Fig. 1. Schematic diagram and physical diagram of double-layer spring FP structure. (a) Schematic diagram of double-layer spring FP structure; (b) physical diagram of double-layer spring FP structure

Fig. 2. Principle diagram of femtosecond laser two-photon polymerization 3D printing technology

Fig. 3. Simulation diagrams of center displacement of springs with different inner and outer radii of spring coils. (a) Outer radii of spring coils are 28, 30, and 32 μm, respectively; (b) inner radii of spring coils are 2.0, 2.5, and 3.0 μm, respectively

Fig. 4. Simulation results of mechanical characteristics of structures with different numbers of spring coils

Fig. 5. Simulation diagrams of spring center displacement with different intervals of upper and lower spring lines. (a) Intervals of upper spring lines are 18.0, 18.1, 18.2, and 18.3 μm, respectively; (b) intervals of lower spring lines are 9.00, 9.05, 9.10, and 9.15 μm, respectively

Fig. 6. Schematic diagram of preparation of double-layer spring FP pressure sensor

Fig. 7. Schematic diagram of pressure detection experimental device

Fig. 8. Reflection spectra of double-layer spring FP pressure sensor at different pressures

Fig. 9. Linear fitting results of reflection spectra of double-layer spring FP pressure sensor under different pressures

Fig. 10. Reflection spectra of double-layer spring FP pressure sensor at different pressures (sample 2)

Fig. 11. Linear fitting results of reflection spectra of double-layer spring FP pressure sensor under different pressures (sample 2)

Fig. 12. Long-term pressure monitoring results of double-layer spring-type FP pressure sensor. (a) Wavelength and intensity versus time plot; (b) reflectance spectra

Fig. 13. Schematic diagram of temperature crosstalk experimental device

Fig. 14. Reflectance spectra and linear fitting results of double-layer spring FP pressure sensors at different temperatures. (a) Reflectance spectra; (b) linear fitting results