Nanofluidic Energy Research Articles

Asymmetric thermo-electro-osmotic responses in charged conical nanochannels

Nanofluidic thermo-electric and thermo-osmotic responses have attracted increasing attention for their potential in low-grade heat energy recovery. However, the synergistic influence of geometric asymmetry and electrolyte physical properties on these responses is often overlooked. This study investigates asymmetric thermo-electro-osmotic responses by systematically varying parameters such as conicity, Debye length, and surface charge density within conical nanochannels. We employ the numerical model coupling extended Poisson-Nernst-Planck-Navier-Stokes and energy equations to simulate ion transport, fluid flow, and heat transfer. Results demonstrate pronounced asymmetries in thermo-electric and thermo-osmotic responses between forward and backward nanochannel configurations. The short-circuit current strongly depends on conicity, Debye length, and surface charge density, while the Seebeck coefficient is primarily influenced by Debye length, and surface charge density. Thermo-osmotic flow is significantly affected by all parameters, with flow direction reversals observed under specific conditions. The study highlights that Debye length and surface charge density significantly influence both thermo-electric and -osmotic responses, whereas geometric asymmetry predominantly affects thermo-osmotic response. This study provides a valuable framework for understanding fundamental thermal-driven transport phenomena at the nanoscale. The observed synergistic effects between various parameters offer insights for optimizing thermo-electric energy conversion and fluidic control within conical nanochannels, paving the way for innovative applications in nanofluidic technology and energy recovery systems.

A nanofluidic chemoelectrical generator with enhanced energy harvesting by ion-electron Coulomb drag

A sufficiently high current output of nano energy harvesting devices is highly desired in practical applications, while still a challenge. Theoretical evidence has demonstrated that Coulomb drag based on the ion-electron coupling interaction, can amplify current in nanofluidic energy generation systems, resulting in enhanced energy harvesting. However, experimental validation of this concept is still lacking. Here we develop a nanofluidic chemoelectrical generator (NCEG) consisting of a carbon nanotube membrane (CNTM) sandwiched between metal electrodes, in which spontaneous redox reactions between the metal and oxygen in electrolyte solution enable the movement of ions within the carbon nanotubes. Through Coulomb drag effect between moving ions in these nanotubes and electrons within the CNTM, an amplificated current of 1.2 mA cm−2 is generated, which is 16 times higher than that collected without a CNTM. Meanwhile, one single NCEG unit can produce a high voltage of ~0.8 V and exhibit a linear scalable performance up to tens of volts. Different from the other Coulomb drag systems that need additional energy input, the NCEG with enhanced energy harvesting realizes the ion-electron coupling by its own redox reactions potential, which provides a possibility to drive multiple electronic devices for practical applications.

The synergistic effects of salinity and pressure gradients on sustainable energy conversion in nanofluidics

In recent years, osmotic energy conversion and electrokinetic energy conversion within nanochannels have received widespread attention. In this work, we propose four kinds of energy conversion models in nanochannels, including pressure-driven power generation, salinity-driven power generation, the positive combination of pressure gradient and salinity gradient and the negative combination. The changes in ion transport behavior and energy conversion characteristics are analyzed. The results show that the combination of salinity gradient and pressure gradient is not a simple superposition. Compared to the power of the single drive mode before optimization, the power under positive combination (PC) can reach 1.02 pW, and the power enhancement ratio is as high as 1.6. The negative combination has a certain optimization potential under a large concentration ratio and small pressure gradient condition. The higher the surface charge density, the greater the output power, but the optimization effect worsens. On the contrary, a larger channel length corresponds to a smaller output power, but the optimization effect becomes better. The reasonable choice of surface charge density and channel length needs to be weighed. These studies provide valuable guidance for the design of future nanofluidic energy conversion devices.

