6,977 research outputs found
An atomistically informed multiscale approach to the intrusion and extrusion of water in hydrophobic nanopores
No full textUnderstanding intrusion and extrusion in nanoporous materials is a
challenging multiscale problem of utmost importance for applications ranging
from energy storage and dissipation to water desalination and hydrophobic
gating in ion channels. Including atomistic details in simulations is required
to predict the overall behavior of such systems, because the statics and
dynamics of these processes depend sensitively on microscopic features of the
pore such as the surface hydrophobicity, geometry, and charge distribution and
on the composition of the liquid. On the other hand, the transitions between
the filled (intruded) and empty (extruded) states are rare events which often
require long simulation times difficult to achieve with standard atomistic
simulations. In this work, we explored the intrusion and extrusion processes by
a multiscale approach in which the atomistic details of the system, extracted
from molecular dynamics simulations, inform a simple Langevin model of water
intrusion/extrusion in the pore. We then used the Langevin simulations to
compute the transition times at different pressures, validating our
coarse-grained model by comparing it with nonequilibrium molecular dynamics
simulations. The proposed approach reproduces experimentally relevant features
such as the time and temperature dependence of the intrusion/extrusion cycles,
as well as specific details about the shape of the cycle. This approach also
drastically increases the timescales that can be simulated allowing to reduce
the gap between simulations and experiments and showing promise for more
complex systems.Comment: This article may be downloaded for personal use only. Any other use
requires prior permission of the author and AIP Publishing. This article
appeared in "Gon\c{c}alo Paulo, Alberto Gubbiotti, Alberto Giacomello; J.
Chem. Phys. 28 May 2023; 158 (20)" and may be found at
https://doi.org/10.1063/5.014764
Mechanism of the Cassie-Wenzel transition via the atomistic and continuum string methods
No full textThe string method is a general and flexible strategy to compute the most probable transition path for an activated process (rare event). We apply here the atomistic string method in the density field to the Cassie-Wenzel transition, a central problem in the field of superhydrophobicity. We discuss in detail the mechanism of wetting of a submerged hydrophobic cavity of nanometer size and its dependence on the geometry of the cavity. Furthermore, we analyze the algorithmic analogies between the continuum “interface” string method and CREaM [Giacomello et al., Phys. Rev. Lett. 109, 226102 (2012)], a method inspired by the string that allows for a faster and simpler computation of the mechanism and of the free-energy profiles of the wetting process
Energy harvesting from flutter instabilities of heavy flags in water through ionic polymer metal composites
No full textUnderwater energy harvesting from a heavy flag hosting ionic polymer metal composites
No full textIn this paper, we analyze underwater energy harvesting from the flutter instability of a heavy flag hosting an ionic polymer metal composite (IPMC). The heavy flag comprises a highly compliant membrane with periodic metal reinforcements to maximize the weight and minimize the bending stiffness, thus promoting flutter at moderately low flow speed. The IPMC is mechanically attached to the host flag and connected to an external load. The entire structure is immersed in a mean flow whose intensity is parametrically varied to explore the onset of flutter instability along with the relation between the vibration frequency and the mean flow speed. Manageable theoretical models for fluid-structure interaction and IPMC response are presented to inform the harvester design and interpret experimental data. Further, optimal parameters for energy scavenging maximization, including resistive load and flow conditions, are identified
Temporomandibular joint disorders treated with articular injection: the effectiveness of plasma rich in growth factors-Endoret
No full textThe objective of this study was to evaluate the effectiveness of the temporomandibular joint (TMJ) osteoarthritis treatment through articular injections of plasma rich in growth factors (PGRF)-Endoret. Thirteen patients (median age, 47.64 y; SD, 7.51; range, 40-64 y; male-female ratio, 2:11) with osteoarthritis of TMJ associated to chronic pain have been selected. They were treated with articular injections of PRGF-Endoret, measuring the maximum mouth opening and pain level before the first injection (t0), 30 days after just before the second (t1), and after 6 months (t2). Data were analyzed using the paired Student's t-test data. The visual analogue scale score at t0 is 7.69 (range, 4-10; SD, 1.9), whereas that at t1 is 1.54 (range, 0-5; SD, 1.74) and that at t2 is 0.23 (range, 0-2; SD, 0.65). These differences in the results are statistically highly significant (P < 0.0001 comparison t0-t1 and t0-t2 and P < 0.01 comparison t1-t2). In terms of maximum mouth opening, it reduced from 30.15 mm at t0 (range, 26-40 mm; SD, 4.44) to 37.54 mm at t1 (range, 31-51 mm; SD, 5.10), with an increase of 7.38 mm (range, 4-11 mm; SD, 2.02) and a highly significant difference (P < 0.0001). At t2, it was 39.54 mm (range, 34-51; SD, 4.55) with an increase of 9.38 mm (range, 5-12 mm; SD, 2.21) compared with t0 and that of 2.00 mm compared with t1. Both differences in the results are statistically significant (P < 0.0001 and P < 0.01, respectively). The articular injections of PRGF-Endoret represent a very efficient method to control pain and to improve the TMJ mobility
What keeps nanopores boiling
No full textThe liquid to vapour transition can occur at unexpected conditions in
nanopores, opening the door to fundamental questions and new technologies. The
physics of boiling in confinement is progressively introduced, starting from
classical nucleation theory, passing through nanoscale effects, and terminating
to the material and external parameters which affect the boiling conditions.
The relevance of boiling in specific nanoconfined systems is discussed,
focusing on heterogeneous lyophobic systems, chromatographic columns, and ion
channels. The current level of control of boiling in nanopores enabled by
microporous materials, as metal organic frameworks, and biological nanopores
paves the way to thrilling theoretical challenges and to new technological
opportunities in the fields of energy, neuromorphic computing, and sensing
- …
