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1.
Opt Lett ; 45(15): 4208-4211, 2020 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-32735260

RESUMO

Surface-enhanced Raman scattering (SERS) is highly promising for ultra-sensitive detection in a series of applications. Although extensive advances have been achieved in SERS technologies, the preparation of highly efficient SERS substrates still suffers from several limitations, including complex preparation procedures, high cost, and instability for long time storage. To address these problems, we report a novel, to the best of our knowledge, SERS platform that combines graphene oxide (GO) and cellulose composite paper with colloidal silver nanoparticle (Ag NP) ink. As an efficient substrate, the GO and cellulose composite paper that features hierarchical micro-nanostructures and improved interaction with target molecules can be fabricated on a large scale, and the Ag NP ink can be well stored, avoiding being oxidized in ambient conditions. In this way, our SERS platform not only reduces the cost, but also improved the stability. The sensitivity, reproducibility, and tunable SERS detection performance were evaluated using rhodamine 6G as probing molecules. To demonstrate the capability of our SERS platform in practical analysis, the SERS spectra of two monosodium salt solutions of different concentrations have been collected. The SERS platform has revealed great potential for practical application of SERS technologies.

2.
Artigo em Inglês | MEDLINE | ID: mdl-32401489

RESUMO

Solar interfacial evaporation has been recognized as a versatile energy conversion protocol for cutting-edge applications such as water treatment and power generation (e.g., hydro voltaic effect). Recently, to enhance water evaporation rates, water temperature and evaporation area have been considered as essential ingredients, and thus photothermal materials and three-dimensional hierarchical structures have been developed to promote light-to-heat conversion efficiency and enhance interfacial evaporation. However, less attention has been paid to the airflow effect, because the interfacial floatability of photothermal membranes should be considered under air blast. Here, inspired from the stable interfacial floatability of lotus leaves, we report the airflow enhanced solar interfacial evaporation approach using a graphene-based Janus membrane. Laser-induced graphene (LIG) film was treated unilaterally by O2 plasma, forming a LIG/oxidized LIG (LIG-O) Janus membrane with distinct wettability on two sides. Higher water evaporation rate of 1.512 kg m-2 h-1 is achieved. The high solar interfacial evaporation performance can be attributed to the two advantages: (i) the combination of microscale capillary water transporting and nanoscale light trapping; (ii) hydrophobic/hydrophilic Janus membrane for stable interfacial floatability under airflow. Our approach is feasible for developing high-performance solar interfacial evaporation devices for practical clean energy utilization.

3.
ACS Appl Mater Interfaces ; 12(9): 10107-10117, 2020 Mar 04.
Artigo em Inglês | MEDLINE | ID: mdl-32046483

RESUMO

Natural compound eyes provide the inspiration for developing artificial optical devices that feature a large field of view (FOV). However, the imaging ability of artificial compound eyes is generally based on the large number of ommatidia. The lack of a tunable imaging mechanism significantly limits the practical applications of artificial compound eyes, for instance, distinguishing targets at different distances. Herein, we reported zoom compound eyes that enable variable-focus imaging by integrating a deformable poly(dimethylsiloxane) (PDMS) microlens array (MLA) with a microfluidic chamber. The thin and soft PDMS MLA was fabricated by soft lithography using a hard template prepared by a combined technology of femtosecond laser processing and wet etching. As compared with other mechanical machining strategies, our combined technology features high flexibility, efficiency, and uniformity, as well as designable processing capability, since the size, distribution, and arrangement of the ommatidia can be well controlled during femtosecond laser processing. By tuning the volume of water injected into the chamber, the PDMS MLA can deform from a planar structure to a hemispherical shape, evolving into a tunable compound eye of variable FOV up to 180°. More importantly, the tunable chamber can functionalize as the main zoom lens for tunable imaging, which endows the compound eye with the additional capability of distinguishing targets at different distances. Its focal length can be turned from 3.03 mm to infinity with an angular resolution of 3.86 × 10-4 rad. This zoom compound eye combines the advantages of monocular eyes and compound eyes together, holding great promise for developing advanced micro-optical devices that enable large FOV and variable-focus imaging.

