Abstract:
An automated machine for filling a plurality of microplates. The automated machine includes at least one input stacking chamber for stacking empty microplates, at least one output stacking chamber for stacking filled microplates, and a microplate filling assembly disposed between the at least one input stacking chamber and the at least one output stacking chamber. The microplate filling assembly has a walking beam indexer, a lid lifter for lifting the lid off each microplate to permit the microplate to be filled, and after filling to replace the lid, and a fill mechanism in communication with a media source and positioned to fill the empty microplates after their lids have been lifted off. An automatic control unit is programmed to cause the walking beam indexer to move empty microplates from the at least one input stacking chamber, to cause the lid lifter to lift the lid off each microplate, to cause the fill mechanism to inject media from the media source into wells in the microplates, to cause the lid lifter to replace the lid after the media is injected, and to cause the walking beam indexer to move the microplates to the at least one output stacking chamber. In a preferred embodiment of the present invention, there are ten input stacking chambers and ten output stacking chambers and they are mounted on an input carousel and output carousel, respectively.

Description:
The present invention relates to microplate filling devices, more specifically it relates to automated microplate filling devices. This application is a continuation-in-part of U.S. patent application Ser. No. 09/411,943, filed Oct. 4, 1999, and soon to issue as U.S. Pat. No. 6,148,878. 
    
    
     BACKGROUND OF THE INVENTION 
     Microplates, also known as micro-well plates, are a standard product and are regularly used in medical, chemical and biological laboratories. A perspective view of a microplate  1  is shown in FIG.  1 A. Microplate  1  has microplate lid  2  and microplate base  4 . Microplate  1  shown in FIG. 1A and 1B has just one well. FIG. 1C shows a microplate with 96 wells in its base  4  and FIG. 1D shows a microplate with 384 wells in its base  4 . Microplates with 1536 wells are also available. 
     In the laboratory, microplates are commonly filled with various media. The media can be either in a liquid form or have a thicker, viscous consistency, such as that found in Agar. It is very important to the efficient productivity of a laboratory to be able to pour media into microplates accurately and rapidly. In order to produce a high volume of prepared microplates, an automated machine can provide the required throughput much faster than a technician can. To this end there are several automated devices that are currently available that will automatically fill microplates with media. Thermo Vision, Inc. with offices in Grand Junction Colorado, makes an automated filling machine that can only handle ten plates at a time and must be monitored continuously to remove filled plates and add new ones. Zymark Corp., with offices in Hopkinton Mass., produces a liquid handling workstation, but it is also for low capacity runs and requires constant supervision. A automated filling machine is known that has slightly greater capacity than those made by Thermo Vision and Zymark Corp., but the increased capacity is limited on the input side and there is no restacking capability. This means that there has to be a technician present at all times to remove filled plates and make room for the new ones. This machine also uses an expensive robot for positioning. The robot adds extra cost to the device. CCS Packard, with offices in Torrance Calif., produces a couple of machines that include both an input and an output chamber that can hold up to 50 plates. These devices rely on a conveyor system. 
     The main problems with the above known devices are that they are very expensive and must be monitored at all times due to low capacity and/or no input/output unstacking and restacking capabilities. 
     In order to save money, there have been attempts to make manual microplate filling machines. U.S. Pat. No. 5,415,060 discloses a device in which a bridge that aligns and holds steady a hand-held liquid dispenser means is positioned over microplate holder for a manual application of liquid. Although this device may be considerably less expensive than prior art automated devices, it is too slow and impractical for many laboratories. What is needed is relatively inexpensive automatic machine with simple mechanisms for rapidly filling a large volume of microplates without constant supervision. 
     SUMMARY OF THE INVENTION 
     The present invention provides an automated machine for filling a plurality of microplates. The automated machine includes at least one input stacking chamber for stacking empty microplates, at least one output stacking chamber for stacking filled microplates, and a microplate filling assembly disposed between the at least one input stacking chamber and the at least one output stacking chamber. The microplate filling assembly has a walking beam indexer, a lid lifter for lifting the lid off each microplate to permit the microplate to be filled, and after filling to replace the lid, and a fill mechanism in communication with a media source and positioned to fill the empty microplates after their lids have been lifted off. An automatic control unit is programmed to cause the walking beam indexer to move empty microplates from the at least one input stacking chamber, to cause the lid lifter to lift the lid off each microplate, to cause the fill mechanism to inject media from the media source into wells in the microplates, to cause the lid lifter to replace the lid after the media is injected, and to cause the walking beam indexer to move the microplates to the at least one output stacking chamber. In a preferred embodiment of the present invention, there are ten input stacking chambers and ten output stacking chambers and they are mounted on an input carousel and output carousel, respectively. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A shows a perspective view of a single-well microplate. 
     FIG. 1B shows a top view of a single-well microplate base. 
     FIG. 1C shows a top view of a 96—well microplate base. 
     FIG. 1D shows a top view of a 384—well microplate base. 
     FIGS. 2A-2D are a flowchart representing the programming for the programmable logic controller. 
     FIG. 3 shows a top view of a preferred embodiment of the present invention. 
     FIG. 4 shows a top view of the microplate filling assembly. 
