Nanopores and nanochannels are ubiquitous, from biological systems to various artificial materials. Taking advantage of size confinement and tailoring the interior components, numerous functions can be achieved such as selectivity, gating, rectification, and so on, which result from diverse interactions between ion/molecule and nanopore/nanochannel. In this Perspective, on account of the summarized critical principles, namely size/shape, wettability, charge, recognition, and other interactions during ion/molecule transportation in nanopores and nanochannels, we introduce four main sections of applications: selective transportation in separation, controllable gating systems, energy conversion devices, and sensors. In addition, some typical challenges and possible future research endeavors in the related fields will also be discussed.

Nanochannels based on smart DNA hydrogels as stimulus-responsive architecture are presented for the first time. In contrast to other responsive molecules existing in the nanochannel in monolayer configurations, the DNA hydrogels are three-dimensional networks with space negative charges, the ion flux and rectification ratio are significantly enhanced. Upon cyclic treatment with K ions and crown ether, the DNA hydrogel states could be reversibly switched between less stiff and stiff networks, providing the gating mechanism of the nanochannel. Based on the architecture of DNA hydrogels and pH stimulus, cation or anion transport direction could be precisely controlled and multiple gating features are achieved. Meanwhile, G-quadruplex DNA in the hydrogels might be replaced by other stimulus-responsive DNA molecules, peptides, or proteins, and thus this work opens a new route for improving the functionalities of nanochannel by intelligent hydrogels.

Current metal film-based electronics, while sensitive to external stretching, typically fail via uncontrolled cracking under a relatively small strain (~30%), which restricts their practical applications. To address this, here we report a design approach inspired by the stereocilia bundles of a cochlea that uses a hierarchical assembly of interfacial nanowires to retard penetrating cracking. This structured surface outperforms its flat counterparts in stretchability (130% versus 30% tolerable strain) and maintains high sensitivity (minimum detection of 0.005% strain) in response to external stimuli such as sounds and mechanical forces. The enlarged stretchability is attributed to the two-stage cracking process induced by the synergy of micro-voids and nano-voids. In-situ observation confirms that at low strains micro-voids between nanowire clusters guide the process of crack growth, whereas at large strains new cracks are randomly initiated from nano-voids among individual nanowires.

gating as a promising candidate has been proposed as it is an easy manipulation and high stability method. [7] However, how to regulate the ion transport in nanoscale with excellent controllability, good stability, and high gating ratio remains a challenge.Ferrofluid as an intelligent liquid, which could reconfigure the surface topography under the magnetic field, could be used as a smart liquid gating to control the ion transport in nanoscale. Herein, we designed a magnetic gated nanofluidic (MGN) based on the integration of superhydrophilic nanochannels and reconfigurable ferrofluid. The reconfigurable shape of the ferrofluid, resembling the biological counterparts of the sebum membrane of the epidermis, is used to control the ion transport. As shown in Figure 1a,b, through manipulating the permanent magnet to change the steric configuration of the ferrofluid, [8] we constructed a switchable gating system with high gating ratio (≈10 000) and excellent stability (130 cycles). And the shapeable ferrofluid not only regulates the ion flow similar to the sebum membrane in immune systems but also realizes fast response to the magnetic field. The experiment and simulation analysis prove that the superhydrophilic surface with bound water is vital to our system, [9] which prevents the ferrofluid from entering the nanochannel of the membrane, and leads to a low oil adhesion further facilitating the high The design of intelligent gating in nanoscale is the subject of intense research motivated by a broad potential impact on science and technology. However, the existing designs require complex modification and are unstable, which restrict their practical applications. Here, a magnetic gated nanofluidic is reported based on the integration of superhydrophilic membranes and reconfigurable ferrofluid, which realizes the gating of the nanochannel by adjusting the steric configuration of the ferrofluid. This system could achieve ultrahigh gating ratio up to 10 000 and excellent stability up to 130 cycles without attenuation. Experiments and theoretical calculations demonstrate that the switch is controlled by the synergy of magnetic force and the interfacial tension. The introduction of ferrofluid and superhydrophilic nanochannels in this work presents an important paradigm for the nanofluidic systems and opens a new and promising avenue to various developments in the fields of materials science, which may be utilized in medical devices, nanoscale synthesis, and environmental analysis. FerrofluidsRegulating substances transport such as ion and water in nanoscale is of great significance in real-world applications, such as biological sensing, [1] drug delivery, [2] species separation, [3] energy harvesting, [4] etc. So far, various functional membranes for ion gating have been widely investigated with external triggers ranging from a single response to multiple responses. [5] Although those gating systems are intelligent and efficient, their applications are plagued with the problem of low stability, slow response, comple...

Reversible switching of water-droplet adhesion on solid surfaces is of great significance for smart devices, such as microfluidics. In this work, we designed a foolproof method for fast and reversible magnet-controlled switching of water-droplet adhesion surfaces by doping iron powders in soft poly(dimethylsiloxane). The water adhesion is adjusted by magnetic field-induced structure changes, avoiding complex chemical or physical surface design. The regulation process is so convenient that only tens of milliseconds are needed. The on-site responsive mechanism extends its use to unusual curved surfaces. Moreover, the excellent reversibility and stability make the film an ideal candidate for real-time applications.