A thermal cycling device for thermally cycling samples of biological material contained in a microcard having a top and bottom surface. The thermal cycling device can include a sample block having an upper surface configured for engaging the bottom surface of a microcard, a vacuum device, and a temperature control system operatively connected with the sample block. The upper surface of the sample block may include a plurality of channels, the channels defining spaces between the sample block and the bottom surface of a microcard that may be positioned thereon. The vacuum device may be in fluid communication with the sample block for drawing gas out of the spaces defined by the channels in the sample block. The vacuum device may be configured for substantially maintaining a vacuum between the sample block and microcard so that a retention force is imparted on the microcard to urge the microcard toward the sample block. Methods of maintaining a microcard on a sample block of a thermal cycling device are also provided.