Flexible and Lightweight Ni/MXene Decorated Polyurethane Sponge Composite with Sensitive Strain Sensing Performance for Ultrahigh Terahertz Absorption

Flexible and lightweight terahertz (THz) absorbers with high absorption performance are urgently indispensable in the application of foreign substance examination, molecular identification and 6G communication. Herein, cost-effective approaches of autocatalytic plating and dip-coating with a series of surface grafting are proposed to construct nickel/Ti3C2Tx (Ni/MXene) decorated polyurethane sponge (PUS) composite. The resultant PUS-Ni/MXene sample exhibits average THz absorption shielding effectiveness (SEA) and absorption proportion of 42.7 dB and 99.9% from 0.1 to 2.2 THz at a thickness of only 1 mm. The THz SEA can achieve 69.8 dB for PUS-Ni/MXene sample with 8 mm thickness while the specific SE is over 65.8 (dB cm(3) g(-1)), surpassing most absorbers. To better understand the propagation characteristics of THz waves, the electromagnetic interference SEs and electric field distributions are calculated through finite difference time domain simulation, and verified by experiments. Moreover, the foldable and electrical properties endow the PUS-Ni/MXene composite with smart pressure sensitivity that is promising for strain monitoring. The optimized PUS-Ni/MXene sensor exhibits high sensitivity under a relatively small strain. And the outstanding long-term stability and durability are also proved by 1200 stretching-releasing cycles. The as-prepared THz absorber with excellent pressure sensing performance demonstrates enormous potential in future military and civilian applications.