Nanofluidics derived from low‐dimensional nanosheets and protein nanochannels are crucial for advanced catalysis, sensing, and separation. However, polymer nanofluidics is halted by complicated ...preparation and miniaturized sizes. This work reports the bottom‐up synthesis of modular nanofluidics by confined growth of ultrathin metal–organic frameworks (MOFs) in a polymer membrane consisting of zwitterionic dopamine nanoparticles (ZNPs). The confined growth of the MOFs on the ZNPs reduces the chain entanglement between the ZNPs, leading to stiff interfacial channels enhancing the nanofluidic transport of water molecules through the membrane. As such, the water permeability and solute selectivity of MOF@ZNPM are one magnitude improved, leading to a record‐high performance among all polymer nanofiltration membranes. Both the experimental work and the molecular dynamics simulations confirm that the water transport is shifted from high‐friction‐resistance conventional viscous flow to ultrafast nanofluidic flow as a result of rigid and continuous nanochannels in MOF@ZNPM.
A rigid‐scaffold‐reinforced polymeric nanoparticles’ interfacial channel strategy is proposed for fabricating nanofluidic membranes that exhibit water permeance and dye/salt selectivity that are 1–2 orders of magnitude higher than conventional polymeric membranes. The unprecedented separation performance is due to the paradigm shift of water transport from conventional viscous flow to ultrafast nanofluidic flow in the membrane nanofluidics.
Abstract
Metal–organic frameworks (MOFs) are highly versatile materials that have been identified as promising candidates for membrane‐based gas separation applications due to their uniformly narrow ...pore windows and virtually unlimited structural and chemical features. Defect engineering of MOFs has opened new opportunities for manipulating MOF structures, providing a simple yet efficient approach for enhancing membrane separation. However, the utilization of this strategy to tailor membrane microstructures and enhance separation performance is still in its infancy. Thus, this summary aims to provide a guideline for tailoring defective MOF‐based membranes. Recent developments in defect engineering of MOF‐based membranes will be discussed, including the synthesis strategies for defective MOFs, the effects of defects on the gas adsorption properties, gas transport mechanisms, and recently reported defective MOF‐based membranes. Furthermore, the emerging challenges and future prospects will be outlined. Overall, defect engineering offers an exciting opportunity to improve the performance of MOF‐based gas membranes. However, there is still a long way to go to fully understand the influence of defects on MOF properties and optimize the design of MOF‐based membranes for specific gas separation applications. Nonetheless, continued research in this field holds great promise for the development of next‐generation membrane‐based gas separation technologies.
Mixed matrix membranes (MMMs), conjugating the advantages of flexible processing‐ability of polymers and high‐speed mass transfer of porous fillers, are recognized as the next‐generation ...high‐performance CO2 capture membranes for solving the current global climate challenge. However, controlling the crystallization of porous metal‐organic frameworks (MOFs) and thus the close stacking of MOF nanocrystals in the confined polymer matrix is still undoable, which thus cannot fully utilize the superior transport attribute of MOF channels. In this study, the “confined swelling coupled solvent‐controlled crystallization” strategy is employed for well‐tailoring the in‐situ crystallization of MOF nanocrystals, realizing rapid (<5 min) construction of defect‐free freeway channels for CO2 transportation in MMMs due to the close stacking of MOF nanocrystals. Consequently, the fabricated MMMs exhibit approximately fourfold enhancement in CO2 permeability, i.e., 2490 Barrer with a CO2/N2 selectivity of 37, distinctive antiplasticization merit, as well as long‐term running stability, which is at top‐tier level, enabling the large‐scale manufacture of high‐performance MMMs for gas separation.
A facile and efficient “confined swelling coupled solvent‐controlled crystallization” strategy is demonstrated to control the in situ crystallization of metal‐organic frameworks nanocrystals in polyethylene oxide membranes, realizing rapid construction of defect‐free freeway channels for CO2 transportation in mixed matrix membranes (MMMs). The optimized MMM showed fourfold enhancement in CO2 permeability, i.e., 2705 Barrer, with a CO2/N2 selectivity of 37.
•Up-to-date development of fiber-optic chemical sensors and biosensors are reviewed.•The role of sensing film in fiber-optic sensors are highlighted.•The fabrication of high-performance fiber-optic ...sensors are emphasized.•Combination of optical fibers with micro/nano-technologies are commented.
