A diagnostic device includes a sensor stack with multiple panels of a porous material disposed in planes parallel to one another and in face-to-face contact with each other. At least a portion of the panels of the porous material include hydrophobic regions and hydrophilic regions configured to provide a sample flow path for migration of a fluid sample through the sensor stack from one panel to another in the hydrophilic regions. A wicking layer is on a major surface of the sensor stack.