to signal the controller if an error condition exists. Depending upon the type of error condition, the controller is programmed to take appropriate action, such as notifying an operator through an audible or visual signal or by jogging the shuttle mechanism to cause a misaligned plate to correct its faulty condition.

The input hopper assembly 12 and shuttle mechanism 22 are illustrated more particularly in Figs. 11-19. Four vertical guide members 90, 91, 92, 93 hold the incoming used microtiter plates in a vertical stack. As noted above, the plates are inserted in the stack inverted with the wells opening downwardly. The input hopper assembly allows plates of different height to be washed sequentially, because the plates are inserted upside down, allowing the flange around the inverted bottom edge of the plate to be engaged by an escapement mechanism 102. Referring to Fig. 43, the dimensions of microtiter plates 302, including the flange

304, are standardized among plate manufacturers to assure compatibility with laboratory robotic systems. By indexing off the flange of the inverted plate, the device of the invention allows plates of different heights to be mixed indiscriminately in the input hopper stack without feeding problems. The flange at the bottom edge of the lowermost plate is engaged by the escapement mechanism 102, which, when actuated, allows the lowermost plate to drop into the shuttle assembly 22 and then catches and retains the next lowermost plate. The escapement mechanism includes a primary pivot bar 104 (Fig. 16) and a secondary pivot bar 106 (Fig. 17) , each pivotably mounted about pivot axes 105, 107 on the frame 18 in opposition to each other. The pivot bars have upper and lower lips 108, 110, 112, 114 on which the flange of the lowermost plate of a stack of used plates rests, as described further below. The primary and secondary pivot bars are interconnected by a linkage 116, such that pivoting of the primary pivot bar 104 causes pivoting of the secondary pivot bar 106 in the opposite direction.

The primary pivot bar 104 is further connected to a pivot bracket 120 (Fig. 18) . The upper end 122 of the pivot bracket is connected to a tension spring 124 that is in turn fixed at its lower end to the frame 18 of the device. The spring biases the upper end of the pivot bracket downwardly and outwardly, as best seen in Figs. 24A, 24C, 24E, 24H (discussed further below) . The lower end 126 of the pivot bracket presses against the shuttle mechanism 22, which during retraction drives the lower end of the pivot bracket against the bias of the spring, as best seen in Figs. 24B, 24D, 24F, 24G, 241, 24J, 24K. A slot 128 is provided in a mounting plate to accommodate the traveling of the lower end of the pivot bracket. The shuttle mechanism 22 is actuated in any suitable manner, such as by a pneumatic or hydraulic cylinder 132. Thus, when the shuttle mechanism is moved away from the scrubber head assembly, the pivot bracket 120 is pushed against the bias of the spring 124 to pivot about the pivot axis of the primary pivot bar 104. This in turn causes the primary pivot bar 104 as well as the secondary pivot bar 106 to pivot. In this manner, if the flange of a used microtiter plate 201 is retained on the lower lips 110, 114 of the pivot bars, the plate is released and drops down to the shuttle mechanism. Furthermore, if a second microtiter plate 202 is stacked on top of plate 201 when it is released, the second plate 202 will be caught at its flange by the upper lips 108, 112 of the pivot bars, and prevented from also falling into the shuttle mechanism with the first plate 201. When the shuttle operates to push plate 201 onto the scrubber manifold 14, the second plate 202 will be released by the upper lips 108, 112 and immediately afterwards will drop down to be caught by the lower lips 110, 114 of the pivot bars. This is the required configuration for releasing plate 202 into the shuttle mechanism when the shutle again retracts from the scrubber head assembly.

The shuttle mechanism 22 is illustrated with more particularity in Fig. 19. The shuttle mechanism travels from a used plate receiving position below the input hopper assembly to a washing position over the scrubber head assembly. The shuttle mechanism includes a back member 134 and two extending arm members 136. Sloped surfaces 138 on the back member and the arm members form a nest to receive and support the well opening surface of a microtiter plate released from the escapement mechanism 102 into the shuttle mechanism 22. One end of the cylinder 132 is connected to the back member 134 to cause travel of the shuttle assembly 22 when the cylinder is actuated.

