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1. An optofluidic metasurface for lateral flow-through detection of cancer biomarker (Conference Presentation)

   https://doi.org/10.1117/12.2288438  

   Wang, Yifei ; Ali, Md Azahar ; Dong, Liang ; Lu, Meng ( March 2018 , Proc. SPIE 10491, Microfluidics, BioMEMS, and Medical Microsystems XVI, 1049113 (15 March 2018))

   The rapid growth of point-of-care tests demands for biomolecule sensors with higher sensitivity and smaller size. We developed an optofluidic metasurface that combined silicon photonics and nanofluidics to achieve a lateral flow-through biosensor to fulfill the needs. The metasurface consists of a 2D array of silicon nanoposts fabricated on a silicon-on-insulator substrate. The device takes advantage of the high-Q resonant modes associated with the optical bound state and the nanofluidic delivery of analyte to overcome the problem of diffusion-limited detection that occurs in almost all conventional biosensors and offer a high refractive index sensitivity. We used rigorous coupled wave analysismore »and finite element analysis to design and optimize the device. We will present its photonic band diagram to identify the optical bound state and high-Q resonance modes near 1550 nm. The device was fabricated using e-beam lithography followed by a lift-off and reactive ion etching process. Reflectance of the sensor was measured using a tunable laser and a photodetector. The preliminary result shows a refractive index sensitivity of 720 nm/RIU. Furthermore, we implemented the optical metasurface as a lateral flow-through biosensor by covering the nanoposts using a PDMS cover. The nanofluidic channels are formed between the nanoposts for the flow of samples. The lateral flow-through sensor was used to detect the epidermal growth factor receptor (ErbB2), a widely used protein biomarker for breast cancer screening. The results show that the device can quantitatively measure the binding of ErBb2 antibody and ErBb2 by the continuous monitoring of the resonant wavelength shift.« less
2. Fabrication of Localized Silicon-on-Insulator Based Rhombus-Shaped Channels in Silicon

   Ogini, Martins ; Voyantzis, Mitchell ; Koech, Philemon ; Francis, Aneeta ; Mohan, Susmitha ; Deo, Makarand ; Albin, Sacharia. ( May 2019 , ECS Meeting Abstracts)

   Fabricating localized silicon-on-insulator (LSOI) on bulk silicon eliminates the need for using expensive SOI wafers for silicon waveguides and MEMS applications. One of the most important building blocks in silicon photonics is optical waveguide, which usually consists of silicon surrounded by silicon dioxide with refractive indices of 3.5 and 1.5, respectively. It was observed that the SOI wafer puts restrictions on the integration of electronics and photonics because the buried oxide is too thin for field confinement. Hence, fabrication of LSOI in standard silicon wafers is considered to have precise control of the oxide thickness which will lead to effectivemore »integration of electronic and photonic devices. We used rhombus-shaped channel method in the fabrication of LSOI structure that can be produced on any part of a bulk silicon wafer.« less
3. Label-free detection of DNA hybridization with a compact LSPR-based fiber-optic sensor

   https://doi.org/10.1039/C7AN00249A  

   Kaye, Savannah ; Zeng, Zheng ; Sanders, Mollye ; Chittur, Krishnan ; Koelle, Paula M. ; Lindquist, Robert ; Manne, Upender ; Lin, Yongbin ; Wei, Jianjun ( January 2017 , The Analyst)

   A miniaturized, robust, localized surface plasmon resonance (LSPR)-coupled fiber-optic (FO) nanoprobe providing an integrated and portable solution for detection of DNA hybridization and measurement of DNA concentrations has been demonstrated. The FO nanoprobe was created by constructing arrays of metallic nanostructures on the end facets of optical fibers utilizing nanofabrication technologies, including electron beam lithography and lift-off processes. The LSPR-FO nanoprobe device offers real-time, label-free, and low-sample-volume quantification of single-strand DNA in water with high sensitivity and selectivity, achieving a limit of detection around 10 fM. These results demonstrate the feasibility of the LSPR-FO nanoprobe device as a compact andmore »low-cost biosensor for detection of short-strand DNA.« less
4. Low-loss composite photonic platform based on 2D semiconductor monolayers

   Ipshita Datta, Sang Hoon ( January 2020 , Nature photographer)

   Two dimensional (2D) materials such as graphene and transition metal dichalcogenides (TMDs) are promising for optical modulation, detection, and light emission since their material properties can be tuned on-demand via electrostatic doping1–21. The optical properties of TMDs have been shown to change drastically with doping in the wavelength range near the excitonic resonances22–26. However, little is known about the effect of doping on the optical properties of TMDs away from these resonances, where the material is transparent and therefore could be leveraged in photonic circuits. Here, we probe the electro-optic response of monolayer TMDs at near infrared (NIR) wavelengths (i.e.more »deep in the transparency regime), by integrating them on silicon nitride (SiN) photonic structures to induce strong light -matter interaction with the monolayer. We dope the monolayer to carrier densities of (7.2 ± 0.8) × 1013 cm-2, by electrically gating the TMD using an ionic liquid [P14+] [FAP-]. We show strong electro-refractive response in monolayer tungsten disulphide (WS2) at NIR wavelengths by measuring a large change in the real part of refractive index ∆n = 0.53, with only a minimal change in the imaginary part ∆k = 0.004. We demonstrate photonic devices based on electrostatically gated SiN-WS2 phase modulator with high efficiency ( ) of 0.8 V · cm. We show that the induced phase change relative to the change in absorption (i.e. ∆n/∆k) is approximately 125, that is significantly higher than the ones achieved in 2D materials at different spectral ranges and in bulk materials, commonly employed for silicon photonic modulators such as Si and III-V on Si, while accompanied by negligible insertion loss. Efficient phase modulators are critical for enabling large-scale photonic systems for applications such as Light Detection and Ranging (LIDAR), phased arrays, optical switching, coherent optical communication and quantum and optical neural networks27–30.« less
5. An integrated microfluidic platform for selective and real-time detection of thrombin biomarkers using a graphene FET

   https://doi.org/10.1039/D0AN00251H  

   Khan, Niazul I. ; Mousazadehkasin, Mohammad ; Ghosh, Sujoy ; Tsavalas, John G. ; Song, Edward ( June 2020 , The Analyst)

   Lab-on-a-chip technology offers an ideal platform for low-cost, reliable, and easy-to-use diagnostics of key biomarkers needed for early screening of diseases and other health concerns. In this work, a graphene field-effect transistor (GFET) functionalized with target-binding aptamers is used as a biosensor for the detection of thrombin protein biomarker. Furthermore, this GFET is integrated with a microfluidic device for enhanced sensing performances in terms of detection limit, sensitivity, and continuous monitoring. Under this platform, a picomolar limit of detection was achieved for measuring thrombin; in our experiment measured as low as 2.6 pM. FTIR, Raman and UV-Vis spectroscopy measurements weremore »performed to confirm the device functionalization steps. Based on the concentration-dependent calibration curve, a dissociation constant of K D = 375.8 pM was obtained. Continuous real-time measurements were also conducted under a constant gate voltage ( V GS ) to observe the transient response of the sensor when analyte was introduced to the device. The target selectivity of the sensor platform was evaluated and confirmed by challenging the GFET biosensor with various concentrations of lysozyme protein. The results suggest that this device technology has the potential to be used as a general diagnostic platform for measuring clinically relevant biomarkers for point-of-care applications.« less