Development of Cellular Structures from 2D Heterogeneous Materials for Sensing Applications

Abstract

2D materials present exceptional mechanical and electrical properties at the micro and mesoscale compared to their bulk precursors. Aiming to enhance the properties of individual 2D materials, these can be combined to tailor their properties, creating heterogeneous materials. The development of a reliable fabrication process for 3D structures is needed to harvest the full potential of heterogeneous materials. Although many attempts to accomplish this have been performed, existing fabrication methods are often time-consuming, complex, and/or require specialized machinery. This thesis presents the development of a practical and reproducible fabrication method for cellular structures made from 2D heterogeneous materials. The process is based on dip-coating a polymeric 3D printed scaffold with graphene oxide. The scaffold is then removed through thermal etching while GO reduction co-occurs. Finally, the freestanding rGO cellular structure is combined with MXene, another 2D material, by submersion-coating. As a result, a heterogeneous cellular structure having a well-defined TPMS geometry is obtained with enhanced properties. Different characterization techniques, such as contact angle testing, thermogravimetric analysis (TGA), x-ray diffraction (XRD), and infrared spectroscopy (FT-IR), were utilized to develop and optimize the presented fabrication method. Furthermore, scanning electron microscopy (SEM) was used to understand better the relationship between the macroscopic morphology of the structure and its macroscopic properties. Finally, it was determined that the structures could be used as pressure sensors through mechanical and electrical characterization. The freestanding rGO lattice presented a maximum load during cyclic testing of 24.92 kPa compared to the heterogeneous structure, 46.14 kPa. This increment is comparable to the increment on density by adding MXene. On the other hand, the sensing properties were improved by almost an order of magnitude going from 9.31 mA to 68.76 mA in current. Furthermore, the addition of MXene stabilized the signal obtained during cyclic testing. This improvement was caused by making the structure less brittle, allowing sensing loads of 3 kPa.

Date of Award	Jul 2021
Original language	American English