An apparatus for preparing a biological specimen on a substrate for examination, the apparatus comprising: a substrate arm including a substrate gripper ; an actuator connected to the substrate arm and configured to move the substrate arm between an open position and a specimen processing position; a platform having a top surface located opposite the substrate when the substrate arm is in the specimen processing position and comprising at least one fluid port (42A-45A) located on a surface of the platform facing the substrate and at least one vacuum port located on the surface of the platform facing the substrate ; and two or more offsets arranged on the top surface of the platform such that when the substrate contacts all of the offsets in the substrate processing position, the substrate and top surface of the platform are substantially parallel and form a separation of at least about 50 microns, wherein during operation, the apparatus is configured to circulate fluid between the at least one fluid port (42A-45A) and the at least one vacuum port by: (a) dispensing a first quantity of fluid from the at least one fluid port (42A-45A) to fill the separation between the substrate and the platform; (b) dispensing multiple additional quantities of fluid from the at least one fluid port (42A-45A) into the separation to displace portions of fluid from the separation; and (c) removing the displaced portions of fluid through the at least one vacuum port ; and wherein the apparatus further comprises a means for controlling the dispensing and removing of fluid which is configured to alternately dispense the multiple additional quantities of fluid and remove the displaced portions of fluid to generate a pulsatile flow of fluid between the at least one fluid port (42A-45A) and the at least one vacuum port . a substrate arm including a substrate gripper ; an actuator connected to the substrate arm and configured to move the substrate arm between an open position and a specimen processing position; a platform having a top surface located opposite the substrate when the substrate arm is in the specimen processing position and comprising at least one fluid port (42A-45A) located on a surface of the platform facing the substrate and at least one vacuum port located on the surface of the platform facing the substrate ; and two or more offsets arranged on the top surface of the platform such that when the substrate contacts all of the offsets in the substrate processing position, the substrate and top surface of the platform are substantially parallel and form a separation of at least about 50 microns, wherein during operation, the apparatus is configured to circulate fluid between the at least one fluid port (42A-45A) and the at least one vacuum port by: (a) dispensing a first quantity of fluid from the at least one fluid port (42A-45A) to fill the separation between the substrate and the platform; (b) dispensing multiple additional quantities of fluid from the at least one fluid port (42A-45A) into the separation to displace portions of fluid from the separation; and (c) removing the displaced portions of fluid through the at least one vacuum port ; and (a) dispensing a first quantity of fluid from the at least one fluid port (42A-45A) to fill the separation between the substrate and the platform; (b) dispensing multiple additional quantities of fluid from the at least one fluid port (42A-45A) into the separation to displace portions of fluid from the separation; and (c) removing the displaced portions of fluid through the at least one vacuum port ; and wherein the apparatus further comprises a means for controlling the dispensing and removing of fluid which is configured to alternately dispense the multiple additional quantities of fluid and remove the displaced portions of fluid to generate a pulsatile flow of fluid between the at least one fluid port (42A-45A) and the at least one vacuum port . <EOS>