Concave Microwell Formation Induced by PDMS Water Vapor Permeability for Spheroid Generation.

This study introduces a novel method for the fabrication of concave microwells involving water vapor permeation through polydimethylsiloxane (PDMS). This method leverages the exceptional water vapor permeability of PDMS to enable a scalable and cost-effective fabrication process, addressing the limitations of existing techniques such as photolithography that are resource-intensive and complex. PDMS is more permeable to water vapor than to other gas molecules, resulting in the formation of microwells.

Characterization and Antibacterial Activity of Silver Nanoparticles Synthesized from (Grasshopper) Extract.

In this study, silver nanoparticles (AgNPs) were synthesized using a green method from an extract of the edible insect (O_extract). The formation of AgNPs (O_AgNPs) was confirmed via UV-vis spectroscopy, and their stability was assessed using Turbiscan analysis. The size and morphology of the synthesized particles were characterized using transmission electron microscopy and field-emission scanning electron microscopy.

Improved analysis of THz metamaterials for glucose sensing based on modified Lorentz dispersion model.

Resonant structures, such as metamaterials, which can focus electromagnetic fields on a localized spot, are essential to perform label-free detection with high sensitivity in the terahertz (THz) range. Moreover, the refractive index (RI) of a sensing analyte is the most important aspect in the optimization of the characteristics of a highly sensitive resonant structure. However, in previous studies, the sensitivity of metamaterials was calculated while considering the RI of an analyte as a constant value.

Changes in Volatile Compounds in Short-Term High CO-Treated 'Seolhyang' Strawberry () Fruit during Cold Storage.

'Seolhyang' strawberry is harvested before it is fully ripened and treated with CO to extend the shelf-life. However, the volatile changes in the 'Seolhyang' strawberry after short-term CO treatment have not been investigated, although the volatile profile is an important quality attribute. Herein, we investigated the effect of short-term high CO treatment on the changes in the composition of volatile compounds in 'Seolhyang' strawberries at two ripening stages (i.

140 GHz Ultra-Long Bessel-Like Beam with Near-Wavelength Beamwidth.

The Bessel-Gauss beam has outstanding features, such as long depth of focus (DOF) and super resolution for nondestructive imaging inspection. However, most approaches for generating a nondiffractive beam have mainly focused on extending the DOF. In this study, the ultra-long high-resolution Bessel-like beam was first demonstrated in a sub-THz wave range (140 GHz).

Photonic-Plasmonic Nanostructures for Solar Energy Utilization and Emerging Biosensors.

Issues related to global energy and environment as well as health crisis are currently some of the greatest challenges faced by humanity, which compel us to develop new pollution-free and sustainable energy sources, as well as next-generation biodiagnostic solutions. Optical functional nanostructures that manipulate and confine light on a nanometer scale have recently emerged as leading candidates for a wide range of applications in solar energy conversion and biosensing. In this review, recent research progress in the development of photonic and plasmonic nanostructures for various applications in solar energy conversion, such as photovoltaics, photothermal conversion, and photocatalysis, is highlighted.

Detection of O157:H7 Using Automated Immunomagnetic Separation and Enzyme-Based Colorimetric Assay.

The food industry requires rapid and simple detection methods for preventing harm from pathogenic bacteria. Until now, various technologies used to detect foodborne bacteria were time-consuming and laborious. Therefore, we have developed an automated immunomagnetic separation combined with a colorimetric assay for the rapid detection of O157:H7 in food samples.

Development of a Cuvette-Based LSPR Sensor Chip Using a Plasmonically Active Transparent Strip.

This research demonstrates the development of a transmission-mode localized surface plasmon resonance (LSPR) sensor chip using a cuvette cell system for the sensitive detection of a biomolecule marker such as C-reactive protein (CRP). In order to develop a highly sensitive LSPR sensor chip, plasmonically active gold nanoparticles (AuNPs) were decorated onto various transparent substrates in the form of a uniform, high-density single layer using a self-assembly process. The transparent substrate surface was modified with amine functional groups via (3-Aminopropyl)triethoxysilane (APTES) treatment, and the ligand concentration and temperature (0.

