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1.
Adv Mater ; 32(26): e1908291, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32363647

RESUMO

Hunger and chronic undernourishment impact over 800 million people, which translates to ≈10.7% of the world's population. While countries are increasingly making efforts to reduce poverty and hunger by pursuing sustainable energy and agricultural practices, a third of the food produced around the globe still is wasted and never consumed. Reducing food shortages is vital in this effort and is often addressed by the development of genetically modified produce or chemical additives and inedible coatings, which create additional health and environmental concerns. Herein, a multifunctional bio-nanocomposite comprised largely of egg-derived polymers and cellulose nanomaterials as a conformal coating onto fresh produce that slows down food decay by retarding ripening, dehydration, and microbial invasion is reported. The coating is edible, washable, and made from readily available inexpensive or waste materials, which makes it a promising economic alternative to commercially available fruit coatings and a solution to combat food wastage that is rampant in the world.

2.
ACS Nano ; 2020 Apr 29.
Artigo em Inglês | MEDLINE | ID: mdl-32330006

RESUMO

Hotspot engineering has the potential to transform the field of surface-enhanced Raman spectroscopy (SERS) by enabling ultrasensitive and reproducible detection of analytes. However, the ability to controllably generate SERS hotspots, with desired location and geometry, over large-area substrates, has remained elusive. In this study, we sculpt artificial edges in monolayer molybdenum disulfide (MoS2) by low-power focused laser-cutting. We find that when gold nanoparticles (AuNPs) are deposited on MoS2 by drop-casting, the AuNPs tend to accumulate predominantly along the artificial edges. First-principles density functional theory (DFT) calculations indicate strong binding of AuNPs with the artificial edges due to dangling bonds that are ubiquitous on the unpassivated (laser-cut) edges. The dense accumulation of AuNPs along the artificial edges intensifies plasmonic effects in these regions, creating hotspots exclusively along the artificial edges. DFT further indicates that adsorption of AuNPs along the artificial edges prompts a transition from semiconducting to metallic behavior, which can further intensify the plasmonic effect along the artificial edges. These effects are observed exclusively for the sculpted (i.e., cut) edges and not observed for the MoS2 surface (away from the cut edges) or along the natural (passivated) edges of the MoS2 sheet. To demonstrate the practical utility of this concept, we use our substrate to detect Rhodamine B (RhB) with a large SERS enhancement (∼104) at the hotspots for RhB concentrations as low as ∼10-10 M. The single-step laser-etching process reported here can be used to controllably generate arrays of SERS hotspots. As such, this concept offers several advantages over previously reported SERS substrates that rely on electrochemical deposition, e-beam lithography, nanoimprinting, or photolithography. Whereas we have focused our study on MoS2, this concept could, in principle, be extended to a variety of 2D material platforms.

3.
Artigo em Inglês | MEDLINE | ID: mdl-32270997

RESUMO

Exploring efficient electrocatalysts for lithium-sulfur (Li-S) batteries is of great significance for the sulfur/polysulfide/sulfide multiphase conversion. Herein, we report nickel-iron intermetallic (Ni3Fe) as a novel electrocatalyst to trigger the highly efficient polysulfide-involving surface reactions. The incorporation of iron into the cubic nickel phase can induce strong electronic interaction and lattice distortion, thereby activating the inferior Ni phase to catalytically active Ni3Fe phase. Kinetics investigations reveal that the Ni3Fe phase promotes the redox kinetics of the multiphase conversion of Li-S electrochemistry. As a result, the Li-S cells assembled with a 70 wt % sulfur cathode and a Ni3Fe-modified separator deliver initial capacities of 1310.3 mA h g-1 at 0.1 C and 598 mA h g-1 at 4 C with excellent rate capability and a long cycle life of 1000 cycles at 1 C with a low capacity fading rate of ∼0.034 per cycle. More impressively, the Ni3Fe-catalyzed cells exhibit outstanding performance even at harsh working conditions, such as high sulfur loading (7.7 mg cm-2) or lean electrolyte/sulfur ratio (∼6 µL mg-1). This work provides a new concept on exploring advanced intermetallic catalysts for high-rate and long-life Li-S batteries.

