Graphene-enhanced decagonal patch antenna for terahertz frequency operation in breast cancer detection.

This paper presents a decagonal patch antenna loaded with graphene designed for terahertz (THz) frequency applications, with a specific emphasis on its potential for early breast cancer detection. The proposed antenna features a hybrid structure, integrating both copper and graphene materials. A decagonal graphene strip is intricately incorporated into the copper patch, yielding significant improvements in reflection coefficient, bandwidth, and gain. The antenna, with dimensions of 155µm×130µm×13µm, is designed on a polyimide substrate, characterized by a dielectric constant of 3.5 and a loss tangent of 0.0027. To ensure relevance in medical contexts, the design is optimized to operate within the frequency range of 2.1 to 5.7 THz, a critical spectrum for medical applications. Simulation results validate the effectiveness of the proposed antenna, demonstrating S 11<-10d B within the frequency band of 2.1 to 5.7 THz (92.3% fractional bandwidth). The antenna exhibits an impressive bandwidth of 3.6 THz and a gain of 7.87 dBi at 4 THz. These findings establish the graphene-loaded decagonal patch antenna as a highly promising solution for breast cancer detection applications, showcasing its potential in the realm of medical diagnostics.

Detection of Low-Concentration Biological Samples Based on a QBIC Terahertz Metamaterial Sensor.

Quasi-bound state in the continuum (QBIC) can effectively enhance the interaction of terahertz (THz) wave with matter due to the tunable high-Q property, which has a strong potential application in the detection of low-concentration biological samples in the THz band. In this paper, a novel THz metamaterial sensor with a double-chain-separated resonant cavity structure based on QBIC is designed and fabricated. The process of excitation of the QBIC mode is verified and the structural parameters are optimized after considering the ohmic loss by simulations. The simulated refractive index sensitivity of the sensor is up to 544 GHz/RIU, much higher than those of recently reported THz metamaterial sensors. The sensitivity of the proposed metamaterial sensor is confirmed in an experiment by detecting low-concentration lithium citrate (LC) and bovine serum albumin (BSA) solutions. The limits of detection (LoDs) are obtained to be 0.0025 mg/mL (12 µM) for LC and 0.03125 mg/mL (0.47 µM) for BSA, respectively, both of which excel over most of the reported results in previous studies. These results indicate that the proposed THz metamaterial sensor has excellent sensing performances and can well be applied to the detection of low-concentration biological samples.

Anti-Inflammatory and Immunomodulatory Effects of 0.1 Sub-Terahertz Irradiation in Collagen-Induced Arthritis Mice.

The primary emphasis of photoimmunology is the impact of nonionizing radiation on the immune system. With the development of terahertz (THz) and sub-terahertz (sub-THz) technology, the biological effects of this emerging nonionizing radiation, particularly its influence on immune function, remain insufficiently explored but are progressively attracting attention. Here, we demonstrated that 0.1 sub-THz radiation can modulate the immune system and alleviate symptoms of arthritis in collagen-induced arthritis (CIA) mice through a nonthermal manner. The application of 0.1 sub-THz irradiation led to a decrease in proinflammatory factors within the joints and serum, reducing the levels of blood immune cells and the quantity of splenic CD4+ T cells. Notably, 0.1 sub-THz irradiation restored depleted Treg cells in CIA mice and re-established the Th17/Treg equilibrium. These findings suggested that sub-THz irradiation plays a crucial role in systemic immunoregulation. Further exploration of its immune modulation mechanisms revealed the anti-inflammatory properties of 0.1 sub-THz on LPS-stimulated skin keratinocytes. Through the reduction in NF-κB signaling and NLRP3 inflammasome activation, 0.1 sub-THz irradiation effectively decreased the production of inflammatory factors and immune-active substances, including IL-1ß and PGE2, in HaCaT cells. Consequently, 0.1 sub-THz irradiation mitigated the inflammatory response and contributed to the maintenance of immune tolerance in CIA mice. This research provided significant new evidence supporting the systemic impacts of 0.1 sub-THz radiation, particularly on the immune system. It also enhanced the field of photoimmunology and offered valuable insights into the potential biomedical applications of 0.1 sub-THz radiation for treating autoimmune diseases.

Coral-Inspired Terahertz-Infrared Bi-Stealth Electronic Skin.

