Abstract
The precise detection of chemicals and biomolecules is of great interest in the areas of biotechnology and medical diagnostics. Thus, there is a need for highly sensitive, small area, and low-cost sensors. We fabricated and optically characterized hydrogenated amorphous silicon photonic resonators for label-free lab-on-chip biosensors. The sensing was performed with small-footprint microdisk and microring resonators that detect a refractive-index change via the evanescent electric field. Homogeneous sensing with NaCl and surface-sensing experiments with immobilized bovine serum albumin (BSA) were carried out. A sensitivity as high as 460 nm/RIU was measured for NaCl dissolved in deionized water for the disk, whereas about 50 nm/RIU was determined for the ring resonator. The intrinsic limits of detection were calculated to be 3.3×10 −4 and 3.2×10 −3 at 1550-nm wavelength. We measured the binding of BSA to functionalized ring resonators and found that molecular masses can be detected down to the clinically relevant femtogram regime. The detection and quantification of related analytes with hydrogenated amorphous silicon photonic sensors can be used in medical healthcare diagnostics like point-of-care-testing and biotechnological screening.
Highlights
Photonic biosensors, which are fabricated with high refractive index photonic resonators, have good prospects in the area of optical evanescent field sensing applications
We present a versatile and CMOS-compatible photonic lab-on-chip platform, which utilizes high-quality amorphous silicon (a-Si):H photonic resonators as the biosensing elements
We suggest that a-Si:H is an attractive photonic material for lab-on-chip sensing applications, especially when combined with microfluidic channels supporting a well-defined analyte flow rate and if functionalized markers with receptors are employed which facilitate a selective detection of target molecules
Summary
Photonic biosensors, which are fabricated with high refractive index photonic resonators, have good prospects in the area of optical evanescent field sensing applications. Silicon is a promising platform to fabricate photonic lab-on-chip sensors for chemical, medical, and biosensing. Instead of using crystalline silicon-on-insulator (SOI) wafers as photonic substrates, low-loss hydrogenated amorphous silicon (a-Si:H) that is deposited by plasma-enhanced chemical vapor deposition (PECVD) is alternatively employed in this work because it provides a high refractive index (n ≈ 3.5) and low-loss material for near-infrared photonics, both comparable to crystalline silicon.[3] a-Si:H offers a more flexible fabrication process since it can be deposited at relatively low temperatures (≤300°C) and allows using glass or plastic materials as substrates.[4,5] This facilitates a low-cost fabrication and offers more processing options, e.g., for the combination with microfluidic channels using split-and-recombine micromixers or for the arrangement of the sensing resonators that can be principally fabricated in a vertically stacked configuration.[6,7]. After exposing the functionalized sensor surface for 1 h in a BSA solution, a wavelength shift of 1.25 nm was measured from which a limit of detection in terms of surface coverage of 8.5 pg∕mm[2] is determined
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call