4.
Artigo em Inglês | MEDLINE | ID: mdl-32123085

RESUMO

The use of potassium (K) metal anodes could result in high-performance K-ion batteries that offer a sustainable and low-cost alternative to lithium (Li)-ion technology. However, formation of dendrites on such K-metal surfaces is inevitable, which prevents their utilization. Here, we report that K dendrites can be healed in situ in a K-metal battery. The healing is triggered by current-controlled, self-heating at the electrolyte/dendrite interface, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. We discover that this process is strikingly more efficient for K as compared to Li metal. We show that the reason for this is the far greater mobility of surface atoms in K relative to Li metal, which enables dendrite healing to take place at an order-of-magnitude lower current density. We demonstrate that the K-metal anode can be coupled with a potassium cobalt oxide cathode to achieve dendrite healing in a practical full-cell device.

5.
Artigo em Inglês | MEDLINE | ID: mdl-32083835

RESUMO

Solar-driven water evaporation has been proposed as a renewable and sustainable strategy for the generation of clean water from seawater or wastewater. To enable such technologies, development of photothermal materials that enable efficient solar steam generation is essential. The current challenge is to manufacture such photothermal materials cost-effectively and at scale. Furthermore, the photothermal materials should be strongly hydrophilic and environmentally stable. Herein, we demonstrate facile and scalable fabrication of carbon nanotube (CNT)-based photothermal nanocomposite foam by igniting an ethanol solution of ferric acetylacetonate [Fe(acac)3] absorbed within nickel (Ni) foam under ambient conditions. The Fe(acac)3 precursor provides carbon and the zero-valent iron catalyst for growing CNTs on the Ni foam, while ethanol facilitates the dispersion of Fe(acac)3 on the Ni foam and supplies heat energy for the growth of CNTs by its burning. A forest of dense and uniform CNTs decorated with Fe2O3 nanoparticles is generated within seconds. The resultant Fe2O3/CNT/Ni nanocomposite foam exhibits "superhydrophilicity" and high light absorption capacity, ensuring rapid transport and fast evaporation of water within the entire foam. Efficient light-to-heat conversion causes the surface temperature of the foam to reach ∼83.1 °C under 1 sun irradiation. The average water evaporation rates of such foam are as high as ∼1.48 and ∼4.27 kg m-2 h-1 with light-to-heat conversion efficiencies of ∼81.3 and ∼93.8% under 1 sun and 3 sun irradiation, respectively. Moreover, the versatile and scalable combustion synthesis strategy presented here can be realized on various substrates, exhibiting high adaptability for different applications.

6.
Nanoscale ; 12(1): 220-229, 2020 Jan 07.
Artigo em Inglês | MEDLINE | ID: mdl-31815990

RESUMO

The field of chemical (gas) sensing has witnessed an unprecedented increase in device sensitivity with single molecule detection now becoming a reality. In contrast to this, the ability to distinguish or discriminate between gas species has lagged behind. This is problematic and results in a high rate of false alarms. Here, we demonstrate a short period sinusoidal thermal modulation strategy to quantitatively and rapidly identify two industrially relevant gases (hydrogen sulfide (H2S) and sulfur dioxide (SO2)) by using a single semiconducting metal oxide sensor device. By applying sinusoidal heating voltages with a fixed short period, we were able to simultaneously obtain distinct patterns of dynamic responses. These characteristic patterns were adopted to build and validate a gas recognition library. Our approach does not rely on large-scale sensor arrays and complex algorithms and is amenable for real-time and low-power gas monitoring.

7.
ACS Nano ; 13(12): 14094-14106, 2019 Dec 24.
Artigo em Inglês | MEDLINE | ID: mdl-31724845

RESUMO

High specific capacity materials that can store potassium (K) are essential for next-generation K-ion batteries. One such candidate material is phosphorene (the 2D allotrope of phosphorus (P)), but the potassiation capability of phosphorene has not yet been established. Here we systematically investigate the alloying of few-layer phosphorene (FLP) with K. Unlike lithium (Li) and sodium (Na), which form Li3P and Na3P, FLP alloys with K to form K4P3, which was confirmed by ex situ X-ray characterization as well as density functional theory calculations. The formation of K4P3 results in high specific capacity (∼1200 mAh g-1) but poor cyclic stability (only ∼9% capacity retention in subsequent cycles). We show that this capacity fade can be successfully mitigated by the use of reduced graphene oxide (rGO) as buffer layers to suppress the pulverization of FLP. We studied the performance of rGO and single-walled carbon nanotubes (sCNTs) as buffer materials and found that rGO being a 2D material can better encapsulate and protect FLP relative to 1D sCNTs. The half-cell performance of FLP/rGO could also be successfully reproduced in a full-cell configuration, indicating the possibility of high-performance K-ion batteries that could offer a sustainable and low-cost alternative to Li-ion technology.