The development of electronic skin with dual stealth functionality is crucial for enabling devices to operate effectively in dynamic electromagnetic environments, thereby facilitating intelligent electromagnetic protection for autonomous perception. However, achieving compatibility between terahertz (THz) and infrared (IR) stealth technologies remains largely unexplored due to their inherent contradictions. Herein, inspired by natural corals, a novel coral-like multi-scale composite foam (CMSF) was proposed that ingeniously reconciles these contradictions. The design capitalizes on the conductive network and heat insulation properties of the foam skeleton, the loss effects and low infrared emission of metal particles, and the infrared transparency of magneto-optical materials. This approach leads to the realization of a THz-IR bi-stealth electronic skin concept. The CMSF exhibits a maximum reflection loss of 84.8 dB in the terahertz band, while its infrared stealth capability ensures environmental adaptability under varying temperatures. Furthermore, the electronic skin exhibits exceptional sensitivity and reliability as a wearable device for perceiving environmental changes. This advanced material, combining multispectral stealth with sensing capabilities, holds immense potential for applications ranging from camouflage technology to smart wearables.

Effect of terahertz waves on the aggregation behavior of neurotransmitters.

Understanding the dynamics of neurotransmitters is crucial for unraveling synaptic transmission mechanisms in neuroscience. In this study, we investigated the impact of terahertz (THz) waves on the aggregation of four common neurotransmitters through all-atom molecular dynamics (MD) simulations. The simulations revealed enhanced nicotine (NCT) aggregation under 11.05 and 21.44 THz, with a minimal effect at 42.55 THz. Structural analysis further indicated strengthened intermolecular interactions and weakened hydration effects under specific THz stimulation. In addition, enhanced aggregation was observed at stronger field strengths, particularly at 21.44 THz. Furthermore, similar investigations on epinephrine (EPI), 5-hydroxytryptamine (5-HT), and γ-aminobutyric acid (GABA) corroborated these findings. Notably, EPI showed increased aggregation at 19.05 THz, emphasizing the influence of vibrational modes on aggregation. However, 5-HT and GABA, with charged or hydrophilic functional groups, exhibited minimal aggregation under THz stimulation. The present study sheds some light on neurotransmitter responses to THz waves, offering implications for neuroscience and interdisciplinary applications.

Split ring multiband refractive index cancer sensor based on terahertz radiation.

A design of a multiband terahertz (THz) metamaterial biosensor for early cancer detection is proposed. The THz biosensor composed of several arc-shaped connecting parts operates at three different frequencies, and the absorptivity of the three resonant frequencies exceeds 99% in free space. In this work, we analyzed the absorption spectrum and polarization independence under different design parameters, improved the performance of the sensor by adjusting the absorption characteristics of the sensor, and gave the calculation results. Additionally, we studied the influence of the refractive index and thickness of different samples on the sensor, and theoretically calculated the sensitivity of the sensor to basal cells, breast cells, cervical cells, and their corresponding cancer cells. The result shows that the maximum sensitivity of the sensor can reach 642.5 GHz/RIU, which is much higher than the reported biosensors. Therefore, the proposed THz sensor has great potential in early detection and early warning of cancer.

Calcium Imaging Characterize the Neurobiological Effect of Terahertz Radiation in Zebrafish Larvae.

(1) Objective: To explore the neurobiological effects of terahertz (THz) radiation on zebrafish larvae using calcium (Ca2+) imaging technology. (2) Methods: Zebrafish larvae at 7 days post fertilization (dpf) were exposed to THz radiation for 10 or 20 min; the frequency was 2.52 THz and the amplitude 50 mW/cm2. The behavioral experiments, neural Ca2+ imaging, and quantitative polymerase chain reaction (qPCR) of the dopamine-related genes were conducted following the irradiation. (3) Results: Compared with the control group, the behavioral experiments demonstrated that THz radiation significantly increased the distance travelled and speed of zebrafish larvae. In addition, the maximum acceleration and motion frequency were elevated in the 20 min radiation group. The neural Ca2+ imaging results indicated a substantial increase in zebrafish neuronal activity. qPCR experiments revealed a significant upregulation of dopamine-related genes, such as drd2b, drd4a, slc6a3 and th. (4) Conclusion: THz radiation (2.52 THz, 50 mW/cm2, 20 min) upregulated dopamine-related genes and significantly enhanced neuronal excitability, and the neurobiological effect of THz radiation can be visualized using neural Ca2+ imaging in vivo.