     FIG. 5 shows a side view of a preferred embodiment of the present invention. 
     FIG. 6 shows a perspective view of the input chamber singulator. 
     FIG. 7 shows a detailed view of the input chamber singulator lifting input stack A. 
     FIG. 8 shows a perspective view of the lid lifter and walking beam indexer. 
     FIG. 9 shows a block diagram of the programmable logic controller other components of a preferred embodiment of the present invention. 
     FIGS. 10-39 show a sequence depicting the operation of a preferred embodiment of the present invention. 
     FIG. 40 shows a perspective view of some components of a preferred embodiment of the present invention. 
     FIG. 41 shows a perspective view of some components of another preferred embodiment of the present invention. 
     FIG. 42 shows a top view of a preferred embodiment of the present invention. 
     FIG. 43 shows a top view of the walking beam indexer and the input chamber lifter. 
     FIGS. 44-49 show a sequence depicting the operation of a preferred embodiment of the present invention. 
     FIG. 50 shows a perspective view of stack support pieces mounted to the output chamber. 
     FIG. 51 shows a side view of a stack support piece mounted to the output chamber. 
     FIGS. 52-55 show a sequence depicting the operation of a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A detailed description of a first preferred embodiment of the present invention can be described by reference to FIGS. 1-39. A top view of a preferred embodiment of the present invention is seen in FIG.  3 . FIG. 3 shows input carousel  3  and output carousel  5  connected by microplate filling assembly  6 . During the operation of the present invention, empty microplates are stacked into input carousel  3 , automatically filled with media via microplate filling assembly  6 , and automatically restacked into output carousel  5 . 
     As shown in FIG. 3, input carousel  3  has ten input chambers  15 A- 15 J and output carousel  5  has ten output chambers  16 A- 16 J. Each input chamber  15  and output chamber  16  is capable of receiving and holding a stack of twenty-four microplates. Therefore, a total of 240 empty microplates may be stacked in input carousel  3 , automatically filled via microplate filling assembly  6 , and automatically restacked into output carousel  5 . 
     FIG. 4 shows a detailed top view of microplate filling assembly  6  with microplates located at positions α-ε along microplate filling assembly  6 . 
     Sequence of Operation of a Preferred Embodiment 
     FIGS. 10-39 illustrate the sequence of operation of the first preferred embodiment of the present invention. 
     In a preferred embodiment of the present invention, the operation of the components is controlled by programmable logic controller (PLC)  200 , as shown in FIG.  9 . FIGS. 2A-2E show a flowchart representing preferred programming of PLC  200  and corresponds with the sequence illustrated in FIGS. 10-34. 
     As shown in FIG. 2A, steps  1000 - 1005 , after the user powers “on” the present invention, PLC  200  automatically conducts a start up routine. In this routine, PLC  200  checks all PLC  200  controlled components, homes all pneumatic devices and checks all sensors. If there are any errors (for example, jammed microplates or component malfunction), the user will be alerted via monitor  204  (FIG.  9 ). 
     As shown in FIG. 2A, step  1010 , the user inputs the type of microplate that he wants to be filled (i.e., either a single-well, 96-well, or 384-well microplate). As shown in step  1015 , because the nozzle type varies depending on the microplate selected, the user must install the correct nozzle. Depending upon the microplate selected by the user in the start up routine, PLC  200  selects walking beam indexer  7  positioning data and nozzle  13  fill rate. 
     All components move to their start position. FIG. 10 shows a stack of twenty-four empty microplates  1 A- 24 A loaded into input chamber  15 A. Microplate  1 A is at the bottom at position α (FIG. 4) and microplate  2 A is directly above microplate  1 A. Microplate  24 A is at the top of the stack. In FIG. 10 output stack A located inside output chamber  16 A is empty with no microplates. 
     In FIG. 11, walking beam indexer  7  has lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     In FIG. 12, input chamber singulator  23  has lifted input stack A 2 -A 24  at microplate  2 A. Microplate  1 A is left at position α, as shown in FIG. 4. A detailed view of input chamber singulator  23  lifting input stack A is seen in FIG.  7 . Tab singulator  33  lifts microplate  2 A allowing a small gap to form between microplate  1 A and  2 A. Since input stack A 2 -A 24  is confined on all sides by input chamber  15 A, instead of tilting input stack A 2 -A 24 , lifting from the front edge lifts the entire stack vertically. Also as shown in FIG. 12, walking beam indexer  7  has moved to the right. 
     In FIG. 13, walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  1 A. 
     In FIG. 14, walking beam indexer  7  has moved to the left pushing microplate  1 A to position β (see FIG. 4) from the bottom of the stack. 
     In FIG. 15, walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . Input chamber singulator  23  has dropped input stack A. Microplate  1 A is at position p and microplate  2 A is at position α. 
     In FIG. 16, walking beam indexer  7  has moved to the right. Input chamber singulator  23  has lifted input stack A 3 -A 24 , leaving behind microplate  2 A at position α. 
     In FIG. 17, lid lifter  41  has dropped to the top of microplate lid  2  of microplate  1 A, has grasped microplate lid  2  with a vacuum force and will lift microplate lid  2  prior to the display shown in FIG.  18 . Walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  2 A. 