Interfacial Super‐Assembly of Vacancy Engineered Ultrathin‐Nanosheets Toward Nanochannels for Smart Ion Transport and Salinity Gradient Power Conversion

AbstractIon‐selective nanochannel membranes assembled from two‐dimensional (2D) nanosheets hold immense promise for power conversion using salinity gradient. However, they face challenges stemming from insufficient surface charge density, which impairs both permselectivity and durability. Herein, we present a novel vacancy‐engineered, oxygen‐deficient NiCo layered double hydroxide (NiCoLDH)/cellulose nanofibers‐wrapped carbon nanotubes (VOLDH/CNF‐CNT) composite membrane. This membrane, featuring abundant angstrom‐scale, cation‐selective nanochannels, is designed and fabricated through a synergistic combination of vacancy engineering and interfacial super‐assembly. The composite membrane shows interlayer free‐spacing of ~3.62 Å, which validates the membrane size exclusion selectivity. This strategy, validated by DFT calculations and experimental data, improves hydrophilicity and surface charge density, leading to the strong interaction with K+ ions to benefit the low ion transport resistance and exceptional charge selectivity. When employed in an artificial river water|seawater salinity gradient power generator, it delivers a high‐power density of 5.35 W/m2 with long‐term durability (20,000s), which is almost 400 % higher than that of the pristine NiCoLDH membrane. Furthermore, it displays both pH‐ and temperature‐sensitive ion transport behavior, offering additional opportunities for optimization. This work establishes a basis for high‐performance salinity gradient power conversion and underscores the potential of vacancy engineering and super‐assembly in customizing 2D nanomaterials for diverse advanced nanofluidic energy devices.

Interfacial Super-Assembly of Vacancy Engineered Ultrathin-Nanosheets Toward Nanochannels for Smart Ion Transport and Salinity Gradient Power Conversion.

Ion-selective nanochannel membranes assembled from two-dimensional (2D) nanosheets hold immense promise for power conversion using salinity gradient. However, they face challenges stemming from insufficient surface charge density, which impairs both permselectivity and durability. Herein, we present a novel vacancy-engineered, oxygen-deficient NiCo layered double hydroxide (NiCoLDH)/cellulose nanofibers-wrapped carbon nanotubes (VOLDH/CNF-CNT) composite membrane. This membrane, featuring abundant angstrom-scale, cation-selective nanochannels, is designed and fabricated through a synergistic combination of vacancy engineering and interfacial super-assembly. The composite membrane shows interlayer free-spacing of ~3.62 Å, which validates the membrane size exclusion selectivity. This strategy, validated by DFT calculations and experimental data, improves hydrophilicity and surface charge density, leading to the strong interaction with K+ ions to benefit the low ion transport resistance and exceptional charge selectivity. When employed in an artificial river water|seawater salinity gradient power generator, it delivers a high-power density of 5.35 W/m2 with long-term durability (20,000s), which is almost 400 % higher than that of the pristine NiCoLDH membrane. Furthermore, it displays both pH- and temperature-sensitive ion transport behavior, offering additional opportunities for optimization. This work establishes a basis for high-performance salinity gradient power conversion and underscores the potential of vacancy engineering and super-assembly in customizing 2D nanomaterials for diverse advanced nanofluidic energy devices.

Optimizing Nanofluidic Energy Harvesting in Synthetic Clay-based Membranes by Annealing Treatment.

Nanofluidic energy harvesting from salinity gradients is studied in 2D nanomaterials-based membranes with promising performance as high ion selectivity and fast ion transport. In addition, moving forward to scalable, feasible systems requires environmentally friendly materials to make the application sustainable. Clay-based membranes are attractive for being environmentally friendly, non-hazardous, and easy to manipulate materials. However, achieving underwater stability for clay-based membranes remains challenging. In this work, the synthetic clay Laponite is used to prepare clay-based membranes with high stability and excellent performance for osmotic energy harvesting. The Laponite membranes (Lap-membranes) are stabilized by low-temperature annealing treatment to effectively reduce the interlayer space, achieving a continuous operation under salinity gradients. Furthermore, the Lap-membranes conserve integrity while soaking in water for more than one month. The output power density improves from ≈4.97W m-2 on the pristine membrane to ≈9.89W m-2 in the membrane treated 12 h at 300°C from a 30-fold concentration gradient. Especially, It is found that the presence of interlayer water to be favorable for ion transport. Different mechanisms are proposed in the Lap-membranes involved for efficient ion selectivity and the states found with varying annealing temperatures. This work demonstrates the potential application of Laponite based nanomaterials for nanofluidic energy harvesting.

Polyoxometalate-based plasmonic electron sponge membrane for nanofluidic osmotic energy conversion.

