Non-Lithography Hydrodynamic Printing of Micro/Nanostructures on Curved Surfaces

A key issue of micro/nano devices is how to integrate micro/nanostructures with specified chemical components onto various curved surfaces. Hydrodynamic printing of micro/nanostructures on three-dimensional curved surfaces is achieved with a strategy that combines template-induced hydrodynamic printing and self-assembly of nanoparticles (NPs). Non-lithography flexible wall-shaped templates are replicated with microscale features by dicing a trench-shaped silicon wafer. Arising from the capillary pumped function between the template and curved substrates, NPs in the colloidal suspension self-assemble into close-packed micro/nanostructures without a gravity effect. Theoretical analysis with the lattice Boltzmann model reveals the fundamental principles of the hydrodynamic assembly process. Spiral linear structures achieved by two kinds of fluorescent NPs show non-interfering photoluminescence properties, while the waveguide and photoluminescence are confirmed in 3D curved space. The printed multiconstituent micro/nanostructures with single-NP resolution may serve as a general platform for optoelectronics beyond flat surfaces.     

An Oxygen‐Insensitive Degradable Resist for Fabricating Metallic Patterns on Highly Curved Surfaces by UV‐Nanoimprint Lithography

In this paper, an oxygen‐insensitive degradable resist for UV‐nanoimprint is designed, com­prising a polycyclic degradable acrylate monomer, 2,10‐diacryloyloxymethyl‐1,4,9,12‐tetraoxa­spiro [4.2.4.2] tetradecane (DAMTT), and a multifunctional thiol monomer pentaerythritol tetra(3‐mercaptopropionate) (PETMP). The resist can be quickly UV‐cured in the air atmosphere and achieve a high monomer conversion of over 98%, which greatly reduce the adhesion force between the resist and the soft mold. High conversion, in company with an adequate Young's modulus (about 1 GPa) and an extremely low shrinkage (1.34%), promises high nanoimprint resolution of sub‐50 nm. The cross‐linked resist is able to break into linear molecules in a hot acid solvent. As a result, metallic patterns are fabricated on highly curved surfaces via the lift off process without the assistance of a thermoplastic polymer layer.

     

Synthesis of Highly Hydrophilic Polyaniline Nanowires and Sub‐Micro/Nanostructured Dendrites on Poly(propylene) Film Surfaces

Summary: Polyaniline (PANI) nanowires and sub‐micro/nanostructured dendrites are synthesized and immobilized on PP‐g‐PAA film surfaces via routine oxidative polymerization of aniline under different conditions, where grafting poly(acrylic acid) (PAA) served as a template and dopant, and SDS as a surfactant. The immobilized PANI enhances the surface hydrophilicity of the poly(propylene) (PP) films, and a superhydrophilic surface is obtained in this way. The mechanism of forming different morphologies of PANI and of correspondingly obtaining a superhydrophilic surface are briefly discussed.

FESEM image shows the PANI sub‐micro/nanostructured dendrites immobilized on the surfaces of PP films. The modified surface is highly hydrophilic with a water contact angle of 3°.     

Some Issues Related to Polyaniline Micro‐/Nanostructures

This feature article reviews the authors' work combined with highlighted specific aspects of polyaniline (PANI) macro/nanostructures, focusing on such issues as the following. 1) The new development of a hard‐template method. 2) Evaluation of a template‐free method in universality, controllability, and simplicity as well as the self‐assembly mechanism. 3) Multi‐functionality based on a template‐free method associated with other approaches. 4) Cooperation effect of a micelle soft‐template and molecular interactions as a new tool to complex 3D microstructures assembled from 2D or 1D nanostructures. 5) Electrical and transport properties of a single PANI nanotube, as measured by a four‐probe method. 6) Sensors guided by reversible switching wettability through a doping/de‐doping process. An outlook is also briefly given.

     

Binary Reactive/Inert Non‐Fouling Polymeric Surfaces

Binary reactive/inert antifouling polymer brushes were grafted via a two step surface initiated polymerization from printed initiator monolayer and provided robust, effective polymeric surfaces for bioattachment with distinguishably reduced non‐specific adsorption. This synthetic strategy can be harnessed to build complex binary polymeric structures on substrate surfaces and the polymer brush surfaces reported in the present paper can be widely used for versatile biological study.