As the shuttle mechanism 22 pushes a used plate over the scrubber head assembly 14, the plate engages a suitable stop mechanism, which retains the used plate at the scrubber head assembly while the shuttle mechanism retracts. In one embodiment, the flange along the inverted bottom edge of the plate slides along channels 144 in opposed guide plates 142 over the scrubber head assembly (Figs. 1, 20) . The guide plates include, e.g., three channels 144 to accommodate a variety of plate depths. Depending on the height of a given plate, the flange around the inverted bottom will engage one of the three channels 144 such that the inverted top of the plate is suspended above the scrubber manifold by a predetermined amount. When the plate reaches its limit of travel along the guide plate, the plate drops downwardly a small distance, and the flange engages against a lip 146 on the guide plate that prevents movement of the plate back toward the input hopper assembly as the shuttle mechanism retracts. During retraction, spring fingers 148 on the shuttle mechanism spread to pass the used plate retained at the scrubber head assembly. The friction produced by the fingers against the sides of the microtiter plate assures that the plate is pulled back tightly against the stops 146, which are specifically located to assure alignment of the inverted well openings with the nozzles of the scrubber manifold. Also, the upper edges 143 of the channels 144 retain the plate at the scrubber head so that the force of the cleaning fluids through the air and liquid ports does not lift and misalign the plate above the scrubber head. After the plate has been cleaned, the shuttle mechanism advances the next used plate to the scrubber head assembly, and the spring fingers on the shuttle mechanism push the just-cleaned plate into the output hopper assembly. As a cleaned plate is moved from the scrubber head assembly to the output hopper assembly, an air knife or air jet arrangement 65 (Fig. 5) can be provided between the scrubber head assembly and the output hopper assembly to provide additional drying of the wells.

The output hopper assembly 16 is illustrated with more particularity in Figs. 21-23. The output hopper assembly includes an elevator assembly 72 including a carrier plate 154 onto which the shuttle assembly slides a clean microtiter plate. Guide blocks 156 along the sides and a stop block 158 at the end ensure the clean microtiter plate is properly positioned on the carrier plate. Once the clean plate is on the carrier plate, a lifting mechanism housed in the base 152 of the elevator assembly raises the carrier plate into the output hopper stack. The output hopper stack includes vertical guide members 160, 161, 162, 163 for holding the stack of clean microtiter plates. At the bottom of the stack, opposed hinged retaining blocks 164 are pivotably mounted. Each retaining block includes an upwardly facing shoulder 166 on which the well opening surface of a clean microtiter plate rests. A sloped or chamfered surface 168 is located below the shoulder. As a clean microtiter plate is raised into the output stack, the clean plate slides up the sloped surface, pivoting the retaining block outwardly to allow the clean microtiter plate to pass. A spring plate 172 biases the retaining block back into position so that, once the clean plate has passed the retaining block, the well opening surface of the clean plate rests on the shoulder of the retaining block. The elevator assembly 152 lowers the carrier plate 154, leaving the clean plate retained on the retaining block. As the next clean microtiter plate is lifted into the output stack, the clean microtiter plates already in the stack are lifted as well. In this manner, the lowermost clean microtiter plate rests on the retaining block.

Operation of the present device is described further with reference to the sequence illustrated in Figs. 24A-24K. In Fig. 24A, two used microtiter plates 201, 202 are located in the input hopper assembly. The flange of the lowermost plate is supported by the lower lips of the pivot bars. The shuttle mechanism is extended to the cleaning position. In Fig. 24B, the shuttle mechanism is retracted, biasing the pivot bracket to pivot the pivot bars, which allows the lowermost used plate 201 to drop into the shuttle mechanism and the flange of the next used plate 202 to drop onto the upper lips of the pivot bars. In Fig. 24C, the shuttle mechanism is extended, pushing the used plate 201 into the cleaning position at the scrubber head assembly. The pivot bracket is biased by the spring to cause the pivot bars to pivot, dropping the next used plate 202 from the upper lips to the lower lips. In Fig. 24D, the shuttle mechanism is again retracted, leaving the used plate 201 at the cleaning position to be cleaned and pushing the pivot bracket against the bias of the spring. The pivot bracket causes the pivot bars to rotate, allowing the next used plate 202 to drop into the shuttle mechanism. It is in this configuration of the shuttle mechanism that the sequence of air and liquid washing materials are applied to the used plate 201.