The Internet-of-Things (IoT) has witnessed exponential growth over the past decade and will significantly reshape human life from every aspect, e.g., defense, environmental monitoring, energy, food safety, knowledge dissemination, healthcare and so on. Fiber-optic sensors, with both communication and sensing functions, have become a bridge to connect people and the whole world, so they are essential parts for accelerating the development of the IoT. Fiber-optic sensors possess the capability of translating a change of target analyte into optical signals and subsequently transmit an optical signal with target analyte information to people, machines or systems in real-time, even from a long distance. Therefore, exploration of high-performance fiber-optic chemical sensors and biosensors could significantly promote the development of the IoT. This review paper presents the foundations of fiber-optic chemical sensing or biosensing, including the sensing mechanisms of various fiber-optic sensors, sensing materials and the novel techniques for sensing materials deposition. Furthermore, recent developments on fiber-optic chemical sensors and biosensors are summarized, analyzed and discussed. Finally, the strategies and guidelines to further promote the development of fiber-optic sensors are also discussed.
Electronic skins (E-skins) have attracted great research interest because of their promising applications in stretchable optoelectronics, soft robotics, and personalized healthcare devices. However, ...it remains a great challenge to fabricate E-skin devices that meet strict practical requirements such as high sensitivity, low-power operation and noise-proof ability. Here, we developed a novel elastic ionic polyacrylamide hydrogel (EIPH) with a high capacitance for the development of low-voltage organic thin-film transistor (OTFT) pressure sensors. The EIPH was prepared by photopolymerization of an acrylamide monomer in an aqueous solution of poly (acrylic acid) and CaCl2 and was then in situ micropatterned on an indium-tin oxide electrode. The fabricated capacitive sensor with 10-µm-wide EIPH micropillar structures achieved a high sensitivity of 2.33 kPa−1 with a capacitance sensitivity of 103.8 nF/kPa. This capacitance sensitivity is more than 100 times higher than that of conventional capacitive pressure sensors due to the formation of an electrical double layer. The micropatterned EIPH was adopted as a dielectric layer in the fabrication of the OTFT-based pressure sensors. Such an EIPH-based OTFT pressure sensor not only greatly enhanced the sensitivity, i.e., 7.7 times higher than its capacitive counterparts, but also largely reduced the operation voltage to 2 V.
An elastic ionic hydrogel is prepared and micropatterned to fabricate capacitive and organic thin-film transistor (OTFT) pressure sensors. By virtue of high elasticity and ionic conducting ability, the microstructures of the hydrogel can enhance the capacitive pressure sensor's performances in terms of operation voltage and sensitivity. Moreover, the microstructured hydrogel provides OTFT-based pressure sensors with an ideal dielectric layer, which can not only greatly enhance sensitivity but also dramatically reduce operation voltage. Display omitted
•An elastic ionic polyacrylamide hydrogels (EIPH) with high elasticity and ionic conducting ability is prepared.•The EIPH is in situ optically micropatterned on electrodes to fabricate flexible capacitive pressure sensors.•By virtue of the formaiton of electrical double layer, high-performance capacitive pressure sensors are fabricated.•Flexible OTFT pressure sensors with enhanced sensitivity and reduced operation voltage are demonstrated.
A multiple-input-multiple-output dielectric resonator antenna with enhanced isolation is proposed in this letter for the future 5G millimeter (mm)-wave applications. Two rectangular dielectric ...resonators (DRs) are mounted on a substrate excited by rectangular microstrip-fed slots underneath DRs. Each DR has a metal strip printed on its upper surface moving the strongest part of the coupling field away from the exciting slot to improve the isolation between two antenna elements. The proposed antenna obtains a simulated impedance bandwidth (S11 ≤ -10 dB) from 27.25 to 28.59 GHz, which covers the 28 GHz band (27.5-28.35 GHz) allocated by the Federal Communications Commission for the 5G applications. A maximum improvement of 12 dB on the isolation over 27.5-28.35 GHz is achieved. The mechanism of the isolation improvement and the design procedure are given in this letter. A prototype is manufactured and measured as a validation of the proposed decoupling method.
Mixed‐matrix membranes (MMMs) have the potential for energy‐efficient gas separation by matching the superior mass transfer and anti‐plasticization properties of the fillers with processability and ...scaling up features of the polymers. However, construction of high‐performance MMMs has been prohibited due to low filler‐loading and the existence of interfacial defects. Here, high MOF‐loaded, i.e., 55 wt %, MMMs are developed by a ‘dormancy and double‐activation’ (DDA) strategy. High MOF precursor concentration suppresses crystallization in the membrane casting solution, realizing molecular level mixing of all components. Then, the polymeric matrix was formed with uniform encapsulation of MOF nutrients. Subsequently, double‐activation was employed to induce MOF crystallization: the alkali promotes MOFs nucleation to harvest small porous nanocrystals while excessive ligands activate the metal ions to enhance the MOFs conversion. As such, quasi‐semi‐continuous mass transfer channels can be formed in the MMMs by the connected MOFs nanocrystals to boost the gas permeability. The optimized MMM shows significantly ameliorated CO2 permeability, i.e., 2841 Barrer, five‐fold enhancement compared with pristine polymer membrane, with a good CO2/N2 selectivity of 36. Besides, the nanosized MOFs intensify their interaction with polymer chains, endowing the MMMs with good anti‐plasticization behaviour and stability, which advances practical application of MMMs in carbon capture.
