Dynamic Tuning of Plasmonic Hot-Spot Generation through Cilia-Inspired Magnetic Actuators

Soft actuators that draw inspiration from nature are powerful and versatile tools for both technological applications and fundamental research, yet their use in hot-spot engineering is very limited. Conventional hot-spot engineering methods still suffer from complexity, high process cost, and static generation of hot-spots, thus, underperforming particularly in the application side. Herein, we demonstrate a strategy based on plasmonic nanoparticles decorated cilia-inspired magnetic actuators that enable highly accessible millimeter-sized hot-spot generation via bending motion under a magnetic field. The hot-spot formation is shown to be reversible and tunable, and leads to excellent Raman signal enhancements of up to approximate to 120 folds compared to the unactuated platforms. Accessible electromagnetic field magnification in the platforms can be manipulated by controlling magnetic field strength, which is further supported by finite difference time domain (FDTD) simulations. As a proof-of-concept demonstration, a centipede-inspired robot is fabricated and used for sample collection/analysis in a target environment. Our results demonstrate an effective strategy in soft actuator platforms for reversible and tunable large-area hot-spot formation, which provides a promising guidance toward studying the fundamentals of hot-spot generation and advancing real-life plasmonic applications.