研究目的
To develop a label-free and cost-effective technique for detecting ultralow molecular weight biomolecules at very low concentrations using lithography-free nanophotonic cavities integrated with microfluidics.
研究成果
The microfluidic channel integrated lithography-free nanophotonic cavity enables extreme sensitive label-free biosensing for small biomolecules at very low concentrations, with a bulk refractive index sensitivity of 3333° per RIU and a detection limit of 1e-12 M for biotin. This cost-effective platform has potential for point-of-care applications, such as noninvasive liquid biopsies for early cancer screening.
研究不足
The sensor's detection limit is constrained by the phase resolution of the ellipsometer and the inability to achieve extreme singular phase in the microfluidics integrated system. Sensitivity decreases with increasing analyte concentration. Further improvements require optimization for lower ψmin values or alternative interrogation schemes like Goos–H?nchen shift.
1：Experimental Design and Method Selection:
The study utilizes a four-layered metal-dielectric-dielectric-metal asymmetric Fabry–Perot cavity with phase singularity for high-sensitivity biosensing. A polymethylmethacrylate (PMMA) microfluidic channel is integrated to enable real-time binding measurements.
2：Sample Selection and Data Sources:
Biotin molecules (244 Daltons) in phosphate-buffered saline (PBS) at concentrations from 1e-12 M to 1e-6 M are used as analytes. Glycerol solutions (
3：25–5% w/v) in distilled water are used for sensor calibration. List of Experimental Equipment and Materials:
Equipment includes a thermal evaporation system (Oerlikon Leopold vacuum system), spin coater (MICROCHEM
4：5MMAEL 11), spectroscopic ellipsometer (J. A. Woollam Co., Inc., V-VASE), laser micromachining system (Epilog Laser), and microfluidic components (PMMA, double-sided adhesive tape from Thorlabs, tubing from Cole-Parmer). Materials include gold (Au), silver (Ag), germanium (Ge), methyl methacrylate (MMA), PMMA, and biotin. Experimental Procedures and Operational Workflow:
Thin films of Au (20 nm), Ag (80 nm), and Ge (10 nm) are deposited by thermal evaporation. MMA layer (520 nm) is spin-coated. PMMA microfluidic channel is fabricated via laser micromachining and assembled with the cavity. Ellipsometry parameters (ψ and Δ) are measured using a variable-angle spectroscopic ellipsometer. Bulk refractive index sensitivity is tested with glycerol solutions, and biotin binding is monitored in batch-mode experiments.
5：Data Analysis Methods:
Data is analyzed using transfer matrix method-based numerical simulations to model phase shifts and sensitivity. Phase shifts are measured and fitted with phenomenological functions to determine detection limits.
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