8.
Langmuir ; 35(38): 12306-12316, 2019 Sep 24.
Artigo em Inglês | MEDLINE | ID: mdl-31474110

RESUMO

Graphene is the thinnest known two-dimensional (2D) material. This thinness is responsible for graphene's well-known optical transparency. In addition to being transparent to light, its extreme thinness and nonpolar nature also render graphene partially transparent to van der Waals and electrostatic interactions. This enables media present on opposite sides of a graphene sheet to sense or feel each other and be influenced by each other. Such crosstalk between materials separated by an impermeable barrier is impossible for typical barrier or coating materials that are usually thick enough to completely screen out such interactions. In this article, we review graphene's partial transparency to atomic interactions at the liquid-solid, solid-solid, and liquid-liquid interfaces. We compare graphene with other 2D materials such as hexagonal boron nitride and show that the extent of graphene's transparency is strongly dependent on the nature and interaction range of the materials placed on opposite sides of the graphene layer. We end with recommendations for future research to better understand the underlying science and to develop practical applications of this exciting phenomena.

9.
Nat Commun ; 10(1): 1764, 2019 04 16.
Artigo em Inglês | MEDLINE | ID: mdl-30992432

RESUMO

Unlike the vast majority of transition metal dichalcogenides which are semiconductors, vanadium disulfide is metallic and conductive. This makes it particularly promising as an electrode material in lithium-ion batteries. However, vanadium disulfide exhibits poor stability due to large Peierls distortion during cycling. Here we report that vanadium disulfide flakes can be rendered stable in the electrochemical environment of a lithium-ion battery by conformally coating them with a ~2.5 nm thick titanium disulfide layer. Density functional theory calculations indicate that the titanium disulfide coating is far less susceptible to Peierls distortion during the lithiation-delithiation process, enabling it to stabilize the underlying vanadium disulfide material. The titanium disulfide coated vanadium disulfide cathode exhibits an operating voltage of ~2 V, high specific capacity (~180 mAh g-1 @200 mA g-1 current density) and rate capability (~70 mAh g-1 @1000 mA g-1), while achieving capacity retention close to 100% after 400 charge-discharge steps.

10.
J Colloid Interface Sci ; 542: 54-62, 2019 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-30731353

RESUMO

Flexible pressure sensors still face a great challenge to combine fast frequency response, wide pressure range, multiple detection modes, satisfactory mechanical and environmental stability, and simple fabrication process into a sensor. Herein, flexible piezoresistive pressure sensors are fabricated by treating the backbone of polyurethane (PU) sponge with chitosan (CS) to obtain positively charged CS@PU sponge, followed by dip-coating of negatively charged Ti3C2Tx MXene sheets. The resulting MXene@CS@PU sponge-based sensor provides a versatile sensing platform with potentials for detecting both small and large pressure signals. Due to the highly compressive resilience of the PU sponge and its polar interaction with the MXene sheets, the MXene@CS@PU sensor has high compressibility and stable piezoresistive response for compressive strains of up to 85% with a stress of 245.7 kPa, and it also exhibits a satisfactory reproducibility for 5000 compression-release cycles. Even after washing in water for 1 h, the sensor still shows good performances. With a rapid response time of only 19 ms and a low detection limit of 30 µN corresponding to a pressure of 9 Pa, the MXene sponge sensor is promising for detecting human physiological signals and insect movements. In addition to the contact mode detection, the sponge sensor could detect voices and human breaths by a non-contact detection mode.

