An All‐Plastic Field‐Effect Nanofluidic Diode Gated by a Conducting Polymer Layer

The design of an all‐plastic field‐effect nanofluidic diode is proposed, which allows precise nanofluidic operations to be performed. The fabrication process involves the chemical synthesis of a conductive poly(3,4‐ethylenedioxythiophene) (PEDOT) layer over a previously fabricated solid‐state nanopore. The conducting layer acts as gate electrode by changing its electrochemical state upon the application of different voltages, ultimately changing the surface charge of the nanopore. A PEDOT‐based nanopore is able to discriminate the ionic species passing through it in a quantitative and qualitative manner, as PEDOT nanopores display three well‐defined voltage‐controlled transport regimes: cation‐rectifying, non‐rectifying, and anion rectifying regimes. This work illustrates the potential and versatility of PEDOT as a key enabler to achieve electrochemically addressable solid‐state nanopores. The synergism arising from the combination of highly functional conducting polymers and the remarkable physical characteristics of asymmetric nanopores is believed to offer a promising framework to explore new design concepts in nanofluidic devices.     

Understanding the Giant Gap between Single‐Pore‐ and Membrane‐Based Nanofluidic Osmotic Power Generators

Nanofluidic blue energy harvesting attracts great interest due to its high power density and easy‐to‐implement nature. Proof‐of‐concept studies on single‐pore platforms show that the power density approaches up to 10³ to 10⁶ W m^–2. However, to translate the estimated high power density into real high power becomes a challenge in membrane‐scale applications. The actual power density from existing membrane materials is merely several watts per square meter. Understanding the origin and thereby bridging the giant gap between the single‐pore demonstration and the membrane‐scale application is therefore highly demanded. In this work, an intuitive resistance paradigm is adopted to show that this giant gap originates from the different ion transport property in porous membrane, which is dominated by both the constant reservoir resistance and the reservoir/nanopore interfacial resistance. In this case, the generated electric power becomes saturated despite the increasing pore number. The theoretical predictions are further compared with existing experimental results in literature. For both single nanopore and multipore membrane, the simulation results excellently cover the range of the experimental results. Importantly, by suppressing the reservoir and interfacial resistances, kW m^–2 to MW m^–2 power density can be achieved with multipore membranes, approaching the level of a single‐pore system.     

Tunable Ionic Transport Control inside a Bio‐Inspired Constructive Bi‐Channel Nanofluidic Device

Inspired by the cooperative functions of the asymmetrical ion channels in living cells, a constructive bi‐channel nanofluidic device that demonstrates the enhanced capability of multiple regulations over both the ion flux amount and the ionic rectification property is prepared. In this bi‐channel system, the construction routes of the two asymmetric conical nanochannels provide a way to efficiently transform the nanodevice into four different functional working modes. In addition, the variation of external pH conditions leads the nanodevice to the uncharged, semi‐charged and charged states, where the multistory ionic regulating function property is enhanced by the charged degree. This intelligent integration of the single functional nanochannels demonstrates a promising future for building more functional multi‐channel integrated nanodevices as well as expands the functionalities of the bio‐inspired smart nanochannels.     

pH‐Regulated Heterostructure Porous Particles Enable Similarly Sized Protein Separation

Porous particles are frequently used for various healthcare applications that involve protein separation processes. However, conventional porous particles, either homogeneous particles or those subjected to surface modification with a layer of specific molecules, often encounter bottlenecks in separating proteins with similar size. Here, it is reported that heterostructure‐enabled separation particles (HESP), synthesized by a double emulsion interfacial polymerization process, can effectively and rapidly separate similarly sized proteins. Double emulsion interfacial polymerization endows the HESP with a nanoscale carboxylic layer outside the particles and inside the pores, allowing pH‐regulated selective adsorption of proteins. Thus, by optimizing the environmental pH, proteins with similar size can be effectively and rapidly separated. These HESP are expected to show potential in widespread applications ranging from biomolecule adsorption, encapsulation, and separation to controlled release and other biomedical fields.     

Light‐Powered Directional Nanofluidic Ion Transport in Kirigami‐Made Asymmetric Photonic‐Ionic Devices

Nacre‐mimetic 2D nanofluidic materials with densely packed sub‐nanometer‐height lamellar channels find widespread applications in water‐, energy‐, and environment‐related aspects by virtue of their scalable fabrication methods and exceptional transport properties. Recently, light‐powered nanofluidic ion transport in synthetic materials gained considerable attention for its remote, noninvasive, and active control of the membrane transport property using the energy of light. Toward practical application, a critical challenge is to overcome the dependence on inhomogeneous or site‐specific light illumination. Here, asymmetric photonic‐ionic devices based on kirigami‐tailored graphene oxide paper are fabricated, and directional nanofluidic ion transport properties therein powered by full‐area light illumination are demonstrated. The in‐plane asymmetry of the graphene oxide paper is essential to the generation of photoelectric driving force under homogeneous illumination. This light‐powered ion transport phenomenon is explained based on a modified carrier diffusion model. In asymmetric nanofluidic structures, enhanced recombination of photoexcited charge carriers at the membrane boundary breaks the electric potential balance in the horizontal direction, and thus drives the ion transport in that direction under symmetric illumination. The kirigami‐based strategy provides a facile and scalable way to fabricate paper‐like photonic‐ionic devices with arbitrary shapes, working as fundamental elements for large‐scale light‐harvesting nanofluidic circuits.     