4.
Adv Mater ; 32(15): e1901981, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-31441164

RESUMO

Recent years have witnessed the rise of graphene and its applications in various electronic devices. Specifically, featuring excellent flexibility, transparency, conductivity, and mechanical robustness, graphene has emerged as a versatile material for flexible electronics. In the past decade, facilitated by various laser processing technologies, including the laser-treatment-induced photoreduction of graphene oxides, flexible patterning, hierarchical structuring, heteroatom doping, controllable thinning, etching, and shock of graphene, along with laser-induced graphene on polyimide, graphene has found broad applications in a wide range of electronic devices, such as power generators, supercapacitors, optoelectronic devices, sensors, and actuators. Here, the recent advancements in the laser fabrication of graphene-based flexible electronic devices are comprehensively summarized. The various laser fabrication technologies that have been employed for the preparation, processing, and modification of graphene and its derivatives are reviewed. A thorough overview of typical laser-enabled flexible electronic devices that are based on various graphene sources is presented. With the rapid progress that has been made in the research on graphene preparation methodologies and laser micronanofabrication technologies, graphene-based electronics may soon undergo fast development.

5.
Nanoscale ; 11(43): 20614-20619, 2019 Nov 21.
Artigo em Inglês | MEDLINE | ID: mdl-31641724

RESUMO

Moisture-responsive actuators based on graphene oxide (GO) have attracted intensive research interest in recent years. However, current GO actuators suffer from low mechanical strength. Inspired by the robustness of nacre's structure, moisture-responsive actuators with high mechanical strength and self-healing properties were successfully developed based on GO and cellulose fiber (CF) hybrids. The hybrid paper demonstrated significantly improved tensile strength, ∼20 times higher than that of pure GO paper, and self-healing properties. A broken paper can be well cured under moist conditions, and the mechanical properties of the self-healed hybrid paper can still maintain similar tensile strength to the pristine one. After controllable ultraviolet light photoreduction treatment, a hybrid paper with a photoreduction gradient along the normal direction was prepared, which can act as a moisture-responsive actuator. A maximum bending curvature of ∼1.48 cm-1 can be achieved under high relative humidity (RH = 97%). As a proof-of-concept, a butterfly-like actuator that can deform itself with moisture actuation was demonstrated. Our approach may pave a new way for designing robust and self-healable graphene actuators.

6.
ACS Appl Mater Interfaces ; 11(41): 38084-38091, 2019 Oct 16.
Artigo em Inglês | MEDLINE | ID: mdl-31547649

RESUMO

Versatile electronic skin devices that enable detection of multimodal signals have revealed great potential for human health monitoring. To make a versatile electronic skin, hierarchical micronanostructures are essential to obtain improved sensing performance and multisignal detection capability. However, current strategies for developing a nanostructured electronic skin usually involve complex procedures, harsh experimental conditions, and the use of expensive equipment, which limit its practical applications. In this paper, we reported the fabrication of a multifunctional wearable electronic skin with hierarchical micronanostructures by using natural reed leaves as templates. The capacitive-type electronic skin is fabricated by double-sided coating of Au electrodes on an artificial polydimethylsiloxane reed leaf that is duplicated from natural reed leaves via soft lithography. The electronic skin features a very simple device structure yet high sensing performance. It permits multimodal signal detection, including that of pressure, deformation, and proximity, and can serve as surface-enhanced Raman scattering substrates for the detection of metabolites in sweat because of the formation of plasmonic structures. The versatile electronic skin can be attached to the human skin, and it enables effective monitoring of multiphysiological signals, revealing great potential for cutting-edge applications, such as human health monitoring.


Assuntos
Materiais Biomiméticos , Ouro , Nanoestruturas , Folhas de Planta , Dispositivos Eletrônicos Vestíveis , Eletrodos , Humanos
7.
ACS Appl Mater Interfaces ; 11(40): 37130-37138, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31500405

RESUMO

Bimorph actuators hold great promise for developing soft robots. However, poor interlayer adhesion between different materials always threatens their stability for long-term usage. In this paper, instead of using a bilayer structure, we reported the gradient assembly of graphene oxide (GO) sheets and polymer nanospheres for developing robust moisture and light dual-responsive actuators. The distribution gradient of poly(methyl methacrylate) (PMMA) nanospheres along the normal direction of a GO paper leads to an asymmetric structure. The front side that mainly consists of GO is quite sensitive to water molecules, which swells upon exposure to moisture, whereas the back side that is rich in PMMA nanospheres expands obviously due to the photothermal effect. The distinct properties of the two sides endow the composite paper with moisture and light dual-responsiveness. Moreover, since GO has been used as a host material, the composite paper shows a moisture-triggered self-healing property, which permits front-to-front and front-to-back healing. The self-healed paper can maintain similar responsive property and reasonable mechanical strength to the pristine one. As a proof of concept, a dual-responsive gripper actuator and a scorpion robot have been fabricated for light and moisture cooperative manipulation. The gradient assembly strategy may open up a new way for developing robust multiresponsive actuators beyond bilayer structures.

