Fig. 1. Schematic diagram of packaged sensor

Fig. 2. Electric field distributions under different tapered fiber diameters. (a) 2.4 μm; (b) 1.6 μm; (c) 1.2 μm

Fig. 3. Electric field distributions of resonator under different wall thicknesses. (a) Thickness is 10 μm; (b) thickness is 6.5 μm; (c) thickness is 2.5 μm; (d) thickness is 2 μm

Fig. 4. Electric field distributions under different coupling distances. (a) Coupling distance is 2 μm; (b) coupling distance is 1 μm; (c) coupling distance is 0.6 μm

Fig. 5. Schematic diagram of experimental device

Fig. 6. Refractive index spectra and sensitivity fitting curve of WGM with 4.5 μm thickness tube. (a) Refractive index spectra; (b) sensitivity fitting curve

Fig. 7. Refractive index spectra and sensitivity fitting curve of WGM with 2 μm thickness tube. (a) Refractive index spectra; (b) sensitivity fitting curve

Fig. 8. Functionalization method of WGM optofluidic resonator

Fig. 9. DNA concentration gradient detection experiment of the proposed sensor. (a) WGM spectra under different concentration gradients; (b) localized spectra monitored by sensing; (c) wavelength shift diagram at different concentrations

Fig. 10. Sensing performance experiments of the proposed sensor. (a) Specificity experiment of sensor; (b) spectral shift diagram under different steps; (c) stability experiment of sensor