Current progress in glass-based nanochannels

Abstract:

Glass-based nanochannels have become powerful tools for chemical and biological sensing due to their advantages of easy preparation, flexible modification, and high sensitivity. Lately, research on ion transport behaviors in glass-based nanochannels and their applications in nanofluidic iontronics has gradually become a focus, including various ion transport behaviors such as resistive-pulse, ion rectification, ionic current memory, etc. In this review, we summarize the progress of manufacturing methods for glass-based nanochannels and discuss several typical ion transport behaviors of glass-based nanochannels, as well as the main application scenarios of glass-based nanochannels in terms of biosensing, detection, and neuromorphic functions. The enormous assistance of artificial intelligence in the standardized manufacturing process of glass-based nanochannels was anticipated, and the potential development of glass-based nanochannels in achieving neuromorphic functions was expected.

Confined gas transport in low-dimensional materials

Abstract:

Gas transport under confinement exhibits a plethora of physical and chemical phenomena that differ from those observed in bulk media, owing to the deviations of continuum description at the molecular level. In biological systems, gas channels play indispensable roles in various physiological functions by regulating gas transport across cell membranes. Therefore, investigating gas transport under such confinement is crucial for comprehending cellular physiological activities. Moreover, leveraging these underlying mechanisms can enable the construction of bioinspired artificial nanofluidic devices with tailored gas transport properties akin to those found in biological channels. This review provides a comprehensive summary of confined gas transport mechanisms, focusing on the unique effects arising from nanoconfinement. Additionally, we categorize nanoconfinement spaces based on dimensionality to elucidate their control over gas transport behavior. Finally, we highlight the potential of bioinspired smart gas membranes that mimic precise modulation of transportation observed in organisms. To conclude, we present a concise outlook on the challenges and opportunities in this rapidly expanding field.

Voltage controlled iontronic switches: a computational method to predict electrowetting in hydrophobically gated nanopores

Abstract:

Reliable and controllable switches are crucial in nanofluidics and iontronics. Ion channels found in nature serve as a rich source of inspiration due to their intricate mechanisms modulated by stimuli like pressure, temperature, chemical species, and voltage. The artificial replication of the properties of these channels is challenging due to their complex chemistry, limited stability range, and intricate moving parts, allosterically modulated. Nonetheless, we can harness some of the gating mechanisms of ion channels for nanofluidic and iontronic purposes. This theoretical and computational study explores the use of electrowetting in simple hydrophobic nanopores to control their conductance using an external applied voltage. We employ restrained molecular dynamics to calculate the free energy required for wetting a model nanopore under different voltages. Utilizing a simple theory, we generate free energy profiles across a wide voltage range. We also computed transition rates between conductive and non-conductive states, showing their voltage dependence and how this behavior can impair memory to the system, resembling the memristor behavior voltage-gated channels in the brain. The proposed framework provides a promising avenue for designing and controlling hydrophobic nanopores via electrowetting, enabling potential applications in neuromorphic iontronics.

Selective and asymmetric ion transport in covalent organic framework-based two-dimensional nanofluidic devices

Abstract:

Two-dimensional (2D) covalent organic framework (COF) membranes featuring well-aligned and programmable vertical nanochannels have emerged as a promising candidate for advanced nanofluidic devices and showcased vast potential in the fields of smart-gating, ion-separation, and energy-harvesting. However, the transverse interlayer nanochannels with a height of sub-nanometer-scale in 2D-COF membranes have scarcely been studied in comparison. Here, we report the ion transport characteristics in 2D interlayer nanochannels of protonated COF membranes. The distinct surface-charge-governed ionic conductance in domination of electrolyte concentration below 10−3 M as well as the exceptional anion/cation (Cl−/K+) selectivity is revealed due to the pronounced charge and nano-confinement effects. Additionally, evident ion current rectification is witnessed when incorporating asymmetric geometry into the system, which is attributed to the dynamic process of ion enrichment and dissipation within the protonated nanochannels. This work offers immense prospects for 2D-COF membranes in the fields of biomimetic nanofluidic devices and cutting-edge electronic devices.