After the used plate 201 has been cleaned, the shuttle mechanism is again extended (see Fig. 24E) , pushing the now clean plate 201 to the elevator assembly with the extended fingers 148 and also pushing the next used plate 202 to the washing position at the scrubber head assembly. In Fig. 24F, the shuttle mechanism is retracted, and the elevator assembly raises the clean plate 201 into the output hopper stack. In Fig. 24G, the elevator assembly is lowered, leaving the clean plate 201 in the output hopper stack. The next used plate 202 is washed at the scrubber head assembly. In Fig. 24H, the shuttle mechanism is extended, pushing the second clean plate 202 to the elevator assembly with the extended fingers 148. In Fig. 241, the shuttle mechanism is retracted, leaving the second clean plate 202 at the elevator assembly. In Fig. 24J, the elevator assembly raises the second clean plate 202 into the output hopper stack, also pushing the first clean plate 201 up the stack. In Fig. 24K, the elevator assembly is lowered.

In another embodiment (see Fig. 25) , a pair of short ramps 212 followed by a vertical lip 214 on the input side of the scrubber head assembly catches the trailing corner of an incoming plate and prevents the plate from sliding backwards as the shuttle mechanism 22 retracts. At the scrubber head assembly, the plate rests on a pair of side strips 216, which maintain a constant distance between the nozzle extensions 236 and the well opening surface of the inverted microtiter plate. The strips can also be provided between rows of nozzles, for example, the first and second rows and the eleventh and twelfth rows of a twelve-row plate. In this case, the narrowness of the strip maximizes the ability of water to drain from the wells as they are being sprayed with high pressure cleaning solutions and air from below.

The force of the cleaning liquids and air projected into each well during the washing process can be sufficient to lift the microtiter plate off the strips 216 and cause the nozzles to lose justification with their corresponding wells in the microtiter plate. Therefore, a weighting mechanism to press the plate down onto the strips and hold the nozzles aligned with the wells is provided. The weighting mechanism is vertically adjustable to accommodate the variety of microtiter plate thicknesses that can be fed through the plate scrubbing device.

Referring to Figs. 26-28, in one embodiment, a hinged arm 172 with a weight of sufficient mass 174 presses downwardly on the inverted underside of the plate 201 and keeps the plate in stationary contact with the top edges of the two strips 216. As plates of different thicknesses are fed from the input hopper assembly to the scrubber head assembly, the plate is pushed between the strips and the retaining arm, causing the arm to be displaced upwardly depending on plate height. The arm and weight remain in contact with the inverted underside of the microtiter plate during the whole cleaning sequence. In this way, no operator adjustment is needed prior to feeding plates through the scrubber head assembly. Contacting the surface of the molded plastic plate with any type of abrasive cleaning device harder than the plastic of the plate itself has the risk of scratching the smooth inner walls of the plate and making it unfit for reuse. Use of compressed air and water to remove particulate matter from the walls of the wells provides for no possibility of damage to the microtiter plates by the cleaning process. Certain tightly bonded material might not, however, be removed, rendering the contaminated plate unsuitable for recycling. Accordingly, in another embodiment, to enhance the ability of the cleaning device to remove stubborn particulates adhering to the walls of the microtiter plate wells, mechanical scrubbing action can be employed to enhance the removal ability of compressed air alone. For example, a cleaning element can be inserted into the bottom of each well and moved against the surface to break the adherence of contaminant particles from the well walls. Such motion can be rotational, utilizing a rotating shaft affixed with a soft brush or other element on the inserted end that is rotated by compressed air or water or both impinging upon a turbine wheel on the opposite end of the shaft from the brush. Other driving mechanisms include direct mechanical driving by a motor connected to the brush of each well through various gear and drive belt arrangements. Because of the close proximity of the wash reagent to this brush driving mechanism, a magnetically coupled drive might serve to isolate the electric motor or other prime mover from the wet cleaning environment.