8.
Adv Mater ; 31(32): e1901585, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-31197895

RESUMO

The strong interaction between graphene oxides (GO) and water molecules has trigged enormous research interest in developing GO-based separation films, sensors, and actuators. However, sophisticated control over the ultrafast water transmission among the GO sheets and the consequent deformation of the entire GO film is still challenging. Inspired from the natural "quantum-tunneling-fluidics-effect," here quantum-confined-superfluidics-enabled moisture actuation of GO paper by introducing periodic gratings unilaterally is reported. The folded GO nanosheets that act as quantum-confined-superfluidics channels can significantly promote water adsorption, enabling controllable and sensitive moisture actuation. Water-adsorption-induced expansion along and against the normal direction of a GO paper is investigated both theoretically and experimentally. Featuring state-of-the-art of ultrafast response (1.24 cm-1 s-1 ), large deformation degree, and complex and predictable deformation, the smart GO papers are used for biomimetic mini-robots including a creeping centipede and a smart leaf that can catch a living ladybug. The reported method is simple and universal for 2D materials, revealing great potential for developing graphene-based smart robots.

9.
Opt Lett ; 44(7): 1714-1717, 2019 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30933129

RESUMO

Herein, we report a simple laser holography technology for hierarchically structuring and synchronous photoreduction of graphene oxides (GO), toward the development of efficient graphene-based electrodes for supercapacitor applications in cost effectively manners. Hierarchical micro-nanostructures, formed due to laser treatment induced photoreduction and ablation effect. Interestingly, both the morphology and reduction degree of the laser holography reduced GO (LHRGO) show strong dependence on the laser intensity, providing the feasibility for controlling the micro-nanostructures, chemical composition, and the conductivity of the graphene electrodes. Furthermore, the supercapacitors based on LHRGO show higher capacitance values and better electrochemical performance compared to that based on thermal reduced GO (TRGO) of same reduction level. Photoredution and micro-nanostructuring of GO using laser holography may hold great promise for production of effective carbon-based electrodes towards practical applications in energy storage devices.

10.
Nanoscale ; 11(18): 9133-9140, 2019 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-31033984

RESUMO

The research interest in wearable electronics has continuously stimulated the development of flexible energy storage systems with high performance and robustness. However, open problems with respect to energy storage efficiency and device integration are still challenging. Here, we demonstrate the laser fabrication of flexible planar supercapacitors based on graphene oxide (GO) and black phosphorus quantum dot (BPQD) nanocomposites. By combining graphene and BPQDs, the resultant supercapacitors feature high conductivity and activity, demonstrating enhanced specific capacity and superior rate performance, compared to those based on reduced GO (RGO) alone. Furthermore, the as-obtained devices present outstanding flexibility. Their performance shows unobvious degradation after repeated cycles of bending and straightening. Additionally, with the help of direct laser writing (DLW) technology, integration of the supercapacitors has been achieved without the need for any metal interconnection. The integrated devices delivered reasonable performance uniformity with a voltage extension of 3 V, which could easily power a LED. The supercapacitor-based RGO and BPQD nanocomposites demonstrate great potential for practical applications in flexible and wearable electronics.

11.
Opt Lett ; 44(6): 1363-1366, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30874651

RESUMO

Electrothermal actuators (ETAs) that can convert electric energy into mechanical works have been extensively studied for their great potential in artificial muscles and robotics. However, the production of ETAs that enable complex and predictable deformation is still challenging. In this Letter, an ETA based on reduced graphene oxide (RGO) and polyethylene (PE) bimorph is developed through a facile laser-scribing method. Since the laser-scribing technology permits flexible patterning, conductive RGO electrodes with complex circuit patterns can be readily produced on a thermally active PE film, forming an ETA capable of fast and reversible deformation. In addition, the laser-scribed ETA demonstrated orientation-defined bending performance, enabling more sophisticated deformation control. The laser scribing of graphene oxide has opened up a new way to produce ETAs towards cutting-edge applications such as soft robotics and intelligent systems.

