Friday, January 17, 2020

Abstract-Terahertz-Based Porosity Measurement of Pharmaceutical Tablets: a Tutorial

  • Prince Bawuah, 
  • Daniel Markl, 
  • Daniel Farrell, 
  • Mike Evans, 
  • Alessia Portieri, 
  • Andrew Anderson, 
  • Daniel Goodwin, 
  • Ralph Lucas, 
  • J. Axel Zeitler,

Porosity, one of the important quality attributes of pharmaceutical tablets, directly affects the mechanical properties, the mass transport and hence tablet disintegration, dissolution and ultimately the bioavailability of an orally administered drug. The ability to accurately and quickly monitor the porosity of tablets during manufacture or during the manufacturing process will enable a greater assurance of product quality. This tutorial systematically outlines the steps involved in the terahertz-based measurement method that can be used to quantify the porosity of a tablet within seconds in a non-destructive and non-invasive manner. The terahertz-based porosity measurement can be performed using one of the three main methods, which are (i) the zero-porosity approximation (ZPA); (ii) the traditional Bruggeman effective medium approximation (TB-EMA); and (iii) the anisotropic Bruggeman effective medium approximation (AB-EMA). By using a set of batches of flat-faced and biconvex tablets as a case study, the three main methods are compared and contrasted. Overall, frequency-domain signal processing coupled with the AB-EMA method was found to be most suitable approach in terms of accuracy and robustness when predicting the porosity of tablets over a range of complexities and geometries. This tutorial aims to concisely outline all the necessary steps, precautions and unique advantages associated with the terahertz-based porosity measurement method.

Presentation and Abstract-Wireless Systems for Joint Communication and Sensing in Terahertz Spectrum

Yasaman Ghasempour
Ph.D. Candidate
Rice University
Event Date:January 22, 2020
Time:10:30 am
Location:MSEE 239
School or Program:Electrical and Computer Engineering
On one side, millimeter-wave and terahertz bands are emerging as the most promising solution to meet the data-rate and latency demands of future wireless applications, including virtual reality and autonomous cars. On the other side, the large spectral availability, together with the mm-scale wavelength, opens the opportunity of ubiquitous and high-resolution sensing. My research builds a foundation for joint communication and sensing in such high-frequency regimes yielding a paradigm shift in the design and development of future wireless systems.
In this talk, I will present the world’s first single-shot and single-antenna motion-sensing system in THz bands. We demonstrate a novel node architecture exploiting a single leaky-wave antenna, which is primarily used for beam steering in THz networks. I will explain how we leverage this device’s spatial-spectral characteristics in new ways to enable motion sensing functionalities with a single THz pulse transmission. I will then discuss the opportunities offered by this platform to enhance next-generation communication in unprecedented ways. In particular, we tackle the mobility, blockage, and scalability challenges of highly directional THz networks by efficiently adapting steering direction.
Finally, I will share with you some of the exciting research directions I would like to pursue in the future. I am broadly interested in exploring novel fundamental concepts and new devices that enable sensing functionality jointly with networking in a broad scope of applications. This interdisciplinary research direction incorporators advancements such as applied physics, machine learning, robotics, and wireless networking.
Yasaman Ghasempour is currently a Ph.D. Candidate in Electrical and Computer Engineering at Rice University. She received her Master’s degree in Electrical and Computer Engineering from Rice University and her Bachelor’s degree in Electrical Engineering from Sharif University of Technology in Iran. Her research interests include wireless communication and sensing, with a focus on emerging millimeter-wave and terahertz spectrum. She has published in top-tier IEEE and ACM conferences and journals and has been named an EECS rising star in 2019. She is also the recipient of Texas Instruments Distinguished Fellowship among multiple IEEE/ACM societies awards.
Prof. Sanjay Rao,

Thursday, January 16, 2020

Abstract-Experimental system for studying bioeffects of intense terahertz pulses with electric field strength up to 3.5 MV/cm

