▎ 摘　　要

NOVELTY - A two dimensional material (2DM) with a hierarchical topography is fabricated by (a) preparing a substrate in an expanded state; (b) adhering the 2DM to the substrate in the expanded state; (c) contracting the substrate from the expanded state to a first contracted state to form a first structure on the 2DM; (d) altering an inter-planar bond within the 2DM and/or an interfacial bond between the 2DM and the substrate in the first contracted state; and (e) contracting the substrate from the first contracted state to a second contracted state to form a second structure below the first structure. The 2DM comprises graphene oxide, MXene (such as titanium carbide), molybdenum disulfide (MoS2), hexagonal boron nitride (h-BN) and montmorillonite (MMT) nanosheets. USE - Fabrication of two dimensional material (2DM) with a hierarchical topography for physical unclonable function for use in authenticating a product (all claimed). ADVANTAGE - Additional altering step allows for an increase in the number of unique patterns, and allows for a larger number of PUFs. Moisture-induced lubrication (MIL) step can be applied between the 2DM and the substrate. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) two dimensional material (2DM) with a hierarchical topography, comprising a first structure superimposed on a second structure; where the first structure is 5 mu mx 5 mu m to 20 mu mx 20 mu m; and where the second structure is 20 mu mx 20 mu m to 100 mu mx 100 mu m; and where the 2DM comprises graphene oxide, MXene (such as titanium carbide), MoS2, hexagonal boron nitride (h-BN) and montmorillonite (MMT) nanosheets; (2) physical unclonable function (PUF) comprising a 2DM for use in authenticating a product; and (3) authenticating a product comprising a 2DM which involves (a) classifying an image of the 2DM using a trained model that is configured to classify images into a category of hierarchical structure, to obtain a class label; (b) determining respective similarity scores of the image to respective stored images labeled with the class label; and (c) outputting a positive authentication result if greater than or equal to 1 of respective similarity scores is greater than a threshold.