Jian-Nan Wang

Bio: Jian-Nan Wang is an academic researcher from Jilin University. The author has contributed to research in topics: Wetting & Graphene. The author has an hindex of 18, co-authored 22 publications receiving 1552 citations. Previous affiliations of Jian-Nan Wang include Tsinghua University.

Three-Level Biomimetic Rice-Leaf Surfaces with Controllable Anisotropic Sliding

Abstract: Rice leaves with anisotropic sliding properties have the ability to directionally control the movement of water microdroplets. However, the realization of artifi cial anisotropic sliding biosurfaces has remained challenging. It is found, by a systematic investigation, that the height of 200μ m-width groove arrays on rice leaves reaches up to 45 μ m, far greater than the smaller microgrooves that are widely adopted for the study of anisotropic wetting. A new model based on three-level microstructures (macro/micro/nano) is developed to interpret the anisotropic sliding behavior. Moreover, artifi cial rice leaves with different macrogrooves are demonstrated by combining micro/nanostructures and macrogrooves, which are prepared by photolithography, PDMS imprinting, and micro/nanostructure coating. Sliding-angle measurement further prove that the third-level macrogroove arrays are the determining factor for anisotropic sliding. Finally, a new testing method, curvature-assisted droplet oscillation (CADO), is developed to quantitatively reveal the anisotropic dynamic behavior of biomimetic rice-leaf-like surfaces.

Femtosecond laser rapid prototyping of nanoshells and suspending components towards microfluidic devices

Abstract: Microfluidic researches are now resorting to advanced micro-nanoprocessing technologies for production of more functional “lab-on-a-chip” systems. However, two-photon polymerization (TPP), a powerful designable micro-nanofabrication approach, has not been put to use on the exciting field, largely due to the difficulties in forming buried channels. Here, we solve the problem by TPP prototyping of nanoshells, for which the usage of the negative tone resin SU-8 is found critical. The fabrication efficiency improved by orders of magnitude, together with the prospect of integration of movable micro-mechanical and optical components into the chip would make TPP a promising enabling tool for the micro-analytical systems. Finally, a 25 μm length functional microvalve in a microfluidic channel was rapidly realized and its “ON” and “OFF” states were tested.

Bioinspired Fabrication of High-Quality 3D Artificial Compound Eyes by Voxel-Modulation Femtosecond Laser Writing for Distortion-Free Wide-Field-of-View Imaging

Abstract: The small field-of-view (FOV) limits the range of vision in various detecting/imaging devices from biological microscopes to commercial cameras and military radar. To date, imaging with FOV over 90° has been realized with fish-eye lenses, catadioptric lens, and rotating cameras. However, these devices suffer from inherent imaging distortion and require multiple bulky elements. Inspired by compound eyes found in nature, here a small-size (84 μm), distortion-free, wide-FOV imaging system is presented via an advanced 3D artificial eye architecture. The 3D artificial eye structure is accomplished by exploiting an effective optical strategy — high-speed voxel-modulation laser scanning (HVLS). The eye features a hexagonal shape, high fill factor (FF) (100%), large numerical aperture (NA) (0.4), ultralow surface roughness (2.5 nm) and aspherical profile, which provides high uniformity optics (error < ±6%) and constant resolution (FWHM = 1.7 ± 0.1 μm) in all directions. Quantitative measurement shows the eye reduces imaging distortion by two/three times under 30°/45° incidence, compared with a single lens. The distortion-free FOV can be controlled from 30° to 90°.

Recent developments in superhydrophobic graphene and graphene-related materials: from preparation to potential applications

Abstract: In the past decade, graphene has revealed a cornucopia of both fundamental science and potential applications due to its exceptional electrical, mechanical, thermal, and optical properties. Recently, increasing effort has been devoted to exploiting its new features, for example, wetting properties. Benefitting from its inherent material properties, graphene shows great potential for the fabrication of superhydrophobic surfaces, which could be potentially used for various anti-water applications. In this review, we summarize the recent developments in superhydrophobic graphene and graphene-related materials. Preparation strategies using pure graphene, graphene oxide, and graphene/polymer hybrids are presented and their potential applications are discussed. Finally, our own perspective of this dynamic field, including both current challenges and future demands, has been discussed. It is anticipated that the cooperation of the numerous merits of graphene and superhydrophobicity will lead to new opportunities for high-performance multifunctional devices.

