Abstract-Single-cell terahertz spectral characteristics in simulated scattering near-field imaging mode

Jie Wang, Shihan Yan, Zaoxia Li, Ziyi Zang, Xingxing Lu, and Hong-Liang Cui

Schematic of the coupled tip–cell model system.

https://www.osapublishing.org/osac/abstract.cfm?URI=osac-3-8-2096

Spectral imaging of a single cell with terahertz (THz) wave is valuable in determination of its physiological state for cell-based precision diagnosis, as THz photon energy is in tune with the vibration-rotation and conformation related excitations of cellular material, and THz absorption is extremely sensitive to the state and degree of hydration of a cell. Because of the severe mismatch between the cell size and the THz wavelength, such imaging has to be carried out in the near-field modality. To make the design and performance assessment of a THz near-field spectral imager effective and systematic, we simulate the scattering THz near-field signals of tumor cells by strictly controlling cell model parameters with representative physiological states. The results demonstrate that the specific physiological characteristics from intracellular hydration state, nucleocytoplasmic ratio, and cell geometric morphology of tumor cells can be characterized quantitatively by their discrepant dielectric response in the THz band, correlating THz near-field scattering signal from a cell with the latter’s corresponding physicochemical state.

© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Broadband stepped-frequency modulated continuous terahertz wave tomography for non-destructive inspection of polymer materials

Xiaoxuan Zhang, Qijia Guo, Tianying Chang, Hong-Liang Cui,


https://www.sciencedirect.com/science/article/pii/S0142941818320683

An all-solid-state electronic three-dimensional terahertz tomography system designed specifically for non-destructive inspection of polymer materials is demonstrated, which is capable of determining the positions and shapes of hidden defects accurately. The imaging radar system, based on stepped-frequency modulated continuous wave (SFMCW), with center frequency at 180 GHz, bandwidth of 60 GHz, and average power 0.5 mW, is tested against thick Teflon (polytetrafluoroethylene, PTFE) plates with internal voids as samples. The locations and shapes of the hidden holes are obtained in both electromagnetic simulation and experimental measurements with a three-dimensional image reconstruction algorithm, which features advantages of accurate reconstructed image details and fast computation speed, demonstrating that the terahertz imaging radar system combined with the algorithm developed is capable of detecting internal defects of thick polymers. Key resolution parameters are established experimentally in detail, demonstrating 2.5 mm and 1.7 mm range resolutions in free space and in Teflon separately, and lateral spot diameters ranging from 3.4 mm to 8 mm at imaging distances from 5 mm to 60 mm.

Abstract-Deep Electrical Modulation of Terahertz Wave Based on Hybrid Metamaterial-Dielectric-Graphene Structure

Liangping Xia, Xin Zhang, Man Zhang, Suihu Dang, Shijian Huang, Yong Tan, Wenjuan Yan, Hong-Liang Cui

https://www.mdpi.com/2076-3417/9/3/507

A terahertz modulation structure based on hybrid metamaterial and graphene is proposed and demonstrated in this work. The metamaterial with a square slit ring array excites terahertz resonance in the slits and enhances the interaction between the terahertz wave and graphene. The graphene layer acting as the active material is tuned by the applied electrical field. With the separation by a dielectric layer between the graphene and the metallic structure, the resonant frequency and transmitted energy are both modulated by the graphene. Experimental result indicates that the modulation depth of the terahertz transmitted amplitude is 65.1% when the applied modulation voltage is tuned 5 V.

Abstract-Terahertz Spectroscopic Signatures of Microcystin Aptamer Solution Probed with a Microfluidic Chip

Mingkun Zhang, Zhongbo Yang, Mingjie Tang , Deqiang Wang , Huabin Wang, Shihan Yan , Dongshan Wei,  Hong-Liang Cui

https://www.mdpi.com/1424-8220/19/3/534

Terahertz signature detection of biological samples in aqueous solution remains a great challenge due to the strong terahertz absorption of water. Here we propose a new preparation process for fabricating a microfluidic chip and use it as an effective sensor to probe the terahertz absorption signatures of microcystin aptamer (a linear single-stranded DNA with 60 nucleotides) dissolved in TE buffer with different concentrations. The microfluidic chip made of silicon includes thousands of 2.4 μm × 2.4 μm square-cross-section channels. One repeatable terahertz absorption signature is detected and recognized around 830 GHz, fitted to a Lorentz oscillator. This signature is theorized to originate from the bending of hydrogen bonds formed between adjacent hydrated DNA bases surrounded by water molecules. Furthermore, the low-lying vibrational modes are also investigated by molecular dynamics simulations which suggest that strong resonant oscillations are highly probable in the 815–830 GHz frequency band