Bioinspired ionic control for energy and information flow

Abstract:

The control of ion transport by responding to stimulus is a necessary condition for the existence of life. Bioinspired iontronics could enable anomalous ion dynamics in the nanoconfined spaces, creating many efficient energy systems and neuromorphic in-sensor computing networks. Unlike traditional electronics based on von Neumann computing architecture, the Boolean logic computing based on the iontronics could avoid complex wiring with higher energy efficiency and programmable neuromorphic logic. Here, a systematic summary on the state of art in bioinspired iontronics is presented and the stimulus from chemical potentials, electric fields, light, heat, piezo and magnetic fields on ion dynamics are reviewed. Challenges and perspectives are also addressed in the aspects of iontronic integrated systems. It is believed that comprehensive investigations in bioinspired ionic control will accelerate the development on more efficient energy and information flow for the futuristic human-machine interface.

Electric-double-layer-gated 2D transistors for bioinspired sensors and neuromorphic devices

Abstract:

Electric double layer (EDL) gating is a technique in which ions in an electrolyte modulate the charge transport in an electronic material through electrical field effects. A sub-nanogap capacitor is induced at the interface of electrolyte/semiconductor under the external electrical field and the capacitor has an ultrahigh capacitance density (~µF cm−2). Recently, EDL gating technique, as an interfacial gating, is widely used in two-dimensional (2D) crystals for various sophisticated materials characterization and device applications. This review introduces the EDL-gated transistors based on 2D materials and their applications in the field of bioinspired optoelectronic detection, sensing, logic circuits, and neuromorphic computation.

SMA-origami coupling: online configuration switches and stability property modulation

Abstract:

Active folding is a crucial requirement for practical applications of multi-stable origami structures. However, research on integrating active materials with origami structures to enable quick configuration switching and modulation of stability properties is still in its early stages. To advance the state-of-the-art, we designed a coupled structure comprising a stacked Miura-origami (SMO) structure and two Shape Memory Alloy (SMA) actuators. One actuator is used for extruding the SMO structure while the other is used for retracting, thereby realizing bidirectional reversible active folding of the coupled structure. Modeling the potential energy of the coupled structure shows that it can be switched between monostable and bistable by heating the SMA actuators. The above findings are also confirmed by experiments conducted on a delicate SMO-SMA coupled structure prototype. The activation of different actuators induces rapid configuration switching of the coupled structure, and the stability profile is qualitatively adjusted by designing the current loading profile to achieve steady-state temperature fluctuations. Overall, this study provides a new approach to coupling origami structures with smart materials for active folding and presents a novel method to regulate the stability property of origami structures, thus promoting their practical applications.

A novel reprocessable chloroprene rubber based on dynamic disulfide metathesis

Abstract:

For sustainable application of chloroprene rubber (CR), a new technology is developed by the vulcanization of CR using 2,2’-dithiodipyridine (DPD) as a cross-linking agent with the reprocessing performance owing to disulfide metathesis. When DPD was incorporated into CR vulcanization, the Menschutkin reaction between allyl chloride group and pyridine group occurred with a maximum exothermic peak at 184°C. The number of effective cross-linking bond at 0.5 phr DPD vulcanizate was higher than that at high DPD content. This vulcanizate showed high tensile strength (11.12 MPa) and elongation at break (1253 ± 120%) owing to the exchangeable disulfide bond in the system. Under the catalysis of triphenylphosphine, the metathesis of disulfide compound was improved obviously, which endowed CR/DPD vulcanizates with good recyclability performance. Disulfide cross-linkage maintains its stability at low temperature, thus ensuring the mechanical stability of CR/DPD vulcanizate under the ambient conditions. Vulcanization and reprocessing of CR/DPD vulcanizate can be conducted with common industrial rubber processing equipment. Such reprocessable chloroprene rubber could have potential application in CR industry, also serve to significantly improve environmental sustainability.

