Integration 3D Micro and Nano Structures with 2D Materials via Self-Assembly Approach

Two-dimensional (2D) materials have been widely researched for the past decades. Despite this, there is recently a large interest in bringing 2D materials to 3D micro/nano architectures as the later one offers many new functionalities in space dimension compared with the 2D plane, such as robotics, electronic skins, molecular sieves, and sensors. In this work, 2D materials are integrated on 3D micro and nano structures via self-assembly technique. This approach can be witnessed with several advantages. First, it is well compatible with traditional two-dimensional (2D) lithographic processes. Second, complex 3D structures which are usually challenging to achieve by traditional top-down techniques can be easily fabricated by this bottom-up method. Third, it is a manual-free and wire-free process. Moreover, it can be well applicable by patterning different kinds of materials on it with different dimensions and subsequently self-assembled together with stimulus-based active layers to realize 3D architectures, which offers great flexibility and strong functionality. Here, two fabrication processes that meet the previously mentioned benefits are introduced. They facilitate the incorporation of 2D materials, including Graphene, Graphene Oxide, and MXenes, onto a wide range of 3D micro and nanostructures. First, electron beam induced in-situ monitored self-assembly technique. 2D materials together with other active nano layers can be firstly patterned on the planar surface and then subsequently curved up to 3D nano structures stimulated by focused electron beam induced stress deformation. This technique offers nanometer resolution control of the 3D object, and the desired 3D shape can be meticulously crafted. Second, 3D self-assembly process uses stress gradient in negative photoresist (SU-8). The stress gradient in the SU-8 enables the formation of 3D graphene-based polyhedral structures. The graphene and SU-8 layers are patterned, then transitioned into 3D structures when the stress gradient, instigated by an UV-energy source, is alleviated. Simulation is performed to demonstrate the strong 3D volumetric light confinement in 3D graphene nano structures and high optical chirality in 3D graphene microstructures. The developed fabrication technique can further be used to construct 2D materials-based fluidic channels, actuators, micro/nano machines and 3D passive elements.