A facile and efficient ‘dormancy and double‐activation’ strategy was demonstrated to construct highly ZIF‐8‐loaded MMM with quasi‐semi‐continuous channels for rapid CO2 transportation.
Novel hierarchical porous carbon materials (HPCs) were fabricated via a reactive template-induced in situ hypercrosslinking procedure. The effects of carbonization conditions on the microstructure ...and morphology of HPCs were investigated, and the adsorption of methylene blue (MB) on HPCs was explored. The as-prepared HPCs has a hierarchical micro-, meso- and macropore structure, which results from the overlap of hollow nanospheres possessing microporous shells and macroporous cavities. The carbonization temperature, carbonization time and carbonization heating rate played important roles in tailoring the nanostructures of HPCs. The BET specific surface area and micropore specific surface area can reach 2388 m
g
and 1892 m
g
, respectively. Benefitting from the well-developed pore structure, the MB removal efficiency can exceed 99% under optimized conditions. The adsorption kinetics and thermodynamics can be well described by a pseudo-second-order model and Langmuir model, respectively. Furthermore, such adsorption was characterized by a spontaneous endothermic process.
Flexible pressure sensors based on organic field‐effect transistors (OFETs) have emerged as promising candidates for electronic‐skin applications. However, it remains a challenge to achieve low ...operating voltages of hysteresis‐free flexible pressure sensors. Interface engineering of polymer dielectrics is a feasible strategy toward sensitive pressure sensors based on low‐voltage OFETs. Here, a novel type of solution‐processed bilayer dielectrics is developed by combining a thick polyelectrolyte layer of polyacrylic acid (PAA) with a thin poly(methyl methacrylate) (PMMA) layer. This bilayer dielectric can provide a vertical phase separation structure from hydrophilic interface to hydrophobic interface which adjoins well to organic semiconductors, leading to improved stability and remarkably reduced leakage currents. Consequently, OFETs using the PMMA/PAA dielectrics reveal greatly suppressed hysteresis and improved mobility compared to those with a pure PAA dielectric. Using the optimized PMMA/PAA dielectric, flexible OFET‐based pressure sensors that show a record high sensitivity of 56.15 kPa−1 at a low operating voltage of −5 V, a fast response time of less than 20 ms, and good flexibility are further demonstrated. The salient features of high capacitance, good dielectric performance, and excellent reliability of the bilayer dielectrics promise a bright future of flexible sensors based on low‐voltage OFETs for wearable electronic applications.
Flexible low‐voltage organic field‐effect transistors (OFETs) for pressure‐sensing applications are demonstrated by using solution‐processed poly(methyl methacrylate)/polyacrylic acid dielectrics that achieve greatly enhanced charge transportation with reduced hysteresis. The resulting OFET‐based pressure sensors exhibit a record high sensitivity of 56.15 kPa−1 at a low operating voltage of −5 V, a fast response time of <20 ms, and good flexibility.
Separation of monovalent salt and antibiotics is of vital importance in membrane field. In this work, zwitterionic polyamide membrane was prepared by incorporating N, N-diethylethylenediamine (DEEDA) ...into interfacial polymerization firstly. Then, zwitterions were introduced into membrane matrix via grafting reaction with 1, 3-propanesultone (1, 3-PS). The resulting zwitterionic membrane exhibited optimal permeability of 14.6 L m−2 h−1.bar−1 and high rejection of organics. Meanwhile, owing to the incorporation of zwitterions, the zwitterionic membrane showed lower rejection of monovalent salt compared with that of the pristine polyamide membrane. Thus, the zwitterionic membrane behaved efficient separation ability of monovalent salt/antibiotics when NaCl/erythromycin mixture solution was chosen as the experimental solution. When bovine serum albumin was used as a foulant, the zwitterionic membrane also exhibited anti-fouling property. This work provided a facile way to prepare zwitterionic membrane with efficient separation ability of monovalent salt/antibiotics, which promoted the development of zwitterions in applications of nanofiltration membrane field.
•DEEDA and 1, 3-PS were utilized to prepare zwitterionic membrane.•Zwitterionic membrane exhibited high permeability and anti-fouling property.•Zwitterionic membrane could realize fast separation of ERY/NaCl.
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