The cleaning action of the water and compressed air jets can be enhanced by the application of mechanical vibration to the microtiter plate during cleaning. As the various cleaning reagents and compressed air are sequenced, the vibration element is energized to help in breaking loose any contaminating material from the walls of the microtiter plate wells. For example, the vibration source can be a rotating device 176 with an eccentric weight affixed to a shaft on the weighting mechanism (see Fig. 28) . An alternate vibration source can be an ultrasonic transducer that generates higher frequency vibrations. The vibrational element will be mounted to the upper side of the weighting device bearing down on the microtiter plate as it is being cleaned.

Additional drying of a cleaned plate can occur after a plate is raised into the outlet hopper assembly stack. The inverted well opening surface of the plate is exposed and available to have warmed air directed at the wells. Referring to Fig. 29, in an alternate embodiment at the output hopper assembly, compressed air is delivered via an array of air nozzles 242 on a nozzle manifold 244 to the bottom of the wells of the inverted microtiter plate. The nozzle manifold is mounted on an elevator assembly 246. The nozzles fit into the wells with the tips contacting the bottom of the wells to lift the microtiter plate into the output hopper assembly. The nozzles can be of any suitable type, such as replaceable plastic nozzles.

In a further embodiment (see Figs. 30-33), the nozzle manifold 244 is permanently attached to the elevator mechanism 246. Between rows 1 and 2 and rows 11 and 12 of air nozzles 242 are two vertical spacer plates 801 with a height set such that the distance from the top of the spacer and the tip of the nozzle is about 1/16 inch less than the depth of the wells in the microtiter plate to be cleaned. The spacer is provided to apply the lifting force to the inverted top surface of the cleaned plate by transmitting the lifting motion of the nozzle manifold 244. In this way, at no time do the nozzles come in contact with the bottom of the sample wells. This prevents damage to the nozzle tips and allows the unrestricted flow of drying air to be delivered to the well.

In use, the clean microtiter plate 201 is slid by the fingers 148 on the shuttle 22 onto a platform 802 with an open center section such that the clean plate is supported by its perimeter. The level of this platform is at the location of carrier plate 154 in the embodiment of the device shown in Fig. 22. The elevator mechanism 246 raises the nozzle array through the opening in the platform such that each nozzle enters a well of the microtiter plate. When the two spacers 801 contact the inverted top surface of the clean plate, the plate is raised into the outlet hopper for storage, in turn, lifting any other plates which may be present in the outlet hopper. The platform 802 is free to be lifted off of its frame supports by contacting the nozzle manifold 244 in order to accommodate sufficient travel to push the clean plate into the outlet hopper latching mechanism.

A microtiter plate weight 252 (see Fig. 34) is provided at the top of the stack of plates in the outlet hopper stack. When the elevator reaches its fully raised position, the microtiter plate comes in contact with either the outlet hopper microtiter plate weight, if it is the first plate being inserted into an empty hopper, or the bottom plate of a stack of inverted microtiter plates already in the outlet hopper. Once the newly washed plate is in contact with the weight or a stack of plates, the high pressure air can be delivered to the elevator manifold where it is directed through each air nozzle onto the bottom surface of each inverted well. The blast of air would lift the plate off of the air nozzle array if the plate weight or the stack of plates were not present.

The blast of drying air can be applied for the full duration of the cleaning cycle of a subsequent plate, for example, for 30 seconds. Applying compressed air to the bottom of the wells drives any residual wash liquid out of the wells and down onto the nozzle manifold and eventually to a liquid drain. This removes substantially all liquid from the wells as the plate is raised into the storage position in the output stacker. The elevator assembly need not be retracted to the downward position until just before the plate currently being washed has finished its wash cycle and is ready to be moved onto the outlet stacking elevator.

Referring now to Figs. 35-38, as an alternative to requiring attachment means between the spacer plate 801 and the nozzle manifold 244, the spacer plate function can also be accomplished by fabricating longitudinal holes in spacer plates 803 such that two plates can be installed over the nozzles of rows two and eleven. Because the spacer plate would be coincident with the sample wells of the clean plate, the top edge of the spacer plate is beveled to allow rinse liquid to be effectively expelled from the sample wells by the air blowing from the nozzle openings.

