Non-Destructive Evaluation of Hidden Defects Beneath the Multilayer Organic Protective Coatings Based on Terahertz Technology

Tu, Wanli, Shuncong Zhong, Manting Luo, and Qiukun Zhang. "Non-Destructive Evaluation of Hidden Defects Beneath the Multilayer Organic Protective Coatings Based on Terahertz Technology." Frontiers in Physics 9 (2021): 304.

Abstract
An organic protective coating system plays an important role for the corrosion protection of offshore metallic structures. It is of practical importance to detect possible coating defects and evaluate coating performance for corrosion degradation monitoring. Reliable defect identification can provide timely and effective maintenance to avoid serious consequences. This work investigated various multilayer organic coating systems by terahertz pulse imaging technology and aimed to explore the inspection ability of terahertz non-destructive testing (THz NDT) of protective coatings. Several types of defective coating samples were measured. The comparison of measurements obtained for sites with and without defects was provided. The changes in the signals caused by the presence of defects were explained. Structural analysis, quantitative evaluation, and defect identification were carried out in detail. The results of measurements showed that corrosion defects, paint bulge defects, and paint detachment defects can be distinguished and identified in combination with the causes of defects. It can provide effective technical guidance for terahertz technology to be gradually extended to engineering applications.


for full paper see https://www.frontiersin.org/articles/10.3389/fphy.2021.676851/full

 In this work, measurement is performed using a commercial THz-TDS system, TeraPulse 4000 (TeraView Ltd., Cambridge, United Kingdom). The system works with a reflection imaging module (RIM), and the stable terahertz spectrum ranges from 0.1–4 THz. The diameter of the terahertz spot at the focal point is about 0.2 mm. The scanning step is set at 0.1 mm with the consideration of measurement effect and measurement speed, and it scans approximately 16 pixels per sec. The achieved signal-to-noise ratio can be up to 90 dB.

For more information click here

Terahertz time domain spectroscopy of graphene and MXene polymer composites

Zeranska‐Chudek, Klaudia, Anna Lapinska, Agnieszka Siemion, Agnieszka M. Jastrzębska, and Mariusz Zdrojek. "Terahertz time domain spectroscopy of graphene and MXene polymer composites." Journal of Applied Polymer Science 138, no. 10 (2021): 49962.

Abstract

The rising demand for faster and more efficient electronic devices forces electronics industry to shift toward terahertz frequencies. Therefore there is a growing need for efficient, lightweight, and easy to produce absorbing materials in the terahertz range for electromagnetic interference (EMI) shielding and related applications. This study presents a study on basic optical properties of two types polymer-based composites loaded with two-dimensional structures—graphene and MXene phases (Ti2C). In said range, total EMI shielding efficiency (SE) and its components, the absorption coefficient (α), refractive index, and complex dielectric function are investigated. The ratio of SE absorption component to reflection component (SEABS:SER) of fabricated composites is equal or higher than 30:1 in over 80% of studied range. The fabricated composites exhibit low (<0.1) loss tangent in studied range. The addition of 1 wt% of graphene increases the composite α over 10-fold in respect to pure polymer–up to 60 cm−1 for frequency higher than 2 THz.

for full paper see https://onlinelibrary.wiley.com/doi/abs/10.1002/app.49962 

… THz‐TDS measurements were conducted using TeraView spectrometer Spectra 3000 … The TeraView software was used to retrieve the refractive index, absorption coefficient, transmittance, reflectance, and the complex dielectric function of the measured composites … 

for more information click here

Structure–dynamic properties relationships in poly(ethylene oxide)/silicon dioxide nanocomposites: dielectric relaxation study

 Mohamed, F., Talaat A. Hameed, A. M. Abdelghany, and G. Turky. "Structure–dynamic properties relationships in poly (ethylene oxide)/silicon dioxide nanocomposites: dielectric relaxation study." Polymer Bulletin (2020): 1-19.

