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 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.
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Highly Sensitive, Affordable, and Adaptable Refractive Index Sensing with Silicon‐Based Dielectric Metasurfaces
A sensing platform is presented that uses dielectric Huygens source metasurfaces to measure refractive index changes in a microfluidic channel with experimentally measured sensitivity of 323 nm RIU−1, a figure of merit (FOM) of 5.4, and a response of 8.2 (820%) change in transmittance per refractive index unit (T/RIU). Changes in the refractive index of liquids flown through the channel are measured by single‐wavelength transmittance measurement, requiring only a simple light source and photodetector, significantly reducing device expense in comparison to state‐of‐the‐art refractive index sensing technologies. A technoeconomic analysis predicts a device costing ≈$2400 that is capable of detecting refractive index changes of the order of 2*10−8. The metasurfaces utilized are low profile, scalable, and use materials and fabrication processes compatible with CMOS and other technologies making them suitable for device integration. The Huygens metasurface system, characterized by spectrally overlapping electric and magnetic dipole modes, offers a high degree of customizability. Interplay between the two resonances may be controlled via metasurface geometry, leading to tunability of device sensitivity and measurement range. Ultrahigh sensitivity of 350 nm RIU−1with FOM of 219, corresponding to single‐wavelength sensitivity of 360 RIU−1, is demonstrated computationally through use of antisymmetric resonances of a Huygens metasurface illuminated at small incidence angles.
more » « less- Award ID(s):
- 1654765
- NSF-PAR ID:
- 10462515
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Materials Technologies
- Volume:
- 4
- Issue:
- 2
- ISSN:
- 2365-709X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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