The Microscopic Mechanisms of Nonlinear Rectification on Si-MOSFETs Terahertz Detector.

Studying the nonlinear photoresponse of different materials, including III-V semiconductors, two-dimensional materials and many others, is attracting burgeoning interest in the terahertz (THz) field. Especially, developing field-effect transistor (FET)-based THz detectors with preferred nonlinear plasma-wave mechanisms in terms of high sensitivity, compactness and low cost is a high priority for advancing performance imaging or communication systems in daily life. However, as THz detectors continue to shrink in size, the impact of the hot-electron effect on device performance is impossible to ignore, and the physical process of THz conversion remains elusive. To reveal the underlying microscopic mechanisms, we have implemented drift-diffusion/hydrodynamic models via a self-consistent finite-element solution to understand the dynamics of carriers at the channel and the device structure dependence. By considering the hot-electron effect and doping dependence in our model, the competitive behavior between the nonlinear rectification and hot electron-induced photothermoelectric effect is clearly presented, and it is found that the optimized source doping concentrations can be utilized to reduce the hot-electron effect on the devices. Our results not only provide guidance for further device optimization but can also be extended to other novel electronic systems for studying THz nonlinear rectification.

The Effects of mmW and THz Radiation on Dry Eyes: A Finite-Difference Time-Domain (FDTD) Computational Simulation Using XFdtd.

The importance of investigating the health effects of RF radiation on the cornea cannot be overstated. This study aimed to address this need by utilizing a mathematical simulation to examine the absorption of millimeter wave (mmW) and terahertz (THz) waves by the cornea, considering both normal and pathological conditions. The simulation incorporated variations in tear film thickness and hydration levels, as these factors play a crucial role in corneal health. To assess the impact of RF radiation on the cornea, the study calculated temperature rises, which indicate heating effects for both dry and normal eyes. XFdtd, a widely used commercial software based on the Finite-Difference Time Domain (FDTD) method, was employed to evaluate the radiation absorption and resulting temperature changes. The outcomes of this study demonstrated a crucial finding, i.e., that changes in the water ratio and thickness of the tear film, which are associated with an increased risk of dry eye syndrome, directly impact the absorption of mmW and THz waves by the cornea. This insight provides valuable evidence supporting the interconnection between tear film properties and the vulnerability of the cornea to RF radiation.

Terahertz Detectors Using Microelectromechanical System Resonators.

The doubly clamped microelectromechanical system (MEMS) beam resonators exhibit extremely high sensitivity to tiny changes in the resonance frequency owing to their high quality (Q-) factors, even at room temperature. Such a sensitive frequency-shift scheme is very attractive for fast and highly sensitive terahertz (THz) detection. The MEMS resonator absorbs THz radiation and induces a temperature rise, leading to a shift in its resonance frequency. This frequency shift is proportional to the amount of THz radiation absorbed by the resonator and can be detected and quantified, thereby allowing the THz radiation to be measured. In this review, we present an overview of the THz bolometer based on the doubly clamped MEMS beam resonators in the aspects of working principle, readout, detection speed, sensitivity, and attempts at improving the performance. This allows one to have a comprehensive view of such a novel THz detector.

High-power two-color plasma-based THz generation driven by a Tm-doped fiber laser.

We report on the efficient generation of broadband THz radiation based on a two-color gas-plasma scheme. Broadband THz pulses covering the whole THz spectral region, from 0.1-35 THz, are generated. This is enabled by a high-power, ultra-fast, thulium-doped, fiber chirped pulse amplification (Tm:FCPA) system and a subsequent nonlinear pulse compression stage that uses a gas-filled capillary. The driving source delivers 40 fs pulses at a central wavelength of 1.9 µm with 1.2 mJ pulse energy and 101 kHz repetition rate. Owing to the long driving wavelength and the use of a gas-jet in the THz generation focus, the highest reported conversion efficiency for high-power THz sources (>20 mW) of 0.32% has been achieved. The high efficiency and average power of 380 mW of the broadband THz radiation make this an ideal source for nonlinear, tabletop THz science.

Translocation and fate of nanospheres in pheochromocytoma cells following exposure to synchrotron-sourced terahertz radiation.

