Ultra-sensitive liquid crystal-coated microbubble resonator based on a whispering gallery mode for penicillin G detection.

Penicillin G detection is of great significance in medical research and disease diagnosis. Liquid crystal (LC), as a branch of sensitive materials, has a broad application prospect in the field of biosensing. Herein, a liquid crystal-coated silica microbubble resonator (LC-MBR), with high sensitivity for penicillin G detection, has been proposed and demonstrated. Whispering gallery mode (WGM) spectra with a Q factor exceeding 10⁶ were excited through the coupling between tapered fiber and LC-MBR. The orientation transition of the LC molecules, combined with WGM resonance, amplified target information and triggered wavelength blueshifts. LC-MBR was then applied in pH detection, achieving a sensitivity of 2.51 nm/pH within a pH range of 3.8-8.5. This resonator was also successfully employed to detect enzymatic reactions of penicillinase, with a detection limit of 6 × 10³ U/mL. The fabricated sensor offers significant advantages, including a simple structure, improved stability, and higher sensitivity across a wide pH detection range, making it a promising candidate for future biomedical applications.