Several methods are used to better define and optimize item sets for short-term memory tests with respect to chunkiness and homogeneity, including dynamically changing the test item set to make it have as few chunkable items as possible. A plurality of electrically conductive ink pathways are applied on a surface of the plastic sheet, and a sealer material is applied to the plastic sheet to cover said pathways. The first semiconductor material can have a critical thickness at which lattice matching of the first semiconductor material causes dislocation.