The routes by which foreign objects enter cells is well studied; however, their fate following uptake has not been explored extensively. Following exposure to synchrotron-sourced (SS) terahertz (THz) radiation, reversible membrane permeability has been demonstrated in eukaryotic cells by the uptake of nanospheres; nonetheless, cellular localization of the nanospheres remained unclear. This study utilized silica core-shell gold nanospheres (AuSi NS) of diameter 50 ± 5 nm to investigate the fate of nanospheres inside pheochromocytoma (PC 12) cells following SS THz exposure. Fluorescence microscopy was used to confirm nanosphere internalization following 10 min of SS THz exposure in the range 0.5-20 THz. Transmission electron microscopy followed by scanning transmission electron microscopy energy-dispersive spectroscopic (STEM-EDS) analysis was used to confirm the presence of AuSi NS in the cytoplasm or membrane, as single NS or in clusters (22% and 52%, respectively), with the remainder (26%) sequestered in vacuoles. Cellular uptake of NS in response to SS THz radiation could have suitable applications in a vast number of biomedical applications, regenerative medicine, vaccines, cancer therapy, gene and drug delivery.

Observation of conical emission from DC-biased filament at 10 THz.

The terahertz (THz) radiation emitted by an air-based femtosecond filament biased by a static electric field is known to have on-axis shape and relatively low frequency spectrum in contrast to the unbiased single-color and two-color schemes. Here, we measure the THz emission of a 15-kV/cm-biased filament in air produced by a 740-nm, 1.8-mJ, 90-fs pulse and demonstrate that a flat-top on-axis THz angular distribution of the emission at 0.5-1 THz transforms into a contrast ring-shaped one at 10 THz.

Generation of sub-MV/cm terahertz fields with large-size Cherenkov-type optical-to-terahertz converters.

It is known that a structure comprising a tens of microns thick, and ∼1 × 1 cm2 in size, layer of LiNbO3 attached to a Si prism can serve as an efficient Cherenkov-type converter of tens of microjoules-energy femtosecond laser pulses to broadband terahertz radiation. Here we experimentally demonstrate scaling up the terahertz energy and field strength by extending the width of the converter to several centimeters, expanding appropriately the pump laser beam, and increasing the pump pulse energy to hundreds of microjoules. In particular, chirped Ti:sapphire laser pulses of 450 fs duration and 600 µJ energy were converted to 1.2 µJ terahertz pulses, and 0.5 MV/cm peak terahertz field was obtained when pumping by unchirped laser pulses of 60 fs duration and 200 µJ energy.

Observation of Magnetic State Dependent Thermoelectricity in Superconducting Spin Valves.

Superconductor-ferromagnet tunnel junctions demonstrate giant thermoelectric effects that are being exploited to engineer ultrasensitive terahertz radiation detectors. Here, we experimentally observe the recently predicted complete magnetic control over thermoelectric effects in a superconducting spin valve, including the dependence of its sign on the magnetic state of the spin valve. The description of the experimental results is improved by the introduction of an interfacial domain wall in the spin filter layer interfacing the superconductor. Surprisingly, the application of high in-plane magnetic fields induces a double sign inversion of the thermoelectric effect, which exhibits large values even at applied fields twice the superconducting critical field.

Sensitivity of Neuroblastoma and Induced Neural Progenitor Cells to High-Intensity THz Radiation.

THz radiation induces a variety of processes in cells and has attracted the attention of researchers in recent decades. Here, data on the effects of high-intensity terahertz (THz) radiation on human directly reprogrammed neural progenitor cells (drNPCs) and on neuroblastoma cells (SK-N-BE (2)) were obtained for the first time. The results demonstrated that the exposure of non-tumor and tumor cells to broadband (0.1-3 THz) THz pulses with the intensity of 21 GW/cm2 and the electric field strength of 2.8 MV/cm for 30 min induced neither a noticeable genotoxic effect nor a statistically significant change in the proliferative activity and cell differentiation. It was also shown that the combined effect of THz radiation and salinomycin, a promising antitumor agent, on neuroblastoma cells did not enhance the genotoxic effect of this antibiotic. However, further studies involving chemotherapy drugs and other exposure parameters are warranted to introduce this new concept into anti-tumor clinical practice and to enhance the efficacy of the existing approaches.