To eliminate the need for a platform at the level of the plate and shuttle mechanism, in a third embodiment (see Figs. 39- 42), two spacer plates 804 are suspended above the nozzle manifold 244 coincident with two rows of nozzles 242 by fixed frame members on either side of nozzle manifold 244. The top edge of each spacer plate 804 is located in the plane of the shuttle to accept the transfer of a clean plate from the scrubber head area to the outlet hopper area. These two spacer plates also have a ramp and notch arrangement to maintain the position of the microtiter plate above the air nozzles as the shuttle mechanism is retracted. The tips of the nozzles are just below the plane of the top surface of the clean microtiter plate 201 and that of the top edge of the spacer plates 804.

The elevator manifold fitted with the air nozzles is then raised causing each nozzle to protrude from its hole in the spacer plates and enter a well of the inverted microtiter plate. Because the spacer plates are suspended by a mechanism other than contacting the elevator manifold, they and the plate resting on them exhibit no movement as the elevator manifold and nozzles begin to rise. Eventually, as the elevator platform continues to rise, the top surface of the elevator manifold will contact the bottom edges of the two spacer plates on which the microtiter plate is resting. Contact of the spacer plates by the manifold occurs just prior to the open end of the air nozzle contacting the closed bottom of the plate wells. In this condition, continued vertical motion of the elevator manifold now causes the inverted plate to rise into the bottom of the outlet hopper assembly and the stack of washed plates that it contains.

Note that maintaining a close spacing between the well bottom and the nozzle outlet requires different sets of spacer plate pairs such that the height of a particular set of plates is tailored to the depth of the well of the plate currently being processed by the cleaning device. In this way the thickness of a pair of spacer strips determines how deeply the nozzle penetrates the well before the spacer strip is captured between the nozzle manifold on the bottom edge and the inverted top surface of the microtiter plate with the downward facing well openings. In this implementation, it is no longer possible to randomly mix plates of different thicknesses in the inlet hopper.

It is desirable to remove as much of the water from the just-washed plate as possible so the excess wash reagents do not become trapped in the nested stack of plates in the outlet hopper. Because the outlet hopper spacer strips are fitted coincident with the air nozzles by a series of corresponding holes in the spacer plates, the long axis of the plates is also aligned with the row of wells into which the nozzles will enter. The interrupted inverted surface of the microtiter plate formed by the pattern of wells offers an opportunity to create a jarring or vibratory motion of the plate as it is slid into position above the air nozzle array by the shuttle mechanism. The top surface of each spacer plate is machined with a series of jagged peaks 805 having an apex spacing equal to that of the well spacing, thus assuring that the plate bounces up and down as each inverted well settles onto each new apex. In this manner, the sliding of the plate into position and the resulting vibration due to the motion shakes a large quantity of the retained washing reagent from within the wells and surrounding areas of the plate.

The continuous processing of plates through the device can be facilitated by providing removable stacks at one or both of the inlet and outlet hopper assemblies. In the case of the inlet hopper assembly, plates can be preloaded into several inlet hopper tubes, for example, by the automation equipment using the plates as a part of the analysis process. Alternatively, plates to be washed could be loaded manually by an operator who subsequently exchanges an empty hopper tube for a full one without even stopping the cleaning device. In the case of the outlet hopper assembly, the stack of clean plates is well contained and conveniently manageable if an entire hopper tube can be removed and replaced with an empty tube by an operator when the outlet hopper assembly becomes full.

The fully automated microtiter plate cleaning device can be installed as a functional module on any automation platform designed to process microtiter plates. Any existing plate handling robot that is a part of the platform can deliver to the inlet hopper of the plate cleaner contaminated plates already used within the process. After the plates are sequenced through the plate scrubber device and stored in the outlet hopper assembly, the same plate handling robot can remove clean plates from the outlet hopper assembly as part of a continuous self-contained assay process.

