Abstract-The terahertz metamaterials for sensitive biosensors in the detection of ethanol solutions

Author links open overlay panelFuyu Li, Ke He, Tingting Tang, Yinghui Mao, Rui Wang, Chaoyang Li, Jian Shen,

                                               

https://www.sciencedirect.com/science/article/abs/pii/S0030401820307045 

Metamaterials have attracted much attention due to their subwavelength characteristics, especially in the field of unlabeled refractive index sensing. Because biomolecular molecules have special biological fingerprint spectra in terahertz band, high sensitivity sensor components can be realized by using the special electromagnetic response of metamaterials. In this paper, a novel biosensor based on electromagnetic induced reflection is designed. We find that the asymmetrically fractured double-ring resonator can effectively enhance the fano-resonance of electromagnetic induction reflection, where the resonance position occurs at 1.57 THz. Oscillating Lorentz model shows that when the resonant detuning continues to increase, the bright mode and the dark mode are strongly coupled. When the light mode decreases, the radiation loss also decreases, which induces the decrease of resonance ability. The sensitivity of pure ethanol solution (analyte) under  coating thickness is 103.7 GHz/RIU, 107.1 GHz/RIU and 112.05 GHz/RIU, respectively. The sensitivity and full width at half maximum (FWHM) of the sensor are studied from the perspectives of analyte concentration, thickness, and proportion, respectively. The results show the great potential of electromagnetic metamaterials as sensitive sensors in biological solution detection.

Squeezing light at the nanoscale

https://www.nanowerk.com/nanotechnology-news/newsid=50446.ph

Nanowerk News) Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a new technique to squeeze infrared light into ultra-confined spaces, generating an intense, nanoscale antenna that could be used to detect single biomolecules.

The researchers harnessed the power of polaritons, particles that blur the distinction between light and matter. This ultra-confined light can be used to detect very small amounts of matter close to the polaritons. For example, many hazardous substances, such as formaldehyde, have an infrared signature that can be magnified by these antennas. The shape and size of the polaritons can also be tuned, paving the way to smart infrared detectors and biosensors.

The research is published in Science Advances ("Ultra-confined mid-infrared resonant phonon polaritons in van der Waals nanostructures").

Nano-discs act as micro-resonators, trapping infrared photons and generating polaritons. When illuminated with infrared light, the discs concentrate light in a volume thousands of times smaller than is possible with standard optical materials. At such high concentrations, the polaritons oscillate like water sloshing in a glass, changing their oscillation depending on the frequency of the incident light. (Image: Harvard SEAS)

"This work opens up a new frontier in nanophotonics," said Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, and senior author of the study. "By coupling light to atomic vibrations, we have concentrated light into nanodevices much smaller than its wavelength, giving us a new tool to detect and manipulate molecules."

Polaritons are hybrid quantum mechanical particles, made up of a photon strongly coupled to vibrating atoms in a two-dimensional crystal.

"Our goal was to harness this strong interaction between light and matter and engineer polaritons to focus light in very small spaces," said Michele Tamagnone, postdoctoral fellow in Applied Physics at SEAS and co-first author of the paper.

The researchers built nano-discs -- the smallest about 50 nanometers high and 200 nanometers wide -- made of two-dimensional boron nitride crystals. These materials act as micro-resonators, trapping infrared photons and generating polaritons. When illuminated with infrared light, the discs were able to concentrate light in a volume thousands of times smaller than is possible with standard optical materials, such as glass.

At such high concentrations, the researchers noticed something curious about the behavior of the polaritons: they oscillated like water sloshing in a glass, changing their oscillation depending on the frequency of the incident light.

"If you tip a cup back-and-forth, the water in the glass oscillates in one direction. If you swirl your cup, the water inside the glass oscillates in another direction. The polaritons oscillate in a similar way, as if the nano-discs are to light what a cup is to water," said Tamagnone.

Unlike traditional optical materials, these boron nitride crystals are not limited in size by the wavelength of light, meaning there is no limit to how small the cup can be. These materials also have tiny optical losses, meaning that light confined to the disc can oscillate for a long time before it settles, making the light inside even more intense.

The researchers further concentrated light by placing two discs with matching oscillations next to each other, trapping light in the 50-nanometer gap between them and creating an infrared antenna. As light concentrates in smaller and smaller volumes, its intensity increases, creating optical fields so strong they can exert measurable force on nearby particles.

"These light-induced forces serve also as one our detection mechanisms," said Antonio Ambrosio, a principal scientist at Harvard's Center for Nanoscale Systems. "We observed this ultra-confined light by the motion it induces on an atomically sharp tip connected to a cantilever."

