Octopus-Inspired, Flexible Plasmonic Arrays for Multi-Modal Laser Sensing

The detection of organic and inorganic pollutants is critical due to their widespread environmental and health impacts. Although spectroscopic techniques offer substantial promise for pollutant analysis, their application is often hindered by challenges in sampling and analyzing contaminants on textured, rough, or non-directly accessible surfaces. Here, a flexible, octopus-inspired, hydrogel-based substrate with plasmonic suction cup arrays for multi-modal laser sensing (surface-enhanced Raman scattering (SERS) and laser-induced breakdown spectroscopy (LIBS)) is introduced. The micro-cavities within the suction cups create negative pressure, facilitating firm contact to complex surfaces with roughness depths (e.g., up to 300 µm) or non-directly detectable surfaces for efficient analyte capture. The suction cup arrays are fabricated by casting hydrogel into the 3D-printed mold, enabling precise and customizable designs that confirm to diverse surface profiles. Additionally, plasmonic materials (MXene and silver nanowires), enabling spectroscopic enhancement, are incorporated into polyvinyl alcohol to form the substrate. Then, molecular and atomic analytes are analyzed by SERS and LIBS, respectively, with promising accuracy and sensitivity. Overall, this flexible substrate enables precise detection on complex surfaces, offering transformative solutions in environmental monitoring, biomedical diagnostics, and cultural heritage preservation.