The thesis examines the adhesive interaction between graphite layers and atomically thin MoS2 crystals. Vertical van der Waals(vdW) heterostructures are fabricated by stacking different two-dimensional (2D) materials on top of each other. Blister test is used to measure the adhesive interactions between 2D heterostructures and their transferred substrates and between the layers themselves. This adhesive interaction is important in maintaining the mechanical integrity of the device during mechanical loadings and its understanding will help pave the way to the design and fabrication of micromechanical device from 2D heterostructures. Furthermore, applying controlled strains can be used to alter the electrical and optical properties thereby improving efficiency and performance. At first, we grew MoS2 and graphene by CVD and stacked the layers on top of each other using a dry transfer method. The MoS2/graphene heterostructure was then transferred onto pre-etched cavities on a silicon wafer. The blister test was used for controllably introducing strain into the heterostructure. Atomic Force Microscopy was used for measuring the shape of the deformed blister and Raman and Photoluminescence(PL) measured the optical response. The strain mismatch between the biaxial strain and a PL-converted strain suggests crumpling of the graphene layer and a substantial softening of the mechanical response. Lastly, we created graphite holes with photolithography to measure the work of separation between an atomically smooth graphite surface and MoS2. We found this value to be at least 320mJ/m2 which is higher than the MoS2/SiOx areas that was previously studied. / 2023-07-02T00:00:00Z

<p>In this dissertation, we show three approaches towards selective vagus nerve stimulation (VNS). First, we investigated VNS using microelectrode with circle and Vicsek fractal shape. Our rat study shows that fractal microelectrode can activate C-fibers in cervical vagus nerve with higher energy efficiency compared to circle microelectrode. Secondly, we developed stretchable and adhesive cuff device for a compliant neural interface for a long-term stability. We designed Y-shaped kirigami thin-film device for stretchable neural interface and applied a tissue-adhesive hydrogel to enable tough adhesion of the cuff electrode, which can be potentially used to fix the position of microelectrode for a reliable selective stimulation with minimal mechanical mismatch. Lastly, we developed a microchannel electrode array device to potentially measure high-quality of single fiber action potential (SFAP) from the abdominal vagal trunk of rat to explore natural patterns selective organ activities which can be used for a fine-tuned selective VNS. Our results show the potential of measuring C-fiber activities evoked by cervical VNS.</p>