Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 188
Filtrar
Mais filtros

Assunto principal
Tipo de estudo
Idioma
Intervalo de ano de publicação
1.
Adv Sci (Weinh) ; 8(10): 2002464, 2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-34026430

##### RESUMO

Graphene oxide (GO), which has many oxygen functional groups, is a promising candidate for use in moisture-responsive sensors and actuators due to the strong water-GO interaction and the ultrafast transport of water molecules within the stacked GO sheets. In the last 5 years, moisture-responsive actuators based on GO have shown distinct advantages over other stimuli-responsive materials and devices. Particularly, inspired by nature organisms, various moisture-enabled soft robots have been successfully developed via rational assembly of the GO-based actuators. Herein, the milestones in the development of moisture-responsive soft robots based on GO are summarized. In addition, the working mechanisms, design principles, current achievement, and prospects are also comprehensively reviewed. In particular, the GO-based soft robots are at the forefront of the advancement of automatable smart devices.

2.
Opt Lett ; 46(9): 2059-2062, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33929418

##### RESUMO

In this work, a method is proposed and demonstrated for fabrication of chirped fiber Bragg gratings (CFBGs) in single-mode fiber by femtosecond laser point-by-point inscription. CFBGs with bandwidths from 2 to 12 nm and dispersion ranges from 14.2 to 85 ps/nm are designed and achieved. The sensitivities of temperature and strain are 14.91 pm/°C and 1.21pm/µÎµ, respectively. Compared to the present phase mask method, femtosecond laser point-by-point inscription technology has the advantage of manufacturing CFBGs with different parameter flexibilities, and is expected to be widely applied in the future.

3.
Opt Lett ; 46(9): 2095-2098, 2021 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-33929427

##### RESUMO

Nonlinear nanophotonics, as an emerging field in nanophotonics, eagerly calls for experimental techniques for probing and analyzing near-field nonlinear optical signals with subwavelength resolution. Here, we report an aperture-type scanning near-field optical microscopic method for probing near-field nonlinear optical processes. As a demonstration, near-field third-harmonic generation from an anapole dark-mode state generated by a silicon nanodisk is probed and imaged. The measured results agree well with the simulations, with a spatial resolution down to $0.14{\lambda _0}$ and a sensitivity of 0.1 nW. This method provides a powerful tool for characterizing nonlinear light-matter interactions at the nanoscale, which can help, for example, to unveil crystal properties involving subwavelength defects or dislocations.

4.
ACS Nano ; 15(4): 5925-5943, 2021 04 27.
Artigo em Inglês | MEDLINE | ID: mdl-33734695

##### RESUMO

The optical manipulation of tiny objects is significant to understand and to explore the unknown in the microworld, which has found many applications in materials science and life science. Physically speaking, these technologies arise from direct or indirect optomechanical coupling to convert incident optical energy to mechanical energy of target objects, while their efficiency and functionalities are determined by the coupling behavior. Traditional optical tweezers stem from direct light-to-matter momentum transfer, and the generation of an optical gradient force requires high optical power and rigorous optics. As a comparison, the opto-thermophoretic manipulation techniques proposed recently originate from high-efficiency opto-thermomechanical coupling and feature low optical power. Through rational design of the light-generated temperature gradient and exploring the mechanical response of diverse targets to the temperature gradient, a variety of opto-thermophoretic techniques were developed, which exhibit broad applicability to a wide range of target objects from colloid materials to biological cells to biomolecules. In this review, we will discuss the underlying mechanism of thermophoresis in different liquid environments, the cutting-edge technological innovation, and their applications in colloidal science and life science. We also provide a brief outlook on the existing challenges and anticipate their future development.

5.
Nano Lett ; 21(4): 1628-1635, 2021 02 24.
Artigo em Inglês | MEDLINE | ID: mdl-33555185

##### RESUMO

Remote manipulation of a micromachine under an external magnetic field is significant in a variety of applications. However, magnetic manipulation requires that either the target objects or the fluids should be ferromagnetic or superparamagnetic. To extend the applicability, we propose a versatile optical printing technique termed femtosecond laser-directed bubble microprinting (FsLDBM) for on-demand magnetic encoding. Harnessing Marangoni convection, evaporation flow, and capillary force for long-distance delivery, near-field attraction, and printing, respectively, FsLDBM is capable of printing nanomaterials on the solid-state substrate made of arbitrary materials. As a proof-of-concept, we actuate a 3D polymer microturbine under a rotating magnetic field by implementing Î³-Fe2O3 nanomagnets on its blade. Moreover, we demonstrate the magnetic encoding on a living daphnia and versatile manipulation of the hybrid daphnia. With its general applicability, the FsLDBM approach provides opportunities for magnetic control of general microstructures in a variety of applications, such as smart microbots and biological microsurgery.

