skip to main content

Title: An optofluidic metasurface for lateral flow-through detection of cancer biomarker (Conference Presentation)
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 analysis 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 more » 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
; ; ;
Award ID(s):
Publication Date:
Journal Name:
Proc. SPIE 10491, Microfluidics, BioMEMS, and Medical Microsystems XVI, 1049113 (15 March 2018)
Page Range or eLocation-ID:
Sponsoring Org:
National Science Foundation
More Like this
  1. The optical resonances of the silicon nanopost array patterned on a silicon-on-insulator (SOI) substrate have been investigated. The fabricated device supports optical resonances in the range of 1.55 μm with a variable Q factor depending on the angle of incidence. By sealing the device on top of the nanoposts, we demonstrated a lateral flow-through label-free biosensor built on SOI. The biosensor exhibits the refractive index sensitivity of 800 nm/RIU and the femtomolar sensitivity for detection of a breast cancer biomarker (ErbB2).
  2. This paper reports an integrated dual-modality microfluidic sensor chip, consisting of a patterned periodic array of nanoposts coated with gold (Au) and graphene oxide (GO), to detect target biomarker molecules in a limited sample volume. The device generates both electrochemical and surface plasmon resonance (SPR) signals from a single sensing area of Au–GO nanoposts. The Au–GO nanoposts are functionalized with specific receptor molecules, serving as a spatially well-defined nanostructured working electrode for electrochemical sensing, as well as a nanostructured plasmonic crystal for SPR-based sensing via the excitation of surface plasmon polaritons. High sensitivity of the electrochemical measurement originates from themore »presence of the nanoposts on the surface of the working electrode where radial diffusion of redox species occurs. Complementarily, the SPR detection allows convenient tracking of dynamic antigen–antibody interactions, to describe the association and dissociation phases occurring at the sensor surface. The soft-lithographically formed nanoposts provide high reproducibility of the sensor response to epidermal growth factor receptor ( ErbB2 ) molecules even at a femtomolar level. Sensitivities of the electrochemical measurements to ErbB2 are found to be 20.47 μA μM −1 cm −2 in a range from 1 fM to 0.1 μM, and those of the SPR measurements to be 1.35 nm μM −1 in a range from 10 pM to 1 nM, and 0.80 nm μM −1 in a range from 1 nM to 0.1 μM. The integrated dual-modality sensor offers higher sensitivity (through higher surface area and diffusions from nanoposts for electrochemical measurements), as well as the dynamic measurements of antigen–antibody bindings (through the SPR measurement), while operating simultaneously in a same sensing area using the same sample volume.« less
  3. Bimetallic plasmonic nanostructures provide composition and spatial distribution of the individual components in the nanostructure in addition to overall size and morphology as degrees of freedom for tuning near- and far-field optical responses. AgAuAg nanorods (NRs) generated through epitaxial deposition of Ag on the tips of Au bipyramids (BPs) are an important bimetallic model system whose longitudinal dipolar plasmon mode first shows a spectral blue-shift upon initial deposition of Ag on the Au BP tips followed by a red-shift after additional deposition of Ag. Here, we quantify the relative contributions from morphological and compositional effects to the far-field spectral shiftmore »of the longitudinal and vertical dipolar plasmon modes during the initial deposition of Ag and compare the near-field in Ag and AgAuAg NRs with lengths between L = 130 nm–280 nm under whitelight illumination through electromagnetic simulations. Subsequently, we experimentally characterize the near-field around AgAuAg NRs with lengths between L = 88.1–749.0 nm at a constant excitation wavelength of 1064 nm on a silicon (Si) support through scattering type near-field scanning microscopy (sNSOM). We detect Fabry–Perot resonance-like higher order multipolar plasmon resonances whose order and near-field pattern depends on the length and composition of the NRs as well as the refractive index of the ambient medium. We find that under oblique illumination higher order multipolar modes with an even symmetry dominate on the high refractive index Si substrate due to strong electromagnetic interactions between the NR and the substrate.« less
  4. To elucidate the secretary function of immune cells, we develop a nanoplasmonic circular interferometric biosensor based on intensity interrogation for label-free and dynamic sensing of molecular secretion. Exceptional sensitivity has been demonstrated through coupling free light and surface plasmon polariton (SPPs) waves, which generates a constructive and deconstructive interference pattern with high contrast and narrow linewidth when illuminated by white light. Alternatively, by adopting a narrow-band LED source and a CCD camera in this work, the transmission intensity of multiple sensing units is monitored simultaneously with a simple collinear optical setup. This intensity-modulated sensing platform yields a resolution of 4.1more »× 10 −5 refractive index unit (RIU) with a high temporal resolution of 1 s and a miniaturized footprint as small as 9.8 × 9.8 μm 2 for a single sensing unit. By integrating the signals from multiple sensor units, the resolution of a 12 × 12 sensor array was found to reach 7.3 × 10 −6 RIU. We apply this sensor array to detect matrix metalloproteinase 9 (MMP-9) secretion from human monocytic cells, THP-1, at different time points after lipopolysaccharide (LPS) simulation and the results are in good agreement with enzyme-linked immunosorbent assay (ELISA) tests, but without the need for labeling. The spatial, temporal and mass resolutions of the sensor array are found to exceed other label-free technologies. These biomolecular arrays, incorporated in a microfluidic sensor platform, hold great potential for the study the dynamics and interplay of cell secretion signals and achieving a better understanding of single cell functions.« less
  5. Microsphere Photolithography (MPL) is a nanopatterning technique that utilizes a self-assembled monolayer of microspheres as an optical element to focus incident radiation inside a layer of photoresist. The microspheres produces a sub-diffraction limited photonic-jet on the opposite side of each microsphere from the illumination. When combined with pattern transfer techniques such as etching/lift-off, MPL provides a versatile, low-cost fabrication method for producing hexagonal close-packed metasurfaces. This article investigates the MPL process for creating refractive index (RI) sensors on the cleaved tips of optical fiber. The resonant wavelength of metal elements on the surface is dependent on the local dielectric environmentmore »and allows the refractive index of an analyte to be resolved spectrally. A numerical study of hole arrays defined in metal films shows that the waveguide mode provides good sensitivity to the analyte refractive index. This can be readily tuned by adjusting the MPL exposure and the simulation results guide the fabrication of a defect tolerant refractive index sensor on the tip of a fiber tip with a sensitivity of 613 nm/RIU. The conformal nature of the microsphere monolayer simplifies the fabrication process and provides a viable alternative to direct-write techniques such as Focused Ion Beam (FIB) milling« less