Chemical-enhanced thyroid cell detection using photonic crystal biosensors with phase-change materials

Area of Science:

• Photonics
• Biomedical Engineering
• Materials Science

Background:

• Thyroid nodules require accurate diagnostic methods.
• Label-free biosensing offers efficient disease detection.
• Photonic crystals provide a platform for sensitive optical biosensors.

Purpose of the Study:

• To propose a one-dimensional defective photonic crystal (1D-DPC) biosensor for label-free thyroid nodule detection.
• To utilize the phase-change material Ge₂Sb₂Te₅ (GST) for enhanced biosensor performance.
• To achieve high sensitivity and specificity in differentiating benign and malignant thyroid nodules.

Main Methods:

• Designing a 1D-DPC structure: [(Diamond/Silica)³ GDG (Diamond/Silica)³] with GST layers and an air-cavity defect.
• Employing the transfer matrix method (TMM) to calculate transmission spectra for TE-polarized incidence.
• Evaluating performance metrics: sensitivity (S), quality factor (Q), and figure of merit (FOM) for GST's amorphous and crystalline states.

Main Results:

• The biosensor demonstrated high sensitivity (267 nm RIU^-1) and quality factor (87.875) at normal incidence in the crystalline GST state.
• The GST material's tunable refractive index and absorption coefficient enabled active resonance tuning.
• The design effectively distinguished between malignant and benign thyroid nodules, showing superior tunability and diagnostic accuracy compared to previous designs.

Conclusions:

• The proposed GST-based 1D-DPC biosensor is a promising tool for accurate, label-free thyroid nodule diagnosis.
• The phase-change properties of GST offer significant advantages in biosensor sensitivity and tunability.
• This technology has the potential to improve diagnostic accuracy and patient outcomes for thyroid conditions.