A future challenge for the Harvard team is to optimize these light nano-concentrators to achieve intensities high enough to enhance the interaction with a single molecule to detectable values.

Source: By Leah Burrows, Harvard John A. Paulson School of Engineering and Applied Sciences

Abstract-Sensitive detection of cancer cell apoptosis based on the non-bianisotropic metamaterials biosensors in terahertz frequency

Zhang Zhang, Hongwei Ding, Xin Yan, Lanju Liang, Dequan Wei, Meng Wang, Qili Yang, and Jianquan Yao

https://www.osapublishing.org/ome/abstract.cfm?uri=ome-8-3-659&origin=search

The apoptosis of cancer cells was experimentally measured by terahertz (THz) biosensors based on the metamaterials (MMs). The non-bianisotropic resonance with an electric field of up to 106 V/m was exhibited at 0.85 THz, where the magnetic dipoles were cancelled in the unit cell. The simulate results show the dependence of the frequency shift on the occupying ratio and refractive index of analytes. The theoretical sensitivity was calculated to 182 GHz/RIU. The experimental results imply that the resonant frequency would red shift with the increase of the concentration of cancer cells. Furthermore, the apoptosis of cancer cells HSC3 under the effect of drug concentration from 1 to 15 μM and drug action time from 24 to 72 hours were also studied by the biosensors, respectively. It shows that the trend agrees with the results measured by the biological CCK-8 kits method. Our proposed MMs-based biosensors may supply a novel viewpoint on cell apoptosis from a physical perspective and be a valuable complementary reference for biological study.

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

Abstract-Ultrasensitive Terahertz Biosensors Based on Fano Resonance of a Graphene/Waveguide Hybrid Structure

Banxian Ruan, Jun Guo, Leiming Wu, Jiaqi Zhu, Qi You, Xiaoyu Dai, Yuanjiang Xiang,

http://www.mdpi.com/1424-8220/17/8/1924

Graphene terahertz (THz) surface plasmons provide hope for developing functional devices in the THz frequency. By coupling graphene surface plasmon polaritons (SPPs) and a planar waveguide (PWG) mode, Fano resonances are demonstrated to realize an ultrasensitive terahertz biosensor. By analyzing the dispersion relation of graphene SPPs and PWG, the tunable Fano resonances in the terahertz frequency are discussed. It is found that the asymmetric lineshape of Fano resonances can be manipulated by changing the Fermi level of graphene, and the influence of the thickness of coupling layer and air layer in sandwich structure on the Fano resonances is also discussed in detail. We then apply the proposed Fano resonance to realize the ultrasensitive terahertz biosensors, it is shown that the highest sensitivities of 3260 RIU−1 are realized. Our result is two orders of a conventional surface plasmon resonance sensor. Furthermore, we find that when sensing medium is in the vicinity of water in THz, the sensitivity increases with increasing refractive index of the sensing medium.

CENT of SCEM receives prestigious DST funding for project

Jaideep Shenoy 

http://timesofindia.indiatimes.com/city/mangaluru/CENT-of-SCEM-receives-prestigious-DST-funding-for-project/articleshow/51808371.cms

MANGALURU: Center of Excellence in Nano-science and Technology (CENT) of Sahyadri College of Engineering and Management (SCEM) has received prestigious department of science and technology (DST) - Science and Engineering Research Board - Extra Mural Research (DST-SERB-EMR) project fund of Rs 55.89 lakh for project design, fabrication and characterization of whispering gallery mode resonators in planar waveguides for detection of bio-molecules using terahertz (THz) radiation.

DST-SERB-EMR released Rs 37.5 lakh to setup THz based bio-molecular detection laboratory at CENT-SCEM. This project was submitted under guidance of Richard Pinto, director, CENT. This is a collaborative project between CENT-SCEM, TIFR-FOTON Group and EE department of IITB. Project aims to develop integrated low loss THz waveguides and WGM resonators with high Q factors suitable for detector applications in area of biosensors/biophotonics.

THz based sensors are among latest developments in single molecular detection in the area of bio-medical engineering and detection of explosives. Among the many possible applications of these sensors include early detection of cancer (molecular level). Eminent scientists Shriganesh Prabhu and Achanta Venu Gopal of TIFR FOTON group are involved in this project. They are the leading experts in the field of plasmonics, a press communique from SCEM here stated.

The Fundamental Optics, Terahertz and Optical Nanostructures (FOTON) group at department of condensed matter physics and material science, TIFR has made significant contributions in the terahertz domain during last decade. Siddhartha Duttgupta, EE department, IITB is another collaborator of this project. He has expertise in tools for processing, characterization and computation as part of the IIT Bombay Nano Fabrication Facility (IITB-NF).