Quantification of reagent mixing in liquid flow cells for Liquid Phase-TEM

Liquid-Phase Transmission Electron Microscopy (LP-TEM) offers the opportunity to study nanoscale dynamics of phenomena related to materials and life science in a native liquid environment and in real time. Until now, the opportunity to control/induce such dynamics by changing the chemical environment in the liquid flow cell (LFC) has rarely been exploited due to an incomplete understanding of hydrodynamic properties of LP-TEM flow systems. This manuscript introduces a method for hydrodynamic characterization of LP-TEM flow systems based on monitoring transmitted intensity while flowing a strongly electron scattering contrast agent solution. Key characteristic temporal indicators of solution replacement for various channel geometries were experimentally measured. A numerical physical model of solute transport based on realistic flow channel geometries was successfully implemented and validated against experiments. The model confirmed the impact of flow channel geometry on the importance of convective and diffusive solute transport, deduced by experiment, and could further extend understanding of hydrodynamics in LP-TEM flow systems. We emphasize that our approach can be applied to hydrodynamic characterization of any customized LP-TEM flow system. We foresee the implemented predictive model driving the future design of application-specific LP-TEM flow systems and, when combined with existing chemical reaction models, to a flourishing of the planning and interpretation of experimental observations.