Highly Sensitive Detection of 4-Methylimidazole Using a Terahertz Metamaterial.

In this study, we demonstrated a highly sensitive detection method of 4-methylimidazole (4-MeI), a carcinogenic material, by using a terahertz (THz) metamaterial at a THz region. The THz metamaterials were fabricated with a metal array, using an electric-field-coupled inductor-capacitor (ELC) resonator structure, and a finite-difference time-domain (FDTD) simulation showed good agreement with the experimental results. We measured the THz spectra of the metamaterials to detect the 4-MeI concentrations of 0, 1, 2, 5, 10, 15, and 20 mg/L.

Qualitative identification of food materials by complex refractive index mapping in the terahertz range.

We investigated the feasibility of qualitative food analysis using complex refractive index mapping of food materials in the terahertz (THz) frequency range. We studied optical properties such as the refractive index and absorption coefficient of food materials, including insects as foreign substances, from 0.2 to 1.

Invisible Security Printing on Photoresist Polymer Readable by Terahertz Spectroscopy.

We experimentally modulate the refractive index and the absorption coefficient of an SU-8 dry film in the terahertz region by UV light (362 nm) exposure with time dependency. Consequently, the refractive index of SU-8 film is increased by approximately 6% after UV light exposure. Moreover, the absorption coefficient also changes significantly.

The interfacing structural effect of Ag/graphene oxide nanohybrid films on surface enhanced Raman scattering.

The interfacing structural effect of Ag/graphene oxide (GO) nanohybrid films on SERS was investigated by using Ag nanostructures immobilized on polyallylamine hydrochloride (PAA) functionalized-GO and reduced GO (RGO) films. We found that the electron transfer from Ag nanostructures to GO derivatives dominantly occurred at the interfaces between Ag nanostructures and the sp carbon domains of GO and RGO films. By utilizing 4-aminothiophenol (4-ATP) as a Raman probe, it was revealed that this electron transfer process augmented the enhancement factor (EF) of 4-ATP up to ∼1.

Toxin Profile, Biofilm Formation, and Molecular Characterization of Emetic Toxin-Producing Bacillus cereus Group Isolates from Human Stools.

Emetic toxin-producing Bacillus cereus group species are an important problem, because the staple food for Korean is grains such as rice. In this study, we determined the prevalence (24 of 129 isolates) of emetic B. cereus in 36,745 stool samples from sporadic food-poisoning cases in Korea between 2007 and 2008.

High-performance sub-terahertz transmission imaging system for food inspection.

Unlike X-ray systems, a terahertz imaging system can distinguish low-density materials in a food matrix. For applying this technique to food inspection, imaging resolution and acquisition speed ought to be simultaneously enhanced. Therefore, we have developed the first continuous-wave sub-terahertz transmission imaging system with a polygonal mirror.

Feasibility of using terahertz spectroscopy to detect seven different pesticides in wheat flour.

This study investigated the feasibility of detecting pesticides using terahertz (THz) spectroscopy in high-density polyethylene and/or wheat flour mixtures. The absorption spectra of seven pesticides (dicofol, chlorpyrifos, chlorpyrifos-methyl, daminozide, imidacloprid, diethyldithiocarbamate, and dimethyldithiocarbamate) were measured in the frequency range 0.1 to 3 THz at room temperature.

High-speed terahertz imaging toward food quality inspection.

In contrast to conventional x-ray food inspection systems that have difficulty in detecting low-density materials, a terahertz imaging system can even identify insects and plastics embedded in a food matrix. A reflection-mode continuous-wave terahertz imaging system was therefore developed for application to food quality inspection, which requires fast, compact, and low-cost detection. High-speed operation of the terahertz imaging system was achieved through the use of a beam-steering tool.

Foreign object detection by sub-terahertz quasi-Bessel beam imaging.

Food quality monitoring, particularly foreign object detection, has recently become a critical issue for the food industry. In contrast to X-ray imaging, terahertz imaging can provide a safe and ionizing-radiation-free nondestructive inspection method for foreign object sensing. In this work, a quasi-Bessel beam (QBB) known to be nondiffracting was generated by a conical dielectric lens to detect foreign objects in food samples.