Abstract-Evaluation of transdermal drug delivery using terahertz pulsed imaging

Jiarui Wang, Hannah Lindley-Hatcher, Kai Liu, and Emma Pickwell-MacPherson

https://www.osapublishing.org/boe/abstract.cfm?uri=boe-11-8-4484

Transdermal drug delivery (TDD) is widely used for painless dosing due to its minimally invasive nature compared to hypodermic needle injection and its avoidance of the gastrointestinal tract. However, the stratum corneum obstructs the permeation of drugs into skin. Microneedle and nanoneedle patches are ways to enhance this permeation. In this work, terahertz (THz) imaging is utilized to compare the efficacy of different TDD methods including topical application and via a needle patch. Our work shows the feasibility and potential of using THz imaging to quantify and evaluate different transdermal application methods.

Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.

Abstract-A flexible, multifunctional, active terahertz modulator with an ultra-low triggering threshold

He Ma,   Yu Wang,   Rong Lu,   Fangrui Tan,  Yulan Fu,  Guang Wang,  Dayong Wang,  Kai Liu,   Shoushan Fan,  Kaili Jiang  Xinping Zhang 

https://pubs.rsc.org/en/content/articlelanding/2020/tc/d0tc02446e#!divAbstract

Active terahertz (THz) modulators play an essential role in THz technology. Because of the excellent THz modulation properties bestowed by its intrinsic metal-insulator transition (MIT) at 68 °C, vanadium dioxide (VO2) is an appealing active THz modulator material. Current active THz modulator designs based on pure VO2 films or metasurfaces deposited on traditional semiconductor substrates are typically subject to high triggering thresholds and slow responses. Therefore, further development of VO2 active THz modulators for superior performance requires new material and device designs. In this paper, we develop a flexible active THz modulator based on an aligned carbon nanotube thin film coated with VO2. THz wave modulation driven by the MIT of VO2 presents a giant modulation depth up to 91% and broad bandwidth (>2.3 THz). Various stimuli can be utilized to trigger the THz modulator. The response time of the THz modulator is 27 ms, which can be further shortened by decreasing the device size. In addition, the light-triggering threshold is quite low (0.58 mW/mm2). Optical anisotropy enables polarization of the THz modulator. Since they combine superior modulation performance, responsive stimuli diversity, versatility, and flexibility, these active THz modulators find applications in THz communication, THz imaging, etc.

Abstract-Highly Efficient Active All-Dielectric Metasurfaces Based on Hybrid Structures Integrated with Phase-Change Materials: From Terahertz to Optical Ranges

Chuwen Lan, He Ma, Manting Wang, Zehua Gao, Kai Liu, Ke Bi, Ji Zhou and Xiangjun Xin

https://pubs.acs.org/doi/abs/10.1021/acsami.8b22466?mi=aayia761&af=R&AllField=nano&target=default&targetTab=std

Recently, all-dielectric metasurfaces (AMs) have emerged as a promising platform for high-efficiency devices ranging from the terahertz to optical ranges. However, active and fast tuning of their properties, such as amplitude, phase and operating frequency, remains challenging. Here, a generic method is proposed for obtaining high-efficiency active AMs from the terahertz to optical ranges by using “hybrid structures” integrated with phase-change materials. Various phase-change mechanisms including metal–insulator phase change, nonvolatile phase change, and ferroelectric phase change are investigated. We first experimentally demonstrate several high-efficiency active AMs operating in the terahertz range based on hybrid structures composed of free standing silicon microstructures covered with ultrathin phase-change nanofilms (thickness d << λ). We show that both the frequencies and the strength of the Mie resonances can be efficiently tuned, resulting in unprecedented modulation depth. Furthermore, detailed analyses of available phase-change materials and their properties are provided to offer more options for active AMs. Finally, several feasible hybrid structures for active AMs in the optical range are proposed and confirmed numerically. The broad platform built in this work for active manipulation of waves from the terahertz to optical ranges may have numerous potential applications in optical devices including switches, modulators and sensors.

