Dual-Mode Metamaterial Absorber for Independent Sweat and Temperature Sensing

Metamaterial absorbers are increasingly studied and applied in sensing, telemedicine, and health monitoring applications. At present, many reported metamaterial-based sensors often exhibit the characteristics of single or multiple resonance modes. However, the sensing characteristics of these multi-mode metamaterial sensors are not independent. Here, a multi-mode metamaterial sensor (localized surface plasmon (LSP) resonance mode, dielectric loss mode) is measured and analyzed. In measurements, absorption peak P1 is sensitive to the thickness of the dielectric layer, while the absorption peak P2 is associated with lattice constant. The metamaterial sensor exhibits dual sensing capabilities for both temperature and sweat. When the metamaterial sensor is covered with sweat (the temperature remains unchanged), peak P2 is strengthened and moved to the low-frequency region, while peak P1 is basically unchanged. When the temperature is increased (the metamaterial sample is not covered by sweat), peak P1 is strengthened and moved to the low-frequency region, while peak P2 is basically unchanged. When the concentration components in sweat and temperature are increased synchronously, peaks P1 and P2 are increased simultaneously. Peak P1 is moved to the high-frequency region, while peak P2 is shifted to the low-frequency region. This proposed metamaterial sensor shows both independent and dual sensing properties.