     In FIG. 18, lid lifter  41  has lifted microplate lid  2  off of microplate  1 A. Walking beam indexer  7  has moved microplate base  4  of microplate  1 A to the left underneath nozzle  13 . If single well plates are being used as shown in FIGS. 1A and 1B, walking beam indexer  7  will move microplate  1 A to a center location to fill microplate  1 A with media. If microplate  1 A is a multi-welled microplate (for example, a 96 or 384-welled plate), walking beam indexer  7  will first move microplate  1 A to so that the first row is underneath nozzle  13 . After the first row is filled, walking beam indexer  7  will move microplate  1 A to the left so that the second row is underneath nozzle  13  so that it can be filled. Walking beam indexer  7  will continue to move microplate  1 A incrementally in this manner until all rows are filled. As shown in FIG. 18, microplate lid  2  is being held directly over microplate base  4  by lid lifter  41 . 
     In FIG. 19, walking beam indexer  7  has moved further to the left. Lid lifter  41  has returned microplate lid  2  of microplate  1 A to microplate base  4 . Microplate  1 A is at position γ (see FIG. 4) and microplate  2 A is at position β. Microplate  1 A is now filled with media  11 . 
     In FIG. 20, input chamber singulator  23  has dropped input stack A. Lid lifter  41  has been raised. Microplate  1 A is at position y (FIG.  4 ), microplate  2 A is at position β, and microplate  3 A is at position a. Walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     In FIG. 21, walking beam indexer  7  has moved to the right. Input chamber singulator  23  has lifted input stack A 4 -A 24 , leaving behind microplate  3 A at position α. 
     In FIG. 22, lid lifter  41  has dropped to the top of microplate lid  2  of microplate  2 A, has grasped microplate lid  2  with a vacuum force and will lift microplate lid  2  prior to the display shown in FIG.  23 . Walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  3 A. 
     In FIG. 23, lid lifter  41  has lifted microplate lid  2  off of microplate  2 A. Walking beam indexer  7  and lid lifter  41  have moved to the left. Microplate base  4  of microplate  2 A is underneath nozzle  13  and is being filled with media  11 . Microplate lid  2  is being held directly over microplate base  4  by lid lifter  41 . 
     In FIG. 24, walking beam indexer  7  has moved further to the left. Lid lifter  41  has returned microplate lid  2  of microplate  2 A to microplate base  4 . Microplate  1 A is at position δ, microplate  2 A is at position γ, microplate  3 A is at position β (FIG.  4 ). Microplate  2 A is now filled with media  11 . 
     In FIG. 25, input chamber singulator  23  has dropped input stack A. Lid lifter  41  has been raised. Walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     In FIG. 26, walking beam indexer  7  has moved to the right. Input chamber singulator  23  has lifted input stack A 5 -A 24 , leaving behind microplate  4 A at position α. 
     In FIG. 27, lid lifter  41  has dropped to the top of microplate lid  2  of microplate  3 A, has grasped microplate lid  2  with a vacuum force and will lift microplate lid  2  prior to the display shown in FIG.  28 . Walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  4 A. 
     In FIG. 28, lid lifter  41  has lifted microplate lid  2  off of microplate  3 A. Walking beam indexer  7  and lid lifter  41  have moved to the left. Microplate base  4  of microplate  3 A is underneath nozzle  13  and is being filled with media  11 . Microplate lid  2  is being held directly over microplate base  4  by lid lifter  41 . Microplate  1 A is being moved inside of output chamber  16 A. 
     In FIG. 29, walking beam indexer  7  has moved further to the left. Lid lifter  41  has returned microplate lid  2  of microplate  3 A to microplate base  4 . Microplate  1 A is at position ε, microplate  2 A is at position δ, microplate  3 A is at position γ, and microplate  4 A is at position β (FIG.  4 ). Microplate  3 A has been filled with media  11 . 
     In FIG. 30, input chamber singulator  23  has dropped input stack A. Lid lifter  41  has been raised. Walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     In FIG. 31, walking beam indexer  7  has moved to the right. Input chamber singulator  23  has lifted input stack A 6 -A 24 , leaving behind microplate  5 A at position α. 
     In FIG. 32, lid lifter  41  has dropped to the top of microplate lid  2  of microplate  4 A, has grasped microplate lid  2  with a vacuum force and will lift microplate lid  2  prior to the display shown in FIG.  33 . Walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  5 A. Output chamber lifter  61  has lifted microplate  1 A to allow room for microplate  2 A to be restacked from the bottom. 
     In FIG. 33, lid lifter  41  has lifted microplate lid  2  off of microplate  4 A. Walking beam indexer  7  and lid lifter  41  have moved to the left. Microplate base  4  of microplate  4 A is underneath nozzle  13  and is being filled with media  11 . Microplate lid  2  is being held directly over microplate base  4  by lid lifter  41 . Output chamber lifter cylinder  61 A has dropped allowing room for microplate  2 A to enter output chamber  16 A. Microplate  1 A is resting on output chamber lifter cylinder  61 B and microplate  2 A. 
