Yan Lu, Litao Yang, Zhenhua Chen, Qinhao Li, Lim Wei Yap, Rui Gao, Aswandi Wibrianto, Haoqing Jerry Wang, Zhian Yao, Md Hemayet Uddin, Xiaorui Cao, Qianqian Shi, Jayraj V Vaghasiya, Shu Gong, Deval Mehta, Yifeng Huang, Fenge Lin, Yuxuan Zhu, Lining Arnold Ju, Zongyuan Ge, Wenlong Cheng
With the rapid expansion of the Internet of Things (IoT), secure authentication has become paramount for safeguarding the digital ecosystem against spoofing attacks and privacy breaches. Optical and acoustic modalities currently dominate biometric authentication; however, they remain inherently vulnerable to environmental interference. Here, we report ultrathin (<50 nm), substrate-free gold nanoplatelet skins that conform intimately to finger-knuckle wrinkles, enabling dynamic and nontransferable wearable authentication. Unlike light- or sound-based systems, these nanocrystal skins generate unique resistive signatures that are insensitive to optical and acoustic perturbations. Fabricated from additive-free, polystyrene-capped gold nanoplatelets, the conformal films establish gapless skin-electronic interfaces that replicate knuckle microtopography with high fidelity. This intimate coupling is the key to converting bending-release motions into finger-specific electrical signatures that are unattainable with the corresponding substrate-supported, nonconformal system. Integrated with a deep-learning framework, the two-finger nanoplatelet skin achieves near-perfect authentication accuracy. Our findings indicate that substrate-free nanocrystal skins could enable next-generation wearable biometric authentication, advancing hardware-level security for the digital world.