The high-volume synthesis of two-dimensional (2D) materials in the form of platelets is desirable for various applications. While water is considered an ideal dispersion medium, due to its abundance and low cost, the hydrophobicity of platelet surfaces has prohibited its widespread use. Here we exfoliate 2D materials directly in pure water without using any chemicals or surfactants. In order to exfoliate and disperse the materials in water, we elevate the temperature of the sonication bath, and introduce energy via the dissipation of sonic waves. Storage stability greater than one month is achieved through the maintenance of high temperatures, and through atomic and molecular level simulations, we further discover that good solubility in water is maintained due to the presence of platelet surface charges as a result of edge functionalization or intrinsic polarity. Finally, we demonstrate inkjet printing on hard and flexible substrates as a potential application of water-dispersed 2D materials.
We propose an interference-aware MAC protocol using a simple transmission strategy motivated by a gametheoretic approach. We formulate a channel access game, which considers nodes concurrently transmitting in nearby clusters, incorporating a realistic wireless communication model -the SINR model. Under inter-cluster interference, we derive a decentralized transmission strategy, which achieves a Bayesian Nash Equilibrium (BNE). The proposed MAC protocol balances network throughput and battery consumption at each transmission.We compare our BNE-based decentralized strategy with a centralized globally optimal strategy in terms of efficiency and balance. We further show that the transmission threshold should be adaptively tuned depending on the number of active users in the network, crosstalk, ambient noise, transmission cost, and radio-dependent receiver sensitivity. We also present a simple dynamic procedure for nodes to efficiently find a Nash Equilibrium (NE) without requiring each node to know the total number of active nodes or the channel gain distribution, and prove that this procedure is guaranteed to converge.
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