     

Local‐Curvature‐Controlled Non‐Epitaxial Growth of Hierarchical Nanostructures

Site‐selective growth on non‐spherical seeds provides an indispensable route to hierarchical complex nanostructures that are interesting for diverse applications. However, this has only been achieved through epitaxial growth, which is restricted to crystalline materials with similar crystal structures and physicochemical properties. A non‐epitaxial growth strategy is reported for hierarchical nanostructures, where site‐selective growth is controlled by the curvature of non‐spherical seeds. This strategy is effective for site‐selective growth of silica nanorods from non‐spherical seeds of different shapes and materials, such as α‐Fe₂O₃, NaYF₄, and ZnO. This growth strategy is not limited by the stringent requirements of epitaxy and is thus a versatile general method suitable for the preparation of hierarchical nanostructures with controlled morphologies and compositions to open up a verity of applications in self‐assembly, nanorobotics, catalysis, electronics, and biotechnology.     

Site‐Directed,On‐Surface Assembly of DNA Nanostructures

Two‐dimensional DNA lattices have been assembled from DNA double‐crossover (DX) motifs on DNA‐encoded surfaces in a site‐specific manner. The lattices contained two types of single‐stranded protruding arms pointing into opposite directions of the plane. One type of these protruding arms served to anchor the DNA lattice on the solid support through specific hybridization with surface‐bound, complementary capture oligomers. The other type of arms allowed for further attachment of DNA‐tethered probe molecules on the opposite side of the lattices exposed to the solution. Site‐specific lattice assembly and attachment of fluorophore‐labeled oligonucleotides and DNA–protein conjugates was demonstrated using DNA microarrays on flat, transparent mica substrates. Owing to their programmable orientation and addressability over a broad dynamic range from the nanometer to the millimeter length scale, such supramolecular architecture might be used for presenting biomolecules on surfaces, for instance, in biosensor applications.     

High‐Conductivity Two‐Dimensional Polyaniline Nanosheets Developed on Ice Surfaces

A new method to develop two‐dimensional PANI nanosheets using ice as a removable hard template is presented. Distinctly high current flows of 5.5 mA at 1 V and a high electrical conductivity of 35 S cm^?1 were obtained for the polyaniline (PANI) nanosheets, which marked a significant improvement from previously values on other PANIs reported over the past decades. These improved electrical properties of ice‐templated PANI nanosheets were attributed to the long‐range ordered edge‐on π‐stacking of the quinoid ring, ascribed to the ice surface‐assisted vertical growth of PANI. The unprecedented advantages of the ice‐templated PANI nanosheets are two‐fold. First, the PANI nanosheet can be easily transferred onto various types of substrates via float‐off from the ice surfaces. Second, PANI can be patterned into any shape using predetermined masks, and this is expected to facilitate the eventual convenient and inexpensive application of conducting polymers in versatile electronic device forms.     

Facile Non‐enzymatic Lactic Acid Sensor Based on Cobalt Oxide Nanostructures

In this study, we have investigated the effect of counter anions on the morphology of cobalt oxide nanostructures. The nanostructures of cobalt oxide are prepared by a low temperature aqueous chemical growth method. The morphology of cobalt oxide nanostructure material was investigated by scanning electron microscopy and the crystalline structure was studied by powder X‐ray diffraction technique. The cobalt oxide nanostructures exhibit the nanowire, lump, bundle of the nanowire and flower‐like morphologies. The XRD study has revealed a cubic phase of cobalt oxide nanostructures. The electro‐catalytic properties of cobalt oxide nanostructures were explored through cyclic voltammetry and amperometric techniques by sensing of lactic acid in the alkaline media. The cobalt oxide nanostructures prepared from cobalt nitrate have shown a well‐resolved redox peak. The proposed mechanism for the non‐enzymatic lactic acid sensor is elucidated by considering the morphology and cyclic voltammetry response. The limit of detection for the sensor was found to be 0.006 mM and it exhibits a linear range from 0.05–3 mM of lactic acid as shown by cyclic voltammetry. The amperometric response has shown the excellent current‐concentration response and the linear range of sensor was found to be 0.1 mM to 5.5 mM. The lactic acid sensor is stable, selective and can be used for practical applications. This study provides an excellent alternative analytical tool for the determination of lactic acid.     

