Electrical Characterization and Nanoindentation of Opto-electro-mechanical Percolative Composites from 2D Layered Materi
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Electrical Characterization and Nanoindentation of Opto-electro-mechanical Percolative Composites from 2D Layered Materials Jorge A. Catalán1, Ricardo Martínez2, Yirong Lin2, and Anupama B. Kaul3* 1 Department of Metallurgical, Materials and Biomedical Engineering, University of Texas at El Paso, El Paso, TX 79968, U.S.A. 2 Department of Mechanical Engineering, University of Texas at El Paso, El Paso, TX 79968, U.S.A. 3 Department of Electrical and Computer Engineering, University of Texas at El Paso, El Paso, TX 79968, U.S.A. * E-mail: [email protected] ABSTRACT In this paper, we have developed composites with Poly-methyl methacrylate (PMMA) as the matrix material, while transition metal dichalcogenides (TMDCs), MoS2 and WS2 and graphite served as the filler materials. The PMMA was chosen as the matrix material due to its low-cost, wide availability, as well as its promising mechanical and optical properties for enabling opto-electro-mechanical sensing devices. The amount of filler material used ranged from 100 mg/ml up to 400 mg/ml. With the aid of designed fixtures we related the electrical properties of the PMMA-based composite sensors to the degree of strain or deformation. Additionally, a nanoindenter was used to measure the modulus of elasticity, with values as low as 2 GPa and as high as 20 GPa for the graphite composites, and hardness values which ranged from 0.1 GPa to ~ 1.6 GPa. INTRODUCTION Since the introduction of the new allotrope of carbon, graphene in 2004 [1] by the Novoselov and Geim, a great deal of research has now led to the exploration of graphene-like layered materials based on binary as well as ternary systems [2]. Graphene has exhibited remarkable flexibility, mechanical strength, high electrical conductivity and transparency [3] which has opened new horizons for promising applications such as, ultra-capacitors, capacitive sensors, chemical sensors, solar cells, transparent conducting electrodes that could replace indium tin oxide (ITO), touch screens, and nanoelectronics [4-7]. Recently, this material has been used in the fabrication of different transparent and stretchable devices for wireless monitoring sensors, and different composite materials that can be utilized as wearable heaters for treating joint grievances [8-11]. Graphene allowed the scientific community to reconsider their thinking on the stability of single atomic layers that were self-standing, which were believed to be thermodynamically unstable [12]. While graphene has fascinated the scientific community for more than a decade, researchers have started exploring graphene-like structures that could overcome graphene’s biggest challenge, its lack of a band gap. Transition metal dichalcogenides (TMDCs) were the selected materials since, much like graphite, they are composed of layers of weakly bonded molecular membranes that are held together by van der Waals interactions [13-15]. Indeed, these materials in their bulk form, are not unfamiliar to the scientific community because of their attractive properties as lubricants which
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