Smart surfaces with tunable wettability have aroused much attention in the past few years. However, to obtain a surface that can reversibly transit between the lotus-leaf-like superhydrophobic isotropic and rice-leaf-like superhydrophobic anisotropic wettings is still a challenge. This paper, by mimicking microstructures on both lotus and rice leaves, reports such a surface that is prepared by creating micro/nanostructured arrays on the shape memory polymer. On the surface, the microstructure shapes can be reversibly changed between the lotus-leaf-like random state and the rice-leaf-like 1D ordered state. Accordingly, repeated switch between the superhydrophobic isotropic and anisotropic wettings can be displayed. Research results indicate that the smart controllability is ascribed to the excellent shape memory effect of the polymer, which endows the surface with special ability in memorizing different microstructure shapes and wetting properties. Meanwhile, based on the smart wetting performances, the surface is further used as a rewritable functional platform, on which various droplet transportation programmes are designed and demonstrated. This work reports a superhydrophobic surface with switchable isotropic/anisotropic wettings, which not only provides a novel functional material but also opens a new avenue for application in controlled droplet transportation.

Zhongjun Cheng    Zhang Dongjie    Lv Tong    Hua Lai    Zhang Enshuang    Kang Hongjun    Wang Yongzhen    Liu Pengchang    Liu Yu-Yan    Du Yi    Shixue Dou    江雷    

Advanced Functional Materials

2018

The homing pigeon-inspired artificial nanochannel can be modulated by moderate magnetic field in a fast and noncontacting way. The ionic current, as well as rectifying ability and conductance is controlled by the magnetic field reversibly through elastic deformation of the nanochannel. Different gating effects are obtained at the two sides of the asymmetrically conical nanochannel due to the different response models. The magnetic gated nanochannel system also exhibits an excellent stability and a quick response in a noncontacting way, which may be promising in electronic devices related to biological or healthcare applications.

Hou Guanglei    Wang Dianyu    肖凯    Zhang Huacheng    Zheng Shuang    Pei Li    Ye Tian-    江雷    

Small

2018

Anisotropic microstructures are widely used by being cleverly designed to achieve important functions. Mammals' respiratory tract is filled with dense cilia that rhythmically swing back and forth in a unidirectional wave to propel mucus and harmful substances out of the lung through larynx. Inspired by the ciliary structure and motion mechanism of the respiratory tract systems, a viscoelastic microsphere transporting strategy based on integration of airway cilium-like structure and magnetically responsive flexible conical arrays is demonstrated. Under external magnetic fields, the viscoelastic microspheres can be directionally and continuously transported alongside the swing of the cilia-like arrays that contain magnetic particles. This work provides a promising route for the design of advanced medical applications in directional transport of microspheres, drug delivery systems, ciliary dyskinesia treating, and self-cleaning without liquid.

Ben Shuang    Tai Jun    Ma Han    Peng Yun    Zhang Yuan    Dongliang Tian    Kesong Liu    江雷    

Advanced Functional Materials

2018

The emerging slippery liquid-infused porous surfaces inspired by Nepenthes pitcher plants have attracted considerable attention because of their excellent self-cleaning properties and potential applications in novel microfluidics, microchips, and liquid transportation and liquid manipulation technologies. However, the development of anisotropic slippery surfaces is in its infancy. Although some information of anisotropic slippery surfaces has been reported, the factors influencing their self-healing properties and electrically driven droplet motion have not been deeply explored. To address this limitation, anisotropic slippery surfaces have been designed and prepared with directional, porous and conductive PCDTPT films and lubricants (silicone oils with different viscosities), which are used here to investigate the influencing factors of the self-healing properties and electrically driven droplet motion. The results elucidate that the critical self-healing thickness increases with increasing silicone oil viscosity and that low-viscosity silicone oils filling in the porous films can reduce the responsive voltage of the electrical control of droplet motion on the anisotropic slippery surfaces with the same lubricant layer thickness.

Wang Zubin    Liping Heng    江雷    

Journal of Materials Chemistry A

2018

Recently, smart surfaces with switchable wettability have aroused much attention. However, only single surface chemistry or the microstructure can be changed on these surfaces, which significantly limits their wetting performances, controllability, and applications. A new surface with both tunable surface microstructure and chemistry was prepared by grafting poly(N-isopropylacrylamide) onto the pillar-structured shape memory polymer on which multiple wetting states from superhydrophilicity to superhydrophobicity can be reversibly and precisely controlled by synergistically regulating the surface microstructure and chemistry. Meanwhile, based on the excellent controllability, we also showed the application of the surface as a rewritable platform, and various gradient wettings can be obtained. This work presents for the first time a surface with controllability in both surface chemistry and microstructure, which starts some new ideas for the design of novel superwetting materials.

Zhang Dongjie    Zhongjun Cheng    Kang Hongjun    Yu Jian-Xin    Liu Yu-Yan    江雷    

Angewandte Chemie - International Edition

2018

Recently, smart interfacial materials that can reversibly transit between the superhydrophobicity and superhydrophilicity have aroused much attention. However, all present performances happen in air, and to realize such a smart transition in complex environments, such as oil, is still a challenge. Herein, TiOnanotube arrays with switchable transition between the superhydrophobicity and superhydrophilicity in oil are reported. The switching can be observed by alternation of UV irradiation and heating process, and the smart controllability can be ascribed to the cooperative effect between the surface nanostructures and the chemical composition variation. By using the controllable wetting performances, some applications such as under-oil droplet-based microreaction and water-removal from oil were demonstrated on our surface. This paper reports a surface with smart water wettability in oil, which could start some fresh ideas for wetting control on interfacial materials.