Nanofluidic membranes have demonstrated great potential in harvesting osmotic energy. However, the output power densities are usually hampered by insufficient membrane permselectivity. Herein, we design a polyoxometalates (POMs)-based nanofluidic plasmonic electron sponge membrane (PESM) for highly efficient osmotic energy conversion. Under light irradiation, hot electrons are generated on Au NPs surface and then transferred and stored in POMs electron sponges, while hot holes are consumed by water. The stored hot electrons in POMs increase the charge density and hydrophilicity of PESM, resulting in significantly improved permselectivity for high-performance osmotic energy conversion. In addition, the unique ionic current rectification (ICR) property of the prepared nanofluidic PESM inhibits ion concentration polarization effectively, which could further improve its permselectivity. Under light with 500-fold NaCl gradient, the maximum output power density of the prepared PESM reaches 70.4 W m-2, which is further enhanced even to 102.1 W m-2 by changing the ligand to P5W30. This work highlights the crucial roles of plasmonic electron sponge for tailoring the surface charge, modulating ion transport dynamics, and improving the performance of nanofluidic osmotic energy conversion.

Highly ion-selective graphene-oxide-based membranes for nanofluidic osmotic energy conversion

Graphene oxide (GO) membranes have shown great potential for water treatment and osmotic energy conversion. However, the inherent challenge with GO membranes lies in their instability in water. While reduction techniques can improve stability, they simultaneously compromise selective ion transport properties due to the loss of functional groups. Here, we report preassembly modified GO (GOTA) membranes by using tannic acid (TA) as modification reagent. It is found that the TA molecules not only act as reducing agent, enhancing the aqueous stability of the membrane by generating stacked graphitic sp2 domains but also serve as intercalating agent, improving the selective ion transport properties by creating localized areas with high charge density and enlarged interlayer spacing. The cation selective number of GOTA membranes is ∼0.94–0.89 for different salinity gradients, much better than the thermally reduced GO membranes. In energy conversion system, the output power density approaches ∼0.32 W m−2 for the artificial seawater and river water with energy conversion efficiency of 41.7%. Meanwhile, the GOTA membranes exhibit excellent structural stability in various solution environments. This work demonstrates the importance of nanofluidic structure in improving the performance of ion-selective membranes and provides insights into the construction of advanced osmotic energy conversion system.

Optimized framework numerical solution for swirling hybrid nanofluid flow with silver/gold nanoparticles on a stretching cylinder with heat source/sink and reactive agents

Abstract The heat and mass transportation for nanofluid across a swirling cylinder under the actions of magnetic effects and Cattaneo–Christov heat flux is reported in the current analysis. The objective of this study is to examine the energy and mass transmissions through hybrid nanofluid under the influence of heat source/sink and reactive species. The hybrid nanoliquid has been prepared by the dispersion of silver (Ag) and gold (Au) nanoparticles (NPs) in the base fluid ethylene glycol (C2H6O2). The flow phenomena are expressed in the form of nonlinear partial differential equations and are converted to a nondimensional form, by employing the similarity substitution. For the computational estimation of the problem, the parametric continuation method is employed. The demonstration of velocity, mass, and energy outlines versus distinct physical factors is exposed in the form of figures. It has been perceived that the axial and swirling velocity outline drops with the influence of the Reynolds number, magnetic effect, and the insertion of Au and Ag NPs in C2H6O2. Furthermore, the hybrid nanofluid energy curve declines with the effect of the Reynolds number, thermal relaxation factor, and the volume friction of NPs.

Ion Transport Behavior in van der Waals Gaps of 2D Materials.

2D materials, with advantages of atomic thickness and novel physical/chemical characteristics, have emerged as the vital building blocks for advanced lamellar membranes which possess promising potential in energy storage, ion separation, and catalysis. When 2D materials are stacked together, the van der Waals (vdW) force generated between adjacent layered nanosheets induces the construction of an ordered lamellar membrane. By regulating the interlayer spacing down to the nanometer or even sub-nanometer scale, rapid and selective ion transport can be achieved through such vdW gaps. The further improvement and application of qualified 2D materials-based lamellar membranes (2DLMs) can be fulfilled by the rational design of nanochannels and the intelligent micro-environment regulation under different stimuli. Focusing on the newly emerging advances of 2DLMs, in this review, the common top-down and bottom-up synthesis approaches of 2D nanosheets and the design strategy of functional 2DLMs are briefly introduced. Two essential ion transport mechanisms within vdW gaps are also involved. Subsequently, the responsive 2DLMs based on different types of external stimuli and their unique applications in nanofluid transport, membrane-based filters, and energy storage are presented. Based on the above analysis, the existing challenges and future developing prospects of 2DLMs are further proposed.