12.
ACS Nano ; 13(4): 4041-4048, 2019 04 23.
Artigo em Inglês | MEDLINE | ID: mdl-30677287

RESUMO

Strategies that can make general materials smart are highly desired for developing artificial shape-morphing systems and devices. However, at present, it still lacks universal technologies that enable designable prototyping of deformable 3D micro-nanostructures. Inspired by natural automation systems, for instance, tendrils, leaves, and flowers deform dynamically under external stimuli by varying internal turgor, we report a dual-3D femtosecond laser processing strategy for fabricating smart and deformable 3D microactuators based on general photopolymers. By programming the size and distributions of voxels at the nanoscale, both the 3D profile and the 3D internetwork of a general photopolymer could be tailored in a controlled manner; thus, 3D microstructures encoded with precisely tailored networks could perform predictable deformations under certain stimuli. Using this dual-3D fabrication approach, energetic 3D microactuators, including a smart microflower, a responsive microvale, and an eight-finger microclaw, that permit controllable manipulation have been successfully developed.

13.
Langmuir ; 35(3): 815-823, 2019 01 22.
Artigo em Inglês | MEDLINE | ID: mdl-30563345

RESUMO

Inspired from fish scales that exhibit unique underwater superoleophobicity, artificial porous membranes featuring similar wettability have been successfully developed for oil-water separation. However, most of the superoleophobic meshes are workable only for underwater oil/water separation and become disabled in air. In this article, we reported the facile fabrication of underwater superoleophobic kraft mesh and demonstrated efficient oil-water separation using kraft mesh origamis. Kraft paper that features porosity, natural hydrophilicity, and relatively high elasticity and tear resistance has been found to be an ideal candidate for developing underwater superoleophobic origami. Direct laser drilling has been employed to make microhole arrays on the kraft paper, forming a flexible mesh. The hydrophilic nature and the hierarchical microstructures that consist of microhole arrays and porous microfiber networks make the resultant kraft mesh superoleophobic underwater, enabling oil-water separation. More importantly, the kraft mesh can retain a large amount of water (2.5 times its weight under dry conditions) owing to its porous and hydrophilic structure. Thus, the wet kraft mesh became a slippery surface for oil droplets when it was taken out of the water. This unique feature makes it possible to directly fish out oil droplets from water using a simple kraft mesh origami. Direct laser drilling of paper mesh for flexible origami may open up a new route to the rational design and fabrication of oil-water separation devices.

14.
Adv Mater ; 31(5): e1806386, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30536794

RESUMO

Muscles and joints make highly coordinated motion, which can be partly mimicked to drive robots or facilitate activities. However, most cases primarily employ actuators enabling simple deformations. Therefore, a mature artificial motor system requires many actuators assembled with jointed structures to accomplish complex motions, posing limitations and challenges to the fabrication, integration, and applicability of the system. Here, a holistic artificial muscle with integrated light-addressable nodes, using one-step laser printing from a bilayer structure of poly(methyl methacrylate) and graphene oxide compounded with gold nanorods (AuNRs), is reported. Utilizing the synergistic effect of the AuNRs with high plasmonic property and wavelength-selectivity as well as graphene with good flexibility and thermal conductivity, the artificial muscle can implement full-function motility without further integration, which is reconfigurable through wavelength-sensitive light activation. A biomimetic robot and artificial hand are demonstrated, showcasing functionalized control, which is desirable for various applications, from soft robotics to human assists.


Assuntos
Materiais Biomiméticos/química , Grafite/química , Ouro/química , Luz , Modelos Anatômicos , Nanotubos/química , Polimetil Metacrilato/química , Robótica , Condutividade Térmica
15.
Appl Opt ; 57(32): 9604-9608, 2018 Nov 10.
Artigo em Inglês | MEDLINE | ID: mdl-30461745

RESUMO

We report rapid and mask-free fabrication of a sapphire concave microlens array by a combined method of femtosecond laser holographic processing and wet etching. The method features high fabrication efficiency, as crater arrays can be created on sapphire through a parallel processing manner, and the subsequent wet etching facilitates the formation of microlens arrays with a smooth surface. More importantly, the size and spacing of the concave microlenses can be well tuned by varying the distance of craters and etching time. Two types of microlens arrays with a spacing of 25 and 40 µm have been successfully fabricated, both of which showed good imaging performance. This method holds great promise for developing sapphire-based micro-optical components.

16.
Nanoscale ; 10(36): 17002-17006, 2018 Sep 20.
Artigo em Inglês | MEDLINE | ID: mdl-30187071

RESUMO

We report here a facile, green and cost-effective fabrication of high-performance capacitive pressure sensors by drawing loop-and disc-shaped graphite electrode arrays on copying tissues. Graphene oxide enhanced foam-like paper is prepared as an efficient dielectric layer. The paper-based capacitive pressure sensor enables sensitive detection of finger touch, motion and proximity.