Engineering 2D Nanofluidic Li‐Ion Transport Channels for Superior Electrochemical Energy Storage

Rational surface engineering of 2D nanoarchitectures‐based electrode materials is crucial as it may enable fast ion transport, abundant‐surface‐controlled energy storage, long‐term structural integrity, and high‐rate cycling performance. Here we developed the stacked ultrathin Co₃O₄ nanosheets with surface functionalization (SUCNs‐SF) converted from layered hydroxides with inheritance of included anion groups (OH^?, NO₃^?, CO₃^2?). Such stacked structure establishes 2D nanofluidic channels offering extra lithium storage sites, accelerated Li‐ion transport, and sufficient buffering space for volume change during electrochemical processes. Tested as an anode material, this unique nanoarchitecture delivers high specific capacity (1230 and 1011 mAh g^?1 at 0.2 and 1 A g^?1, respectively), excellent rate performance, and long cycle capability (1500 cycles at 5 A g^?1). The demonstrated advantageous features by constructing 2D nanochannels in nonlayered materials may open up possibilities for designing high‐power lithium ion batteries.     

Direct Fabrication of Freestanding and Patterned Nanoporous Junctions in a 3D Micro‐Nanofluidic Device for Ion‐Selective Transport

In the field of micro‐nanofluidics, a freestanding configuration of a nanoporous junction is highly demanded to increase the design flexibility of the microscale device and the interfacial area between the nanoporous junction and microchannels, thereby improving the functionality and performance. This work first reports direct fabrication and incorporation of a freestanding nanoporous junction in a microfluidic device by performing an electrolyte‐assisted electrospinning process to fabricate a freestanding nanofiber membrane and subsequently impregnating the nanofiber membrane with a nanoporous precursor material followed by a solidification process. This process also enables to readily control the geometry of the nanoporous junction depending on its application. By these advantages, vertically stacked 3D micro‐nanofluidic devices with complex configurations are easily achieved. To demonstrate the broad applicability of this process in various research fields, a reverse electrodialysis‐based energy harvester and an ion concentration polarization‐based preconcentrator are produced. The freestanding Nafion‐polyvinylidene fluoride nanofiber membrane (F‐NPNM) energy harvester generates a high power (59.87 nW) owing to the enlarged interfacial area. Besides, 3D multiplexed and multi‐stacked F‐NPNM preconcentrators accumulate multiple preconcentrated plugs that can increase the operating sample volume and the degree of freedom of handling. Hence, the proposed process is expected to contribute to numerous research fields related to micro‐nanofluidics in the future.     

Plasmonic Elastic Capsules as Colorimetric Reversible pH‐Microsensors

There is a crucial need for effective and easily dispersible colloidal microsensors able to detect local pH changes before irreversible damages caused by demineralization, corrosion, or biofilms occur. One class of such microsensors is based on molecular dyes encapsulated or dispersed either in polymer matrices or in liquid systems exhibiting different colors upon pH variations. They are efficient but often rely on sophisticated and costly syntheses, and present significant risks of leakage and photobleaching damages, which is detrimental for mainstream applications. Another approach consists of exploiting the distance‐dependent plasmonic properties of metallic nanoparticles. Still, assembling nanoparticles into dispersible colloidal pH‐sensitive sensors remains a challenge. Here, it is shown how to combine optically active plasmonic gold nanoparticles and pH‐responsive thin shells into “plasmocapsules.” Upon pH change, plasmocapsules swell or shrink. Concomitantly, the distance between the gold nanoparticles embedded in the polymeric matrix varies, resulting in an unambiguous color change. Billions of micron‐size sensors can thus be easily fabricated. They are nonintrusive, reusable, and sense local pH changes. Each plasmocapsule is an independent reversible microsensor over a large pH range. Finally, their potential use for the detection of bacterial growth is demonstrated, thus proving that plasmocapsules are a new class of sensing materials.     

pH‐Sensitive Polymeric Nanoparticles Modulate Autophagic Effect via Lysosome Impairment

In drug delivery systems, pH‐sensitive polymers are commonly used as drug carriers, and significant efforts have been devoted to the aspects of controlled delivery and release of drugs. However, few studies address the possible autophagic effects on cells. Here, for the first time, using a fluorescent autophagy‐reporting cell line, this study evaluates the autophagy‐induced capabilities of four types of pH‐sensitive polymeric nanoparticles (NPs) with different physical properties, including size, surface modification, and pH‐sensitivity. Based on experimental results, this study concludes that pH‐sensitivity is one of the most important factors in autophagy induction. In addition, this study finds that variation of concentration of NPs could cause different autophagic effect, i.e., low concentration of NPs induces autophagy in an mTOR‐dependent manner, but high dose of NPs leads to autophagic cell death. Identification of this tunable autophagic effect offers a novel strategy for enhancing therapeutic effect in cancer therapy through modulation of autophagy.