Detecting trace amounts of explosives to ensure personal safety is important, and this is possible by using laser-based spectroscopy techniques. We performed surface-enhanced Raman scattering (SERS) using plasmonic nanogap substrates for the solution phase detection of some nitro-based compounds, taking advantage of the hot spot at the nanogap. An excitation wavelength of 785 nm with an incident power of as low as ≈0.1 mW was used to excite the nanogap substrates. Since both RDX and PETN cannot be dissolved in water, acetone was used as a solvent. TNT was dissolved in water as well as in hexane. The main SERS peaks of TNT, RDX, and PETN were clearly observed down to the order of picomolar concentration. The variations in SERS spectra observed from different explosives can be useful in distinguishing and identifying different nitro-based compounds. This result indicates that our nanogap substrates offer an effective approach for explosives identification.

Plasmonic molecules, which are geometrically well-defined plasmonic metal nanoparticle clusters, have attracted significant attention due to their enhancement of light–matter interactions owing to a stronger electric field enhancement than that by single particles. High-resolution lithography techniques provide precise positioning of plasmonic nanoparticles, but their fabrication costs are excessively high. In this study, we propose a lithography-free, self-assembly fabrication method, termed the dual-dewetting process, which allows the control of the size and density of gold nanoparticles. This process involves depositing a gold thin film on a substrate and inducing dewetting through thermal annealing, followed by a second deposition and annealing. The method achieves a uniform distribution of particle size and density, along with increased particle density, across a 6-inch wafer. The superiority of the method is confirmed by a 30-fold increase in the signal intensity of surface-enhanced Raman scattering following the additional dewetting with an 8 nm film, compared to single dewetting alone. Our findings indicate that the dual-dewetting method provides a simple and efficient approach to enable a variety of plasmonic applications through efficient plasmonic molecule large-area fabrication.

Over the last decade, the M13 bacteriophage has been used widely in various applications, such as sensors, bio-templating, and solar cells. The M13 colorimetric sensor was developed to detect toxic gases to protect the environment, human health, and national security. Recent developments in phage-based colorimetric sensor technologies have focused on improving the sensing characteristics, such as the sensitivity and selectivity on a large scale. On the other hand, few studies have examined precisely controllable micro-patterning techniques in phage-based self-assembly. This paper developed a color patterning technique through self-assembly of the M13 bacteriophages. The phage was self-assembled into a nanostructure through precise temperature control at the meniscus interface. Furthermore, barcode color patterns could be fabricated using self-assembled M13 bacteriophage on micrometer scale areas by manipulating the grooves on the SiO₂ surface. The color patterns exhibited color tunability based on the phage nano-bundles reactivity. Overall, the proposed color patterning technique is expected to be useful for preparing new color sensors and security patterns.

High Purcell enhancement structures and stable emitters are essential prerequisites for the successful development of novel fast‐operating active devices. Furthermore, a uniform enhancement of the spontaneous emission rate is critical for practical applications. Despite considerable efforts being made to meet these requirements, achieving them still remains a challenging task. In this work, we demonstrate that placing stable core−shell perovskite quantum dots (PQDs) in the nanogap region of hole/sphere‐based nanogap structures (HSNGs) can enhance the spontaneous emission rate by more than a thousand‐fold (up to a factor of ∼1080) compared to PQDs in solution. This enhancement factor is the highest value reported using PQDs, exceeding previously reported values by two orders of magnitude. Notably, the enhancement factor of the emission rate in the HSNG maintains large values across the samples, with values ranging from ∼690 to ∼1080. Furthermore, the structural stabilities of the PQDs are remarkably enhanced with the incorporation of SiO ₂ shells, which is validated by monitoring the changes in photoluminescence intensities over time during continuous laser exposure. As a result, the HSNG with stable core−shell PQDs offers great potential for fast optical device applications that require high performance and long‐term operational stability.

Soft microrobots are gaining interest in various fields including microelectromechanical systems (MEMS), bioelectronics, and soft robotics due to their adaptable and compliant motion at the microscale. Magnetic soft microactuators often require a balance between mechanical robustness and magnetic responsiveness, which can be challenging to achieve simultaneously. Here, a magnetically controlled soft micro actuator based on a composite of magnetite and PEDOT:PSS (poly(3,4‐ethylenedioxythiophene)) is presented, fabricated using a meniscus‐assisted microfabrication technique. In this design, the PEDOT:PSS layer provides structural flexibility while the magnetite layer enables precise magnetic actuation. The fabrication method ensures high spatial precision and surface compatibility, allowing the actuator to be integrated onto various substrates. Experimental results confirm stable, reversible, and tunable motion under an external magnetic field, with a linear displacement response of 0.20°/V. The actuator's flexibility and reliability make it promising for soft robotic manipulation, bioelectronics, and micromanipulation applications. This study paves the way for advanced, magnetically responsive microactuators in next‐generation MEMS and biomedical systems.