Photosynthetic-Membrane-Like Ion Translocation in Visible-Light-Harvesting Nanofluidic Channels.

The selective uphill and downhill movement of protons in and out of photosynthetic membrane enabled by ion pumps and ion channels is key to photosynthesis. Reproducing the functions of photosynthetic membranes in artificial systems has been a persistent goal. Here, a visible-light-harvesting nanofluidic channels is reported which experimentally demonstrates the ion translocation functions of photosynthetic membranes. A molecular junction consisting of photosensitive ruthenium complexes linked to TiO2 electron acceptors forms the reaction centers in the nanofluidic channels. The visible-light-triggered vectorial electron injection into TiO2 establishes a difference in transmembrane potential across the channels, which enables uphill transport of ions against a 5-fold concentration gradient. In addition, the asymmetric charge distribution across the channels enables the unidirectional downhill movement of ions, demonstrating an ion rectification effect with a ratio of 18:1. This work, for the first time, mimics both the uphill and downhill ion translocation functions of photosynthetic membranes, which lays a foundation for nanofluidic energy conversion.

Bio‐inspired Double Angstrom‐Scale Confinement in Ti‐deficient Ti0.87O2 Nanosheet Membranes for Ultrahigh‐performance Osmotic Power Generation

AbstractOsmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade‐off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom‐scale confinement (DAC) to design ion‐permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC‐Ti0.87O2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2 Å, which not only generates a profitable confinement effect for Na+ ions to enable high ion selectivity but also induces a strong interaction with Na+ ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC‐Ti0.87O2 membranes achieved an ultrahigh power density of 17.8 W m−2 by mixing 0.5/0.01 M NaCl solution and up to 114.2 W m−2 with a 500‐fold salinity gradient, far exceeding all the reported macroscopic‐scale membranes. This work highlights the potential of the construction of DAC ion‐permselective channels for two‐dimensional materials in high‐performance nanofluidic energy systems.

Bio-inspired Double Angstrom-Scale Confinement in Ti-deficient Ti0.87 O2 Nanosheet Membranes for Ultrahigh-performance Osmotic Power Generation.

Osmotic power, a clean energy source, can be harvested from the salinity difference between seawater and river water. However, the output power densities are hampered by the trade-off between ion selectivity and ion permeability. Here we propose an effective strategy of double angstrom-scale confinement (DAC) to design ion-permselective channels with enhanced ion selectivity and permeability simultaneously. The fabricated DAC-Ti0.87 O2 membranes possess both Ti atomic vacancies and an interlayer free spacing of ≈2.2 Å, which not only generates a profitable confinement effect for Na+ ions to enable high ion selectivity but also induces a strong interaction with Na+ ions to benefit high ion permeability. Consequently, when applied to osmotic power generation, the DAC-Ti0.87 O2 membranes achieved an ultrahigh power density of 17.8 W m-2 by mixing 0.5/0.01 M NaCl solution and up to 114.2 W m-2 with a 500-fold salinity gradient, far exceeding all the reported macroscopic-scale membranes. This work highlights the potential of the construction of DAC ion-permselective channels for two-dimensional materials in high-performance nanofluidic energy systems.

Construction of metal-organic framework/cellulose nanofibers-based hybrid membranes and their ion transport property for efficient osmotic energy conversion

The development of advanced nanofluidic membranes with better ion selectivity, efficient energy conversion and high output power density remains challenging. Herein, we prepared nanofluidic hybrid membranes based on TEMPO oxidized cellulose nanofibers (T-CNF) and manganese-based metal organic framework (MOF) using a simple in situ synthesis method. Incorporated T-CNF endows the MOF/T-CNF hybrid membrane with a high cation selectivity up to 0.93. Nanoporous MOF in three-dimensional interconnected nanochannels provides massive ion transport pathways. High transmembrane ion flux and low ion permeation energy barrier are correlated with a superior energy conversion efficiency (36 %) in MOF/T-CNF hybrid membrane. When operating under 50-fold salinity gradient by mixing simulated seawater and river water, the MOF/T-CNF hybrid membrane achieves a maximum power density value of 1.87 W m−2. About 5-fold increase in output power density was achieved compared to pure T-CNF membrane. The integration of natural nanofibers with high charge density and nanoporous MOF materials is demonstrated an effective and novel strategy for the enhancement of output power density of nanofluidic membranes, showing the great potential of MOF/T-CNF hybrid membranes as efficient nanofluidic osmotic energy generators.

