W. Guan, A. Islam, C. Lum, S. Nam
University of California, Irvine,
United States
Keywords: 2D materials, adhesion, friction, wettability
Summary:
Van der Waals (vdW) materials exhibit surface properties that can be exquisitely tuned through electronic and mechanical perturbations. In this presentation, I will discuss how charge doping and morphological bending can systematically control how atomically thin materials—such as graphene and MoS₂—interact with their surrounding environment, thereby modulating their adhesion, friction, and wettability at the nanoscale. Using chemical and electrostatic doping, we demonstrate that modulation of graphene’s carrier density alters its non-bonded interactions with water and other adsorbates, modulating wettability. Our results reveal that doped graphene becomes increasingly hydrophilic as charge density enhances the water–graphene binding energy and modifies local van der Waals potentials. Further, electrostatic gating of graphene enables dynamic friction tuning—where friction varies reversibly with gate voltage through carrier-dependent electron–phonon coupling—illustrating an electrically controlled pathway to tune interfacial dissipation. Complementary to electronic doping, structural modulation through bending and crumpling provides a mechanical route to engineer vdW interactions. Hierarchical, dual-scale MoS₂ nanostructures exhibit a wide range of wettability tunability as the surface morphology transitions from flat to crumpled configurations, while maintaining reversible strain-controlled behavior over thousands of cycles. These studies establish doping and bending as orthogonal yet synergistic strategies to tune the coupling between vdW materials and their environments.