Abstract

Films of polyethylene oxide (PEO) filled with silicon dioxide (SiO2) were synthesized via casting method. The formation of the PEO/SiO2 nanocomposites was characterized by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) measurements. The XRD patterns confirmed that increasing SiO2 in semicrystalline PEO enhances the amorphousity and causes a disturbance in the crystalline phase. The influence of the SiO2 on the dielectric relaxation spectra of PEO in wide temperature and frequency ranges was investigated. Two molecular relaxation processes are observed: main (α-) and secondary (β-) relaxations. For the α-process, the process slowed down with adding SiO2 fillers reflecting an increase in the glass transition temperature, Tg. This trend was also verified by differential scanning calorimetry (DSC). The findings indicated that adding SiO2 restricted the motion of PEO segments, while such changes were not observed in the glassy state. Further, the attenuation of the electric field of the terahertz waves passed through PEO/SiO2 samples was evaluated. In the terahertz range, the resonant peaks of PEO originated from lattice vibration feature the complex dielectric function. These peaks were weakened broadened and red-shifted by increasing of SiO2 concentrations.

for full paper see https://link.springer.com/article/10.1007/s00289-020-03368-0

… The measurements were taken at a heating ramp rate of 10 °C/min. Terahertz spectroscopy.  All terahertz measurements in the frequency range of 60 GHz and 3 THz (2–100 cm −1 ) were executed using TPS spectra 3000 system, Teraview Ltd., England 

for more information click here

TeraCota – Terahertz Coating thickness analysis

 A Non-Contact, Multi-Layer Coating & Paint Thickness Sensor with Scanning Capability.

Designed for the coatings industry, the TeraCota 2000 sensor can determine the individual thickness of multiple paint layers on both metallic and non-metallic substrates and offers significant benefits over existing techniques.

The sensor is non-contact, suitable for working on curved surfaces and capable of performing horizontal and vertical line scans.

Based on terahertz technology, the sensor represents a significant leap beyond the current method of measurement for quality and process control in automotive paint application, and also provides significant economic and environmental benefits.

for more information click here 

Rotational coherence of encapsulated ortho and para water in fullerene-C60 revealed by time-domain terahertz spectroscopy

Zhukov, Sergey S., Vasileios Balos, Gabriela Hoffman, Shamim Alom, Mikhail Belyanchikov, Mehmet Nebioglu, Seulki Roh et al. "Rotational coherence of encapsulated ortho and para water in fullerene-C 60 revealed by time-domain terahertz spectroscopy." Scientific reports 10, no. 1 (2020): 1-9.

Abstract

We resolve the real-time coherent rotational motion of isolated water molecules encapsulated in fullerene-C60 cages by time-domain terahertz (THz) spectroscopy. We employ single-cycle THz pulses to excite the low-frequency rotational motion of water and measure the subsequent coherent emission of electromagnetic waves by water molecules. At temperatures below ~ 100 K, C60 lattice vibrational damping is mitigated and the quantum dynamics of confined water are resolved with a markedly long rotational coherence, extended beyond 10 ps. The observed rotational transitions agree well with low-frequency rotational dynamics of single water molecules in the gas phase. However, some additional spectral features with their major contribution at ~2.26 THz are also observed which may indicate interaction between water rotation and the C60 lattice phonons. We also resolve the real-time change of the emission pattern of water after a sudden cooling to 4 K, signifying the conversion of ortho-water to para-water over the course of 10s hours. The observed long coherent rotational dynamics of isolated water molecules confined in C60 makes this system an attractive candidate for future quantum technology.

for full paper see https://www.nature.com/articles/s41598-020-74972-3

....We use two commercial THz spectrometers namely, TeraPulse and TeraView to perform the experiments. The sample is cooled down to liquid helium temperatures in an Optistat (Oxford Instruments) helium-flow optical cryostat with Mylar windows. The THz pulse path is purged by nitrogen or vacuumed to exclude water vapor absorption lines. Each signal is obtained by averaging of about 200–500 pulses and accumulating for 30–40 seconds. The step size of the time-delay line movement provides a temporal resolution of 3 fs on the TeraView spectrometer and 8 fs on the TeraPulse spectrometer. In the temperature dependent measurements, the sample temperature is gradually lowered and the THz response of the system is measured at 10-degree steps and after 60 min waiting time......

for more information about TeraView and its products click here.