     In FIG. 34, walking beam indexer  7  has moved further to the left. Lid lifter  41  has returned microplate lid  2  of microplate  4 A to microplate base  4 . Microplate  2 A is at position ε, microplate  3 A is at position δ, microplate  4 A is at position γ, and microplate  5 A is at position β (FIG.  4 ). Microplate  3 A has been filled with media  11 . Output chamber lifter cylinder  61 B has dropped and microplate  1 A is resting on microplate  2 A inside output chamber  16 A. 
     The sequence continues as described above until input stack A is empty, as shown in FIG.  35 . FIG. 35 shows a stack of twenty-one filled microplates loaded into output chamber  16 A. Microplate  1 A is at the top of output stack A and microplate  2 A is directly underneath microplate  1 A. Microplate  21 A is at the bottom of output stack A at position ε. Microplate  22 A is at postion δ, microplate  23 A is at position γ, and microplate  24 A is at position β. Input stack A is empty with no microplates. Once sensor  100  (FIGS. 35 and 4) registers input stack A is empty, input carousel  3  (FIG. 3) rotates to so that input stack B is aligned with microplate filling assembly  6 , as shown in FIG.  36 . 
     FIG. 36 shows a stack of twenty-four empty microplates  1 B- 24 B loaded into input chamber  15 B. Microplate  1 B is at the bottom at position α (FIG. 4) and microplate  2 B is directly above microplate  1 B. Microplate  24 B is at the top of the stack. Microplate  21  A is at the bottom of output stack A at position ε. Microplate  22 A is at postion δ, microplate  23 A is at position γ, and microplate  24 A is at position β. Lid lifter  41  has been raised. Walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     The sequence continues until output stack A is completely filled, as shown in FIG.  37 . FIG. 37 shows microplate  1 A at the top of output stack A. Microplate  24 A is at the bottom of output stack A at position β. Microplate  1 B is at position δ, microplate  2 B is at position γ, and microplate  3 B is at position β. As soon as sensor  104  registers that microplate  1 A is at the top of output stack A, output carousel  5  rotates so that output stack B inside output chamber  16 B is aligned with microplate filling assembly  6 , as shown in FIG.  38 . 
     FIG. 38 shows microplate  1 B at position  6 , microplate  2 B at position γ, and microplate  3 B at position β. Input chamber singulator  23  has dropped input stack B and microplate  4 B is at position α. 
     The above sequence continues until all the empty microplates that were originally in input carousel  3  have been filled and are restacked in output carousel  5 . FIG. 39 shows an empty input chamber  15 J and an output chamber  16 J that has a full output stack J with filled microplates. If the operator desires, empty input chambers  15  from input carousel  3  can be reloaded with empty microplates while the machine is in operation, and it will continue to run. 
     Sensors  100  and  104  (FIGS. 4 and 37) and sensors  101 ,  102  and  103  (FIG. 4) continuously check for microplate presence. If there are no microplates in input carousel  3 , this is recognized as an error and the process is stopped until more microplates are added to the system and the machine is restarted. The same is true for output carousel  5 . If all 240 positions are filled in output carousel  5 , the machine will recognize this as an error and will not continue until output chambers  16 A- 16 J are emptied and the machine is restarted. If input carousel  3  is empty but sensors  101  though  103  report there are still microplates present in fill assembly  6  and sensor  104  reports there is still room in output carousel  5 , the process will continue until all microplates are restacked in output carousel  5 . 
     COMPONENTS OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
     Output and Input Carousels 
     In a preferred embodiment, input carousel  3  and output carousel  5  are fabricated from 0.060 thick  304  stainless steel. Base  17  (FIG. 3) has a diameter of approximately 16 inches. Input carousel  3  has 10 input chambers  15  mounted to base  17 . Likewise, output carousel  5  has ten output chambers  16  mounted to base  17 . Input chambers  15  and output chambers  16  are approximately 16.5 inches tall, have a depth of approximately 3.400 inches and are approximately 5.063 inches wide. Each input chamber  15  and output chamber  16  can hold twenty-four microplates  1 . Chambers  15  and  16  are fabricated so that microplates  1  fit snuggly inside, but are able to slide freely up and down, as shown in FIG.  3 . Chambers  15  and  16  are rigidly mounted to base  17  with mounting plates  19 . As shown in FIG. 5, input carousel  3  and output carousel  5  are both rigidly mounted to position indexing tables  210 A and  210 B. Indexing tables  210 A and  210 B (part no. MT200S 10R) are manufactured by Kamo Seiko, Inc. and supplied by Land Sea, Inc. Indexing Tables  210 A and  210 B function to rotate input carousel  3  and output carousel  5  to ten different positions each so that each input chamber  15  and output chamber  16  can be directly aligned with walking beam indexer  7 . As shown in FIG. 3, input chamber  15 A and output chamber  16 A are directly aligned with walking beam indexer  7 . 