Recent Development on Controlled Synthesis of Metal Sulfides Hollow Nanostructures via Hard Template Engaged Strategy: A Mini‐Review

In this mini‐review, we highlighted the recent progresses in the controlled synthesis of metal sulfides hollow nanostructures via hard template technique. After a brief introduction about the formation mechanism of the inorganic hollow nanostructures via hard template technique, the discussions primarily focused on the emerging development of metal sulfides hollow nanostructures. Various synthetic strategies were summarized concerning the use of the hard template engaged strategies to fabricate various metal sulfides hollow nanostructures, such as hydrothermal method, solvothermal method, ion‐exchange, sulfidation or calcination etc. Finally, the perspectives and summaries have been presented to demonstrate that a facile synthetic technique would be widely used to fabricate metal sulfides hollow nanostructures with multi‐shells and components.     

Micro‐Nanostructures of Cellulose‐Collagen for Critical Sized Bone Defect Healing

Bone tissue engineering strategies utilize biodegradable polymeric matrices alone or in combination with cells and factors to provide mechanical support to bone, while promoting cell proliferation, differentiation, and tissue ingrowth. The performance of mechanically competent, micro‐nanostructured polymeric matrices, in combination with bone marrow stromal cells (BMSCs), is evaluated in a critical sized bone defect. Cellulose acetate (CA) is used to fabricate a porous microstructured matrix. Type I collagen is then allowed to self‐assemble on these microstructures to create a natural polymer‐based, micro‐nanostructured matrix (CAc). Poly (lactic‐co‐glycolic acid) matrices with identical microstructures serve as controls. Significantly higher number of implanted host cells are distributed in the natural polymer based micro‐nanostructures with greater bone density and more uniform cell distribution. Additionally, a twofold increase in collagen content is observed with natural polymer based scaffolds. This study establishes the benefits of natural polymer derived micro‐nanostructures in combination with donor derived BMSCs to repair and regenerate critical sized bone defects. Natural polymer based materials with mechanically competent micro‐nanostructures may serve as an alternative material platform for bone regeneration.     

Low‐Cost,Thermoresponsive Wettability of Surfaces: Poly(N‐isopropylacrylamide)/Polystyrene Composite Films Prepared by Electrospinning

Low‐cost, responsive poly(N‐isopropylacrylamide)/polystyrene composite films were prepared by a facile electrospinning technique. The surface structures and wettabilities of the composite films are tunable by simply controlling the concentration of polymer. With a proper proportion of each polymer, the wettability of the surface can be switched between superhydrophilicity and superhydrophobicity when the temperature is changed from 20 °C to 50 °C. The combination of a stimuli‐responsive polymer with micro/nanostructures on the surface of the composite film contributes to this unique surface property.

     

微纳米图案化表面对细胞行为的影响

在再生医学领域中,材料对细胞生长和组织修复的调节作用一直是极为关键的问题.随着表面图案化技术的发展,在材料表面制备规则、可控、种类多样的图案化区域成为可能,因而该技术被广泛应用于再生医学、组织工程以及细胞诊断等相关学科领域.通过微纳米表面图案化方法,改变材料的化学性质和拓扑结构,从而实现对细胞粘附、迁移、增殖、凋亡、基...     

Turn‐Number‐Dependent Motion Behavior of Catalytic Helical Carbon Micro/Nanomotors

Helical micro/nanomotors (MNMs) can be propelled by external fields to swim through highly viscous fluids like complex biological environments, which promises miniaturized robotic tools to perform assigned tasks at small scales. However, the catalytic propulsion method, most widely adopted to drive MNMs, is seldom studied to actuate helical MNMs. Herein, we report catalytic helical carbon MNMs (CHCM) by sputtering Pt onto helical carbon nano‐coils (HCNC) that are in bulk prepared by a thermal chemical vapor deposition method. The Pt‐triggered H₂O₂ decomposition can drive the MNMs by an electrokinetic mechanism. The MNMs demonstrate versatile motion behaviors including both directional propulsion and rotation depending on the turn number of the carbon helix. Besides, due to the ease of surface functionalization on carbon and other properties such as biocompatibility and photothermal effect, the helical carbon MNMs promise multifunctional applications for biomedical or environmental applications.     