PH-temperature coupled regulation for promoted nanofluidic osmotic energy conversion

pH and temperature regulation effectively enhance the performance of nanofluidic osmotic energy conversion, but their combination is rarely studied numerically, causing unclear influences on selective ion transport and power generation. In this study, a model considering the coupled influence of pH and temperature on interfacial reactions is established for osmotic energy conversion. The increases in pH and temperature synergistically promote the interfacial deprotonation reaction and increase the surface charge density. Accordingly, the dimensionless number called the electrical double layer intensity is defined to describe the neutral deviation of the electrical double layer, which is obviously enhanced by raising the pH and temperature at low pH. Moreover, according to the pH value and ion selectivity, the energy conversion performance under temperature regulation is divided into the interface-dominant zone and the solution-dominant zone. The elevated temperature improves the osmotic energy conversion mainly by improving the interface property at a low pH but mainly by altering the solution properties at a high pH. Finally, fluid convection plays an important role at a relatively high pH value. This work provides a comprehensive understanding of the pH and temperature coupled regulation mechanisms and points out the design route for high output power.

Effect of solid obstacle and thermal conditions on convective flow and entropy generation of nanofluid filled in a cylindrical chamber

PurposeOne of the major challenges in the design of thermal equipment is to minimize the entropy production and enhance the thermal dissipation rate for improving energy efficiency of the devices. In several industrial applications, the structure of thermal device is cylindrical shape. In this regard, this paper aims to explore the impact of isothermal cylindrical solid block on nanofluid (Ag – H2O) convective flow and entropy generation in a cylindrical annular chamber subjected to different thermal conditions. Furthermore, the present study also addresses the structural impact of cylindrical solid block placed at the center of annular domain.Design/methodology/approachThe alternating direction implicit and successive over relaxation techniques are used in the current investigation to solve the coupled partial differential equations. Furthermore, estimation of average Nusselt number and total entropy generation involves integration and is achieved by Simpson and Trapezoidal’s rules, respectively. Mesh independence checks have been carried out to ensure the accuracy of numerical results.FindingsComputations have been performed to analyze the simultaneous multiple influences, such as different thermal conditions, size and aspect ratio of the hot obstacle, Rayleigh number and nanoparticle shape on buoyancy-driven nanoliquid movement, heat dissipation, irreversibility distribution, cup-mixing temperature and performance evaluation criteria in an annular chamber. The computational results reveal that the nanoparticle shape and obstacle size produce conducive situation for increasing system’s thermal efficiency. Furthermore, utilization of nonspherical shaped nanoparticles enhances the heat transfer rate with minimum entropy generation in the enclosure. Also, greater performance evaluation criteria has been noticed for larger obstacle for both uniform and nonuniform heating.Research limitations/implicationsThe current numerical investigation can be extended to further explore the thermal performance with different positions of solid obstacle, inclination angles, by applying Lorentz force, internal heat generation and so on numerically or experimentally.Originality/valueA pioneering numerical investigation on the structural influence of hot solid block on the convective nanofluid flow, energy transport and entropy production in an annular space has been analyzed. The results in the present study are novel, related to various modern industrial applications. These results could be used as a firsthand information for the design engineers to obtain highly efficient thermal systems.

Advanced Janus membrane (MXene/CoAl-LDH) for efficient asymmetric ion transport and nanofluidic energy harvesting