     Input Chamber Singulator 
     A detailed perspective view of a preferred embodiment of input chamber singulator  23  is shown in FIG.  6 . Pneumatic cylinder  25  is pivotally mounted to bracket  27 . Preferably, pneumatic cylinder  25  is a double acting/single rod pneumatic cylinder (part no. NCDJ2D04OOHB) manufactured by SMC, Inc. Link singulator  29  is pivotally mounted to pneumatic cylinder  25  and rigidly connected to rod singulator  31 . Rod singulator  31  is mounted to singulator bearing blocks  35  and is free to rotate on plastic flange bearings  37 . Tab singulators  33  are rigidly mounted to rod singulator  31 . Bearing blocks  35  are rigidly mounted to supports  39 , as shown in FIG.  6  and FIG.  10 . 
     FIG. 12 shows pneumatic cylinder  25  in its retracted position with tab singulators  33  lifting microplate  2 A. A detailed side view of tab singulator  33  lifting input stack A is shown in FIG.  7 . Note that the triangular shape of tab singulators  33  (FIG. 6) corresponds to 45° recess  2 A in microplates  1  (FIG.  1 ). Therefore, tab singulator  33  is able to lift input stack A without bumping into microplate lid  2 , as shown in FIG.  7 . 
     Walking Beam Indexer and Lid Lifter 
     FIG. 8 shows a perspective view of walking beam indexer  7  and lid lifter  41 . Lid lifter  41  is rigidly mounted to lid lifter brackets  43 . Lid Lifter brackets is rigidly connected to linear actuator threaded connector  47  (FIGS.  8  and  10 ). Linear actuator threaded connector is threaded onto lead screw  49  of linear actuator  45 . Preferably, linear actuator  45  is an actuated linear motion system (part no. LC332001A-3001-P10) manufactured and available from Bearing Engineers, Inc. Lead screw  49  is actuated via servo motor  48 . Preferably, servo motor  48  is an animatics motor (part no. SM2310) with amplifier and encoder all in one package 
     Walking beam indexer  7  is mounted to compact pneumatic cylinders  52 . When pneumatic cylinders  52  expand, walking beam indexer  7  is raised, as shown in FIG.  10 . When pneumatic cylinders  52  retract, walking beam indexer  7  is lowered, as shown in FIG.  11 . Preferably, compact cylinders are part number NCDQ2B20-10D-J79L manufactured by SMC and supplied by A &amp; H Sales. 
     Pneumatic cylinder  53  is rigidly mounted to the back of indexer bracket  43 , as shown in FIG.  8 . Preferably, pneumatic cylinder  53  is a dual rod pneumatic cylinder (part no. CXSM-15-50-Y59B) manufactured by SMC, Inc. and available from A&amp;H Sales. Lid lifter top  41 A is rigidly connected to the top of pneumatic cylinder  53 . Vacuum cups  55  extend downward from lid lifter top  41 A. Vacuum lines connect vacuum cups  55  to vacuum generator  57 , as shown in FIG.  9 . 
     Linear actuator servo motor  48  (FIG. 10) rotates lead screw  49 . As lead screw  49  rotates, linear actuator threaded connector  47  moves horizontally back and forth. Consequently, indexer bracket  43  moves horizontally back and forth. As it does so, it changes the horizontal location of both walking beam indexer  7  and lid lifter  41  together with an accuracy of plus or minus 0.0001 inches. 
     Output Chamber Lifter 
     As shown in FIG. 32, output chamber lifter  61  includes pneumatic cylinders  61 A and  62 A rigidly attached to bracket  62 . Preferably, pneumatic cylinders  61 A and  61 B are dual rod pneumatic cylinders (part no. CXSM-15-50-Y59B) manufactured by SMC, Inc. and available from A&amp;H Sales. As shown in FIGS. 32-34, output chamber lifter  61  functions to lift microplate  1 A up while microplate  2 A is inserted into output chamber  16 A. 
     Programmable Logic Controller (PLC) 
     FIG. 9 depicts a block diagram of Programmable Logic Controller (PLC)  200  and other components of a preferred embodiment of the present invention. PLC  200  includes CPU  201  with associated memory (RAM  202 , and ROM  203 ). Input/output port  205  connects PLC  200  with other components of the present invention. A user of the present invention can monitor the status of the operation of the present invention by way of monitor  204 . 
     OPERATION OF A PREFERRED EMBODIMENT OF THE PRESENT INVENTION 
     Operating the Input Chamber Singulator 
     Input chamber singulator  23  can be in the drop position as shown in FIG. 11 or in the lift position as shown in FIG.  12 . The drop position is to lower input stack A so that the bottommost microplate (microplate  1 A) is at position α. The lift position is to lift input stack A (except for microplate  1 A) off of microplate  1 A so that microplate  1 A can then be removed from the bottom. 
     In FIG. 10, two way solenoid valve  23 F (FIG. 9) is in the open position and the rod in cylinder  25  of input singulator  23  is fully extended. To lift input stack A in input chamber  15 A, PLC  200  sends an electric signal to return solenoid valve  23 F to the closed position. This allows compressed air to enter cylinder  25  above its internal piston and the air below the piston is allowed to escape, causing the rod in pneumatic cylinder  25  to retract, as shown in FIG.  12 . When the rod in pneumatic cylinder  25  is fully retracted, pneumatic retraction sensor  23 D will send an electric signal to PLC  200  indicating the movement has been completed. 