Synthesis of Sm3+ and Gd3+ Ions Embedded in Nano-Structure Barium Titanate Prepared bySol-Gel Technique: Terahertz, Dielectric and Up-Conversion Study

 Hameed, Talaat A., F. Mohamed, A. M. Mansour, and I. K. Battisha. "Synthesis of Sm3+ and Gd3+ ions embedded in nano-structure barium titanate prepared by sol-gel technique: terahertz, dielectric and up-conversion study." ECS Journal of Solid State Science and Technology 9, no. 12 (2020): 123005.

Abstract

Nano-structure Barium Titanate (BaTiO3) doped with 1 mole% Sm3+ and Gd3+ ions have been synthesized by modified sol-gel process. The tetragonal perovskite structure has been demonstrated by means of X-ray diffraction and selected area electron diffraction obtained by high resolution transmission microscopy. The XRD and HRTEM have been used for estimation the grain size, which found to be around 38.36 and 33.26 nm. The scanning electron microscope micrographs asserted the formation of agglomerated particles, which is characteristic of many nano-systems. The green emission has been observed at 528, 567 and 597 nm, whereas red group emission at 604, 611, 632, 643, 660, 672, 688, 716 and 732. The thermal stability and the purity of the synthesized material were confirmed by the results of Thermogravimetric Analysis (TGA) and differential scanning calorimetry (DSC). Two relaxation processes were observed in the dielectric loss εʹ as well as in the modulus spectra of both samples. The dielectric behavior was further discussed in the range of terahertz by using the time domain terahertz spectrophotometer. the refractive index in terahertz were found to be dwindle, whereas the absorption coefficient improved upon increasing THz frequencies.

for full paper see https://iopscience.iop.org/article/10.1149/2162-8777/abc96b/meta

… was kept to be better than ± 0.1 K. All terahertz measurements in the frequency range of 0.01 and 3 THz were conducted using TPS spectra 3000 system, Teraview Ltd. England whose number of scans of 1800 scans …

for more information about TeraView and its products click here.

TeraView's TeraSolve tablet porosity measurement system

TeraSolve – a porosity measurement tool for the pharmaceutical industry

TeraPulse Lx Core Unit and tablet imager

This module is an addition to the TeraPulse Lx product-range. It has been optimized for non- destructive determination of the disintegration and dissolution performance of finished pharmaceutical tablets and other solid dosage forms.

Based upon TeraView’s proprietary semiconductor based THz pulsed technology and over 70 Patented technologies and processes, the system yields real time monitoring of the dissolution properties of tablets during manufacture.

It is based on many years of experience in tablet imaging accumulated through work with TeraView customers and collaborators. In particular ground- breaking work with the University of Cambridge and Huxley Bertram Engineering.

The system may be integrated into full production environments for in-line for ribbon blend measurements, on-line in a tablet press or continuous manufacturing environments. A further configuration is a fully integrated solution with the Huxley Bertram HB50 tablet simulator for formulators and pilot production. 

for more information click here or visit https://teraview.com/terasolve/

TeraPulse Lx: Future-proof your research with the TeraPulse Lx Modular System

 

TeraPulse Lx

Future-proof your research with the TeraPulse Lx Modular System

The TeraPulse Lx system is the latest addition to TeraView’s world-leading product family for terahertz analysis. It has been designed to meet the needs of the researcher in imaging or spectroscopy applications.

The system’s modular architecture gives the user both flexibility and expandability and is compatible with TeraView’s extensive and unique Terahertz Toolbox range of accessories. For the first time, these robust fibre-connected modules are available as user exchangeable plug and play devices. All systems include the TeraView patented laser-gated photoconductive emitters and detectors. The new TeraPulse Lx sample chamber has optical fibre coupling throughout, for unprecedented stability
and portability.

The lightweight compact core unit allows for easy transport between locations, and is available in both table-top and 19” rack-compatible formats. The system boasts an industry-leading 3,200 ps time-delay line, as standard.

For more information click here

THz diffractive lens manufactured using 3D printer working for 0.6 THz

 Siemion, Agnieszka, Aneta Melaniuk, Przemysław Zagrajek, Paweł Komorowski, Michał Walczakowski, Mateusz Surma, Piotr Sobotka, Izabela Ducin, and Elżbieta Czerwińska. "THz diffractive lens manufactured using 3D printer working for 0.6 THz." In 2020 23rd International Microwave and Radar Conference (MIKON), pp. 225-228. IEEE, 2020.