Two-dimensional (2D) material membranes with nanometer or sub-1 nanometer confined space present enormous potential for water permeation, ion sieving and transport. In addition, electrolyte flowing through the asymmetric channels exhibits ion asymmetric transport behavior which provides a basis to control the ion flow. Therefore, it is an opportunity to develop Janus membranes by 2D materials for alleviating the concentration polarization and enhancing the performance in nanofluidic energy harvesting. Whereas the previously reported 2D material-based Janus laminated membranes were adjusted interlayer charge distribution by modifying positively charged polymer, due to the intrinsically negative surface charge of these 2D nanosheets. Thus, design of 2D/2D Janus membrane from positive and negative changed 2D materials will have great opportunity for efficient asymmetric ion transport and nanofluidic energy harvesting. In this work, Janus MXene/LDH (MXLDH) membranes containing negatively charged MXene and positively charged CoAl-LDH were designed without additional modifying process for efficient ion asymmetric transport and neutralization energy harvesting. The ratio of MXene/LDH draws a significant effect on ion rectification factor, osmotic voltage, ion selectivity and energy conversion efficiency. The Janus membrane with 86 wt% LDH (MXLDH-86) revealed the highest rectification factor of ∼6.2 in 0.1 mM NaCl aqueous solution. And the osmotic power density of MXLDH-86 under 1 M HCl/ 1 M NaOH can reach ∼8.75 W/m2, ∼17.7 % higher than that of the pristine MXene membrane, indicating that the Janus membrane with asymmetric charges is a promising material for harvesting neutralization energy.

Thermoenviroeconomic performance augmentation of solar desalination unit integrated with wick, nanofluid, and different nano-based energy storage materials

The current paper introduces conducted efforts to augment the thermo-enviroeconomic characteristics of a hemispherical solar still (HSS) incorporating various improvements. These proposed modifications were applied to the HSS in sequence and each case was tested and compared to another ordinary HSS. In the first stage, corrugated copper covered with black cotton fabric was used as absorber and paraffin wax, used as phase change material (PCM), was filled under the absorber. Then, the second stage was tested using the same design but with sheep fat instead of the paraffin wax. In the third stage, graphite nanofluid was used in the basin of the previous design. Finally, the pure sheep fat was replaced with nano-based one by dispersing graphite nanoparticles in the sheep fat. Taking the experimental data as independent parameters, the thermo-enviroecomonic indicators were calculated. The daily yield augmentation ratios were 43 %, 59.77 %, 78.77 %, and 95.2 %, for the four cases, respectively. The best thermos-economic performance was reached using the final case as it had thermal and exergy efficiencies of 61.7 % and 5.8 %, likewise, equivalent improvements by 94.76 %, and 110.1 %. Furthermore, the freshwater price was decreased to 0.0106 $/L referring to a cost reduction of 33.90 %. Moreover, the environmental analysis resulted a 6.27-ton CO2/year reduction in CO2 emission, which refers to a cost of 90.89 $/year.

Study of Temperature Effect on Cascade Characteristics of Nanofluidic Energy Absorption System

Nanofluidic energy absorption system (NEAS) with cascade energy absorption characteristics can absorb energy on different levels simultaneously in one system, which greatly enriches its functions and applications. The pore structure and size distribution of porous media play a crucial role in the design and construction of cascade nanofluidic systems. In this paper, two cascade pore models were constructed using carbon nanotubes with different diameters, one was the model of two tubes with both one end immersed in water (DNEAS), and the other was the model of two tubes end to end, with the end of the big tube immersed in water (SNEAS). The effects of temperature-coupled pore size on the infiltration processes of water molecules into two models were investigated. The fitting correlations between critical pore size difference and temperature were established. The microscopic mechanism of temperature effect was illuminated. With the increase in temperature, systems displaying cascade characteristics transformed into a single-stage system without cascade characteristics. Due to the significant size effect of system temperature, the critical pore difference increased with both system temperature and the pore size. The research results expanded the basic database of cascade nanofluidic systems and provided guidance for the application design of cascade nanofluidic systems.

Nature-Inspired Stalactite Nanopores for Biosensing and Energy Harvesting.

Nature provides a wide range of self-assembled structures from the nanoscale to the macroscale. Under the right thermodynamic conditions and with the appropriate material supply, structures like stalactites, icicles, and corals can grow. However, the natural growth process is time-consuming. This work demonstrates a fast, nature-inspired method for growing stalactite nanopores using heterogeneous atomic deposition of hafnium dioxide at the orifice of templated silicon nitride apertures. The stalactite nanostructures combine the benefits of reduced sensing region typically for 2-dimensional material nanopores with the asymmetric geometry of capillaries, resulting in ionic selectivity, stability, and scalability. The proposed growing method provides an adaptable nanopore platform for basic and applied nanofluidic research, including biosensing, energy science, and filtration technologies.