6.
Opt Lett ; 46(3): 520-523, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33528399

##### RESUMO

We developed a simple multi-foci-shaped femtosecond pulsed (MFSFP) method for processing circular cross section waveguides in transparent materials. With this flexible processing method, the focus energy distribution can be designed freely and arbitrarily, and single-mode waveguides with cross section circularity better than 96.0% were achieved. The mode shape difference (1.93%) of circular waveguides is smaller than the difference (7.01%) of normal elliptical waveguides. The coupling abilities of the two kinds of waveguides were investigated with three-dimensional (3D) directional couplers in both experiments and theoretical simulations. The coupling coefficient difference of circular waveguides in vertical and horizontal coupling directions was â¼0.01mm-1, which was smaller than 0.33mm-1 of normal waveguides. The circular symmetric waveguides will play an important role in large-scale high-intensity 3D photonic integrated circuits.

7.
Opt Lett ; 46(3): 536-539, 2021 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-33528403

##### RESUMO

We systematically studied femtosecond laser-inscribed self-organized nanogratings and geometric phase elements such as a polarization diffraction focusing lens and Q-plate in sapphire crystal. Besides the void structures observed in the focus, nanogratings with periods of 150~300 nm were observed, depending on a nanoslit that took the role of a seeding effect by localized light field enhancement. The non-polarized refractive index change and birefringence were measured with values around 1â¼2×10-3 and 6×10-4, respectively. Based on the laser-inscribed form birefringence, a geometric phase lens and Q-plate were successfully demonstrated in sapphire with high imaging and a focusing effect. We expect that our findings may promote the understanding of laser-induced nanogratings in bulk and potential applications in geometric phase elements.

8.
Nanotechnology ; 32(13): 135208, 2021 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-33427201

##### RESUMO

Band renormalization effects play a significant role for two-dimensional (2D) materials in designing a device structure and customizing their optoelectronic performance. However, the intrinsic physical mechanism about the influence of these effects cannot be revealed by general steady-state studies. Here, band renormalization effects in organic superacid treated monolayer MoS2, untreated monolayer MoS2 and few-layer MoS2 are quantitatively analyzed by using broadband femtosecond transient absorption spectroscopy. In comparison with the untreated monolayer, organic superacid treated monolayer MoS2 maintains a direct bandgap structure with two thirds of carriers populated at K valley, even when the initial exciton density is as high as 2.05 × 1014 cm-2 (under 400 nm excitations). While for untreated monolayer and few-layer MoS2, many-particle induced band renormalizations lead to a stronger imbalance for the carrier population between K and Q valleys in k space, and the former experiences a direct-to-indirect bandgap transition when the initial exciton density exceeds 5.0 × 1013 cm-2 (under 400 nm excitations). Those many-particle induced band renormalization processes further suggest a band-structure-controlling method in practical 2D devices.

9.
Micromachines (Basel) ; 11(11)2020 Nov 04.
Artigo em Inglês | MEDLINE | ID: mdl-33158095

##### RESUMO

An active surface with an on-demand tunable topography holds great potential for various applications, such as reconfigurable metasurfaces, adaptive microlenses, soft robots and four-dimensional (4D) printing. Despite extensive progress, to achieve refined control of microscale surface structures with large-amplitude deformation remains a challenge. Moreover, driven by the demand of constructing a large area of microstructures with increased complexity-for instance, biomimetic functional textures bearing a three-dimensional (3D) gradient-novel strategies are highly desired. Here, we develop an active surface with a dynamic topography and three-tier height gradient via a strain-tunable mismatching-bonding process. Pneumatic actuation allows for rapid, reversible and uniform regulation of surface microstructures at the centimeter scale. The in-situ modulation facilitates large-amplitude deformation with a maximum tuning range of 185 µm. Moreover, the structural gradient can be modulated by programming the strain value of the bonding process. With our strategy, another two types of surfaces with a four-tier gradient and without gradient were also prepared. By providing active modulation and design flexibility of complicated microstructures, the proposed strategy would unlock more opportunities for a wealth of novel utilizations.

10.
Front Chem ; 8: 835, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-33195040

##### RESUMO

Bioinspired superhydrophobic surfaces are an artificial functional surface that mainly extracts morphological designs from natural organisms. In both laboratory research and industry, there is a need to develop ways of giving large-area surfaces water repellence. Currently, surface modification methods are subject to many challenging requirements such as a need for chemical-free treatment or high surface roughness. Laser micro-nanofabrications are a potential way of addressing these challenges, as they involve non-contact processing and outstanding patterning ability. This review briefly discusses multiple laser patterning methods, which could be used for surface structuring toward creating superhydrophobic surfaces.