Abstract-Composite multiscale entropy analysis of reflective terahertz signals for biological tissues

Rui Zhang, Yuezhi He, Kai Liu, Liangliang Zhang, Shijing Zhang, Emma Pickwell-MacPherson, Yuejin Zhao, and Cunlin Zhang

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-25-20-23669

We demonstrate a composite multiscale entropy (CMSE) method of terahertz (THz) signal complexity analysis to distinguish different biological tissues. The THz signals reflected from fresh porcine skin and muscle tissues were measured and analyzed. The statistically significant difference and separation of the two tissues based on several parameters were analyzed and compared for THz spectroscopy and imaging, which verified the better performance of the CMSE method and further enhancement of the contrast among THz signals that interact with different tissues. This process provides a better analysis and discrimination method for THz spectroscopy and imaging in biomedical applications.

© 2017 Optical Society of America

Engineers Are Catching Rainbows: Material That Slows Light Opens New Possibilities in Solar Energy, Other Fields

An up-close look at the “hyperbolic metamaterial waveguide,” which catches and ultimately absorbs wavelengths (or color) in a vertical direction. (Credit: Image courtesy of University at Buffalo)
http://www.sciencedaily.com/releases/2013/02/130217085259.htm
Feb. 15, 2013 — University at Buffalo engineers have created a more efficient way to catch rainbows, an advancement in photonics that could lead to technological breakthroughs in solar energy, stealth technology and other areas of research.

Qiaoqiang Gan, PhD, an assistant professor of electrical engineering at UB, and a team of graduate students described their work in a paper called "Rainbow Trapping in Hyperbolic Metamaterial Waveguide," published Feb. 13 in the online journal Scientific Reports.
They developed a "hyperbolic metamaterial waveguide," which is essentially an advanced microchip made of alternate ultra-thin films of metal and semiconductors and/or insulators. The waveguide halts and ultimately absorbs each frequency of light, at slightly different places in a vertical direction, to catch a "rainbow" of wavelengths.
Gan is a researcher within UB's new Center of Excellence in Materials Informatics.
"Electromagnetic absorbers have been studied for many years, especially for military radar systems," Gan said. "Right now, researchers are developing compact light absorbers based on optically thick semiconductors or carbon nanotubes. However, it is still challenging to realize the perfect absorber in ultra-thin films with tunable absorption band.
"We are developing ultra-thin films that will slow the light and therefore allow much more efficient absorption, which will address the long existing challenge."
Light is made of photons that, because they move extremely fast (i.e., at the speed of light), are difficult to tame. In their initial attempts to slow light, researchers relied upon cryogenic gases. But because cryogenic gases are very cold -- roughly 240 degrees below zero Fahrenheit -- they are difficult to work with outside a laboratory.
Before joining UB, Gan helped pioneer a way to slow light without cryogenic gases. He and other researchers at Lehigh University made nano-scale-sized grooves in metallic surfaces at different depths, a process that altered the optical properties of the metal. While the grooves worked, they had limitations. For example, the energy of the incident light cannot be transferred onto the metal surface efficiently, which hampered its use for practical applications, Gan said.
The hyperbolic metamaterial waveguide solves that problem because it is a large area of patterned film that can collect the incident light efficiently. It is referred to as an artificial medium with subwavelength features whose frequency surface is hyperboloid, which allows it to capture a wide range of wavelengths in different frequencies including visible, near-infrared, mid-infrared, terahertz and microwaves.
It could lead to advancements in an array of fields.
For example, in electronics there is a phenomenon known as crosstalk, in which a signal transmitted on one circuit or channel creates an undesired effect in another circuit or channel. The on-chip absorber could potentially prevent this.
The on-chip absorber may also be applied to solar panels and other energy-harvesting devices. It could be especially useful in mid-infrared spectral regions as thermal absorber for devices that recycle heat after sundown, Gan said.
Technology such as the Stealth bomber involves materials that make planes, ships and other devices invisible to radar, infrared, sonar and other detection methods. Because the on-chip absorber has the potential to absorb different wavelengths at a multitude of frequencies, it could be useful as a stealth coating material.
Additional authors of the paper include Haifeng Hu, Dengxin Ji, Xie Zeng and Kai Liu, all PhD candidates in UB's Department of Electrical Engineering. The work was sponsored by the National Science Foundation and UB's electrical engineering department.