     To lower input stack A in input chamber  15 , PLC  200  sends an electric signal to open two way solenoid valve  23 F (FIG.  9 ). This allows compressed air from compressed air source  250  to flow into pneumatic cylinder  25  below the internal piston and air above the piston is allowed to escape through an exhaust manifold, which causes the the rod in the cylinder to extend, as shown in FIG.  11 . When the rod in pneumatic cylinder  25  is fully extended, pneumatic extension sensor  21 C will send an electric signal to PLC  200  indicating the move has been completed. 
     Operating the Lid Lifter 
     Pneumatic cylinder  53  (FIG. 6) raises and lowers lid lifter  41 . Lid lifter  41  is lowered so that the vacuum cups can rest on microplate lid  2 , as shown in FIG.  17 . Lid lifter  41  is raised so that it can lift microplate lid of microplate base  4  as shown in FIG.  18 . 
     In FIG. 16, lid lifter  41  is in the fully extended position with two-way solenoid valve  41 F open. To lower lid lifter  41 , PLC  200  sends an electric signal to close two-way solenoid valve  41 F. This allows compressed air below the internal piston inside pneumatic cylinder  53  to escape while allowing air to enter above the piston, causing the rod in pneumatic cylinder  53  to retract. This causes lid lifter  41  to drop, as shown in FIG.  17 . When the rod in pneumatic cylinder  53  is fully retracted pneumatic retraction sensor  41 D will send an electric signal to PLC  200  indicating the movement has been completed. 
     To raise lid lifter  41 , PLC  200  sends an electric signal to open the two-way solenoid valve  41 F (FIG.  9 ). This allows compressed air from compressed air source  250  to flow into pneumatic cylinder  53  below the piston and allows air above the piston to escape through the exhaust manifold, causing it to extend. This causes lid lifter  41  to raise, as shown in FIG.  18 . When pneumatic cylinder  53  is fully extended pneumatic extension sensor  41 C will send an electric signal to PLC  200  indicating the movement has been completed. 
     Operating the Output Chamber Lifter 
     Output chamber lifter  61  can be fully lowered (as shown in FIG.  31 ), filly raised (as shown in FIG.  32 ), or pneumatic cylinder  61 A can be lowered while pneumatic cylinder  61 B is raised (as shown in FIG.  33 ). The lowered position is to allow microplate  1 A to slide into output chamber  16 A and the raised position is to lift microplate  1 A so that microplate  2 A to enter output chamber  16 A. The position where the rod in pneumatic cylinder  61 A is lowered while the rod in pneumatic cylinder  61 B is raised is to allow microplate  2 A to provide support for microplate  1 A while microplate  2 A enters further into output chamber  16 A. 
     The procedure to raise and lower output chamber lifter pneumatic cylinder  61 A is identical to the procedure to raise and lower output chamber lifter pneumatic cylinder  61 B. To raise output chamber lifter  61 A, PLC  200  sends an electric signal to open two-way solenoid valve  61 F. This allows compressed air from compressed air source  250  to flow into output chamber lifter pneumatic cylinder  61 A below the internal piston and allows air above the piston to escape, which causes it to extend. When the rod in output chamber lifter pneumatic cylinder  61 A is fully extended, pneumatic extension sensor  61 C will send an electric signal to PLC  200  indicating the movement has been completed. 
     To lower output chamber lifter  61 , PLC  200  sends an electric signal to close two-way solenoid valve  61 F. This allows compressed air to enter output chamber lifter pneumatic cylinder  61 A above the piston and allows the air below the piston to escape, causing the rod in output chamber lifter pneumatic cylinder  61 A to retract. When the rod in output chamber lifter pneumatic cylinder  61 A is fully retracted pneumatic retraction sensor  61 D will send an electric signal to PLC  200  indicating the movement has been competed. 
     Raising and Lowering the Walking Beam Indexer 
     Walking beam indexer  7  is attached to compact pneumatic cylinders  52 , as shown in FIG.  14 . Walking beam indexer  7  can be raised (as shown in FIG.  14 ), or lowered (as shown in FIG.  15 ). Walking beam indexer  7  is raised in order to permit dowel pins  14  to push microplate  1 A, as shown in FIG.  14 . Walking beam indexer  7  is lowered so that as it moves from left to right, dowel pins  14  do not contact microplate  1 A, as shown in FIGS. 15-16. 
     To raise the rod in compact pneumatic cylinder  52 , PLC  200  sends an electric signal to open two-way solenoid valve  52 F. This allows compressed air from compressed air source  250  to flow into compact pneumatic cylinder  52  below the internal piston and allows air above the piston to escape, which causes it to extend. When the rod in compact pneumatic cylinder  52  is fully extended, pneumatic extension sensor  52 C will send an electric signal to PLC  200  indicating the movement has been completed. 
     To lower the rod in compact pneumatic cylinder  52 , PLC  200  sends an electric signal to close two-way solenoid valve  52 F. This allows compressed air to enter compact pneumatic cylinder  52  above the piston and allows the air below the piston to escape, causing the rod in compact pneumatic cylinder  52  to retract. When the rod in compact pneumatic cylinder  52  is fully retracted pneumatic retraction sensor  52 D will send an electric signal to PLC  200  indicating the movement has been competed. 