A minimal scrubbing station can be incorporated as a part of an automated process. By placing just a scrubber head manifold within an enclosure to collect and direct to waste the liquid reagents used in the cleaning process, a preexisting robotic hand could invert and locate a used plate above the scrubber head manifold for cleaning. When the sequence of cleaning steps is complete, the robotic hand of the existing automation system can retrieve the plate from the cleaning station and return it to the beginning of the automated assay process.

Like the scrubber head manifold in the previous paragraph, the air nozzle array associated with the outlet hopper elevator can be configured as part of an automated assay system in a freestanding configuration. The plate handling robot associated with the assay setup can present the plates to be dried to the air nozzle array after the wash sequence has been completed.

Referring to Fig. 43, microtiter plates 302 suitable for cleaning by this scrubbing device can be any of the hundreds of configurations available. Well densities on a plate can vary from a single large reservoir through 96-well and 384-well versions which are the most common, to a maximum density of 1534 wells for the preferred embodiment shown. Materials of construction are typically polystyrene or polypropylene. Teflon plates are also available. The present plate cleaning device works equally well on plates molded from a variety of materials.

The detergent reservoir can be equipped with a heat source to warm the detergent that is applied to the plate during the cleaning process. The detergent dispensing system can be equipped with a pump to feed the liquid soap from a floor-level container up to the level of the manifold plate, presumably operating at a convenient benchtop height.

The present device can also employ cleaning reagents such as organic solvents, acids, and bases that might be required to produce required cleaning results. Such reagents might generate hazardous waste that could not be disposed of in a municipal sewer system. Redirection of the reagent unsuitable for the municipal sewer would be required. A closed loop system to collect and reuse the hazardous reagent (s) can be employed in this case. The redirected reagent could be stored for future reuse or disposed of following accepted hazardous waste procedures.

Multiple scrubber heads can be implemented, each with a dedicated reagent to better isolate hazardous from non-hazardous waste. Having a dedicated scrubber head would mean less reagent volume being required to purge a previous reagent from a wash head with the next reagent in the sequence. A dedicated hazardous reagent head would minimize the volume of collected cleaning solution.

The invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims.

Claims

CLAIMS What is claimed is:

1. A microtiter plate scrubbing device for cleaning microtiter plates, the microtiter plates having a plurality of wells therein, the device comprising: an input hopper assembly configured to hold used microtiter plates in a vertical stack; a scrubber head assembly disposed to receive, from the input hopper assembly, a microtiter plate in an inverted position with the wells opening downwardly, the scrubber head assembly comprising a plurality of nozzles extending upwardly to direct fluid flow into the downwardly opening wells of the microtiter plate; a shuttle mechanism operative to move a lowermost microtiter plate in the inverted position from the input hopper assembly to the scrubber head assembly; and an output hopper assembly disposed to receive a clean microtiter plate from the scrubber head assembly.

2. The device of claim 1, wherein the input hopper assembly further comprises an escapement mechanism disposed to support a microtiter plate in the inverted position by a flange at the bottom of the plate.

3. The device of claim 1, wherein the shuttle mechanism comprises a microtiter plate receiving element to receive a microtiter plate when the shuttle mechanism is located at the input hopper assembly and a microtiter plate pushing element to push a clean microtiter plate from the scrubber head assembly to the output hopper assembly when the shuttle mechanism moves from the input hopper assembly to the scrubber head assembly.

4. The device of claim 3, wherein the microtiter plate pushing element comprises a pair of spring fingers configured to move past a microtiter plate at the scrubber head assembly when the shuttle mechanism is retracted from the scrubber head assembly to the input hopper assembly.

5. The device of claim 1, further comprising an escapement mechanism operative in conjunction with the shuttle mechanism to release the lowermost microtiter plate in the stack in the input hopper assembly to the shuttle mechanism.

6. The device of claim 5, wherein the escapement mechanism comprises opposed bars having upper lips and lower lips biased to catch the flange along the inverted bottom edge of a microtiter plate, the bars pivotable upon actuation of the shuttle mechanism to release a plate on the upper lips to the lower lips and to release a plate on the lower lips to the shuttle mechanism.

