Yanan Li

Rate-dependent interface capture beyond the coffee-ring effect.

The mechanism of droplet drying is a widely concerned fundamental issue since controlling the deposition morphology of droplet has significant influence on printing, biology pattern, self-assembling and other solution-based devices fabrication. Here we reveal a striking different kinetics-controlled deposition regime beyond the ubiquitous coffee-ring effect that suspended particles tend to kinetically accumulate at the air-liquid interface and deposit uniformly. As the interface shrinkage rate exceeds the particle average diffusion rate, particles in vertical evaporation flow will be captured by the descending surface, producing surface particle jam and forming viscous quasi-solid layer, which dramatically prevents the trapped particles from being transported to drop edge and results in uniform deposition. This simple, robust drying regime will provide a versatile strategy to control the droplet deposition morphology, and a novel direction of interface assembling for fabricating superlattices and high quality photonic crystal patterns.

Flexible Circuits and Soft Actuators by Printing Assembly of Graphene

An effective way to improve the electrical conductivity of printed graphene patterns was demonstrated by realizing the assembly of giant graphene oxide sheets during the printing process. The synergetic effect of printing-induced orientation and evaporation-induced interfacial assembly facilitated the formation of laminar-structured patterns. The resulting patterns after chemical reduction showed excellent electrical conductivity in printed graphene electronics. Because of their high conductivity, mechanical flexibility, and advantage in pattern design, printed graphene electrodes were applied in electrical-driven soft actuators, which can realize controllable deformation with low driving voltage. Such achievements will be of great significance for the development of graphene-based flexible and printed electronics.

A Rainbow Structural-Color Chip for Multisaccharide Recognition.

A critical requirement for the successful recognition of multiple analytes is the acquisition of abundant sensing information. However, for this to be achieved requires massive chemical sensors or multiplex materials, which complicates the multianalysis. Thus, there is a need to develop a strategy for the facile and efficient recognition of multiple analytes. Herein, we explore the angle-dependent structural colors of photonic crystals to provide abundant optical information, thereby generating a rainbow-color chip to realize the convenient recognition of multiple analytes. By simply using a multiangle analysis method, the monophotonic crystal matrix chip can differentially enhance fluorescence signals over broad spectral ranges, thereby resulting in abundant sensing information for highly efficient multiple analysis. Twelve saccharides with similar structures, as well as saccharides in different concentrations and mixtures, were successfully discriminated.

Patterned photonic crystals for hiding information

Coding techniques are not only a popular strategy for information recording and communication, but also an efficient strategy for information protection. Many species in nature, such as chameleons and peacocks, demonstrate brilliant colourful appearances for camouflage, courtship or communication. The unique optical property that originates from the interaction of light with the periodic nanostructures on their surfaces, known as photonic crystals (PCs), provides an attractive candidate for coding and anti-counterfeiting. Here we present a prototype design for hiding information in photonic crystals by building a coding and encryption relationship between optical stopbands and information units. The hidden messages are protected by three different defense strategies: characteristic optical stopbands, algorithm encryption and angle-dependent encryption, which could dramatically improve the security level of the hidden information. In combination with the large coding capacity, inherent optical stability and robust fabrication process, this PC coding system has great potential for secure information storage and communication, anti-counterfeiting and massively parallelized sensors.

Transparent Ag@Au–graphene patterns with conductive stability via inkjet printing

A patterned electrode film with ultrahigh conductive stability and transparency is obtained via inkjet printing based on a kind of high-stability conductive ink and a viscoelastic state substrate. The Ag@Au nanotriangle platelets and graphene oxide hybrid (Ag@Au NTPs–GO) nanomaterial ink was synthesized. Then, it is inkjet-printed on the specific viscoelastic state base to improve the accuracy of patterns, and a flexible and transparent conductive film with Ag@Au nanotriangle platelets and reduced graphene oxide hybrid (Ag@Au NTPs–rGO) patterns was obtained after reduction. The patterns show no undesirable coffee ring effects, and the inkjet-printed rGO-based lines with ∼7 μm width and a film with high transparency (∼98%)are achieved. Meanwhile, the structure models of Ag–rGO and Ag@Au–rGO are built and calculated. It is found that the addition of a thin layer of Au coated on the surface of Ag can effectively reduce the surface energy of the Ag–reduced graphene oxide material and improve the stability of the materials conductivity. These enhancements of the printed film benefit from the core@shell structured nanomaterial, the viscoelastic state substrate and the high resolution patterns. This facile strategy will be significant for highly stable integrated circuit boards and highly transparent devices.

