Many assays used in drug discovery methods utilize an incubation period at either room temperature or at an elevated temperature such as 37°C. Many assays use live cells that require humidity and a CO2 atmosphere. Such incubators are a key requirement for robotic systems for drug screening. Some robotic systems use commercial incubators that have been modified for robotic use by adding an automatic door opener. But these designs are not optimal for robotic systems, because the single door faces the robot, making it difficult to service the incubator manually. More convenient designs have two incubator doors, opposite each other, one facing the robot and the other easily accessible by the operator. This allows the user to service the incubator safely and still provides convenient access for the robot.
With easy access to the interior of the incubator, the operator can easily stock the incubator with incoming plates to augment the plate storage unit. Also, the operator can periodically clean or otherwise service the incubator. For safety reasons, when the incubator has separate doors for both the robot and the operator, there should be interlocks so that the robot cannot open a door if the operator door is open, and vice versa. In order to maintain reliably the interior atmosphere, the doors must have tight, flexible, and compliant elastomeric seals. Silicone rubber is an excellent material for the door seals, because it is flexible and compliant yet can easily withstand an elevated temperature. To supplement the mechanism to automatically open and close each of the doors, an additional automatic latch can be used to hold the door securely closed and maintain the integrity of the interior environment.
With so many variables associated with the proper operation of the incubator, some manufacturers have found it useful to dedicate a PLC (programmable logic controller) to each incubator for distributed control of the many mechanisms, sensors, electrical contact switches, etc. These variables include the door open and closed sensors, the open and close actuators for each door, the door latches on each side, the heating, CO2, and humidity controls, circulation fans, and so forth. Certainly these functions can be monitored at a central PLC as part of the controls for the robotic system, but the distributed control allows the incubator to be a self-contained module that can be easily integrated into a new system or retrofitted to an existing system. A typical robotic tissue culture incubator is shown in Figure 6.
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