11.
J Phys Chem Lett ; 11(22): 9649-9655, 2020 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-33125851

##### RESUMO

Understanding and controlling the charge transfer processes of two-dimensional (2D) materials are fundamental for the optimized device performance based on 2D semiconductors and heterostructures. The charge transfer rate is very robust in transition metal disulfide (TMD) heterostructures with type II band alignments, which can be manipulated by intercalating a dielectric layer like hBN to isolate the donor and acceptor monolayers. This study shows that there is an alternative way to change the electron transfer and recombination rates in the case of nLMoS2/mLWSe2 multilayer heterostructures, where the donor-acceptor distance is maintained, but the rate of electron transfer is strongly layer dependent and shows asymmetry for the layer number of donor and acceptor monolayers. Especially, the 1LMoS2/2LWSe2 heterostructure slows electron transfer and charge recombination rates â¼2.3 and â¼12 times that of the 1LMoS2/1LWSe2 heterostructure, respectively, which have been competitive with that in the 1LMoS2/hBN/1LWSe2 heterostructure. From an application perspective, the noninterfacial electron transfer in which photogenerated electrons should across more than one atomically thin layer is not favorable due to the built-in electric field established by the initial interfacial electron transfer.

12.
Opt Lett ; 45(18): 5156-5159, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32932476

##### RESUMO

We report an improved light extraction in all-inorganic perovskite light-emitting devices (PeLEDs) by integrating a periodic corrugated nanostructure at the metallic cathode/organic interface. Nanoimprinting lithography was used to introduce the nanostructures onto the surface of the electron transport layer directly to avoid influencing the morphology and crystallinity of the perovskite film underneath. The trapped energy at the metallic electrode has been successfully outcoupled by the excitation of the surface plasma polariton (SPP) modes induced by the periodic corrugations. The luminance and current efficiency of the periodically corrugated PeLED exhibit enhancements of 42% and 28%, respectively, compared to those of the planar PeLED. The finite-difference time-domain simulation was used to confirm the efficient outcoupling of the SPP modes.

13.
Artigo em Inglês | MEDLINE | ID: mdl-32967829

##### RESUMO

As a superior self-protection strategy, invisibility has been a topic of long-standing interest in both academia and industry, because of its potential for intriguing applications that have only appeared thus far in science fiction. However, due to the strong dispersion of passive materials, achieving cross-wavelength invisibility remains an open challenge. Inspired by the natural ecological relationship between transparent midwater oceanic animals and the cross-wavelength detection strategy of their predators, we propose a cross-wavelength invisibility concept that integrates various invisibility tactics, where a Boolean metamaterial design procedure is presented to balance divergent material requirements over cross-scale wavelengths. As proof of concept, we experimentally demonstrate longwave cloaking and shortwave transparency simultaneously through a nanoimprinting technique. Our work extends the concept of stealth techniques from individual invisibility tactics targeting a single-wavelength spectrum to an integrated invisibility tactic targeting a cross-wavelength applications and may pave the way for development of cross-wavelength integrated metadevices.

14.
Nat Commun ; 11(1): 4536, 2020 09 10.
Artigo em Inglês | MEDLINE | ID: mdl-32913189

##### RESUMO

Natural musculoskeletal systems have been widely recognized as an advanced robotic model for designing robust yet flexible microbots. However, the development of artificial musculoskeletal systems at micro-nanoscale currently remains a big challenge, since it requires precise assembly of two or more materials of distinct properties into complex 3D micro/nanostructures. In this study, we report femtosecond laser programmed artificial musculoskeletal systems for prototyping 3D microbots, using relatively stiff SU-8 as the skeleton and pH-responsive protein (bovine serum albumin, BSA) as the smart muscle. To realize the programmable integration of the two materials into a 3D configuration, a successive on-chip two-photon polymerization (TPP) strategy that enables structuring two photosensitive materials sequentially within a predesigned configuration was proposed. As a proof-of-concept, we demonstrate a pH-responsive spider microbot and a 3D smart micro-gripper that enables controllable grabbing and releasing. Our strategy provides a universal protocol for directly printing 3D microbots composed of multiple materials.