Review on nanoparticles and nanostructured materials: history, sources, toxicity and regulations.

Abstract: Nanomaterials (NMs) have gained prominence in technological advancements due to their tunable physical, chemical and biological properties with enhanced performance over their bulk counterparts. NMs are categorized depending on their size, composition, shape, and origin. The ability to predict the unique properties of NMs increases the value of each classification. Due to increased growth of production of NMs and their industrial applications, issues relating to toxicity are inevitable. The aim of this review is to compare synthetic (engineered) and naturally occurring nanoparticles (NPs) and nanostructured materials (NSMs) to identify their nanoscale properties and to define the specific knowledge gaps related to the risk assessment of NPs and NSMs in the environment. The review presents an overview of the history and classifications of NMs and gives an overview of the various sources of NPs and NSMs, from natural to synthetic, and their toxic effects towards mammalian cells and tissue. Additionally, the types of toxic reactions associated with NPs and NSMs and the regulations implemented by different countries to reduce the associated risks are also discussed.

Emerging Droplet Microfluidics

Abstract: Droplet microfluidics generates and manipulates discrete droplets through immiscible multiphase flows inside microchannels Due to its remarkable advantages, droplet microfluidics bears significant value in an extremely wide range of area In this review, we provide a comprehensive and in-depth insight into droplet microfluidics, covering fundamental research from microfluidic chip fabrication and droplet generation to the applications of droplets in bio(chemical) analysis and materials generation The purpose of this review is to convey the fundamentals of droplet microfluidics, a critical analysis on its current status and challenges, and opinions on its future development We believe this review will promote communications among biology, chemistry, physics, and materials science

Ultrafast lasers—reliable tools for advanced materials processing

Abstract: The unique characteristics of ultrafast lasers, such as picosecond and femtosecond lasers, have opened up new avenues in materials processing that employ ultrashort pulse widths and extremely high peak intensities. Thus, ultrafast lasers are currently used widely for both fundamental research and practical applications. This review describes the characteristics of ultrafast laser processing and the recent advancements and applications of both surface and volume processing. Surface processing includes micromachining, micro- and nanostructuring, and nanoablation, while volume processing includes two-photon polymerization and three-dimensional (3D) processing within transparent materials. Commercial and industrial applications of ultrafast laser processing are also introduced, and a summary of the technology with future outlooks are also given. Scientists in Asia have reviewed the role of ultrafast lasers in materials processing. Koji Sugioka from RIKEN in Japan and Ya Cheng from the Shanghai Institute of Optics and Fine Mechanics in China describe how femtosecond and picosecond lasers can be used to perform useful tasks in both surface and volume processing. Such lasers can cut, drill and ablate a variety of materials with high precision, including metals, semiconductors, ceramics and glasses. They can also polymerize organic materials that contain a suitable photosensitizer and can three-dimensionally process inside transparent materials such as glass, and are already being used to fabricate medical stents, repair photomasks, drill ink-jet nozzles and pattern solar cells. The researchers also explain the characteristics of such lasers and the interaction of ultrashort, intense pulses of light with matter.

Graphene-based gas sensors

Abstract: Graphene materials have been widely explored for the fabrication of gas sensors because of their atom-thick two-dimensional conjugated structures, high conductivity and large specific surface areas. This feature article summarizes the recent advancements on the synthesis of graphene materials for this purpose and the techniques applied for fabricating gas sensors. The effects of the compositions, structural defects and morphologies of graphene-based sensing layers and the configurations of sensing devices on the performances of gas sensors will also be discussed.