Highly Sensitive, Flexible, Stable, and Hydrophobic Biofoam Based on Wheat Flour for Multifunctional Sensor and Adjustable EMI Shielding Applications

Biofoam materials are attractive alternatives for petroleum-based foams to be used to solve environmental problems. Inspired by steamed bread, we report herein a novel utilization of wheat flour (WF) with the introduction of carbon nanotubes (CNTs) to form an environmentally friendly WF/CNT composite foam. This foam displayed a high elasticity (nearly 100% shape recovery), recyclable (5000 cycles), fast (100 ms), and superstability pressure-sensing response. It could serve as a new pressure sensor to detect the tiny pressure (1.76 Pa) and acoustic vibrations from piano notes. As an acoustic sensor, WF/CNT foam detected and recognized different volumes and frequencies of piano sounds. As an electromagnetic interference (EMI) shielding switch, the EMI shielding effectiveness (SE) of the foam could be easily regulated under self-fixable compression–recovery cycles. In addition, the WF/CNT foam could be converted into the WF/CNT film by a hot-compress process. This flexible film was applied as a multifunctional sensing device for detecting various motions. Therefore, wheat flour as a renewable resource could be designed into various WF-based biofoams with new functionalities and outstanding mechanical properties through a simple process.