Analysis of nonlinear multi-field coupling responses of piezoelectric semiconductor rods via machine learning

Abstract:

Piezoelectric semiconductors (PSs) have widespread applications in semiconductor devices due to the coexistence of piezoelectricity and semiconducting properties. It is very important to conduct a theoretical analysis of PS structures. However, the present of nonlinearity in the partial differential equations (PDEs) that describe those multi-field coupling mechanical behaviors of PSs poses a significant mathematical challenge when studying these PS structures. In this paper, we present a novel approach based on machine learning for solving multi-field coupling problems in PS structures. A physics-informed neural networks (PINNs) is constructed for predicting the multi-field coupling behaviors of PS rods with extensional deformation. By utilizing the proposed PINNs, we evaluate the multi-field coupling responses of a ZnO rod under static and dynamic axial forces. Numerical results demonstrate that the proposed PINNs exhibit high accuracy in solving both static and dynamic problems associated with PS structures. It provides an effective approach to predicting the nonlinear multi-field coupling phenomena in PS structures.

Nanodiamond reinforced self-healing and transparent poly(urethane–urea) protective coating for scratch resistance

Abstract:

With increasing demand for scratch-resistant flexible electronics, the development of transparent coatings with good scratch resistance and self-healing properties has emerged as a key research topic. In this study, a high-strength self-healing poly(urethane – urea) (PUU)-based nanocomposite coating was prepared by introducing functionalized nanodiamond (ND) into a PUU matrix via solution blending. The PUU matrix had hard-segment repeating units and was constructed using isophorone diamine and isophorone isocyanate. The ND particles were modified using a silane coupling agent, 3-aminopropyltriethoxysilane, to obtain well-dispersed KH-ND nanoparticles. KH-ND promoted microphase separation in the PU matrix, inducing the formation of dense and homogeneous hard domains that dissipated stress, prevented further crack development, and improved the mechanical properties and scratch resistance of the coating. In addition, the coating exhibited excellent self-healing properties. Fourier-transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy were used to characterize the self-healing and hardening mechanisms of the coating. The environmentally friendly PUU/KH-ND coating is easy to prepare and has broad application prospects in transparent and anti-scratch coatings for flexible electronics, automobiles, and home appliances.

Multi-stable straw-like carbon nanotubes for mechanical programmability at microscale

Abstract:

Inspired by macroscale 3D pixel mechanical metamaterials and microscale straw-like carbon nanotube, we propose a design of multi-stable straw-like carbon nanotubes (MSCNT) via optimizing the structure of a unit to obtain multiple stable states under displacement loading by molecular dynamics. The unit of MSCNT is mirror-symmetrically connected two truncated graphene cones with specific apex angles. By switching the LJ term in AIREBO potential, we verify that the bistability of unit is co-determined by snap-through instability and microscale adhesions. Moreover, we examine the validity of the multi-stability of the unit cells arranged in series and in parallels. Simulation results indicate that the MSCNT can achieve mechanical programmability in microscale, which triggers many potential applications in need of customizing nanoscale mechanical behaviors.

The rate dependence of the dielectric strength of dielectric elastomers

Abstract:

Elastomers are widely used in electronics and electrical devices, either as insulators or transducers. The insulation and actuation performance of elastomers are highly susceptible to their dielectric strength. Among the factors that influence the dielectric strength of elastomers, material viscoelasticity is an important factor that needs further investigation. Since the material viscoelasticity is often characterized by rate-dependent behaviors, we present two different sample configurations to experimentally examine the electrical and mechanical rate dependence of the dielectric strength of VHB 4905 elastomers. At pre-stretch ratio of 4, the improvement of the dielectric strength is about 30% from voltage ramp of 50 V/s to 800 V/s. Particularly, with an in-house biaxial test platform, the effect of the stretching rate on the dielectric strength is examined for the first time. The improvement of the dielectric strength is about 35% from stretching rate of 0.1 mm/s to 5 mm/s. Moreover, a dielectric strength predictor based on configurational stress is adopted to describe the experimental data. According to the predictor, the loading rate affects the dielectric strength of the elastomer mainly by influencing the evolution of the inelastic deformation.