➀ A photonic crystal biosensor with an eye-shaped cavity achieves high sensitivity (243 nm/RIU) and stability for cancer cell detection, outperforming traditional designs;

➁ The sensor uses refractive index changes in biological samples and maintains functionality under ±2 nm fabrication errors and 25–75°C temperature variations;

➂ Label-free operation and tolerance to environmental variations make it practical for clinical diagnostic applications.