Gen IV TEM liquid flow sample holder — nanoscale phonon dynamics

How can nanoparticle phonon dynamics be studied using Liquid-phase TEM?

Chang Qian and Qian Chen from University of Illinois, along with their colleagues at the University of Michigan and the University of Wisconsin – Madison, have used the Hummingbird Scientific Gen IV liquid flow TEM holder to develop a method to map phonon dynamics in real time. By extending the principle of topologically engineered mechanical frames to self-assembled gold nanoparticle (NP) lattices, key properties such as phonon band structure, nanoscale spring constants, and nonlinear lattice deformation paths were measured to inform modeling and simulation.

a) Schematics of macroscopic Maxwell lattices and a hinge exhibiting rotational freedom. b) Schematic of a rhombic lattice with structural degeneracy. c) Self-assembly of gold nanocubes into a rhombic Maxwell lattice in a silicon nitride (SiN_x) chamber via liquid-phase TEM. Time-lapse liquid-phase TEM images overlaid with d) tracked NP centroids (yellow filled circles) and e) the bond network with rhombuses colored according to θtilt, which describes the angle at which each rhombus leans. Scale bars, 150 nm. f) Drift-corrected trajectory mapped over a selected region of a stable rhombus lattice. g) Example of the instantaneous displacement of the NPs in one frame, fromwhich correlations of the displacements are calculated to derive the dynamical matrix D and the phonon band Scale bars, 200 nm. Copyright © 2025 Springer Nature Limited

This study adapts the TEM into a phonon-mode nanoscopy (PMN) platform to track the vibrations of individual NPs. These vibrations were used to determine phonon dynamics in Maxwell lattices, revealing the critical role played by particles beyond nearest neighbors in accurately modeling the structural stability and flexibility of these systems. The stability of these lattices during self-assembly was found to be tunable by the shape anisotropy of the NPs. These complex interactions demonstrate the adjustability of phonon bands via changes in NP and lattice properties and are key to controlling topological states of self assembled nanostructures for applications in mechanical metamaterials.

Reference: Chang Qian, Ethan Stanifer, Zhan Ma, Lehan Yao, Binbin Luo, Chang Liu, Jiahui Li, Puquan Pan, Wenxiao Pan, Xiaoming Mao & Qian Chen, Nanoscale phonon dynamics in self-assembled nanoparticle lattices. Nature Materials (2025). DOI: 10.1038/s41563-025-02253-3

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