Label-free optical biosensing using a horizontal air-slot SiNx microdisk resonator

Area of Science:

• Photonics and optical sensing
• Biotechnology and biosensing
• Materials science

Background:

• Label-free optical biosensing offers sensitive detection without sample modification.
• Silicon nitride (SiNx) microdisk resonators provide a platform for high-performance optical devices.
• Air-slot waveguides enhance light confinement for improved sensing.

Purpose of the Study:

• To demonstrate label-free optical biosensing using a novel horizontal air-slotted SiNx microdisk resonator.
• To quantify the sensor's performance in detecting streptavidin.
• To evaluate the potential of this platform for sensitive biomolecule detection.

Main Methods:

• Fabrication of a horizontal air-slotted silicon-rich SiNx microdisk resonator.
• Functionalization of the microdisk surface with biotin.
• Exposure of the functionalized sensor to varying concentrations of streptavidin solution.
• Measurement of optical resonance shifts using spectroscopy.
• Finite-Difference Time-Domain (FDTD) simulations for surface sensitivity analysis.

Main Results:

• A significant resonance shift of 6.2 nm was observed with 2.5 μg/ml streptavidin.
• The estimated sensitivity was determined to be 2.5 ± 0.2 nm/(μg/ml).
• A detection limit of 30 ± 2 ng/ml was extrapolated based on experimental and simulation data.

Conclusions:

• The horizontal air-slotted SiNx microdisk resonator is effective for label-free optical biosensing.
• The demonstrated sensitivity and low detection limit highlight the potential for quantitative biomolecule analysis.
• This platform shows promise for developing advanced biosensor devices.