Monitoring Tensile-Induced Subsurface Damages of Woven Glass Fiber Reinforced Polymer Using Terahertz Time-of-Flight Tomography

 Zhai, Min, Haoyue Pan, Bin Xiao, Haolian Shi, Zhang Qu, Wenlong He, Cong Zhai, and Yi Tang. "Monitoring tensile-induced subsurface damages of Woven Glass Fiber Reinforced Polymer using terahertz time-of-flight tomography." NDT & E International (2026): 103645.

Abstract

Woven Glass Fiber Reinforced Polymer (GFRP) composites were studied using terahertz time-of-flight tomography to characterize failure modes in GFRP composite in a nondestructive and contactless fashion during in-situ tensile testing. The fracture morphologies of GFRP composite under different applied stresses were discussed by comparing terahertz C-and B-scan images to evaluate the dynamic evolution of tensile-induced microstructure. Our results show that significant THz-detectable damage initiation was observed at stress levels exceeding 60 MPa. In addition, tensile-induced damage can be observed not only on the surface, but also within the inner piles of GFRP composites. Finally, our work verifies the effectiveness of THz-based approach on three-dimensional dynamic monitoring the quality of GFRP composite in service and evaluating the influence of different loading conditions on structural properties and failure pattern of composite materials.

see https://www.sciencedirect.com/science/article/abs/pii/S0963869526000162

Real-time observation of coherent spin wave handedness

 Ha, Taewoo, Kyung Ik Sim, Howon Lee, Hyun Jun Shin, Sanghoon Kim, Se Kwon Kim, Jae Hoon Kim, Dong-Soo Han, Young Jai Choi, and Byung Cheol Park. "Real-time observation of coherent spin wave handedness." npj Spintronics 2, no. 1 (2024): 37.

Abstract

Magnonics, a crucial domain in information science and technology, utilizes spin waves in magnets as efficient information carriers. While antiferromagnets have been suggested for versatile magnonic platform because of the coexistence of right- and left-handed spin waves, their energetic degeneracy poses challenges for observation through spectral measurements, limiting their applicability. Recent observations of distinct spin wave handedness within the gigahertz regime have reported but, are yet to be demonstrated in terahertz (THz) frequencies of antiferromagnetic spin waves. Most of all, the coherence of spin waves is a key aspect of quantum information. Here, employing THz time-domain spectroscopy—a direct, precise, and easy probe for monitoring coherent spin wave dynamics—we discern chiral antiferromagnetic spin waves of opposite phase windings in the time domain, noting their handedness reversal across the angular momentum compensation temperature in ferrimagnets. We establish a principle for directly measuring the handedness of coherent antiferromagnetic spin waves in ferrimagnets with net magnetic moment M ≠ 0 but angular momentum L = 0. Our multidimensional access in the time and spectral domain enables the accurate determination of critical temperature and the dynamic observation of coherent chiral spin waves simultaneously in a single experiment, with potential applications in exploring other quantum chiral entities.

see https://www.nature.com/articles/s44306-024-00040-5

Optical and terahertz methods for studying easel oil paintings

 Bolshakov, Ivan S., Anastasiya A. Lykina, Olga V. Kravtsenyuk, Sergey V. Sirro, Vyacheslav Y. Toropov, Andrey R. Tsvetkov, Philip F. Taday, Donald D. Arnone, and Olga A. Smolyanskaya. "Optical and terahertz methods for studying easel oil paintings." Journal of Optical Technology 91, no. 5 (2024): 323-329.

Abstract

Subject of study. This study focuses on the application of terahertz tomography methods to easel oil paintings. 

Aim of study. The aim of this study is to assess the effectiveness of terahertz tomography in analyzing the layered structure of artworks and detecting hidden damage, elements, and annotations. 

Method. The study employed traditional analysis methods, such as infrared, ultraviolet fluorescence, and X-ray imaging. Special emphasis was placed on terahertz tomography, which enables non-invasive imaging of internal structures. 

Main results. The study showed that terahertz tomography allows for the differentiation of materials used in oil paintings. This method enables a detailed examination of the layered structure without damaging the object under investigation, revealing elements that cannot be detected using other methods. The novelty of this study lies in the proposed application of terahertz tomography for preliminary in situ examination of paintings to detect hidden defects and possible inscriptions on the reverse side of artworks. 

Practical significance. The results obtained from this study are valuable for researching, assessing the preservation status of, and restoring oil paintings. Specifically, the proposed method is suitable for detecting defects and hidden elements beneath paint layers without damaging the colorful surface. The terahertz tomography method proves particularly effective when applied in situ, as it does not require paintings to be dismantled.

see https://opg.optica.org/jot/abstract.cfm?uri=jot-91-5-323

Measuring Solute Concentration with Terahertz Time-Domain Spectroscopy in Single and Multiphase Systems

 Kolbel, Johanna, Qi Li, Terence L. Threlfall, and J. Axel Zeitler. "Measuring solute concentration with terahertz time-domain spectroscopy in single and multiphase systems." Analytical Chemistry 94, no. 3 (2022): 1713-1716.

Abstract

A versatile setup based on a microfluidic platform allows investigation of liquid samples at various temperatures with terahertz time-domain spectroscopy. The setup is applied to develop a novel method that performs temperature and concentration calibrations of liquid samples at terahertz frequencies. Other than measuring the concentration of pure liquid phase solutions, it enables the studies of local concentration of semicrystalline systems. An equivalent solute concentration during crystallization can be calculated from the extracted absorption at low frequencies. The MgSO4–water system is discussed as an example to illustrate the idea of this method.

see https://pubs.acs.org/doi/10.1021/acs.analchem.1c04279

Terahertz imaging of titanium dioxide-free film coating hydration and tablet core interactions

 

Ma, Mingrui, Marwa Nassar, Jason Teckoe, and J. Axel Zeitler. "Terahertz imaging of titanium dioxide-free film coating hydration and tablet core interactions." International Journal of Pharmaceutics (2026): 126596.

Abstract

Titanium dioxide (TiO2) is often used as a white base pigment in film coatings, but recent EU restrictions on its use in food have prompted pharmaceutical manufacturers to seek alternatives. Terahertz pulsed imaging (TPI) was used to examine the hydration of TiO2-free immediate release formulations, either without an opacifier or using calcium carbonate (CaCO3). The coatings, made from polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose (HPMC), were approximately 100 µm thick. TPI results indicated that the type of film coating influenced hydration and scattering effects. However, there was no evidence that TiO2-free coatings compromised tablet disintegration. Although the HPMC coating with CaCO3 gelled upon hydration, the tablets fully hydrated within the required time. These findings offer insights into the mechanistic impacts of alternative coatings in the industry.

see https://www.sciencedirect.com/science/article/pii/S037851732600044X