Field-portable optofluidic plasmonic biosensor for wide-field and label-free monitoring of molecular interactions

We demonstrate a field-portable optofluidic plasmonic sensing device, weighing 40 g and 7.5 cm in height, which merges plasmonic microarrays with dual-wavelength lensfree on-chip imaging for real-time monitoring of protein binding kinetics

Lensfree optofluidic plasmonic sensor for real-time and label-free monitoring of molecular binding events over a wide field-of-view

We demonstrate a high-throughput biosensing device that utilizes microfluidics based plasmonic microarrays incorporated with dual-color on-chip imaging toward real-time and label-free monitoring of biomolecular interactions over a wide field-of-view of >20 mm^2. Weighing 40 grams with 8.8 cm in height, this biosensor utilizes an opto-electronic imager chip to record the diffraction patterns of plasmonic nanoapertures embedded within microfluidic channels, enabling real-time analyte exchange. This plasmonic chip is simultaneously illuminated by two different light-emitting-diodes that are spectrally located at the right and left sides of the plasmonic resonance mode, yielding two different diffraction patterns for each nanoaperture array. Refractive index changes of the medium surrounding the near-field of the nanostructures, e.g., due to molecular binding events, induce a frequency shift in the plasmonic modes of the nanoaperture array, causing a signal enhancement in one of the diffraction patterns while suppressing the other. Based on ratiometric analysis of these diffraction images acquired at the detector-array, we demonstrate the proof-of-concept of this biosensor by monitoring in real-time biomolecular interactions of protein A/G with immunoglobulin G (IgG) antibody. For high-throughput on-chip fabrication of these biosensors, we also introduce a deep ultra-violet lithography technique to simultaneously pattern thousands of plasmonic arrays in a cost-effective manner

Handheld high-throughput plasmonic biosensor using computational on-chip imaging

We demonstrate a handheld on-chip biosensing technology that employs plasmonic microarrays coupled with a lens-free computational imaging system towards multiplexed and high-throughput screening of biomolecular interactions for point-of-care applications and resource-limited settings. This lightweight and field-portable biosensing device, weighing 60 g and 7.5 cm tall, utilizes a compact optoelectronic sensor array to record the diffraction patterns of plasmonic nanostructures under uniform illumination by a single-light emitting diode tuned to the plasmonic mode of the nanoapertures. Employing a sensitive plasmonic array design that is combined with lens-free computational imaging, we demonstrate label-free and quantitative detection of biomolecules with a protein layer thickness down to 3 nm. Integrating large-scale plasmonic microarrays, our on-chip imaging platform enables simultaneous detection of protein mono- and bilayers on the same platform over a wide range of biomolecule concentrations. In this handheld device, we also employ an iterative phase retrieval-based image reconstruction method, which offers the ability to digitally image a highly multiplexed array of sensors on the same plasmonic chip, making this approach especially suitable for high-throughput diagnostic applications in field settings

Asymmetric Ring/Disk Nanocavities on Conducting Substrates for Strong Fano-Interference

We introduce a Fano resonant asymmetric ring/disk cavity system employing a conducting layer underneath. Our system shows stronger electromagnetic fields that are highly accessible to surrounding medium and sharper spectral features that result in more reliable and sensitive biodetection platforms

Fano Resonant Ring/Disk Plasmonic Nanocavities on Conducting Substrates for Advanced Biosensing

By introducing a conducting metal layer underneath a Fang resonant asymmetric ring/disk plasmonic nanocavity system, we demonstrate that electromagnetic fields. can be strongly enhanced. These large electromagnetic fields extending deep into the medium are highly accessible and increase the interaction volume of analytes and optical fields. As a result, we demonstrate high refractive Index sensitivities as large as 648 nm/RIU. By exciting Fano resonances with much sharper spectral features, as narrow as 9 nm, we experimentally show high figure of merits as large as 72 and reliable detection of protein mono- and bilayers. Furthermore, the conducting substrate enables strong interaction between fundamental and higher order modes of the system by minor structural asymmetries. This is very advantageous for experimental realization of systems supporting resonances with well-defined Fano-like line shape without requiring challenging fabrication resolution. Exploiting conducting metallic substrates and the associated propagating surface plasmons at their interface could be extended to other Fano resonant cavity geometries for improved biosensing performance

Multi-Band Plasmonic Platform Utilizing UT-Shaped Graphene Antenna Arrays

Cetin, Arif E./0000-0002-0788-8108WOS: 000431971500042In this work, we introduce a plasmonic platform based on UT-shaped graphene antenna arrays. the proposed multi-resonant platform shows three different resonances, which can be independently tuned. the physical origin of these modes is shown with finite-difference time-domain (FDTD) nearfield distribution analyses, which are used to statically tune each resonance wavelength via the geometrical parameters, corresponding to different nearfield localization. We achieve statistical tuning of multiple resonances also by changing the number of graphene layers. Another static tuning of the optical response of the UT-shaped graphene antenna is achieved via the chemical potential and the relaxation time.Istanbul Kemerburgaz University Scientific Research Foundation [PB2016-I-012]Yasa Eksioglu acknowledges the support of Istanbul Kemerburgaz University Scientific Research Foundation project No: PB2016-I-012

A multiple-band perfect absorber for SEIRA applications

Cetin, Arif E./0000-0002-0788-8108WOS: 000445264000021Recently perfect absorbers (PAs) have received significant interest due to their characteristics of complex electric permittivity (epsilon) and magnetic permeability (mu). By rationally designing these artificial structures, the impedance of the perfect absorber can be matched to free space with an independent adjustment in the electric and magnetic resonances, where this structure leads to strong absorption from mid- to near-IR wavelength. in this article, we proposed a multiband PA platform, which simultaneously operates with a near unity absorption at different resonances that could be an ideal candidate for multiple sensing of molecular fingerprints. We numerically analyzed the dependence of the optical response of the PA platform through finite-difference time domain (FDTD) simulations for a fine-tuning mechanism of the PA platform. We theoretically demonstrated the surface enhanced infrared absorption (SEIRA) capability of our PA platform by studying its optical response with a thin protein bilayer and a polymethyl-methacrylate (PMMA) film. As an initial step we experimentally showed the vibrational modes of a thin PMMA film. We believe, our findings could open new avenues for reliable SERIA platforms through providing multiple vibrational finger print information compared to its conventional counterparts relying only on a single sensing data.Recep Tayyip Erdogan University Scientific Research Foundation [FUA-2017-762]; Boston University Photonics CenterHabibe Durmaz acknowledges the support of Recep Tayyip Erdogan University Scientific Research Foundation (project No: FUA-2017-762) and Boston University Photonics Center

Plasmonic Nanoantennas on Nanopedestals for Ultra-Sensitive Vibrational IR-Spectroscopy

We experimentally demonstrate that elevating polarization-insensitive nanoring antennas on nanopedestals enables high surface enhanced infrared absorption (SEIRA) signals. This is due to larger and accessible nearfields offering better overlap with biomolecules