Department Colloquium | Nanoscale Soft Matter Under Electron Microscopy

We are fascinated with nanoscale soft matter, which crosses the boundaries of synthetic and living systems and defies simple mean-field theories or coarse-grained models. In this talk, I will show a few of our recent case studies, with new understandings provided by our multimodal “electron videography.” The first is the measurement and significance of interactions beyond nearest neighbors in colloidal nanoparticles in and out of equilibrium. These interactions not only determine the phase behaviors of nucleation and crystal growth, but the phonon mode structures if we treat nanoparticle self-assemblies as a new type of mechanical metamaterials. We establish accordingly the rules of nanoscale phonon manipulation in complex and new assembly structures such as Maxwell lattice with floppy modes and moiré lattices with angle-dependent band structures. The second is the measurement and design of structural heterogeneity of nanoparticles, polymers, and biological systems. We show that scaling theory needs to be coupled with atomic functional density theory to predict, for example, nanopatterning of polymers on surfaces. We also show the spatiotemporal fluctuations of proteins and cells during interactions, which can impact greatly the function and efficacy of interactions. The third is the existence and generation of defects and strain in crystalline nanomaterials, let them be catalysts or electrodes. Atomic lattices are “softened” in these systems, leading to extended strain patterns in three dimensions that we visualize at the nanoscale. All these new observations are aligned with our push of electron videography and automation to make the invisible visible, and we see this as the beginning of a more comprehensive understanding and utilization of nanoscale soft matter.

Biography:
Prof. Qian Chen is currently a professor and Racheff Scholar in the Department of Materials Science and Engineering at the University of Illinois Urbana-Champaign. She got her BS degree in chemistry from Peking University and her PhD degree from the same department with Prof. Steve Granick. She completed her postdoctoral research with Prof. Paul Alivisatos at the University of California, Berkeley, under a Miller Fellowship. She became a faculty in 2015 and since then has received awards for the research in her group, such as the Forbes 30 under 30 Science List (2016), the AFOSR YIP (2017), the NSF CAREER award (2018), the Sloan Research Fellow in Chemistry (2018), the ACS Unilever Award (2018), the Hanwha-TotalEnergies IUPAC Young Scientist Award (2022), the Soft Matter Lectureship (2023), the Provost's Award for Excellence in Graduate Student Mentoring (2024), the MRS Outstanding Early-Career Investigator Award (2024), the ACS Langmuir lectureship (2025) and ACS Nano lectureship (2025). Her group’s research focuses on imaging, understanding, and engineering soft, biological, and energy materials at the nanoscale.