Fig. 1. (a) The fabrication process of laser direct writing; (b) The schematic diagram of antenna measurement

Fig. 2. (a) The electronical property of polyimide after carbonization under different laser power and laser speed; (b) The Raman curve; (c), (d) The SEM and (e), (f) the TEM of carbonized polyimide film

Fig. 3. (a) The curves of the refection coefficient (S11) for the circle antenna sensor at different applied strain; (b) The schematic diagram of antenna sensor for measuring the strain of metal sample and the curves of the refection coefficient (S11); (c) The fitting curves of circle antenna sensor by experiments and simulation; (d) The curves of the refection coefficient (S11) for the circle antenna sensor at different times and the curves of the refection coefficient (S11) for different circle antenna sensors; (e) The resonance frequencies and sensitivities of the antenna sensor at different times; (f) The resonance frequencies and sensitivities of different samples

Fig. 4. (a) The curves of the refection coefficient (S11) for the circle antenna sensor at different humidity; (b) The resonance frequency shift of the circle antenna at different humidity.

Fig. 5. (a) The curves of the refection coefficient (S11) for the circle antenna sensor at different temperature; (b) The resonance frequency shift of the circle antenna at different temperature