Abstract:

Rapid development of terahertz technologies causes constant search for new possibilities of making optical elements, needed for proper beam shaping. Large optical elements are often used in THz setups to collect as much power as possible. Unfortunately, traditional refractive optical lenses significantly absorb already weak signal. This is the reason for searching for new solutions in the form of diffractive optical elements (DOEs). For higher terahertz frequencies however, it is challenging to find an appropriate material as well as uncomplicated manufacturing methods. In this article, we present a higher-order kinoform (HOK) made of paraffin, cast from 3D-printed mold, efficiently working for 0.6 THz.

for full paper see https://ieeexplore.ieee.org/abstract/document/9253821

"… 1. Refractive index and absorption coefficient of paraffine have been determined using time-domain spectroscopy (TPS 3000 TeraView) and for the frequency of 0.6 THz are equal to 1.51 and 0.26 cm-1, respectively. "

For more information click here

Polarization-selective modulation of supercavity resonances originating from bound states in the continuum

 Kyaw, Chan, Riad Yahiaoui, Joshua A. Burrow, Viet Tran, Kyron Keelen, Wesley Sims, Eddie C. Red et al. "Polarization-selective modulation of supercavity resonances originating from bound states in the continuum." Communications Physics 3, no. 1 (2020): 1-8.

Abstract

Bound states in the continuum (BICs) are widely studied for their ability to confine light, produce sharp resonances for sensing applications and serve as avenues for lasing action with topological characteristics. Primarily, the formation of BICs in periodic photonic band gap structures are driven by symmetry incompatibility; structural manipulation or variation of incidence angle from incoming light. In this work, we report two modalities for driving the formation of BICs in terahertz metasurfaces. At normal incidence, we experimentally confirm polarization driven symmetry-protected BICs by the variation of the linear polarization state of light. In addition, we demonstrate through strong coupling of two radiative modes the formation of capacitively-driven Freidrich-Wintgen BICs, exotic modes which occur in off-Γ points not accessible by symmetry-protected BICs. The capacitance-mediated strong coupling at 0° polarization is verified to have a normalized coupling strength ratio of 4.17% obtained by the Jaynes-Cummings model. Furthermore, when the polarization angle is varied from 0° to 90° (0° ≤ ϕ < 90°), the Freidrich-Wintgen BIC is modulated until it is completely switched off at 90°.

For full paper see https://www.nature.com/articles/s42005-020-00453-8

.....A high-resolution continuous wave THz spectrometer (Teraview CW Spectra 400) that produces linearly polarized collimated terahertz beams was utilized to measure the transmission spectra of the aforementioned fabricated metasurface......

Terahertz Time-domain Spectroscopy (THz-TDS) for classification of blueberries according to their maturity

 Cruz, Jimy Oblitas. "Terahertz Time-domain Spectroscopy (THz-TDS) for classification of blueberries according to their maturity." In 2020 IEEE Engineering International Research Conference (EIRCON), pp. 1-4. IEEE, 2020.

Abstract:

Non-destructive determination of blueberry compound using spectral detection method is still a challenge due to the spectral THZ variation caused by abundant biological variations, such as geographic origins and harvest seasons. In order to investigate the potential of Terahertz time-domain spectroscopy to classify fruit maturity states, terahertz spectra (0.5-10 THz) of 4 states of blueberry maturity were examined. The acquired data matrices were submitted to the application of MATLAB 2019b Classification Learner by using 24 classifier models. 84.3 is the highest accuracy, obtained by the Fine Gaussian SVM Algorithm Model with a 0.35 Kernel Scale and a Multiclass Method One vs One. The coefficients for this application of PCA are PC1 (79.9%) and PC2 (20.1%). It was concluded that the combined processing and classification of images obtained from Terahertz time-domain spectroscopy and using Machine learning algorithms can be used to classify the different maturity states of blueberries.

for full paper see https://ieeexplore.ieee.org/abstract/document/9254046

.....Imaging equipment in the THZ range Terahertz time-domain measurements were obtained by using a Terapulse 4000 spectrometer (Teraview Ltd., Cambridge, UK) in transmission mode. The transmission chamber … 

Evaluation of in vivo THz sensing for assessing human skin hydration

Lindley-Hatcher, Hannah, A. I. Hernandez-Serrano, Jiarui Wang, Juan Cebrian, Joseph Hardwicke, and Emma Pickwell-MacPherson. "Evaluation of in vivo THz sensing for assessing human skin hydration." Journal of Physics: Photonics 3, no. 1 (2020): 014001.