Abstract-Temporal and Spatial Variability of Water Status in Plant Leaves by Terahertz Imaging

Zheyu Song,  Shihan Yan,   Ziyi Zang,  Yun Fu, Dongshan Wei,  Hong-Liang Cui,  Puxiang Lai,

https://ieeexplore.ieee.org/document/8403254/

Water and its distribution and transport dynamics in green plant leaves are vital to the growth of plants. Owing to the high sensitivity of terahertz (THz) wave to water, THz spectroscopy has great advantages in analyzing the water status of plant leaves. This paper presents a new approach to estimate the water status of plant leaves by the THz time-domain spectroscopy (THz-TDS) technique. Spatial distribution of THz transmission amplitudes located in vein xylem and mesophyll of all three kinds of leaves including wintersweet, ginkgo, and bamboo is detected by THz-TDS measurements. Based on the transmission amplitude, reconstructed THz images show that the water loss in the basal leaf region is more than that in the distal region during the natural drying process for all three plants. A good agreement is reached between the THz imaging method and the direct water weight measurement. To illustrate the accuracy and the sensitivity of the THz technique, the temporal and spatial variations of the water content in the damaged ginkgo leaf with a wound by cutting are also investigated for comparison. The water flow from the basal region to the distal region of the leaf is inferred according to the variation of THz transmission amplitude with the leaf region in different dehydration periods, which is consistent with the string-of-lakes model prediction. This paper shows the feasibility of using THz technology to monitor the temporal and spatial variability of the water status in plant leaves.

Abstract-Reliable Origin Identification of Scutellaria Baicalensis Based on Terahertz Time-Domain Spectroscopy and Pattern Recognition

Jie Liang, Qijia Guo, Tianying Chang, Ke Li, Hong-Liang Cui



https://www.sciencedirect.com/science/article/pii/S0030402618311574

An effective approach for identification of the origin of Scutellaria baicalensis, an essential member of the family of Chinese herbal medicine and known to be an effective anti-inflammatory, is proposed based on terahertz time-domain spectroscopy (THz-TDS) and pattern recognition. Terahertz absorption spectra of Scutellaria baicalensis collected from its main growth areas in China, including Inner Mongolia, Shanxi and Shaanxi are investigated using the proposed method, in the frequency range from 0.2 to 1.7 THz. To reduce the dimensionality of the original spectral data and extract useful features of the data, principal component analysis is employed. The matrix of the selected principal component scores is fed into a classification model established by support vector machines. We use the particle swarm optimization to optimize the parameters of the classification model to achieve an identification rate of 95.56% for the samples, demonstrating that terahertz time-domain spectroscopy combined with particle swarm-support vector machines approach can be efficiently utilized for automatic identification of the origin of Scutellaria baicalensis.

Abstract-Label-free protein detection using terahertz time-domain spectroscopy

Xiaohui Han, Shihan Yan, Ziyi Zang, Dongshan Wei, Hong-Liang Cui, and Chunlei Du

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-9-3-994

Protein analysis is the foundation to understanding the mechanisms of complex biological processes. As one of the most widely used techniques to determine protein species and contents, protein dot blot aids biology research but needs corresponding antibodies for marking. A label-free detection method based on terahertz time-domain spectroscopy (THz-TDS) is proposed and demonstrated to improve this traditional technology. A membrane loaded with protein samples is directly scanned using a transmission THz-TDS system for spectral imaging. Different kinds of proteins can be distinguished by the refractive index extracted from the THz transmission spectrum. The intensity or shade imaged with the THz transmission spectrum can help detect the protein quantitatively. The feasibility of this new protein assay is demonstrated by the results of systematic testing with actual samples prepared with the dot-blot protocol.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Detection of DNA oligonucleotides with base mutations by terahertz spectroscopy and microstructures

Mingjie Tang,  Mingkun Zhang, Shihan Yan,  Liangping Xia, Zhongbo Yang, Chunlei Du, Hong-Liang Cui, Dongshan Wei,

http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0191515

DNA oligonucleotides with a 5-base mutation at the 3'-terminus were investigated by terahertz (THz) spectroscopy in a marker-free manner. The four single-stranded oligonucleotides with 17nt have been detected with specificity on a microfluidic chip, and corroborated by spectral measurements with split-ring resonators. The number of hydrogen bonds formed between the oligonucleotide and its surrounding water molecules, deemed a key contribution to the THz absorption of biological solutions, was explored by molecular dynamics simulations to explain the experimental findings. Our work underlies the feasibility of THz spectroscopy combined with microstructures for marker-free detection of DNA, which may form the basis of a prospective diagnostic tool for studying genic mutation.