     Error Checks 
     A preferred embodiment of the present invention has a variety of sensors that PLC  200  utilizes to conduct error checks. As shown in FIG. 4, sensor  100  is located beneath position α to verify a microplate is present at position α. Likewise sensor  101  verifies microplate placement at position β, sensor  102  verifies microplate placement at position γ, sensor  103  verifies microplate placement at position δ, and sensor  104  verifies microplate placement at the top of output chamber  16 A, as shown in FIG.  10 . Sensors  100  and  104  are photoelectric switches (part no. EQ-22-PN-J) supplied by Clayton Controls, and manufactured by SUNX. These sensors work by emitting a beam of light and switch “on” when the beam is blocked at a certain distance from the emitter. Sensors  101 ,  102 ,  103  are also photoelectric sensors (part number EX-14A-PN Manufactured by SUNX and supplied by Clayton Controls). 
     As shown in FIG. 9, each pneumatic component (input chamber singulator  23 , lid lifter  41 , output chamber lifter pneumatic cylinders  61 A and  61 B, and compact pneumatic cylinders  52 ) has two sensors: one that transmits an electrical signal when the component is fully extended (pneumatic extension sensors  61 C,  41 C,  23 C, and  52 C) and another sensor when it is fully retracted (pneumatic retraction sensors  61 D,  41 D,  23 D, and  52 D). 
     Linear actuator servo motor  48  includes a motor relay  50 . If linear actuator servo motor  48  is jammed or malfunctioning, motor relay  50  will report an error to PLC  200  which will be displayed on monitor  204 . 
     In a preferred embodiment of the present invention, PLC  200  is programmed to check its sensors continuously. It will check to verify that the microplates have correctly been moved to their appropriate positions, that linear actuator servo motor  48  is not jammed or malfunctioning, and that the pneumatic components have correctly extended or retracted. 
     In a preferred embodiment of the present invention, PLC  200  is Ethernet compatible and will allow the invention to be monitored for errors and throughput from another computer. 
     Performance 
     Applicants have built and tested a prototype model of the preferred embodiment of the present invention. During a dry run (i.e., not actually filling microplates with media), Applicants observed that the prototype model successfully moved six hundred microplates from input carousel  3  to output carousel  5  in one hour. This rate for moving microplates greatly exceeds that of the closest prior art. It should be noted that when filling microplates, the performance rate will vary depending on the type of microplate (i.e. single-well or multi-well) and on the type of media (i.e., Agar or liquid). 
     Other Preferred Embodiment with Improved Microplate Stack Handling FIG. 40 shows a perspective view of input chamber  15 A, output chamber  16 A, walking beam indexer  7 , input chamber singulator  23 , and output chamber lifter  61 . The preferred embodiment shown in FIG. 40 was explained in detail in the sequence shown in FIGS. 10-39. FIG. 42 shows a top view of another preferred embodiment of the present invention with improved microplate stack handling. FIG. 41 shows some major components of the preferred embodiment depicted in FIG.  42 . Output chamber  116 A has stack support piece  120  mounted to both of its sides. Pneumatic output chamber lifter  161  is located directly underneath output chamber  116 A and pneumatic input chamber lifter  162  is located directly underneath input chamber  15 A. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT WITH IMPROVED MICROPLATE STACK HANDLING 
     Input Chamber with Input Chamber Lifter 
     As shown in FIG. 41, this preferred embodiment of the present invention includes input chamber lifter  162 . Input chamber lifter  162  was added in order to help prevent tipping of the input stack after being lifted by input chamber singulator  23 . A sequence illustrating the operation of pneumatic input chamber lifter  162  is seen by reference to FIGS. 44-49. 
     FIG. 44 shows a stack of twenty-four empty microplates  1 A- 24 A loaded into input chamber  15 A. Microplate  1 A is at the bottom at position α (FIG. 4) and microplate  2 A is directly above microplate  1 A. Microplate  24 A is at the top of the stack. In FIG. 44 output stack A located inside output chamber  116 A is empty with no microplates. 
     In FIG. 45, walking beam indexer  7  has lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . 
     In FIG. 46, input chamber singulator  23  has lifted input stack A 2 -A 24  at microplate  2 A. Microplate  1 A is left at position α, as shown in FIG.  4 . Also as shown in FIG. 12, walking beam indexer  7  has moved to the right. As shown in FIG. 43, walking beam indexer  7  is fabricated so that it does not contact input chamber lifter  162  when it is moved to the right. 
     In FIG. 47, walking beam indexer  7  is raised so that dowel pin  14  is located directly behind microplate  1 A. 
     In FIG. 48, walking beam indexer  7  has moved to the left pushing microplate  1 A to position β (see FIG. 4) from the bottom of the stack. As soon as microplate  1 A is clear, input chamber lifter  162  extends to support input stack A 2 -A 24 . This helps prevent tipping of input stack A 2 -A 24 . 