Biomass‐derived Nitrogen and Phosphorus Co‐doped Hierarchical Micro/mesoporous Carbon Materials for High‐performance Non‐enzymatic H2O2 Sensing

Nitrogen and phosphorus co‐doped hierarchical micro/mesoporous carbon (N,P‐MMC) was prepared by simple thermal treatment of freeze‐dried okra in the absence of any other additives. The 0.96 wt % of N and 1.47 wt % of P were simultaneously introduced into the graphitic framework of N,P‐MMC, which also possesses hierarchical porous structure with mesopores centered at 3.6 nm and micropores centered at 0.79 nm. Most importantly, N,P‐MMC carbon exhibits excellent catalytic activity for electrocatalytic reduction of H₂O₂, resulting in a new strategy to construct non‐enzymatic H₂O₂ sensor. The N,P‐MMC‐based H₂O₂ sensor displays two linear detection range about 0.1 mM–10 mM (R²=0.9993) and 20 mM–200 mM (R²=0.9989), respectively. The detection limit is estimated to be 6.8 μM at a signal‐to‐noise ratio of 3. These findings provide insights into synthesizing functional heteroatoms doped porous carbon materials for biosensing applications.     

Design and Fabrication of Tubular Micro/Nanomotors via 3D Laser Lithography

Catalytic tubular micro/nanomachines convert chemical energy from a surrounding aqueous fuel solution into mechanical energy to generate autonomous movements, propelled by the oxygen bubbles decomposed by hydrogen peroxide and expelled from the microtubular cavity. With the development of nanotechnology, micro/nanomotors have attracted more and more interest due to their numerous potential for in vivo and in vitro applications. Here, highly efficient chemical catalytic microtubular motors were fabricated via 3D laser lithography and their motion behavior under the action of driving force in fluids was demonstrated. The frequency of catalytically‐generated bubbles ejection was influenced by the geometrical shape of the micro/nanomotor and surrounding chemical fuel environment, resulting in the variation in motion speed. The micro/nanomotors generated with a rocket‐like shape displayed a more active motion compared with that of a single tubular micro/nanomotor, providing a wider range of practical micro‐/nanoscale applications in the future.     

聚合物基微纳米功能复合材料3D打印加工的研究

高分子材料3D打印加工可制备传统加工不能制备的形状复杂的高分子制件,是近年来发展很快的先进制造技术。但适用于3D打印加工的高分子材料种类少,结构功能单一,难以制备高分子功能器件。本文介绍了我们在聚合物基微纳米功能复合材料3D打印加工方面的研究工作:通过有机/无机杂化、固相剪切碾磨、超声辐照、分子复合等技术制备适合于选择性激光烧结(SLS)和熔融沉积成型(FDM)的聚合物基微纳米功能复合材料;实现了聚合物基微纳米功能复合粉体的SLS加工和功能复合丝条的FDM加工;研究了3D打印低维构建、层层叠加、自由界面成型、复杂固-液-固转变过程;建立了功能复合粉体球形化技术,发明了直接熔融挤出新型FDM打印机;制备了常规加工方法不能制备的数种形状复杂的功能器件,如尼龙11/钛酸钡压电器件、柔性聚氨酯/碳纳米管传感器、个性化人颌骨模型等,突破了传统加工难以制备复杂形状制品和目前3D打印难以制备功能制品的局限。     

Versatile Micropatterns of N‐Heterocyclic Carbenes on Gold Surfaces: Increased Thermal and Pattern Stability with Enhanced Conductivity

Patterned monolayers of N‐heterocyclic carbenes (NHCs) on gold surfaces were obtained by microcontact printing of NHC–CO₂ adducts and NHC(H)[HCO₃] salts. The NHC‐modified areas showed an increased conductivity compared to unmodified gold surface areas. Furthermore, the remaining surface areas could be modified with a second, azide‐functionalized carbene, facilitating further applications and post‐printing modifications. Thorough elucidation by a variety of analytical methods offers comprehensive evidence for the viability of the methodology reported here. The protocol enables facile access to versatile, microstructured NHC‐modified gold surfaces with highly stable patterns, enhanced conductivity, and the option for further modification.