17.
Langmuir ; 34(20): 5712-5718, 2018 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-29706078

RESUMO

Reported here is a high-efficiency preparation method of amorphous nickel phosphide (Ni-P) nanoparticles by intense femtosecond laser irradiation of nickel sulfate and sodium hypophosphite aqueous solution. The underlying mechanism of the laser-assisted preparation was discussed in terms of the breaking of chemical bond in reactants via highly intense electric field discharge generated by the intense femtosecond laser. The morphology and size of the nanoparticles can be tuned by varying the reaction parameters such as ion concentration, ion molar ratio, laser power, and irradiation time. X-ray diffraction and transmission electron microscopy results demonstrated that the nanoparticles were amorphous. Finally, the thermogravimetric-differential thermal analysis experiment verified that the as-synthesized noncrystalline Ni-P nanoparticles had an excellent catalytic capability toward thermal decomposition of ammonium perchlorate. This strategy of laser-mediated electrical discharge under such an extremely intense field may create new opportunities for the decomposition of molecules or chemical bonds that could further facilitate the recombination of new atoms or chemical groups, thus bringing about new possibilities for chemical reaction initiation and nanomaterial synthesis that may not be realized under normal conditions.

18.
ACS Appl Mater Interfaces ; 10(21): 18416-18425, 2018 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-29722522

RESUMO

Controlling the wettability of graphene and its derivatives is critical for broader applications. However, the dynamic dewetting performance of graphene is usually overlooked. Currently, superhydrophobic graphene with an anisotropic wettability is rare. Inspired by natural reed leaves, we report an ingenious fabrication process combining photolithography and laser holography technologies to create biomimetic graphene surfaces that demonstrate anisotropic wettability along two directions of grooved hierarchical structures, which are similar to reed leaf veins. Microgrooved structures with a period of 200 µm were fabricated via photolithography to endow the substrate with an obvious anisotropic wettability. Two-beam laser interference treatments of the graphene oxide (GO) film on the grooved substrate removed most of the hydrophilic oxygen-containing groups on the GO sheets and increased the surface roughness by introducing additional hierarchical micro-nanostructures. The combined effects endowed the resultant graphene films with a unique anisotropic superhydrophobicity similar to that of reed leaves. Superhydrophobic graphene surfaces with anisotropic antiwetting behavior might allow further innovations based on graphene in the fields of bionics and electronics.

19.
Sci Rep ; 8(1): 4918, 2018 Mar 20.
Artigo em Inglês | MEDLINE | ID: mdl-29559672

RESUMO

We report on the fabrication of a NO2 gas sensor from room-temperature reduction of graphene oxide(GO) via two-beam-laser interference (TBLI). The method of TBLI gives the distribution of periodic dissociation energies for oxygen functional groups, which are capable to reduce the graphene oxide to hierarchical graphene nanostructures, which holds great promise for gaseous molecular adsorption. The fabricated reduced graphene oxide(RGO) sensor enhanced sensing response in NO2 and accelerated response/recovery rates. It is seen that, for 20 ppm NO2, the response (Ra/Rg) of the sensor based on RGO hierarchical nanostructures is 1.27, which is higher than that of GO (1.06) and thermal reduced RGO (1.04). The response time and recovery time of the sensor based on laser reduced RGO are 10 s and 7 s, which are much shorter than those of GO (34 s and 45 s), indicating that the sensing performances for NO2 sensor at room temperature have been enhanced by introduction of nanostructures. This mask-free and large-area approach to the production of hierarchical graphene micro-nanostructures, could lead to the implementation of future graphene-based sensors.

20.
Opt Lett ; 43(5): 1139-1142, 2018 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-29489799

RESUMO

We report on the fabrication of ion exchangeable microstructures by femtosecond laser direct writing of an ion exchange photopolymer, poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAMPS). The resultant microstructures are negatively charged in aqueous solution, and can adsorb positively charged species, such as metal ions, nanoparticles, and proteins by electrostatic interaction, forming functional components for chip functionalization. In addition, it is possible to modify the microstructures with positively charged species that make the microstructures sensitive to negatively charged species. As a typical example, a crossed 3D microvessel functionalized with antibodies was fabricated, which reveals great potential for organ-on-a-chip systems. The fabrication of ion exchangeable microstructures holds great promise for flexible chip functionalization.


Assuntos
Lasers , Nanotecnologia/métodos , Polímeros/química , Ácidos Sulfônicos/química , Redação , Desenho de Equipamento
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