Labyrinthine Microstructures with a High Dipole Moment Boron Complex for Molecular Physically Unclonable Functions

Abstract

The design and development of novel molecular-physically unclonable functions (PUFs) with advanced encoding characteristics and ease of fabrication have recently attracted attention in cryptography, secure authentication, and anticounterfeiting. Here, we report the development of a new high dipole-moment small molecule, InIm-BF2, a difluoroborate complex of an indolyl-imine ligand, and the fabrication of unique labyrinthine patterns through a facile two-step thin film process under ambient conditions. The new molecule has a dipolar, coplanar pi-backbone and arranges in the solid state with antisymmetric cofacial pi-stackings (3.86 & Aring;). These properties, along with short C-H<middle dot><middle dot><middle dot>pi contacts (2.74-2.88 & Aring;) and nonclassical C-H<middle dot><middle dot><middle dot>F hydrogen bonds (2.47-2.51 & Aring;) (23.4% and 11.5% of the Hirshfeld surfaces, respectively), drive the formation of amorphous molecular PUF patterns with disordered, short-range interactions. Spin-coating followed by thermal annealing at a moderate temperature produces nanoscopic molecular thin films with intricate labyrinthine patterns. These patterns, characterized by interconnected, irregularly shaped, micron-sized (approximate to 50-100 mu m) features, exhibit excellent PUF characteristics, verified through advanced image analysis and computational algorithms. Unlike randomly positioned isolated features in classical binarized keys, the interconnected labyrinthine patterns possess rich entropy and complex features, directly authenticated via deep-learning methodologies. Our work not only demonstrates a facile, promising approach to fabricating unique high-entropy PUF patterns but also provides critical insights into designing advanced molecular materials for next-generation security applications.