Nanoconfined Water and Flow near solid surfaces
The flow of liquid matter, such as aqueous solutions or biological fluids, in a channel or at the interface with a solid surface, is found at the heart of many biological systems, technological applications and natural phenomena. Our laboratory has performed pioneer atomic force microscopy (AFM) studies on water behavior at the nanoscale. In particular, our nano-rheology experiments showed for the first time that nanoconfined water is a non-linear viscoelastic fluid, with viscosity up to three orders of magnitude larger than bulk water. By measuring the viscoelastic modulus at different frequencies and strains, we found that the intrinsic relaxation time of nanoconfined water is in the range 0.1 – 0.0001 s, orders of magnitude longer than that one of bulk water, and comparable to the dielectric relaxation time measured in supercooled water at 170–210 K.
More recently, our group performed a set of experiments showing that the effective viscosity of nanoconfined water is strongly dependent on the chemistry of the confining surfaces. In fact, the physical-chemical interaction between the fluid and the confining surface becomes predominant in highly confined geometries and it determines a surface-dependent effective viscosity. The beauty of this work is that we are able to understand and model the measured effective viscosity by introducing the concept of boundary slip at the interface. These new simple equations can predict the viscous forces at interfaces depending on the solid surface hydrophobicity. This work is therefore defining a new set of laws in fluid dynamics when the flow occurs in highly confined geometries and the interfaces are dominant.
By developing novel experimental tools and materials, and by establishing strong collaborations with theorists and biomedical researchers, we plan to generate a blueprint for understanding liquids flow in interfacial layers and in nano-, meso-scale confinement where current models fail and effects are unknown. Our research also aims at answering fundamental and long-standing questions about interfacial water, such as understanding water structure and transport near chemically complex surfaces, e.g. in protein complexes, fuel cells and cell membranes.
Ortiz-Young, H.-C. Chiu, S. Kim, K. Voïtchovsky and E. Riedo, "The interplay between apparent viscosity and wettability in nanoconfined water", Nature Communications 4 (2013)
H.-C. Chiu, D. Ortiz-Young and E. Riedo, "Nanorheology by atomic force microscopy", Review of Scientific Instruments 85 (12), 123707 (2015)
T.-D. Li, E. Riedo, "Nonlinear viscoelastic dynamics of nanoconfined wetting liquids", Physical Review Letters 100 (10), 106102 (2008)
D. Wang, R. Szoszkiewicz, M. Lucas, T. Okada, S. Jones, S. Marder, J. Lee, W. King and E. Riedo, "Local wettability modification by thermochemical nanolithography with write-read-overwrite capability", Applied Physics Letters 91, 24 (2007)
J. Gao, R. Szoszkiewicz, U. Landman and E. Riedo, "Structured and viscous water in subnanometer gaps", Physical Review B 75 (11), 115415 (2007)
E Riedo, "Water behaves like a viscous fluid on the nano-scale", Membrane Technology 2007 (8)
L. Sirghi, R. Szoszkiewicz and E. Riedo, "Volume of a nanoscale water bridge", Langmuir 22 (3), 1093-1098 (2006)
R. Szoszkiewicz, E. Riedo, "Nucleation time of nanoscale water bridges", Physical Review Letters 95 (13), 135502 (2005)
R. Szoszkiewicz, E. Riedo, "Nanoscopic friction as a probe of local phase transitions", Applied Physics Letters 87 (3), 033105 (2005
E. Riedo, I. Palaci, C. Boragno, H. Brune, ¨2/3 power law dependence of Capillary Force in Nanoscopic Friction¨, J. Phys. Chem. B 108, 5324 (2004)
E. Riedo, F. Levy, H. Brune, ¨Kinetics of capillary condensation in nanoscopic sliding friction¨, Phys. Rev. Lett. 88, 185505-4, (2002). (Highlighted by Nature Material May 2002 and Virtual Journal of Nanoscale Science & Technology April 29, 2002).