Fig. 1. Schematic diagram of metamaterial sensor and spectral response. (a) Single period structure diagram of metamaterial sensor; (b) resonance unit cell; (c) simulated reflection coefficient and absorption spectrum

Fig. 2. Surface current distributions and response spectra of different resonance unit cell. (a) Interconnected square resonance structure;(b) surface current distribution of interconnected square resonance structure;(c) split square ring structure;(d) surface current distribution of split square ring structure; dependence of reflection coefficient on elongated periodicity ε for (e) interconnected square resonance structure and (f) split square ring structure

Fig. 3. Effects of different structural parameters on reflection coefficient and sensitivity. (a)(b) Effect of width of square ring d₁; (c)(d) effect of distance between square rings d₂; (e)(f) effect of PDMS substrate thickness h

Fig. 4. Measurement setup and results. (a) Fabricated sample; (b) measurement setup; (c) variation of unit cell under different tension

Fig. 5. Sensing performance of sample. (a) Simulated and (b) measured reflection spectra of metamaterial sensor under different tensile forces; (c) sensitivity of sensor

Fig. 6. Variation of response characteristics of sample under different stretch-relaxation cycles. Variations of (a) reflection spectrum and (b) resonant frequency with increasing number of stretch-relaxation cycle; (c) photos of unit cell structure with different stretching cycles

Table 1. Comparison of several strain sensors