7. The device of claim 1, wherein each nozzle in the scrubber head assembly includes separate liquid and air ports.

8. The device of claim 7, wherein the plurality of nozzles extend from a manifold plate, a liquid inlet fitting is disposed in the manifold plate and a plurality of fluid passages extend from the liquid inlet fitting through the manifold plate in fluid communication with each of the liquid ports of the nozzles.

9. The device of claim 8, further comprising a plurality of cleaning liquid sources in fluid communication with the liquid inlet fitting in the manifold plate and valving upstream of the liquid inlet fitting to control delivery of cleaning liquid from the cleaning liquid sources to the manifold plate.

10. The device of claim 9, wherein the cleaning liquid sources include a detergent source.

11. The device of claim 9, wherein the cleaning liquid sources include a hot water source.

12. The device of claim 9, wherein the cleaning liquid sources include a de-ionized water source.

13. The device of claim 9, wherein the cleaning liquid sources include a solvent source.

14. The device of claim 7, wherein the scrubber head assembly further includes an air plenum comprising an air plenum chamber in fluid communication with each of the air ports of the nozzle extensions, and an air inlet fitting is provided in the air plenum in communication with a switchable compressed air source.

15. The device of claim 1, wherein the scrubber head assembly further comprises a microtiter plate stop mechanism configured to retain a microtiter plate at the scrubber head assembly when the shuttle mechanism retracts from the scrubber head assembly to the input hopper assembly.

16. The device of claim 15, wherein the stop mechanism comprises a lip disposed to engage the flange along the inverted bottom edge of the microtiter plate.

17. The device of claim 16, wherein the lip is disposed adjacent a ramp surface over which the microtiter plate rides.

18. The device of claim 1, wherein the output hopper assembly comprises an elevator assembly disposed to receive a clean microtiter plate from the scrubber head assembly and raise the clean microtiter plate into a vertical stack.

19. The device of claim 18, wherein the output hopper assembly further comprises a retaining block to hold a lowermost clean microtiter plate in the vertical stack above the elevator assembly by the flangs along the inverted bottom of the plate, the retaining block movable to allow a clean microtiter plate to pass and biased to return to a retaining position after the clean microtiter plate has passed.

20. The device of claim 1, wherein the output hopper assembly further comprises a plurality of air drying nozzles disposed to direct air into inverted sample wells of a clean microtiter plate.

21. The device of claim 1, further comprising a controller in communication with the scrubber head assembly to control a cleaning sequence of a microtiter plate.

22. The device of claim 1, further comprising a controller in communication with the shuttle mechanism to control movement of a microtiter plate from the inlet hopper assembly to the scrubber head assembly.

23. The device of claim 1, further comprising an air drying element disposed in the output hopper assembly to direct drying air into the inverted wells of a cleaned microtiter plate.

24. A scrubber head assembly for cleaning microtiter plates, the microtiter plates having a plurality of wells therein, the scrubber head assembly comprising: a microtiter plate support disposed to receive a microtiter plate in an inverted position with the wells opening downwardly; and a manifold comprising a plurality of nozzles extending upwardly to direct fluid flow into the downwardly opening wells of the microtiter plate.

25. The scrubber head assembly of claim 24, wherein each nozzle extending from the manifold includes separate liquid and air ports.

26. The scrubber head assembly of claim 25, wherein a liquid inlet fitting is disposed in the manifold and a plurality of fluid passages extend from the liquid inlet fitting through the manifold in fluid communication with each of the liquid ports of the nozzles.

27. The scrubber head assembly of claim 25, further including an air plenum comprising an air plenum chamber in fluid communication with each of the air ports of the nozzle extensions, and an air inlet fitting is provided in the air plenum in communication with a switchable compressed air source.

28. A method of cleaning used microtiter plates, said method comprising the steps of: supporting a used microtiter plate in an inverted position with the wells of the plate opening downwardly; spraying a wash liquid and an air jet from closely spaced ports in a wash nozzle upwardly into each downwardly opening well of the microtiter plate; spraying a rinse liquid upwardly into each downwardly opening well of the plate; and drying the clean microtiter plate.

29. The method of claim 28, wherein the steps of the cleaning sequence are automated.

30. The method of claim 29, wherein the steps of the cleaning sequence are controlled by a programmable computer.