Dmitry S. Sitnikov;  Inna V. Ilina;  Alexander A. Pronkin

 Terahertz (THz) waves can influence a diverse range of cellular processes. The use of high-power THz sources in biological studies may lead to major advances in understanding biological systems and help to determine safe exposure levels for existing THz technologies. We are devoted to the development of an experimental system for irradiating cells with intense broadband THz pulses. Subpicosecond pulses of THz radiation with intensities of 32  GW  /  cm2 and electric field strength up to 3.5 MV/cm are obtained by optical rectification, using an OH1 organic crystal, of near-infrared femtosecond pulses generated by a Cr:forsterite laser. The system has been developed to allow cells to be kept in suitable conditions for long-term exposure and to be irradiated with THz pulses in single-point mode as well as in scanning mode. The transmission in the THz region of various plastic dishes for cell culture is estimated.
   © 2020 Society of Photo-Optical Instrumentation Engineers (SPIE) 

Abstract-An overview of semiconductor rectifier operating in the millimeter wave and terahertz region

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M. B. Mohd MokharShahrir R. Kasjoo,  N. J. Juhari N. F. Zakaria

An imaging system operated at millimeter (MM) waves and terahertz (THz) frequencies can be used in many applications such as safety monitoring, public security, medical, healthcare and manufacturing. Typically, these systems utilize rectifying antenna (rectenna) to convert electromagnetic radiation into usable DC power which will be used to generate images. One of the main components of rectenna is the rectifier. Hence, this paper explores the current review on several semiconductor rectifiers that have been significantly deployed for MM-wave/THz imaging systems. This includes Schottky diodes, metal-insulator-metal (MIM) diodes, self-switching diodes (SSDs) and ballistic rectifiers (BRs). The rectifying performance of these devices are discussed in terms of their voltage responsivity and noise-equivalent power (NEP). The standard fabrication process of each device is also presented in this paper as well as their recent development and achievement as high-frequency rectifiers for MM-wave/THz imaging systems.

Wednesday, January 15, 2020

Abstract-Application of a Terahertz System Combined with an X-Shaped Metamaterial Microfluidic Cartridge

Terahertz (THz) radiation has attracted wide attention for its ability to sense molecular structure and chemical matter because of a label-free molecular fingerprint and nondestructive properties. When it comes to molecular recognition with terahertz radiation, our attention goes first towards the absorption spectrum, which is beyond the far infrared region. To enhance the sensitivity for similar species, however, it is necessary to apply an artificially designed metamaterial sensor for detection, which confines an electromagnetic field in an extremely sub-wavelength space and hence receives an electromagnetic response through resonance. Once the resonance is caused through the interaction between the THz radiation and the metamaterial, a minute variation might be observed in the frequency domain. For a geometric structure of a metamaterial, a novel design called an X-shaped plasmonic sensor (XPS) can create a quadrupole resonance and lead to sensitivity greater than in the dipole mode. A microfluidic system is able to consume reagents in small volumes for detection, to diminish noise from the environment, and to concentrate the sample into detection spots. A microfluidic device integrated with an X-shaped plasmonic sensor might thus achieve an effective and highly sensitive detection cartridge. Our tests involved not only measurements of liquid samples, but also the performance of a dry bio-sample coated on an XPS.

Abstract-Dual-controlled switchable broadband terahertz absorber based on a graphene-vanadium dioxide metamaterial

Tongling Wang, Yuping Zhang, Huiyun Zhang, and Maoyong Cao

Schematic of graphene- and VO2-based metamaterial broadband absorber geometry. P = 15 µm, Lin= 3.8 µm, Lout= 6.8 µm, win = 0.5 µm, wout = 2 µm, d = 28 µm, and h = 0.7 µm.

We propose a dual-controlled switchable broadband terahertz (THz) metamaterial absorber based on a hybrid of vanadium dioxide (VO2) and graphene that demonstrates strong polarization-independent characteristics and works well at a wide range of incidence angles. The peak absorptance of the proposed absorber can be tuned from 26 to 99.2% by changing the Fermi energy of the graphene; the absorptance can be dynamically tuned from 9 to 99.2% by adjusting the conductivity of the vanadium dioxide because of its unique insulator-to-metal transition characteristic. Using these two independent controls in tandem, we found that the state of the proposed absorber can be switched from absorption (>96%) to reflection (>73.5%), and the transmittance can be tuned from 0% to 65% while maintaining broad bandwidth (1.05-1.6 THz), resulting in a better-performing switchable broadband terahertz absorber. Furthermore, we have provided a discussion of the interference theory in which the physical mechanism of the absorption is explained from an optical point of view. The absorber achieves dual-controlled absorptance switching via two independently controllable pathways, offering a new method for switching and modulation of broadband THz radiation.
© 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement