Development of a high-performance sensor based on advanced 2D materials

Abstract

Flexible strain, pressure, and conductivity are crucial properties for real-time detection or human-body interaction sensors. However, traditional three-dimensional porous materials, such as MXene aerogel, frequently show weakness due to their weak inter-sheet connections, and randomized porous architectures lead to brittle fracture, irreversible deformation, and severe electrical signal drift under long-term cyclic loading. Further, traditional hydrophilic polymer binders such as poly (vinyl alcohol) fail to address these issues due to their high moisture sensitivity, which compromises long-term environmental and structural integrity. To address these limitations, this thesis introduces a dual strategy that combines advanced composite chemistry with microstructural control. First, a polyamic acid triethylamine salt (PAA-TEA) solution is combined with a highly conductive MXene suspension to form a high-performance polyimide (PI) hybrid network that serves as an extrinsic structural reinforcement phase. Second, intrinsic anisotropic microstructural alignment is achieved during freeze casting by applying an alternating current (AC) electric field. This process leverages Maxwell-Wagner interfacial polarization to induce an electrical dipole moment on the MXene nanosheets, generating a rotational dielectrophoretic torque that systematically aligns them parallel to the electric field lines. Finally, subsequent thermal imidization converts the matrix into a robust aromatic polyimide framework, permanently locking the ordered pathways. Mechanical characterization demonstrated that the 65%:35% PAA-TEA: MXene ratio provides superior performance over other investigated compositions. The application of an AC electric field substantially reinforced the material’s network strength, positioning its compressive strain-stress loops consistently higher along the stress axis compared to untreated aerogel. This structural ordering allows the aligned aerogel to tolerate significantly higher strain displacements and stresses without mechanical collapse, while simultaneously optimizing contact resistance and electrontransport continuity. Ultimately, this scalable integration of high-strength polyimide chemistry and dynamic electrical alignment offers a robust framework for designing highly resilient, durable, and multifunctional flexible sensing materials that can be used in a sensor.