Abstract 

Terahertz (THz) in vivo reflection imaging can be used to assess the water content of the surface of the skin. This study presents the results of treating 20 subjects with aqueous, anhydrous and water-oil emulsion samples and observing the changes induced in the skin using THz sensing. These regions were also measured with a corneometer, the present gold standard for skin hydration assessment within the cosmetics industry. We find that THz sensing is effective at observing the presence of oil and water on the surface of the skin, these results can be verified with the measurements of capacitance taken by the corneometer. The THz measurements reveal a distinction between the responses of subjects with initially dry or well hydrated skin, this observation is particularly noticeable with the oil-based samples. Additionally, moderate correlation was found between the THz reflected amplitude and capacitance of untreated skin with a correlation coefficient of r = −0.66, suggesting THz sensing has promising potential for assessing skin hydration. 

for full paper see https://iopscience.iop.org/article/10.1088/2515-7647/abcb71/pdf

............The individual samples were measured in the transmission unit of the TeraPulse 4000 THz TDS system (TeraView Ltd, Cambridge) .............

Terahertz probing of sunflower leaf multilayer organization

 Abautret, Yannick, Dominique Coquillat, Myriam Zerrad, Xavier Buet, Ryad Bendoula, Gabriel Soriano, Nicolas Brouilly et al. "Terahertz probing of sunflower leaf multilayer organization." Optics Express 28, no. 23 (2020): 35018-35037.

Abstract

We analyze the multilayer structure of sunflower leaves from Terahertz data measured in the time-domain at a ps scale. Thin film reverse engineering techniques are applied to the Fourier amplitude of the reflected and transmitted signals in the frequency range f < 1.5 Terahertz (THz). Validation is first performed with success on etalon samples. The optimal structure of the leaf is found to be a 8-layer stack, in good agreement with microscopy investigations. Results may open the door to a complementary classification of leaves.

Sunflower (c) TeraView Limited

for full paper see https://www.osapublishing.org/DirectPDFAccess/6ADBE498-5E73-4C39-AAEDFBD79986C4ED_442301/oe-28-23-35018.pdf?da=1&id=442301&seq=0&mobile=no

They used a TeraPulse 4000 for their research.

For more information please click here

THz Fingerprints of Cement-Based Materials

Dolado, Jorge S., Guido Goracci, Eduardo Duque, Pavel Martauz, Yibing Zuo, and Guang Ye. "THz fingerprints of cement-based materials." Materials 13, no. 18 (2020): 4194.

Abstract

To find materials with an appropriate response to THz radiation is key for the incoming THz technology revolution. Unfortunately, this region of the electromagnetic spectra remains largely unexplored in most materials. The present work aims at unveiling the most significant THz fingerprints of cement-based materials. To this end transmission experiments have been carried out over Ordinary Portland Cement (OPC) and geopolymer (GEO) binder cement pastes in combination with atomistic simulations. These simulations have calculated for the first time, the dielectric response of C-S-H and N-A-S-H gels, the most important hydration products of OPC and GEO cement pastes respectively. Interestingly both the experiments and simulations reveal that both varieties of cement pastes exhibit three main characteristic peaks at frequencies around ~0.6 THz, ~1.05 THz and ~1.35 THz, whose origin is governed by the complex dynamic of their water content, and two extra signals at ~1.95 THz and ~2.75 THz which are likely related to modes involving floppy parts of the dried skeleton 

for full paper see https://www.mdpi.com/1996-1944/13/18/4194

… 2.2. THz Measurements The time-domain THz transmission experiments were performed by using a TPS Spectra 3000 spectrometer (TeraView Ltd., Cambridge, UK). Samples were measured covering the spectral range 0.05 …

Case studies of accurate fault localization in advanced packages

 Gourikutty, Sajay Bhuvanendran Nair, Jesse Alton, Desmond Yeo, Kok Keng Chua, Sharon Lim Seow Huang, and Surya Bhattacharya. "Case studies of accurate fault localization in advanced packages." In 2021 IEEE 71st Electronic Components and Technology Conference (ECTC), pp. 850-855. IEEE, 2021.

