We describe a straightforward approach to fabricating perfluoropolyether (PFPE)-based nanocoatings, significantly decreasing the spreading of oil and water on coated surfaces. In the fabrication, polyglycidyl methacrylate (PGMA) is used as an anchoring layer deposited on the silicon surface before PFPE attachment. Perfluoropolyether-based polyester acid (PFPE-COOH) is then grafted to the PGMA surface to reduce its surface energy and, consequently, wettability. The grafted surface demonstrates a hexadecane contact angle of 40–46° and a water contact angle of 80–98°. The surface’s wettability strongly depends on the grafted layer thickness, where grafting of the thicker PFPE layers results in lower oil and water wettability. We expect that the employment of PFPE-based grafted nanocoatings will eliminate the health and environmental concerns of long perfluoroalkyls, which are typically used to obtain surfaces with decreased spreading of oil and water.

No abstract

Molecular sensing based on plasmonic materials is of great interest not only for basic scientific research but also for real-life applications. For plasmonic sensing, tunable hot-spot generation, in which the electromagnetic field is maximized, plays a key role. Herein, we developed a platform consisting of a thermoresponsive polymer brush with colloidal plasmonic particles and 3-D ordered/vertically aligned gold nanorod (AuNR) arrays for surface-enhanced Raman spectroscopy (SERS) applications. Poly(di(ethylene glycol) methyl ether methacrylate) brushes were synthesized via the interface-mediated reversible addition fragmentation chain transfer polymerization method. 3-D AuNR arrays were also fabricated by the oblique angle physical vapor deposition method. Highdensity hot-spot generation on the platforms was achieved by reducing the distance between the plasmonic particles and the underlying AuNR array as a result of phase transition of the polymer brushes. The design and optimization of such a platform will pave the way for molecular detection applications in a broad range of fields such as medicine, environmental protection, food safety, and homeland security.

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 ≈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.