Ultrathin Flexible Terahertz Metamaterial Absorber With High Sensitivity for Bending Strain Sensing

Flexible terahertz metamaterial absorber (FTMA) has great potential in sensing applications, such as trace biochemical molecules’ detection and strain sensing. However, the research about bending strain sensors based on the FTMAs is still very lacking. Here, an ultrathin, dual-band FTMA is proposed with high sensitivity for bending strain sensing, which is easily fabricated by an advanced microfabrication technology. The FTMA shows excellent mechanical flexibility, attributed to its ultrathin thickness of only <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 11.2~\mu $ </tex-math></inline-formula>m. Experimental results demonstrate optical performance stability and outstanding bending strain sensitivity of FTMAs. After 100 times bending cycles, the optical responses of FTMAs could still remain stable. In addition, for bending strain sensing, experimental results show that the FTMA sensor achieves a 9.85% amplitude change and 30.52-GHz frequency shift, when applying only around 4.44% bending strain, corresponding to the frequency sensitivity up to ~6.18 GHz/%. Hence, this strategy shows the sensing potentials of flexible devices and broadens the application of the THz technology.