Thin film mechanics

Keywords: Bulge test, Indentation, Instabilities, Bendability, Stiffness

When materials become slender, they often exhibit flexibility and deformability. My interest lies in obtaining quantitative insights into the flexibility and deformability of ultrathin materials, particularly atomically thin sheets, commonly known as 2D materials. This encompasses various fundamental mechanical behaviors and parameters, including fracture, stretching modulus, and bending modulus. Understanding these properties proves beneficial for a wide range of applications that rely on the material's elasticity and mechanical robustness, such as strain engineering. To characterize such materials, several methods are employed. Recent works have utilized bulge and indentation tests to investigate graphene and other 2D materials. These tests have shed light on the effects of chemical modifications. Below are a few notable publications:

Z. Fang, Z. Dai* et al. Pull-to-peel of two-dimensional materials for the simultaneous determination of elasticity and adhesion. Nano Letters 23, 2, 742–749 (2023)

Z. Dai et al. "Mechanical Responses of Boron-doped Monolayer Graphene." Carbon 147, 594 (2019).

G. Wang†, Z. Dai†, et al. "Bending of Multilayer van der Waals Materials." Physical Review Letters 123, 116101 (2019).

Z. Dai et al. "Interface-Governed Deformation of Nanobubbles and Nanotents Formed by Two-Dimensional Materials." Physical Review Letters 121, 266101 (2018).

Surfaces and interfaces

Keywords: Elastocapillarity, Elastic wetting, Dewetting, Self-cleaning, Adhesion, Friction

The high slenderness of thin films makes the subtleties associated with their area-related properties crucial. Surface and interface energies often induce bending, stretching, and even cracking of the film. These phenomena belong to a class of problems spanning various length scales, involving both elastic and intermolecular forces (elastocapillarity being an example at the submillimeter scale). I am interested in understanding how interactions between surfaces, interfaces, and elasticity govern the equilibrium geometry of thin films. This understanding can, in turn, lead to new topology-based methodologies for interface mechanics, such as friction and adhesion. Here are some relevant publications:

Y. Hou†, Z. Dai† et al. "Elastocapillary Cleaning of Twisted Bilayer Graphene Interfaces." Nature Communications 12, 5069 (2021).

Z. Dai et al. "Mechanics at the Interfaces of 2D Materials: Challenges and Opportunities." Current Opinions in Solid State & Material Science 24, 100837 (2020).

D. A. Sanchez†, Z. Dai† et al. "Mechanics of Spontaneously Formed Nanoblisters Trapped by Transferred 2D Crystals." Proceedings of the National Academy of Sciences 115, 7884 (2018).

G. Wang†, Z. Dai† et al. "Measuring Interlayer Shear Stress in Bilayer Graphene." Physical Review Letters 119, 036101 (2017).

Z. Dai et al. "Mechanical Behavior and Properties of Hydrogen-Bonded Graphene/Polymer Nano-Interfaces." Composites Science and Technology 136, 1 (2016).

Nanocomposites

Keywords: Graphene films, CNT sponges, Foams

My previous research focused on the fabrication and mechanical characterization of nanomaterial-based composites. The objective was to transfer the unique functional and mechanical properties of nanoscale building blocks to macroscopic assemblies, such as compressible graphene/carbon nanotube foams. I was primarily interested in characterizing the structure-property relationship in these systems, utilizing experimental techniques such as DMA (Dynamic Mechanical Analysis), Raman spectroscopy, in situ SEM (Scanning Electron Microscopy), and TEM (Transmission Electron Microscopy). Here are some notable publications related to my work:

Z. Dai et al. "Hierarchical Graphene-Based Films with Dynamic Self-stiffening for Biomimetic Artificial Muscle." Advanced Functional Materials 26, 7003 (2016).

Z. Dai et al. "Multifunctional Polymer-Based Graphene Foams with Buckled Structure and Negative Poisson's Ratio." Scientific Reports 6, 32989 (2016).

Z. Dai et al. "Three-dimensional Sponges with Superior Mechanical Stability: Harnessing the True Elasticity of Individual Carbon Nanotubes in Macroscopic Architectures." Scientific Reports 6, 18930 (2016).

Z. Dai et al. "Creep-resistant behavior of MWCNT-polycarbonate fibers elevated melt nanocomposites spun at temperature." Polymer 54, 3723 (2013).

4. 2023-2024，基于单原子层的超高灵敏度力学传感原理及器件研究，17 万元，2023新工科交叉青年专项项目，主持

3. 2022-2024，微纳米力学与多尺度力学，300 万元，国家级人才计划青年项目，国家自然科学基金委，主持

2. 2022-2024，液体调解的可变形固-固界面作用，100 万元，北京大学学科建设项目，主持

1. 2020-2022，Liquids Under Confinement In 2D-MATERials (LUCiD-Mater)，约170 万元，玛丽居里奖学金项目，欧盟，主持，已结题