Non-destructive Evaluation of Defects of Glass fiber Composites using Imaging System based on Photo-mixer Terahertz Technique

In this study, non-destructive evaluation using photo-mixer terahertz technique was studied to visualize the hidden damage in composite structures. A terahertz wave system was developed based on photo-mixer to detect the internal defects of the composite structure, and foreign material was simulated in a glass fiber-reinforced plastic (GFRP) specimen using PET film coated with silver nano-wire. For the visualization, an imaging algorithm for terahertz signal processing and stage control was developed using a GUI based on LABVIEW. The inspection was performed using the developed continuous terahertz inspection system and the terahertz waveform acquired in the single frequency was used to visualize defects.ope

Measurement of Optical Properties of Nano-Cement Using THz Electromagnetic Waves

Enhancing mechanical strength of concrete has been fascinated using carbon-based nanomaterials such as CNT and graphene. The key to improving strength is a dispersion of nanomaterials. A novel method is required to investigate the dispersion inner concrete nondestructively. In this study, the optical optical properties such as refractive index and absorption coefficient are measured in nano-cement mortar specimens containing MWCNT and GO using THz electro-magnetic waves. From the results, the properties of nano-cement mortar are confirmed to be 1.0% to 2.5% higher in refractive index, and –14% to 28% higher in absorption coefficient than those of cement mortar at the average values. Using these characteristics, visualizing the dispersion of nano-concrete structures seems possible in future.ope

Improvement of Terahertz Wave Radiation for InAs Nanowires by Simple Dipping into Tap Water

We report improvement of terahertz (THz) wave radiation for Si-based catalyst-free InAs nanowires (NWs) by simple dipping into tap water (DTW). In addition, the possibility of using InAs NWs as a cost-effective method for biomedical applications is discussed by comparison to bulk InAs. The peak-to-peak current signals (PPCSs) of InAs NWs measured from THz time-domain spectroscopy increased with increasing NW height. For example, the PPCS of 10?μm-long InAs NWs was 2.86 times stronger than that of 2.1?μm-long NWs. The THz spectra of the InAs NWs obtained by applying a fast Fourier transformation to the current signals showed a main frequency of 0.5?THz, which can be applied to a variety of medical imaging systems. After the DTW process, structural variation was not observed for 2.1?μm-long InAs NWs. However, the top region of several InAs NWs with heights of 4.6 and 5.8?μm merged into a conical structure. InAs NWs with a height of 10?μm resulted in a bundle feature forming above the conical shape, where the length of bundle region was 4?μm. After the DTW process, the PPCS for 10?μm-long InAs NWs increased by 15 percent compared to that of the as-grown case.ope

Terahertz Characteristics of InGaAs with Periodic InAlAs Insertion Layers

We presented terahertz (THz) generation and detection characteristics of an InGaAs epilayer with periodic InAlAs insertion layers (InGaAs-PIL). The peak-to-peak current signal (PPCS) from a THz transmitter with the InGaAs-PIL was three times higher than that of a simple InGaAs epilayer. Moreover, the detection properties of a THz receiver with the low-temperature grown (LT) InGaAs-PIL showed more than twenty-five times higher than that of the LT-InGaAs epilayer. The PPCS of the LT-InGaAs-PIL was significantly improved with increasing the periods of the InAlAs insertion layer.ope

Low-Loss Polytetrafluoroethylene Hexagonal Porous Fiber for Terahertz Pulse Transmission in the 6G Mobile Communication Window

Hexagonal porous optical fiber without a central defect is proposed and numerically analyzed with the finite element method (FEM) for transmitting terahertz (THz) electromagnetic wave pulse. In experiments, the transmission characteristics of polytetrafluoroethylene (PTFE) hexagonal porous optical fibers were measured using a THz time-domain spectroscopy (THz-TDS) system. To precisely estimate the effective material loss (EML), we measured the refractive index and absorption coefficient of PTFE in the THz range to use them in FEM analyses, and the EML of the porous fiber was estimated to be lower than that of a bulk rod as large as by a factor of 2 in the frequency range from 0.1 to 0.33 THz. In experiments, we measured the transmission characteristics of both the porous fibers and the bulk rod, to confirm a significant improvement in THz wave transmission nearly by an order of magnitude in the 6G telecommunication window, showing a better performance than theoretical estimations.ope

Terahertz Spectral Properties of PEO-Based Anti-Adhesion Films Cross-Linked by Electron Beam Irradiation

We investigated the spectral property changes in anti-adhesion films, which were cross-linked and surface-modified through electron beam irradiation, using terahertz time-domain spectroscopy (THz-TDS). Polyethylene oxide (PEO), which is a biocompatible and biodegradable polymer, was the main component of these anti-adhesion films being manufactured for testing. The terahertz characteristics of the films were affected by the porosity generated during the freeze-drying and compression processes of sample preparation, and this was confirmed using optical coherence tomography (OCT) imaging. An anti-adhesion polymer film made without porosity was measured by using the THz-TDS method, and it was confirmed that the refractive index and absorption coefficient were dependent on the crosslinking state. To our knowledge, this is the first experiment on the feasibility of monitoring cross-linking states using terahertz waves. The THz-TDS method has potential as a useful nondestructive technique for polymer inspection and analysis.ope

Gold nanorod-mediated photothermal modulation for localized ablation of cancer cells

We estimated the photothermal transduction efficiency of gold nanorod (GNR) solutions for different GNR concentrations and irradiation laser power. In particular, we verified that the degree of cell death area could be modulated by GNR concentration and irradiation laser power. The efficacy of GNR-produced photothermal ablation of cancer cells was evaluated by irradiating GNRs in the presence of MDA-MB-231 breast cancer cells with a near-infrared (NIR) laser at different laser power densities and irradiation times. GNR-induced photothermal ablation was applied successfully to cancer cells at various NIR laser power densities and irradiation times and was characterized with live-dead cell staining. Through these techniques, we established the system for not only verification of induced photothermal effect using NIR laser and thermocouple, but also identification of uptake efficiency for GNRs and cell viability using dark field and fluorescence imaging, respectively.ope

Gold-layered calcium phosphate plasmonic resonants for localized photothermal treatment of human epithelial cancer

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Characterization of Proton-Irradiated Polyaniline Nanoparticles Using Terahertz Thermal Spectroscopy

In this study, we investigated the changes in the molecular structure of polyaniline (PANI) nanoparticles illuminated by a proton beam using terahertz (THz) thermal spectroscopy based on the terahertz time-domain spectroscopy technique. PANI nanoparticles in water were exposed to a proton beam of 35 MeV energy with a particle fluence of 1013 particles/cm2. The photothermal properties of this solution of PANI nanoparticles were characterized using THz thermal spectroscopy. We measured the changes in the amplitudes of the reflected THz pulses to identify the variations in temperature induced by the photothermal effects of the PANI nanoparticle solution. The amplitude of a reflected THz pulse of the PANI solution not exposed to the proton beam increased when illuminated by an infrared light source, whereas that of THz signals of the PANI solution exposed to the proton beam hardly exhibited any changes. This implies that the molecular structure of PANI nanoparticles can be varied by a proton beam with a particle fluence above 1013 particles/cm2.ope

Terahertz otoscope and potential for diagnosing otitis media

We designed and fabricated a novel terahertz (THz) otoscope to help physicians to diagnose otitis media (OM) with both THz diagnostics and conventional optical diagnostics. We verified the potential of this tool for diagnosing OM using mouse skin tissue and a human tympanic membrane samples prior to clinical application.ope