Epigenetic modification of gene expression in cancer cells by terahertz demethylation.

Terahertz (THz) radiation can affect the degree of DNA methylation, the spectral characteristics of which exist in the terahertz region. DNA methylation is an epigenetic modification in which a methyl (CH3) group is attached to cytosine, a nucleobase in human DNA. Appropriately controlled DNA methylation leads to proper regulation of gene expression. However, abnormal gene expression that departs from controlled genetic transcription through aberrant DNA methylation may occur in cancer or other diseases. In this study, we demonstrate the modification of gene expression in cells by THz demethylation using resonant THz radiation. Using an enzyme-linked immunosorbent assay, we observed changes in the degree of global DNA methylation in the SK-MEL-3 melanoma cell line under irradiation with 1.6-THz radiation with limited spectral bandwidth. Resonant THz radiation demethylated living melanoma cells by 19%, with no significant occurrence of apurinic/apyrimidinic sites, and the demethylation ratio was linearly proportional to the power of THz radiation. THz demethylation downregulates FOS, JUN, and CXCL8 genes, which are involved in cancer and apoptosis pathways. Our results show that THz demethylation has the potential to be a gene expression modifier with promising applications in cancer treatment.

Effects of Terahertz Radiation on the Aggregation of Alzheimer's Aß42 Peptide.

The pathophysiology of Alzheimer's disease is thought to be directly linked to the abnormal aggregation of ß-amyloid (Aß) in the nervous system as a common neurodegenerative disease. Consequently, researchers in many areas are actively looking for factors that affect Aß aggregation. Numerous investigations have demonstrated that, in addition to chemical induction of Aß aggregation, electromagnetic radiation may also affect Aß aggregation. Terahertz waves are an emerging form of non-ionizing radiation that has the potential to affect the secondary bonding networks of biological systems, which in turn could affect the course of biochemical reactions by altering the conformation of biological macromolecules. As the primary radiation target in this investigation, the in vitro modeled Aß42 aggregation system was examined using fluorescence spectrophotometry, supplemented by cellular simulations and transmission electron microscopy, to see how it responded to 3.1 THz radiation in various aggregation phases. The results demonstrated that in the nucleation aggregation stage, 3.1 THz electromagnetic waves promote Aß42 monomer aggregation and that this promoting effect gradually diminishes with the exacerbation of the degree of aggregation. However, by the stage of oligomer aggregation into the original fiber, 3.1 THz electromagnetic waves exhibited an inhibitory effect. This leads us to the conclusion that terahertz radiation has an impact on the stability of the Aß42 secondary structure, which in turn affects how Aß42 molecules are recognized during the aggregation process and causes a seemingly aberrant biochemical response. Molecular dynamics simulation was employed to support the theory based on the aforementioned experimental observations and inferences.

Enhanced in-situ liquid transport investigation setup for pharmaceutical tablet disintegration analysis using terahertz radiation.

The disintegration process of pharmaceutical solid dosage forms commences on contact with the dissolution medium and continues with subsequent spontaneous imbibition of the medium in the tablet matrix. Identifying the location of the liquid front in situ during imbibition, therefore, plays a significant role in understanding and modelling the disintegration process. Terahertz pulsed imaging (TPI) technology can be used to investigate this process by its ability to penetrate and identify the liquid front in pharmaceutical tablets. However, previous studies were limited to samples suitable for a flow cell environment, i.e. flat cylindrical disk shapes; thus, most commercial tablets could only be measured with prior destructive sample preparation. This study presents a new experimental setup named open immersion to measure a wide range of pharmaceutical tablets in their intact form. Besides, a series of data processing techniques to extract subtle features of the advancing liquid front are designed and utilised, effectively increasing the maximum thickness of tablets that can be analysed. We used the new method and successfully measured the liquid ingress profiles for a set of oval convex tablets prepared from a complex eroding immediate-release formulation.

Biological responses to terahertz radiation with different power density in primary hippocampal neurons.

Terahertz (THz) radiation is a valuable imaging and sensing tool which is widely used in industry and medicine. However, it biological effects including genotoxicity and cytotoxicity are lacking of research, particularly on the nervous system. In this study, we investigated how terahertz radiation with 10mW (0.12 THz) and 50 mW (0.157 THz) would affect the morphology, cell growth and function of rat hippocampal neurons in vitro.