Smart Adhesives with Multilevel Security Features for Real-World Anticounterfeiting Applications

Counterfeiting in the manufacturing and publishing industries poses serious threats, including brand damage, financial losses, compromised quality, and infringement of intellectual property rights. Although existing anticounterfeiting technologies like RFID tags, QR codes, holograms, and blockchain offer protection, increasingly advanced counterfeiting methods challenge their effectiveness. Adhesives, despite being essential in manufacturing and bookbinding for their bonding and durability properties, remain underexplored as anticounterfeiting tools. This study presents a novel approach by developing glue formulations embedded with multilevel security markers for real-world applications. Hot melt adhesives are integrated with infrared (IR) emissive and up-conversion green phosphors, offering covert yet verifiable security features while maintaining the adhesive's key functional properties, including melting point, viscosity, and bonding strength. Under a 980 nm laser light, the secure adhesive exhibits greenish-yellow and red emissions, when viewed without and with a 610 nm band-pass filter, in addition to IR emission at 1020 nm under a 340 nm UV light, detectable by IR cameras or readers. The multisecure glue shows bright green and pink emissions upon a 980 nm illumination along with IR signals similar to the secure adhesive. These hidden yet easily verifiable features provide a promising, tamper-resistant solution to counterfeiting, particularly for book authenticity, enabling discrete verification by authorized users while remaining undetectable to counterfeiters.