##### Assuntos
Biomimética/métodos , Compostos de Epóxi/efeitos da radiação , Fenômenos Fisiológicos Musculoesqueléticos , Polímeros/efeitos da radiação , Robótica/métodos , Soroalbumina Bovina/efeitos da radiação , Biomimética/instrumentação , Compostos de Epóxi/química , Hidrogéis/química , Hidrogéis/efeitos da radiação , Concentração de Íons de Hidrogênio , Lasers , Polimerização/efeitos da radiação , Polímeros/química , Impressão Tridimensional , Robótica/instrumentação , Soroalbumina Bovina/química
15.
Opt Lett ; 45(17): 4879-4882, 2020 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-32870881

##### RESUMO

An ultrathin metal film with high transmittance and conductivity has been demonstrated to be a promising transparent electrode for organic light-emitting devices (OLEDs). However, mediocre surface morphology and continuity of evaporated metal films and the surface plasmon-polaritons (SPPs) energy loss between the metal electrode and organic layer still limit the external quantum efficiency (EQE) of OLEDs. Here, nanoimprint lithography has been directly applied on the ultrathin Au film with underlying uncured photopolymer to fabricate the nanopillared anode. Both the conductivity and transmittance of the nanopillared ultrathin Au film have been improved due to the improvement of continuity and surface smoothness. As we expected, the SPPs mode has been coupled into photons and further extracted from OLEDs by using the nanopillared Au film anode. Finally, 19.2% and 70.1% enhancement of current efficiency were achieved compared to the planar device with ultrathin Au anode and ITO anode, respectively.

16.
Opt Lett ; 45(16): 4630-4633, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32797027

##### RESUMO

The introduction of non-Hermiticity into photonics has enabled new design principles for photonic devices. Here we propose the design of a tunable non-Hermitian on-chip mode converter working at telecommunication wavelengths. The key component of the converter is a phase change material, and switching its working state can enable a topological change in the energy surface of the system. The conversion functionality can be realized by dynamically encircling an exceptional point in the parameter space of the device. The device based on this non-Hermitian principle is robust to perturbations of structural parameters and works in broadband. The non-Hermitian principle can be applied for the design of more complex on-chip photonic devices.

17.
Front Chem ; 8: 525, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32656183

##### RESUMO

The past decades have seen growing research interest in developing efficient fabrication techniques for preparing bioinspired graphene surfaces with superwettability. Among the various fabrication methods, laser fabrication stands out as a prominent one to achieve this end and has demonstrated unique merits in the development of graphene surfaces with superwettability. In this paper, we reviewed the recent advances in this field. The unique advantages of laser fabricated graphene surfaces have been summarized. Typical graphene surfaces with superwettability achieved by laser fabrication, including superhydrophobic graphene surfaces, oil/ water separation, fog collection, antibacterial surfaces, surface enhanced Raman scattering (SERS), and desalination, have been introduced. In addition, current challenges and future perspectives in this field have been discussed. With the rapid progress of novel laser physical/ chemical fabrication schemes, graphene surfaces with superwettability prepared by laser fabrication may undergo sustained development and thus contribute greatly to the scientific research and our daily life.

18.
Adv Mater ; 32(28): e2001998, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32500553

##### RESUMO

Compared with thin-film morphology, 1D perovskite structures such as micro/nanowires with fewer grain boundaries and lower defect density are very suitable for high-performance photodetectors with higher stability. Although the stability of perovskite microwire-based photodetectors has been substantially enhanced in comparison with that of photodetectors based on thin-film morphology, practical applications require further improvements to the stability before implementation. In this study, a template-assisted method is developed to prepare methylammonium lead bromide (MAPbBr3 ) micro/nanowire structures, which are encapsulated in situ by a protective hydrophobic molecular layer. The combination of the protective layer, high crystalline quality, and highly ordered microstructures significantly improve the stability of the MAPbBr3 single-crystal microwire arrays. Consequently, these MAPbBr3 single-crystal microwire-array-based photodetectors exhibit significant long-term stability, maintaining 96% of the initial photocurrent after 1 year without further encapsulation. The lifetime of such photodetectors is hence approximately four times longer than that of the most stable previously reported perovskite micro/nanowire-based photodetector; this is thought to be the most stable perovskite photodetector reported thus far. Furthermore, this work should contribute further toward the realization of perovskite 1D structures with long-term stability.

19.
Opt Lett ; 45(11): 3058, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32479458

##### RESUMO

This publisher's note contains corrections to Opt. Lett.45, 2580 (2020).OPLEDP0146-959210.1364/OL.391232.

20.
Opt Lett ; 45(9): 2580-2583, 2020 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-32356821

##### RESUMO

Here a continuous axial-spiral phase microplate (CAsPP), based on combining a logarithmic axicon and a spiral phase plate, was proposed for generating high-quality higher-order Bessel vortex beams. The novel optical component implemented via femtosecond laser direct writing possesses compact geometry and unique optical properties. The CAsPP with a diameter of 80 µm possesses a controllable long focus ranging from 50 to 600 µm and exhibits a good self-healing ability after free transmission of about 45 µm. Unique optical properties were demonstrated in both experiments and simulations, which were well matched to each other. This Letter provides new opportunities for applications in integrated optics, optical trapping, laser machining, and information reconstruction.

...