Abstract-Cell viability and hydration assay based on metamaterial-enhanced terahertz spectroscopy

Yu Liu,  Mingjie Tang,  Liangping Xia,  Wenjing Yu,  Jia Peng, Yang Zhang,  Marc Lamy de la Chapelle,  Ke Yang,  Hong-Liang Cui,  Weiling Fu

http://pubs.rsc.org/en/content/articlelanding/2017/ra/c7ra09609g#!divAbstract

As a fast-growing technology, terahertz time-domain spectroscopy (THz-TDS) is becoming increasingly pervasive in biological applications, targeting a range of biomaterials from biomolecules to tissues. However, THz-TDS studies at the cellular level are quite limited. Thus, a study to analyze the living state and hydration state of a tumor cell in a label-free manner is carried out and reported here. Combined with a specially designed THz metamaterial, a tumor cell monolayer was detected continuously over a period of time. In addition, in order to explore the possible impact of the metamaterial on tumor cells, the secretion of IL-6, IL-8, GM-CSF and GROα of cell supernatants was detected. The results demonstrated that the technology could characterize the living state by monitoring the extracellular water and investigate the hydration state inside a tumor cell in real time, showing great application potential for the label-free detection of normal cells and tumor cells of diverse malignant degree.

Abstract-Terahertz Scattering and Spectroscopic Characteristics of Polymethacrylimide Microstructures

Liyun Xing , Hong-Liang Cui * , Jing Bai * , Zhenxiong Zhou * , Qingyu Zhou * , Dongshan Wei , Chunlei Du , Jun Yin , Songnian Zhang

https://www.preprints.org/manuscript/201708.0058/v1

We carried out systematic measurements of Polymethacrylimide (PMI)’s Terahertz (THz) spectroscopic and scattering parameters with various thicknesses and models. The Terahertz time domain spectroscopy (THz-TDS) would be useful as a nondestructive testing (NDT) tool for PMI. While the index of refraction is very close to that of air, with flat frequency dependency, the attenuation constant exhibits a remarkable strong frequency variation, suggesting a scattering dominated attenuation process. Based on the Mie scattering model, we gave the satisfactory explanation: the THz wave propagating through the PMI suffer scattering from the micro sized particles, and the sizes of the particles (shown to obey a normal distribution) determine the frequency characteristics of the interaction.

Abstract-Hilbert-Transform-Based Accurate Determination of Ultrashort-Time Delays in Terahertz Time-Domain Spectroscopy

Tianying Chang ;  Qijia Guo ;  Lingyu Liu ;  Hong-Liang Cui

http://ieeexplore.ieee.org/document/7951024/

Accurate determination of time delays is crucial for distinguishing a sample's different interfaces in terahertz time-domain spectroscopy (THz-TDS), especially for ultrathin samples or interfacial gaps. In this paper, Hilbert transform (HT) is invoked, along with posttransform signal spectral estimation of several varieties, including the conventional, that based on multiple-signal classification spectrum estimation (HT-MUSIC), and that based on autoregressive spectrum estimation using Yule–Walker law (HT-AR), to determine the sample's different interfaces. The results are compared with the traditional method of obtaining time delays in THz-TDS, along with analysis of the resolution and accuracy, as well as advantages and deficiencies of the various approaches. It is demonstrated that HT is an effective method for determining different interfaces of an ultrathin sample by simulation and experiments. The simulation results show that MUSIC-HT has the best resolution, at about 0.35 ps and AR-HT has the best accuracy, whose error is less than 0.075 ps. Experimental results for ultrathin air gaps and polymer films confirmed that MUSIC-HT can distinguish time delays as short as 0.44 ps from the THz time-domain spectra.