11.
Adv Mater ; 30(21): e1707025, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29611242

RESUMO

The development of fully foldable energy storage devices is a major science and engineering challenge, but one that must be overcome if next-generation foldable or wearable electronic devices are to be realized. To overcome this challenge, it is necessary to develop new electrically conductive materials that exhibit superflexibility and can be folded or crumpled without plastic deformation or damage. Herein, a graphene film with engineered microvoids is prepared by reduction (under confinement) of its precursor graphene oxide film. The resultant porous graphene film can be single folded, double folded, and even crumpled, but springs back to its original shape without yielding or plastic deformation akin to an elastomeric scaffold after the applied stress is removed. Even after thermal annealing at ≈1300 °C, the folding performance of the porous graphene film is not compromised and the thermally annealed film exhibits complete foldability even in liquid nitrogen. A solid-state foldable supercapacitor is demonstrated with the porous graphene film as the device electrode. The capacitance performance is nearly identical after 2000 cycles of single-folding followed by another 2000 cycles of double folding.

12.
ACS Appl Mater Interfaces ; 10(16): 13442-13451, 2018 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-29620865

RESUMO

High specific capacity anode materials such as silicon (Si) are increasingly being explored for next-generation, high performance lithium (Li)-ion batteries. In this context, Si films are advantageous compared to Si nanoparticle based anodes since in films the free volume between nanoparticles is eliminated, resulting in very high volumetric energy density. However, Si undergoes volume expansion (contraction) under lithiation (delithiation) of up to 300%. This large volume expansion leads to stress build-up at the interface between the Si film and the current collector, leading to delamination of Si from the surface of the current collector. To prevent this, adhesion promotors (such as chromium interlayers) are often used to strengthen the interface between the Si and the current collector. Here, we show that such approaches are in fact counter-productive and that far better electrochemical stability can be obtained by engineering a van der Waals "slippery" interface between the Si film and the current collector. This can be accomplished by simply coating the current collector surface with graphene sheets. For such an interface, the Si film slips with respect to the current collector under lithiation/delithiation, while retaining electrical contact with the current collector. Molecular dynamics simulations indicate (i) less stress build-up and (ii) less stress "cycling" on a van der Waals slippery substrate as opposed to a fixed interface. Electrochemical testing confirms more stable performance and much higher Coulombic efficiency for Si films deposited on graphene-coated nickel (i.e., slippery interface) as compared to conventional nickel current collectors.

13.
Science ; 359(6383): 1513-1516, 2018 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-29599241

RESUMO

Lithium (Li) metal electrodes are not deployable in rechargeable batteries because electrochemical plating and stripping invariably leads to growth of dendrites that reduce coulombic efficiency and eventually short the battery. It is generally accepted that the dendrite problem is exacerbated at high current densities. Here, we report a regime for dendrite evolution in which the reverse is true. In our experiments, we found that when the plating and stripping current density is raised above ~9 milliamperes per square centimeter, there is substantial self-heating of the dendrites, which triggers extensive surface migration of Li. This surface diffusion heals the dendrites and smoothens the Li metal surface. We show that repeated doses of high-current-density healing treatment enables the safe cycling of Li-sulfur batteries with high coulombic efficiency.

14.
ACS Nano ; 12(3): 2242-2252, 2018 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-29432687

RESUMO

We report the use of a single layer of two-dimensional hexagonal boron nitride (SL-hBN) as the thinnest insulating barrier to microbial corrosion induced by the sulfate-reducing bacteria Desulfovibrio alaskensis G20. We used electrochemical methods to assess the corrosion resistance of SL-hBN on copper against the effects of both the planktonic and sessile forms of the sulfate-reducing bacteria. Cyclic voltammetry results show that SL-hBN-Cu is effective in suppressing corrosion effects of the planktonic cells at potentials as high as 0.2 V ( vs Ag/AgCl). The peak anodic current for the SL-hBN coatings is ∼36 times lower than that of bare Cu. Linear polarization resistance tests confirm that the SL-hBN coatings serve as a barrier against corrosive effects of the G20 biofilm when compared to bare Cu. The SL-hBN serves as an impermeable barrier to aggressive metabolites and offers ∼91% corrosion inhibition efficiency, which is comparable to much thicker commercial coatings such as polyaniline. In addition to impermeability, the insulating nature of SL-hBN suppresses galvanic effects and improves its ability to combat microbial corrosion.


