Electrically Suppressed Outflow of Confined Liquid in Hydrophobic Nanopores

Abstract

Confining liquid in a hydrophobic nanoenvironment has enabled a broad spectrum of applications in biomedical sensors, mechanical actuators, and energy storage and converters, where the outflow of confined liquid is spontaneous and fast due to the intrinsic hydrophobic nature of nanopores with extremely low interfacial friction, challenging design capacity and control tolerance of structures and devices. Here, we present a facile approach of suppressing the outflow of water confined in hydrophobic nanopores with an electric field. Extensive molecular dynamics simulations show that the presence of an electric field could significantly strengthen hydrogen bonds and retard degradations of the associated networks during the outflow. The outflow deformation and strength are extracted to quantitatively characterize the electrical suppression to outflow and agree well with simulations. This study proposes a practical means of impeding the fast liquid outflow in hydrophobic nanopores, potentially useful for devising nanofluidics-based functional structures and devices with controllable performance.

A Nanoconfined Water–Ion Coordination Network for Flexible Energy‐Dissipation Devices

“…Immersing a hydrophobic nanopore in a liquid environment can form an energy‐dissipation system (Figure S15, Supporting Information), which relies on the infiltration–outflow process to attenuate external mechanical impact. [ 46 ] In this section, we demonstrate that the water–ion interaction mechanisms can be used to suppress the electrolyte outflow. Owing to the hydrophobic nature of the nanopore, no water molecules or ions can spontaneously infiltrate the nanopore.…”

Spontaneous Dipole Reorientation in Confined Water and Its Effect on Wetting/Dewetting of Hydrophobic Nanopores

“…For hydrophobic tubes with an aperture diameter of 20−30 Å, MD simulations showed that the same electric field does decrease the extrusion pressure. 67 The main problem is the achievement of such a strong field in experiments. An isolated monovalent ion in a vacuum creates an electric field of ca.…”

“…10 8 V/m decreases the diffusion coefficient of water in CNTs while increasing the average number of H bonds. For hydrophobic tubes with an aperture diameter of 20–30 Å, MD simulations showed that the same electric field does decrease the extrusion pressure …”

Material assembly by droplet drying: From mechanics theories to applications

“…This technique can reduce the coffee ring effect and lead to more uniform deposition by reducing the concentration gradient caused by differential evaporation rates. 111,112 Researchers have found that electrowetting hinders coffee ring formation at low alternating current frequencies, 101 as the internal flow field generated by electrowetting prevents the accumulation of solutes along the CL, resulting in a shift from a coffee ring to a dot pattern (Figure 4c), but at high frequencies above 100 kHz, the CL becomes pinned and produces a coffee ring-like pattern due to inertia. In addition to the reduction of the coffee ring effect, electrowetting can also be used to induce the formation of specific patterns during droplet evaporation by applying a spatially varying electric field, 113 leading to the creation of complex structures with potential applications in microfabrication and surface patterning.…”

“…Electrowetting alters the wetting behavior of a droplet on a substrate by applying an electric field. This technique can reduce the coffee ring effect and lead to more uniform deposition by reducing the concentration gradient caused by differential evaporation rates 111,112 . Researchers have found that electrowetting hinders coffee ring formation at low alternating current frequencies, 101 as the internal flow field generated by electrowetting prevents the accumulation of solutes along the CL, resulting in a shift from a coffee ring to a dot pattern (Figure 4c), but at high frequencies above 100 kHz, the CL becomes pinned and produces a coffee ring‐like pattern due to inertia.…”