Abstract:

Advanced wafer-level packaging has been successfully used in state-of-the-art FPGA ICs, smart-phone application processors, and GPU units to provide power-performance-form factor boosts that are not obtainable by conventional packaging. In addition, very fine pitch interconnects approaches such as high-density fan-out on organic substrates and fine pitch silicon interposers enable the need for heterogeneous integration and scaling demand. However, this increased the intricacy of package architecture which leads to a higher possibility of failures making it challenging to attain high yield in volume production. Therefore, high failure analysis success is required in this area and without accurate fault localization, failure analysis is difficult and often reliant on a best-guess approach which tends to be time-consuming and relatively expensive to be implemented. In this work, we demonstrated a rapid methodology for non-destructive accurate defect isolation at various levels of the advanced ICs preventing potential artifacts. First, fault isolation is verified on a 2.5D advanced package where an open fault is successfully localized after the micro-bump in the die side metal layer. Secondly, the methodology is validated by employing fine pitch interposer chip samples by isolating defects including high resistance fault in RDL metal lines.

for full paper see https://ieeexplore.ieee.org/abstract/document/9501570

For more information about EOTPR see https://teraview.com/eotpr/

Low-voltage driven graphene-loaded metal wire grating device in total internal reflection geometry for broadband THz modulation

 Liu, Xudong, Hao Chen, Teng Li, and Yiwen Sun. "Low-voltage driven graphene-loaded metal wire grating device in total internal reflection geometry for broadband THz modulation."

Abstract

Terahertz modulators with capability of both intensity and phase are essential for THz imaging and communication systems. The low-voltage driven THz modulation technique is crucial for integrating the modulators with electronics components. There is still a lack of broadband devices able to achieve both amplitude and phase modulation with low voltage, due to the underlying physics behind existing approaches. Here, we demonstrate a graphene-loaded metal wire grating THz modulator in the total internal reflection geometry to achieve intensity modulation of 80% and phase modulation of 70 degree within 3 volts gate voltage. Quite different from using the strategy of metamaterials based on the electromagnetic resonance effects, our design has performed a broadband modulation for over 1 THz bandwidth.

… grating. The gate voltage between graphene and HR-Si was swept from -3 V to 3 V. The transmitted THz time-domain signal was measured by a THz time-domain spectroscopy (TDS) system from TeraView Ltd. (TeraPulse 4000).......

For full paper see http://www.tstnetwork.org/June2021/tst-v14n2-44driven.pdf

Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography

 Zhai, Min, Alexandre Locquet, Cyrielle Roquelet, L. Agrizzi Ronqueti, and D. S. Citrin. "Thickness characterization of multi-layer coated steel by terahertz time-of-flight tomography." NDT & E International 116 (2020): 102358.

Abstract

Terahertz time-of-flight tomography is employed to characterize the individual layers in a multilayer coating on steel substrates. The multilayers, containing up to three layers, consist first of a cataphoretic layer, sealer, and varnish progressing upward from the steel substrate. The individual layer thicknesses were reconstructed from the experimental data using autoregressive spectral extrapolation based on the modified covariance method (AR/MCM), which extrapolates the frequency components of the transfer function into the low signal-to-noise-ratio (SNR) regions from the high SNR regions. Due to the high sensitivity of AR/MCM to the presence of noises, wavelet denoising, in some cases, was needed to precondition the data prior to application of AR/MCM. The method is verified numerically and experimentally, showing that it can reconstruct individual layers in the 10-μm range, and good agreement is found between the thicknesses of individual layers extracted by AR/MCM and characterized by eddy-current measurements.

for full paper see https://www.sciencedirect.com/science/article/abs/pii/S0963869520302425

… learning model [16]. In this study, a set of multilayer coated steel coupons were measured by THz TOF tomography using a TPS spectra 3000 on a reflection module (TeraView Ltd., Cambridge, UK). Individual layer thicknesses …

Sensing Water Absorption in Hygrothermally Aged Epoxies with Terahertz Time-Domain Spectroscopy

 Lin, Hungyen, Benjamin P. Russell, Prince Bawuah, and J. Axel Zeitler. "Sensing water absorption in hygrothermally aged epoxies with terahertz time-domain spectroscopy." Analytical Chemistry 93, no. 4 (2021): 2449-2455.

