Ultrashort nanopores of large radius can generate anomalously high salinity gradient power

Reverse Electrodialysis with Continuous Random Variation in Nanochannel Shape: Salinity Gradient-Driven Power Generation

The shape of nanochannels plays a crucial role in the ion selectivity and overall performance of reverse electrodialysis (RED) systems. However, current research on two-dimensional nanochannel shapes is largely limited to a few fixed asymmetric forms. This study explores the impact of randomly shaped nanochannels using dimensionless methods, controlling their randomness by varying their length and shape amplitude. The research systematically compares how alterations in the nanochannel length and shape amplitude influence various system performance parameters. Our findings indicate that increasing the nanochannel length can significantly enhance the system performance. While drastic changes in the nanochannel shape amplitude positively affect the system performance, the most significant improvements arise from the interplay between the nanochannel length and shape amplitude. This compounding effect creates a local optimum, resulting in peak system performance. Within the range of dimensionless lengths from 0 to 30, the system reaches its optimal performance at a dimensionless length of approximately 25. Additionally, we explored two other influencing factors: the nanochannel surface charge density and the concentration gradient of the solution across the nanochannel. Optimal performance is observed when the nanochannel has a high surface charge density and a low concentration gradient, particularly with random shapes. This study advances the theoretical understanding of RED systems in two-dimensional nanochannels, guiding research towards practical operational conditions.

Nanoarchitectonics in Advanced Membranes for Enhanced Osmotic Energy Harvesting

Osmotic energy, often referred to as "blue energy", is the energy generated from the mixing of solutions with different salt concentrations, offering a vast, renewable, and environmentally friendly energy resource. The efficacy of osmotic power production considerably relies on the performance of the transmembrane process, which depends on ionic conductivity and the capability to differentiate between positive and negative ions. Recent advancements have led to the development of membrane materials featuring precisely tailored ion transport nanochannels, enabling high-efficiency osmotic energy harvesting. In this review, ion diffusion in confined nanochannels and the rational design and optimization of membrane architecture are explored. Furthermore, structural optimization of the membrane to mitigate transport resistance and the concentration polarization effect for enhancing osmotic energy harvesting is highlighted. Finally, an outlook on the challenges that lie ahead is provided, and the potential applications of osmotic energy conversion are outlined. This review offers a comprehensive viewpoint on the evolving prospects of osmotic energy conversion.

Nanosensing of Acetylcholine Molecules: Influence of the Association Mechanism

A bullet-shaped nanopore surface modified by two polyelectrolyte (PE) layers, an inner polyethyleneimine (PEI) layer and an outer p-sulfonatocalix[4]-arene (SCX4) layer, is applied to sense trace levels of acetylcholine (Ach) molecules. We show that the higher the order of the association reaction of Ach with SCX4, the smaller the difference between the ionic current when Ach is present and that when it is absent, and so is the difference in the space charge density. In addition, the larger the binding constant K of that reaction, the lower the detection limit but narrower the detection range. Choosing pH 7 is most appropriate because if the pH is low, the concentration polarization of H⁺ is significant, and as it gets high, both PE layers become uncharged. At pH 7 and K = 2 × 10⁷ L/mol, the detection limit of the nanopore ranges from 1 to 10 nM, which is orders of magnitude lower than that of the other approaches.

Nanofluidic osmotic power generators - advanced nanoporous membranes and nanochannels for blue energy harvesting

The increase of energy demand added to the concern for environmental pollution linked to energy generation based on the combustion of fossil fuels has motivated the study and development of new sustainable ways for energy harvesting. Among the different alternatives, the opportunity to generate energy by exploiting the osmotic pressure difference between water sources of different salinities has attracted considerable attention. It is well-known that this objective can be accomplished by employing ion-selective dense membranes. However, so far, the current state of this technology has shown limited performance which hinders its real application. In this context, advanced nanostructured membranes (nanoporous membranes) with high ion flux and selectivity enabling the enhancement of the output power are perceived as a promising strategy to overcome the existing barriers in this technology. While the utilization of nanoporous membranes for osmotic power generation is a relatively new field and therefore, its application for large-scale production is still uncertain, there have been major developments at the laboratory scale in recent years that demonstrate its huge potential. In this review, we introduce a comprehensive analysis of the main fundamental concepts behind osmotic energy generation and how the utilization of nanoporous membranes with tailored ion transport can be a key to the development of high-efficiency blue energy harvesting systems. Also, the document discusses experimental issues related to the different ways to fabricate this new generation of membranes and the different experimental set-ups for the energy-conversion measurements. We highlight the importance of optimizing the experimental variables through the detailed analysis of the influence on the energy capability of geometrical features related to the nanoporous membranes, surface charge density, concentration gradient, temperature, building block integration, and others. Finally, we summarize some representative studies in up-scaled membranes and discuss the main challenges and perspectives of this emerging field.

Selective target protein detection using a decorated nanopore into a microfluidic device

Solid-state nanopores provide a powerful tool to electrically analyze nanoparticles and biomolecules at single-molecule resolution. These biosensors need to have a controlled surface to provide information about the analyte. Specific detection remains limited due to nonspecific interactions between the molecules and the nanopore. Here, a polymer surface modification to passivate the membrane is performed. This functionalization improves nanopore stability and ionic conduction. Moreover, one can control the nanopore diameter and the specific interactions between protein and pore surface. The effect of ionic strength and pH are probed. Which enables control of the electroosmotic driving force and dynamics. Furthermore, a study of polymer chain structure and permeability in the pore are carried out. The nanopore chip is integrated into a microfluidic device to ease its handling. Finally, a discussion of an ionic conductance model through a permeable crown along the nanopore surface is elucidated. The proof of concept is demonstrated by the capture of free streptavidin by the biotins grafted into the nanopore. In the future, this approach could be used for virus diagnostic, nanoparticle or biomarker sensing.

Improved Rectification and Osmotic Power in Polyelectrolyte-Filled Mesopores

Ample studies have shown the use of nanofluidics in the ionic diode and osmotic power generation, but similar ionic devices performed with large-sized mesopores are still poorly understood. In this study, we model and realize the mesoscale ionic diode and osmotic power generator, composed of an asymmetric cone-shaped mesopore with its narrow opening filled with a polyelectrolyte (PE) layer with high space charges. We show that, only when the space charge density of a PE layer is sufficiently large (>1×106 C/m3), the considered mesopore system is able to create an asymmetric ionic distributions in the pore and then rectify ionic current. As a result, the output osmotic power performance can be improved when the filled PE carries sufficiently high space charges. For example, the considered PE-filled mesopore system can show an amplification of the osmotic power of up to 35.1-fold, compared to the bare solid-state mesopore. The findings provide necessary information for the development of large-sized ionic diode and osmotic power harvesting device.