Viscosity at the Nanoscale: Confined Liquid Dynamics and Thermal Effects in Self-Recovering Nanobumpers

Abstract

Understanding the effect of liquid viscosity in nanoconfinement is of paramount importance from both the fundamental and practical points of view. In particular, unexpected dynamic phenomena are ubiquitous in a broad range of nanofluidic applications. In this work, we used state-of-the-art high-pressure (P,V,T) calorimetry for direct observation of pressure, volume, temperature, and thermal effects during controlled intrusion/extrusion of liquids in nanoporous materials. It was discovered that the liquid extrusion pressure and the accompanying thermal effects can be controlled by changing solely the liquid viscosity. Such knowledge allowed us to propose the {nanoporous material + nonwetting liquid} system as a self-recovering nanobumper and to clarify the parameters for its optimization. Experimental results were interpreted in terms of confined classical nucleation theory as the slowdown of bubble expansion in the nanopores because of the high liquid viscosity. The present results are of practical value for designing energy storage/dissipation devices based on intrusion/extrusion cycles, as well as of fundamental importance for understanding the effect of viscosity in nanoconfined liquids.

Compact Thermal Actuation by Water and Flexible Hydrophobic Nanopore

“…19,45 It was also demonstrated experimentally that increasing viscosity can turn the intrusion process from endothermic to exothermic. 44 For microporous materials endothermic intrusion and exothermic extrusion was reported for MFI zeolites, 21−23 while opposite signs of thermal effects were recorded for chabazite zeolite. 46 This difference was attributed to topology.…”

“…It should be noted that, even though the majority of the studied systems feature endothermic intrusion and exothermic extrusion, it is not the general case. When a pore is large enough for a macroscopic description to be appropriate, thermodynamics suggest that intrusion/extrusion can be endothermic or exothermic depending on the contact angle and surface entropy. , It was also demonstrated experimentally that increasing viscosity can turn the intrusion process from endothermic to exothermic . For microporous materials endothermic intrusion and exothermic extrusion was reported for MFI zeolites, − while opposite signs of thermal effects were recorded for chabazite zeolite .…”

Liquid intrusion in and extrusion from non-wettable nanopores for technological applications

“…This is why in the literature it is often reported that wetting of cavities is irreversible [32]. One should remark that the extrusion barrier decreases with the characteristic length of the cavity; thus for nanometric lyophobic cavities (contact angle θ Y > 90 • ) extrusion can take place at positive pressures [33][34][35][36][37][38].…”

Turning Molecular Springs into Nano-Shock Absorbers: The Effect of Macroscopic Morphology and Crystal Size on the Dynamic Hysteresis of Water Intrusion–Extrusion into-from Hydrophobic Nanopores

“…Typical examples of shock-absorber HLSs include mesoporous grafted silica gels + water/aqueous solutions − and recently extensions were made to metal–organic framework (MOF) + water/aqueous solution systems . MOFs, due to their unique mechanical properties, , allow additional tuning of the intrusion–extrusion process and novel applications. , Alternatives to water/aqueous systems have also been studied using ionic liquid, ferromagnetic fluids or glycerin, and glycerol. , These systems demonstrated good reproducibility and durability , and were rather quickly used as a basis to construct novel shock-absorbers and bumpers. ,, On the other hand, examples for molecular spring behavior have only been reported for the intrusion of water/aqueous solutions into a handful of microporous materials such as zeolites − and MOFs …”