Abstract 

In the field of non-destructive testing, terahertz sensing has been used to analyze a wide range of materials where the most successful applications have involved materials that are semi-transparent to terahertz radiation. In this work, we demonstrate the sensitivity of terahertz time-domain spectroscopy to quantify water absorption in hygrothermally aged simple and commercial epoxy systems supported by conventional gravimetric analysis.

for full paper see https://pubs.acs.org/doi/full/10.1021/acs.analchem.0c04453

...................We performed transmission terahertz spectroscopy using a commercial THz-TDS setup (Terapulse 4000, TeraView Ltd.,Cambridge, U.K.) shown in Figure 1c. For the measurements, we selected the high-resolution scanning mode with 20 waveform averages, which took approximately 40 s per measurement. Given the sharp and distinct absorption features due to the rotational transitions of water molecules in the gas phase, all terahertz measurements were performed under a continuous purge with dry nitrogen in the sample chamber of the spectrometer................................

Terahertz Shielding Properties of Carbon Black Based Polymer Nanocomposites

 Zeranska-Chudek, Klaudia, Agnieszka Siemion, Norbert Palka, Ahmed Mdarhri, Ilham Elaboudi, Christian Brosseau, and Mariusz Zdrojek. "Terahertz Shielding Properties of Carbon Black Based Polymer Nanocomposites." Materials 14, no. 4 (2021): 835.

Abstract

The majority of industry using high-speed communication systems is shifting towards higher frequencies, namely the terahertz range, to meet demands of more effective data transfer. Due to the rising number of devices working in terahertz range, effective shielding of electromagnetic interference (EMI) is required, and thus the need for novel shielding materials to reduce the electromagnetic pollution. Here, we show a study on optical and electrical properties of a series of ethylene co-butyl acrylate/carbon black (EBA/CB) composites with various CB loading. We investigate the transmittance, reflectance, shielding efficiency, absorption coefficient, refractive index and complex dielectric permittivity of the fabricated composites. Finally, we report a material that exhibits superior shielding efficiency (SE)—80 dB at 0.9 THz (14.44 vol% CB loading, 1 mm thick)—which is one of the highest SE values among non-metallic composite materials reported in the literature thus far. Importantly, 99% of the incoming radiation is absorbed by the material, significantly increasing its applicability. The absorption coefficient (α) reaches ~100 cm⁻¹ for the samples with highest CB loading. The EBA/CB composites can be used as lightweight and flexible shielding packaging materials for electronics, as passive terahertz absorbers or as radiation shields for stealth applications.

.......Measurements in terahertz range were conducted via time-domain spectroscopy, using TeraView spectrometer Spectra 3000, (Cambridge, United Kingdom). The spectrometer is based on an 800 nm femtosecond laser generating 50 fs pulses and provides data in range 0.06−4 THz (2–120 cm−1 ). For the terahertz measurements, Rapid Scan mode was used, which employs 30 scans per second with 1.25 cm−1 resolution..........

for full paper see https://www.mdpi.com/1996-1944/14/4/835

Microfluid-based soft metasurface for tunable optical activity in THz wave

 Zhang, Wu, Bingzhi Zhang, Xiaohui Fang, Kejun Cheng, Weiqian Chen, Zihuang Wang, Dou Hong, and Meng Zhang. "Microfluid-based soft metasurface for tunable optical activity in THz wave." Optics Express 29, no. 6 (2021): 8786-8795.

Abstract

Metasurfaces are usually planar structures and do not possess intrinsic chirality and therefore hardly generate optical activity. Here we realized a tunable optical activity in a terahertz wave through a microfluid-based soft metasurface. The meta-atom is a chiral structured microchannel made of soft polydimethylsiloxane and injected with the liquid metal Galinstan. A microfluid pressure system is bonded to the metasurface to reconfigure all meta-atoms simultaneously. By pumping glycerol liquid into the pressure system, the metasurface is deformed from a planar structure to a three dimensional one, which manifests intrinsic chirality for optical activity realization. By controlling the injected glycerol volume, a polarization rotation from 0°to 14° at 0.19 THz is demonstrated. The soft metasurface with tunable optical activity can be flexibly applied in various applications such as polarization microscopy, bio-detection and material analysis, etc.