Kang Hongjun    Liu Yu-Yan    Hua Lai    Yu Xiaoyan    Zhongjun Cheng    江雷    

ACS Nano

2018

Biosurfaces with geometry-gradient structures or special wettabilities demonstrate intriguing performance in manipulating the behaviors of versatile fluids. By mimicking natural species, that is, the cactus spine with a shape-gradient morphology and the Picher plant with a lubricated inner surface, we have successfully prepared an asymmetric slippery surface by following the processes of CO-laser cutting, superhydrophobic modification, and the fluorinert infusion. The asymmetric morphology will cause the deformation of gas bubbles and subsequently engender an asymmetric driven force on them. Due to the infusion of fluorinert, which has a low surface energy (∼16 mN/m, 25 °C) and an easy fluidic property (∼0.75 cP, 25 °C), the slippery surface demonstrates high adhesive force (∼300 μN) but low friction force on the gas bubbles. Under the cooperation of the asymmetric morphology and fluorinert infused surface, the fabricated asymmetric slippery surface is applicable to the directional and continuous bubble delivery in an aqueous environment. More importantly, due to the hard-compressed property of fluorinert, the asymmetric slippery surface is facilitated with distinguished bubble transport capability even in a pressurized environment (∼0.65 MPa), showing its feasibility in practical industrial production. In addition, asymmetric slippery surfaces with a snowflake-like structure and a star-shaped structure were successfully fabricated for the real-world applications, both of which illustrated reliable performances in the continuous generation, directional transportation, and efficient collection of COand Hmicrobubbles.

Zhang Chunhui    Zhang Bo    Ma Hongyu    Li Zhe    Xiao Xiao    Zhang Yuheng    Cui Xinyu    Yu Cunming    Moyuan Cao    江雷    

ACS Nano

2018

Development of stimulus-responsive anisotropic slippery surfaces is important because of the high demand for such materials in the field of liquid directional-driven systems. However, current studies in the field of slippery surfaces are mainly conducted to prepare isotropic slippery surfaces. Although we have developed electric-responsive anisotropic slippery surfaces that enable smart control of the droplet motion, there remain challenges for designing temperature-responsive anisotropic slippery surfaces to control the liquid droplet motion on the surface and in the tube. In this work, temperature-responsive anisotropic slippery surfaces have been prepared by using paraffin, a thermo-responsive phase-transition material, as a lubricating fluid and directional porous polystyrene (PS) films as the substrate. The smart regulation of the droplet motion of several liquids on this surface was accomplished by tuning the substrate temperature. The uniqueness of this surface lies in the use of an anisotropic structure and temperature-responsive lubricating fluids to achieve temperature-driven smart control of the anisotropic motion of the droplets. Furthermore, this surface was used to design temperature-driven anisotropic microreactors and to manipulate liquid transfer in tubes. This work advances the understanding of the principles underlying anisotropic slippery surfaces and provides a promising material for applications in the biochip and microreactor system.

Wang By Lili    Liping Heng    江雷    

ACS Applied Materials and Interfaces

2018

Inspired by the densely covered capillary structure inside a dog's nose, we report an artificial nanostructure, i.e., poly(sodium p-styrenesulfonate)-functionalized reduced graphene oxide nanoscrolls (PGNS), with high structural perfection and efficient gas sensing applications. A facile supramolecular assembly is introduced to functionalize graphene with the functional polymer, combined with the lyophilization technique to massively transform the planar graphene-based nanosheets to nanoscrolls. Detailed characterizations reveal that the bioinspired nanoscrolls exhibit a wide-open tubular morphology with uniform dimensions that is structurally distinct from the previously reported ones. The detailed morphologies of the graphene-based nanosheets in each scrolling stage during lyophilization are monitored by cryo-SEM. This unravels an asymmetric polymer-induced graphene scrolling mechanism including the corresponding scrolling process, which is directly presented by molecular dynamics simulations. The fabricated PGNS sensors exhibit superior gas sensing performance with reliable repeatability, excellent linear sensibility, and, especially, an ultrahigh response (R/R= 5.39, 10 ppm) toward NO. The supramolecular assembly combined with the lyophilization technique to fabricate PGNS provides a strategy to design biomimetic materials for gas sensors and chemical trace detectors.

Chen Zhuo    Wang Jinrong    Pan Dou-Xing    Wang Yao    Noetzel Richard    Li Hao    Xie Peng    Pei Wenle    Umar Ahmad    江雷     Li Nan    De Rooij Nicolaas Frans    Zhou Guofu   

ACS Nano

2018

A kind of superhydrophobic magnetic nano/micropillar array (MNA) with optimized intrinsic dynamic wetting property has characteristics of magnetically induced dynamic tilt-angle changes, which achieves the controlling of the directional droplet transport effectively. It is revealed that MNA has a low adhesive gradient along the direction of magnetically induced tilt-angles. A tilt-angles of nano/micropillars in the range of 0°-59° is realized by controlling the magnetic field intensity (0-490 mT), so that a droplet (10 μL) can be transported on MNA from one pillar to the next along the tilt-angle direction. It is proposed that the continuous changes of magnetically induced dynamic tilt-angles on MNA induce a gradient driving force to act on the droplet, in addition to cooperation with the low adhesive direction that results from unidirectional gradient discontinuous solid-liquid-gas three phase contact lines. The finding offers insight into designing of surface materials that can be extended into microfluidics for controlling of droplet motion and others.

Lin Yucai    Hu Ziying    Zhang Miaoxin    Xu Ting    Feng Shile    江雷     Zheng Yongmei   

Advanced Functional Materials

2018