     In FIG. 49, walking beam indexer  7  has been lowered so that dowel pins  14  are below the horizontal plane formed by the top surface of beam  8 . Input chamber singulator  23  and input chamber lifter  162  have dropped input stack A. Microplate  1 A is at position β and microplate  2 A is at position α. 
     In a fashion similar to that described by reference to FIGS. 44-49, input chamber lifter  162  continues to operate in conjunction with input chamber singulator  23  to raise and lower the input stack in a manner to prevent tilting of the input stack. 
     Output Chamber with Stack Support Pieces 
     As shown in FIG. 42, output chambers  116 A- 116 J each have two stack support pieces  120  mounted to their sides. FIG. 41 shows a perspective view of output chamber  116 A with stack support piece  120  mounted to its side. Output chamber lifter  161  is directly under output chamber  116 A. As shown in FIG. 41, output chamber lifter  161  has a single large lifting pad  161 A. Single large lifting pad  161 A provides a more stable support for the output stack than does the two lifting pad output chamber lifter  61  depicted in FIG.  40 . 
     FIG. 50 shows a detailed perspective view of stack support piece  120  mounted to output chamber  116 A and FIG. 51 shows a detailed side view of stack support piece  120  mounted to output chamber  116 A. Mount  130  is rigidly attached to output chamber  116 A. Axis  131  extends through mount  130  and stack support piece  120 . Torsion spring  132  is wound around axis  131  and applies a force to mount  130  and stack support piece  120 . This force tends to rotate stack support piece  120  in a counter-clockwise direction (FIG. 51) so that tapered support end  134  extends through hole  133  until stack support piece  120  is abutted by output chamber  116 A. 
     A sequence illustrating the operation of output chamber  116 A with stack support pieces  120  is seen by reference to FIGS. 52-55. 
     In FIG. 52, output stack A 1 -A 6  is in output chamber  116 A. Microplate  6 A is at the bottom of the output stack a position ε (FIG.  4 ). Microplate  5 A is above microplate  6 A and is resting on stack support pieces  120 . 
     In FIG. 53, output chamber lifter  161  is lifting output stack A 1 -A 6  by pressing upward on microplate  6 A. Tapered support end  134  of stack support piece  120  allows the upward movement of microplate  6 A. As shown in FIG. 41, output chamber lifter  161  has a single large lifting pad  161 A. Single large lifting pad  161 A provides a more stable support for the output stack than does the two lifting pad output chamber lifter  61  depicted in FIG.  40 . 
     In FIG. 54, output chamber lifter  161  has lifted microplate  6 A beyond tapered support ends  134 . The force applied by torsion spring  132  against stack support piece  120  then moves tapered support end back through holes  133 . 
     In FIG. 55, output chamber lifter  161  has lowered. Output stack A 1 -A 6  is resting on stack support pieces  120 . The space at position ε (FIG. 4) is clear to make room for the next microplate in the stack. 
     In a fashion similar to that described by reference to FIGS. 52-55, microplates are continually stacked in the output chambers of this preferred embodiment. The embodiment utilizing output chamber lifter  161  in conjunction with stack support pieces  120  is a preferred method of stacking because a microplate can be moved into the output chamber without sliding against or contacting the microplate that is directly above it. As shown in FIGS. 52-55, there is essentially no tipping of microplates in this embodiment. As the microplates are stacked, the base of upper microplate fits snuggly into the lid of the microplate immediately below it. This helps prevent microplates from becoming askew within the output chamber and helps prevent spillage of any solution contained within the microplates. 
     Although the above-preferred embodiments have been described with specificity, persons skilled in this art will recognize that many changes to the specific embodiments disclosed above could be made without departing from the spirit of the invention. For example, although a preferred embodiment for an input chamber singulator was described above, it would be possible to utilize a different input chamber lifting mechanism, provided that the mechanism was able to lift the stack of empty microplates in input chamber  15 , while leaving behind a bottommost microplate at position a, as shown in FIG.  4 . Those of ordinary skill in the art will recognize that a variety of pneumatic driven or motor driven lifting mechanisms could be substituted for the preferred input chamber singulator discussed above. Also, although the preferred embodiment disclosed using two compact pneumatic cylinders  52 , it would also be possible to use just one. Also, although the preferred embodiments described a plurality of input chambers  15  in input carousel  3  and a plurality of output chambers  16  in output carousel  5 , it would also be possible to have just one input chamber  15  and just one output chamber  16  into which the microplates would be stacked. Microplate filling assembly  6  (FIGS. 3-4) would remove empty microplates from input chamber  15 , fill them and then restack them in output chamber  16  utilizing the process shown in FIGS. 10-35. Also, although it was previously described how a user of the present invention would stack empty microplates inside of input chamber  15 , it would also be possible to save time by attaching pre-stacked input chambers  15  containing empty microplates onto input carousel  3 . Also, although it was previously stated that in a preferred embodiment there are three vacuum cups  55  extending downward from lid lifter top  42 , it is possible to modify the number of vacuum cups. For example, one large vacuum cup would work, or more than three vacuum cups would work. Also, one of ordinary skill in the art would recognize that an electrical-mechanical gripper that grabs the microplate lid would also work as a lid lifter. Therefore, the attached claims and their legal equivalents should determine the scope of the invention.