Assuntos
Biofilmes , Compostos de Boro/química , Cobre/química , Desulfovibrio/fisiologia , Biofilmes/efeitos dos fármacos , Corrosão , Desulfovibrio/efeitos dos fármacos , Técnicas Eletroquímicas , Eletrodos , Propriedades de Superfície
15.
Phys Chem Chem Phys ; 20(6): 4058-4066, 2018 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-29354839

RESUMO

Tellurene is a new member of the two-dimensional (2D) materials' family, whose existence has been recently confirmed by first principles calculation and experimental work. Tellurene is also the first 2D mono-elemental material of group-VI predicted by scientists, and investigations of its basic properties are still in their infancy. In this study, we use first principles calculation based on density functional theory to investigate the adsorption of nineteen typical adatoms (Li, Na, K, Ca, Fe, Co, Ni, Cu, Zn, Ag, Au, Pd, Pt, B, N, O, Si, Cl, and Al), and five typical gas molecules (H2, O2, H2O, NO2, and NH3) on α-phase as well as ß-phase tellurene sheets. Our calculations shows that most adatoms are chemisorbed on tellurene sheets with large adsorption energies. Moreover, some of the adatoms are observed to give rise to distinct structural deformations and even local reconstructions. We report that a variety of electronic states are induced by the adatoms, which implies that different electronic structures can be engineered by the adsorption of adatoms. In fact, n-type doping, p-type doping, half-metal, and spin-gapless semiconductor features can be acquired by doping adatoms on tellurene sheets. Our calculations also show that the five gas molecules are all physisorbed on tellurene sheets, and no splitting behaviors are observed. Therefore, the adsorption of the five gas molecules has a weak effect on the electronic properties of tellurene. To conclude, our results indicate that adatom engineering may be used to greatly expand the potential applications of 2D tellurene.

16.
ACS Appl Mater Interfaces ; 10(6): 5373-5384, 2018 Feb 14.
Artigo em Inglês | MEDLINE | ID: mdl-29350901

RESUMO

Single-layer rhenium disulfide (ReS2) is a unique material with distinctive, anisotropic electronic, mechanical, and optical properties and has the potential to be used as an anode in alkali-metal-ion batteries. In this work, first principles calculations were performed to systematically evaluate the potential of monolayer pristine and defective ReS2 as anodes in lithium (Li)- and sodium (Na)-ion batteries. Our calculations suggest that there are several potential adsorption sites for Li and Na on pristine ReS2, owing to its low-symmetry structure. Additionally, the adsorption of Li and Na over pristine ReS2 is very strong with adsorption energies of -2.28 and -1.71 eV, respectively. Interestingly, the presence of point defects causes significantly stronger binding of the alkali-metal atoms with adsorption energies in the range -2.98 to -3.17 eV for Li and -2.66 to -2.92 eV for Na. Re single vacancy was found to be the strongest binding defect for Li adsorption, whereas S single vacancy was found to be the strongest for Na. The diffusion of these two alkali atoms over pristine ReS2 is anisotropic, with an energy barrier of 0.33 eV for Li and 0.16 eV for Na. The energy barriers associated with escaping a double vacancy and single vacancy for Li atoms are significantly large at 0.60 eV for the double-vacancy case and 0.51 eV for the single-vacancy case. Similarly, for Na, they are 0.59 and 0.47 eV, respectively, which indicates slower migration and sluggish charging/discharging. However, the diffusion energy barrier over a Re single vacancy is found to be merely 0.42 eV for a Li atom and 0.28 eV for Na. Overall, S single and double vacancies can reduce the diffusion rate by 103-105 times for Li and Na ions, respectively. These results suggest that monolayer ReS2 with a Re single vacancy adsorbs Li and Na stronger than pristine ReS2, with negligible negotiation with the charging/discharging rate of the battery, and therefore they can be used as an anode in Li- and Na-ion batteries.

17.
ACS Nano ; 11(5): 5051-5061, 2017 05 23.
Artigo em Inglês | MEDLINE | ID: mdl-28414906

RESUMO

Silicon (Si) shows promise as an anode material in lithium-ion batteries due to its very high specific capacity. However, Si is highly brittle, and in an effort to prevent Si from fracturing, the research community has migrated from the use of Si films to Si nanoparticle based electrodes. However, such a strategy significantly reduces volumetric energy density due to the porosity of Si nanoparticle electrodes. Here we show that contrary to conventional wisdom, Si films can be stabilized by two strategies: (a) anchoring the Si films to a carbon nanotube macrofilm (CNM) current collector and (b) draping the films with a graphene monolayer. After electrochemical cycling, the graphene-coated Si films on CNM resembled a tough mud-cracked surface in which the graphene capping layer suppresses delamination and stabilizes the solid electrolyte interface. The graphene-draped Si films on CNM exhibit long cycle life (>1000 charge/discharge steps) with an average specific capacity of ∼806 mAh g-1. The volumetric capacity averaged over 1000 cycles of charge/discharge is ∼2821 mAh cm-3, which is 2 to 5 times higher than what is reported in the literature for Si nanoparticle based electrodes. The graphene-draped Si anode could also be successfully cycled against commercial cathodes in a full-cell configuration.

