Microporous Multiresonant Plasmonic Meshes by Hierarchical Micro–Nanoimprinting for Bio-Interfaced SERS Imaging and Nonlinear Nano-Optics

Due to their low elastic moduli and high permeability to nutrients and oxygen, mesh-like flexible microporous devices confer significant biocompatibility advantages to interface with cell networks and tissues for biomedical sensing or actuation applications. Microporous mesh plasmonic devices have the potential to combine the biocompatibility of microporous polymeric meshes with the capabilities of plasmonic nanostructures to enhance nanoscale light-matter interactions for bio-interfaced optical sensing and actuation. However, scalable integration of dense and uniformly structured plasmonic hotspot arrays with microporous polymeric meshes remains challenging due to the processing incompatibility of conventional nanofabrication methods with flexible microporous substrates. For the first time, we have created microporous multiresonant plasmonic mesh (MMPM) devices via a dissolvable template-based hierarchical micro-/nanoimprinting approach. The MMPMs carry 2-tier nanolaminate plasmonic crystals (NLPCs) consisting of two optically coupled nanodome and nanohole multiresonant sub-systems. The NLPCs can support many hybridized plasmonic modes with spatial overlap and can allow for multiresonant nanoscale light concentration across a wide wavelength range between 400 and 1400 nm. We demonstrate that MMPMs can serve as broadband nonlinear nanoplasmonic devices to generate second-harmonic generation (SHG), third-harmonic generation (THG), and upconversion photoluminescence (UCPL) signals with multiresonant plasmonic enhancement under fs pulse excitation. Moreover, we demonstrate that MMPMs can function as bio-interfaced surface-enhanced Raman spectroscopy (SERS) mesh sensors that enable in-situ spatiotemporal molecular profiling of bacterial biofilm activity. We envision that microporous mesh plasmonic devices can open exciting avenues for bio-interfaced optical sensing and actuation applications, such as inflammation-free epidermal sensors in conformal contact with skin, combined tissue-engineering and biosensing scaffolds for in vitro 3D cell culture models, and minimally invasive implantable probes for long-term disease diagnostics and therapeutics.