For full paper see https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-29-6-8786&id=448942

"A THz Time-domain spectroscopy (THz-TDS) Teraview spectra 3000 was used to measure the optical activity of the metasurface."

LTCC and Bulk Zn4B6O13–Zn2SiO4 Composites for Submillimeter Wave Applications

 Szwagierczak, Dorota, Beata Synkiewicz-Musialska, Jan Kulawik, and Norbert Pałka. "LTCC and Bulk Zn4B6O13–Zn2SiO4 Composites for Submillimeter Wave Applications." Materials 14, no. 4 (2021): 1014.

Abstract

New zinc metaborate Zn4B6O13–willemite Zn2SiO4 composites were investigated as promising materials for LTCC (low temperature cofired ceramics) substrates of microelectronic circuits for submillimeter wave applications. Composites were prepared as bulk ceramics and LTCC multilayer structures with cofired conductive thick films. The phase composition, crystal structure, microstructure, sintering behavior, and dielectric properties were studied as a function of willemite content (0, 10, 13, 15, 20, 40, 50, 60, 100 wt %). The dielectric properties characterization performed by THz time domain spectroscopy proved the applicability of the composites at very high frequencies. For the 87% Zn4B6O13–13% Zn2SiO4 composite, the best characteristics were obtained, which are suitable for LTCC submillimeter wave applications. These were a low sintering temperature of 930 ◦C, compatibility with Ag-based conductors, a low dielectric constant (5.8 at 0.15–1.1 THz), a low dissipation factor (0.006 at 1 THz), and weak frequency and temperature dependences of dielectric constant. 

for full paper see https://www.mdpi.com/1996-1944/14/4/1014

Morphological, impedance and terahertz properties of zinc titanate/Fe nanocrystalline for suppression of Pseudomonas aeruginosa biofilm

 El Nahrawy, Amany M., Bahaa A. Hemdan, and Ali B. Abou Hammad. "Morphological, impedance and terahertz properties of zinc titanate/Fe3+ nanocrystalline for suppression of Pseudomonas aeruginosa biofilm." Nano-Structures & Nano-Objects 26 (2021): 100715.

Abstract

Perovskite zinc titanate/ Fe3＋ nanocrystalline were expertly produced through the sol–gel method. The SEM morphology gives the cubic and rhombohedral phases of ZnTiO 3/Fe3＋ porous nanostructures calcined at 800 °C, composed of highly connected, uniform, and small nanoparticles. TEM reveals that the ZnTiO3/Fe3＋ are nanocrystals with nanoporous structures. The real impedance of nanostructures shows a decrease in the impedance value with increasing Fe3＋ ions, and it was a predicted performance because the replacement of Ti4＋ by Fe3＋ increases the oxygen vacancies that act as a charge carrier and hence decrease the impedance of the samples. Potential examinations of the antibiofilm properties for all tested antibiofilm nanostructures on planktonic and biofilm of Pseudomonas aeruginosa were performed using agar-diffusion assays growth-inhibition effects. Likewise, environmental and toxicological risks were measured. Results disclose that the conductivity was increased from 0.07 S/cm −1 to 2.37 S/cm −1 with changing the Fe3＋ content from (0.05-0.2 mol. %), which implicates complex conduction mechanisms and loss of oxygen vacancies in Fe2O3-zinc titanate mesostructures in the THz range. The results indicate that tested, prepared magnetic nanoparticles (20MNP) were the most operative nanomaterial than others. Further, the planktonic cells of Ps. aeruginosa were more sensitive to all tested nanomaterials than biofilm cells. Besides, the lowest inactivation effects toward biofilm and planktonic cells were recorded for base zinc titanate nanopervoskite. Likewise, the MIC of 20MNP values for planktonic and biofilm cells were 30ppm/20min, whereas, for planktonic and biofilm cells, only 10MPN MIC values were 30ppm/30min. Results supposed that 20MNP is an excellent antibiofilm agent for control and eradicating the biofilm formation of Ps. aeruginosa.

for full paper see https://www.sciencedirect.com/science/article/abs/pii/S2352507X2100024X