Martensitic transformation in ZrO2-based ceramics at cryogenic temperatures

The microstructural changes associated with the tetragonal to monoclinic martensitic transformation at cryogenic temperatures in sintered CeO2-ZrO2 ceramics containing 15.5-16.5 mol% CeO2 have been studied by means of TEM observations. X-ray diffraction analysis indicates that the stress-induced martensitic phase increases with decreases in both temperature and CeO2 content. The effects of martensitic morphologies, anti-phase boundaries (APBs) and various dislocation features on mechanical properties are also discussed in the paper.

Precise Assembly of Particles for Zigzag or Linear Patterns

Precise control of particles assembly has tremendous potential for fabricating intricate structures and functional materials. However, it is still a challenge to achieve one-dimensional assembly with precisely controlled morphology. An effective strategy is reported to precisely assemble particles into well-defined patterns by liquid confinement through controlling the viscosity of the assembly system. It is found that high viscosity of the system impedes particles rearrangement and facilitates the generation of zigzag or twined zigzag assembly structures, while low viscosity of the system allows particles to rearrange into linear or zipper structures driven by lowering the surface deformation of the liquid. As a result, precise control of different assembly patterns can be achieved through tuning the viscosity of solvent and size confinement ratios. This facile approach shows generality for particles assembly of different sizes and materials.

Programmed Coassembly of One-Dimensional Binary Superstructures by Liquid Soft Confinement

Precise control of particles co-assembly has attracted great attention for fabricating intricate structures and functional materials. However, achieving precise co-assembly of one-dimensional (1D) binary superstructures remains challenging due to the constrained thermodynamic stability and lack of general strategies to control the 1D ordered arrangement of mixed particles. Here, we propose a facile strategy to achieve programmed co-assembly of 1D binary superstructures by liquid soft confinement without particle modification or external field. It reveals that binary particles undergo stepwise confinement and programmed co-assembly in the gradually shrinking and spatially tunable liquid soft confinement. Through tuning the liquid confined space and particles composition, diverse 1D binary superstructures with precisely controlled periodicity, orientation and symmetry are achieved, which shows generality for various particles of different sizes and materials. This work provides a promising route to refined patterning and manufacturing complex materials.

pH-Responsive nano sensing valve with self-monitoring state property based on hydrophobicity switching

Nano valves have been used in functional porous materials to control molecular transport by changing their properties in response to external stimuli. But most of them are limited by the blocking units and cannot show their state by themselves. Herein, pH switchable nano valves were constructed using mesoporous inverse opal photonic crystal, which realized free-blockage nano valves and achieved the monitoring of the state of the valve by the naked eye without an external indicator. The nano valves were modified by phenylamine groups, which has a convertible hydrophobic/hydrophilic property between deprotonation and protonation. The valves were hydrophobic enough to prevent solution passing through at pH 7.0, and meanwhile a green color was presented. With the decrease of the pH value of the solution, the valves became open and presented a yellow to red color because of the protonation of phenylamine groups followed by the invasion of solution. Thus, in this study not only a free-blockage valve but also nano sensing valve was constructed. We believe that our studies provide new insights into photonic crystal sensors and nano sensing valve.

Voltage-Responsive Controlled Release Film with Cargo Release Self-Monitoring Property Based on Hydrophobicity Switching

Herein, voltage-responsive controlled release film was constructed by grafting ferrocene on the mesoporous inverse opal photonic crystal (mIOPC). The film achieved free-blockage controlled release and realized the monitoring of cargo release without external indicator. Free-blockage was attributed to the voltage switchable nanovalves which undergo hydrophobic-to-hydrophilic transition when applying voltage. Monitoring of cargo release was attributed to the optical property of mIOPC, the bandgap of mIOPC had a red shift when the solution invaded in. The film was hydrophobic enough to stop solution intrusion. Once the voltage was applied, the film became hydrophilic, leading to invasion of the solution. As a result, the cargos were released and the bandgap of mIOPC was red-shifted. Therefore, in this paper both a free-blockage controlled release film and a release sensing system was prepared. The study provides new insights into highly effective controlled release and release sensing without indicator.