18.
Environ Sci Process Impacts ; 19(2): 141-153, 2017 Feb 22.
Artigo em Inglês | MEDLINE | ID: mdl-28091679

RESUMO

Biodiesel is a widely used fuel that meets the renewable fuel standards developed under the Energy Policy Act of 2005. However, biodiesel is known to pose a series of abiotic and biotic corrosion risks to storage tanks. A typical practice (incumbent system) used to protect the tanks from these risks include (i) coating the interior surface of the tank with a solvent-free epoxy (SFE) liner, and (ii) adding a biocide to the tank. Herein, we present a screening-level life-cycle assessment study to compare the environmental performance of a graphene oxide (GO)-epoxy (GOE) liner with the incumbent system. TRACI was used as an impact assessment tool to model the midpoint environmental impacts in ten categories: global warming potential (GWP, kg CO2 eq.); acidification potential (AP, kg SO2 eq.); potential human health damage impacts due to carcinogens (HH-CP, CTUh) and non-carcinogens (HH-NCP, CTUh); potential respiratory effects (REP, kg PM2.5 eq.); eutrophication potential (EP, kg N eq.); ozone depletion potential (ODP kg CFC-11 eq.); ecotoxicity potential (ETXP, CTUe); smog formation potential (SFP kg O3 eq.) and fossil fuel depletion potential (FFDP MJ surplus). The equivalent functional unit of the LCA study was designed to protect 30 m2 of the interior surface (unalloyed steel sheet) of a 10 000 liter biodiesel tank against abiotic and biotic corrosion during its service life of 20 years. Overall, this LCA study highlights the improved environmental performance for the GOE liner compared to the incumbent system, whereby the GOE liner showed 91% lower impacts in ODP impact category, 59% smaller in REP, 62% smaller in AP, 67-69% smaller in GWP and HH-CP, 72-76% smaller in EP, SFP, and FFDP, and 81-83% smaller ETXP and HH-NCP category results. The scenario analysis study revealed that these potential impacts change by less than 15% when the GOE liners are functionalized with silanized-GO nanosheets or GO-reinforced polyvinyl carbazole to improve the antimicrobial properties. The results from an uncertainty analysis indicated that the impacts for the incumbent system were more sensitive to changes in the key modeling parameters compared to that for the GOE liner system.


Assuntos
Biocombustíveis , Resinas Epóxi , Grafite , Aço , Corrosão , Meio Ambiente , Eutrofização , Combustíveis Fósseis , Aquecimento Global , Humanos , Modelos Teóricos , Medição de Risco
19.
Adv Mater ; 29(2)2017 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-27797133

RESUMO

Theoretical and experimental studies together show phosphorene as a highly potent polysulfide immobilizer for lithium-sulfur batteries, enabling a high capacity, good rate capability, and excellent cycling stability.

20.
Nat Commun ; 7: 13345, 2016 10 31.
Artigo em Inglês | MEDLINE | ID: mdl-27796291

RESUMO

The wettability of graphene on various substrates has been intensively investigated for practical applications including surgical and medical tools, textiles, water harvesting, self-cleaning, oil spill removal and microfluidic devices. However, most previous studies have been limited to investigating the intrinsic and passive wettability of graphene and graphene hybrid composites. Here, we report the electrowetting of graphene-coated metal meshes for use as electroactive flow control devices, utilizing two antagonistic functions, hydrophobic repellency versus liquid permeability. Graphene coating was able to prevent the thermal oxidation and corrosion problems that plague unprotected metal meshes, while also maintaining its hydrophobicity. The shapes of liquid droplets and the degree of water penetration through the graphene-coated meshes were controlled by electrical stimuli based on the functional control of hydrophobic repellency and liquid permeability. Furthermore, using the graphene-coated metal meshes, we developed two active flow devices demonstrating the dynamic locomotion of water droplets and electroactive flow switching.

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