Abstract-Dielectric properties of coal in the terahertz frequency region of 100–500 GHz

• Wei Fan^a, 
• Tianying Chang^a, b, 
• Lingyu Liu^b, 
• Hong-Liang Cui^a

• ^a College of Instrumentation and Electrical Engineering, Jilin University, Changchun, Jilin 130061, China
• ^b Institute of Automation, Shandong Academy of Sciences, Jinan, Shandong 250103, China
• 
  

http://www.sciencedirect.com/science/article/pii/S0016236116309942

The dielectric properties of anthracite and bituminous coals were investigated in the terahertz (THz) frequency region from 100 GHz to 500 GHz. We developed two types of THz material measurement systems that can be operated in this frequency region, including one based on a vector network analyzer (VNA) with frequency extension modules, and another based on a THz time-domain spectroscopy (TDS) system. Employing the free-space configuration, we obtained the variation of dielectric property of coals in the frequency region of 100–500 GHz. By comparing the VNA and TDS systems, we evaluated the continuity and consistency of the two systems and verified the dielectric property measurement results of coal in the entire frequency region. We first outlined the fundamental theory of dielectric property with both methods, followed by estimating the measurement error in consideration with the system stability, the time span of the time-domain gating, and measurement uncertainty. We evaluated the dielectric property of coal samples through the measured results of the VNA and TDS systems. Comparison is also made of the variation of measured dielectric property with the lower THz frequency region (W-band) in our previous work. The results show that different coal type exhibited different variation with increasing frequency in the THz band considered.

Abstract-A High Precision Terahertz Wave Image Reconstruction Algorithm

Qijia Guo 1, Tianying Chang 1,2,*, Guoshuai Geng 1, Chengyan Jia 1 and Hong-Liang Cui 1

1

School of Instrumentation Science and Electrical Engineering, Jilin University, Changchun 130012, China

2

Institute of Automation, Shandong Academy of Sciences, Jinan 250014, China

*

Correspondence: Tel.: +86-186-1251-9976

Academic Editors: Vincenzo Spagnolo and Dragan Indjin

http://www.mdpi.com/1424-8220/16/7/1139/htm

With the development of terahertz (THz) technology, the applications of this spectrum have become increasingly wide-ranging, in areas such as non-destructive testing, security applications and medical scanning, in which one of the most important methods is imaging. Unlike remote sensing applications, THz imaging features sources of array elements that are almost always supposed to be spherical wave radiators, including single antennae. As such, well-developed methodologies such as Range-Doppler Algorithm (RDA) are not directly applicable in such near-range situations. The Back Projection Algorithm (BPA) can provide products of high precision at the the cost of a high computational burden, while the Range Migration Algorithm (RMA) sacrifices the quality of images for efficiency. The Phase-shift Migration Algorithm (PMA) is a good alternative, the features of which combine both of the classical algorithms mentioned above. In this research, it is used for mechanical scanning, and is extended to array imaging for the first time. In addition, the performances of PMA are studied in detail in contrast to BPA and RMA. It is demonstrated in our simulations and experiments described herein that the algorithm can reconstruct images with high precision.

Abstract-Enhancement Effects of the Terahertz Near-Field Microscopy

Jian Huang 1,†

, Zhongbo Yang 1,†

, Dongshan Wei 1,* , Chunlei Du 1

 and Hong-Liang Cui 1,2,* 

1 Chongqing Key Laboratory of Multi-scale Manufacturing Technology, Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 400714, China2 College of Instrumentation Science and Electrical Engineering, Jilin University, Changchun 130061, China† These authors contributed equally to this work

http://www.mdpi.com/2076-3417/5/4/1745

Terahertz near-field detection based and imaging on a nanotip has drawn wide attention following extensive applications of terahertz imaging technologies. Through the local enhanced electric field created by a terahertz nanotip in the near field, it is very likely to attain superior detection sensitivity and higher spatial resolution. This paper simulates the local enhancement effects of the terahertz near-field microscopy using a two-dimension finite difference time domain (2D-FDTD) method. Factors that influence the enhancement effects are investigated and analyzed in detail. Simulation results show that the size of the nanotip apex, the apex-substrate distance, dielectric properties of the substrate and the detected sample, etc., have significant impacts on the electric field enhancement and spatial resolution of the terahertz near-field nanotip, which can be explained from the effective polarizability of the nanotip-sample/substrate system.