To hold samples during testing a four-layered tray was designed to allow for water circulation while maintaining a tight tolerance on the substrate's position. This was achieved by adding large bevels to the lower layer so that when released, a sample would naturally settle to the center. The larger submerged tray also features small bevels on the upper layer to aid in the case that a sample experiences warping during testing. The interface between the robot and the balance also uses this geometry, although it is more robust and enclosed for better stability.