Concave microstructures such as microwells and microgrooves are widely utilized in fields such as biochips, microfluidics, and functional devices. Previously, concave microstructure fabrication was mostly based on laser etching or lithography which is either costly or of multisteps. The inkjet etching method is a direct structuring technique, but limited by its inherent transverse ink diffusion that leads to low feature resolution. Nanoimprint lithography can reach submicro and even nano ranges, whereas an elaborate template is needed. Thus, it is still a challenge to realize controllable fabrication of concave microstructures in large areas with high efficiency and resolution. Here, a template-free strategy to fabricate concave microstructures with high resolution by inkjet imprinting is provided. In this method, a sacrificial ink is inkjet-printed onto a precured viscoelastic surface and imprints its shapes to construct concave microstructures. The morphology of the microstructures could be adjusted by controlling the interaction between the two immiscible phases. The microwells/microgrooves could be used to pattern single cells and functional materials such as optical, electronic, and magnetic nanoparticles. These results will open a new pathway to fabricate concave microstructures and broaden their applications in various functional devices.

The preparation of fine 3D microstructures is an attractive issue; however, it is limited at large-area fabrication process and fineness morphology manipulation. Here, we propose a strategy to fabricate controllable 3D structures and morphologies from one single droplet via ink-jet printing. Based on the surface energy difference between the hydrophilic patterns and hydrophobic surface, the three phase contact line of a droplet contained nanoparticles is forced to pin on the patterned hydrophilic points and asymmetrically dewets on the hydrophobic surface, which leads to various morphologies. Through the regulation of pinning patterns and solution properties, the 3D morphology can be well manipulated. This strategy to control the 3D morphology of nanoparticle assembly based on hydrophilic patterns would be of great importance for fabricating controllable 3D structures.

Inkjet printing has attracted wide attention due to the important applications in fabricating biological, optical, and electrical devices. During the inkjet printing process, the solutes prefer to deposit along the droplet periphery and form an inhomogeneous morphology, known as the coffee-ring effect. Besides, the feature size of printed dots or lines of conventional inkjet printing is usually limited to tens or even hundreds of micrometers. The above two issues greatly restrict the extensive application of printed patterns in high-performance devices. This paper reviews the recent advances in precisely controlling the printing droplets for high-resolution patterns and three-dimensional structures, with a focus on the development to suppress the coffee-ring effect and minimize the feature size of printed dots or lines. A perspective on the remaining challenges of the research is also proposed.

Ultratrace detection attracts great interest because it is still a challenge to the early diagnosis and drug testing. Enriching the targets from highly diluted solutions to the sensitive area is a promising method. Inspired by the fog-collecting structure on Stenocara beetle’s back, a photonic-crystal (PC) microchip with hydrophilic–hydrophobic micropattern was fabricated by inkjet printing. This device was used to realize high-sensitive ultratrace detection of fluorescence analytes and fluorophore-based assays. Coupled with the fluorescence enhancement effect of a PC, detection down to 10⁻¹⁶ mol L⁻¹ was achieved. This design can be combined with biophotonic devices for the detection of drugs, diseases, and pollutions of the ecosystem.

A reversible color change of a polyaniline-infiltrated TiO₂ inverse opal photonic crystal (PC) film can be obtained when the PC is switched from an acidic to alkali vapor environment. In a saturated NH₃ environment, the stopband of the as-prepared PCs changes from 556 to 688 nm; such large shift of 132 nm could be observed, corresponding to a clear color change from green to red. After placing in HCl vapor, the stopband undergoes a blue-shift and the color turns back to green. The result is ascribed to PANI being doped or dedoped by acid or base and the effective refractive index of the PC film varying accordingly. The naked-eye detection of NH₃ and HCl vapors can be realized by the reversible color change of the PC film, which is of importance for chemical and biological sensors.

In this review we focus on recent developments in applications of bio-inspired special wettable surfaces. We highlight surface materials that in recent years have shown to be the most promising in their respective fields for use in future applications. The selected topics are divided into three groups, applications of superhydrophobic surfaces, surfaces of patterned wettability and integrated multifunctional surfaces and devices. We will present how the bio-inspired wettability has been integrated into traditional materials or devices to improve their performances and to extend their practical applications by developing new functionalities.

A controllable underwater oil-adhesion-interface is presented based on colloidal crystals assembled from nonspherical latex particles. The underwater oil-adhesive force of the as-prepared film can be effectively controlled from high to low adhesion by varying the latex structures from spherical or cauliflower-like to single cavity, which effectively adjusts the solid/liquid contact mode/wetting state of oil droplets on the films. This facile fabrication of functional films with special underwater oil-adhesion properties based on a flexible design of a latex structure will offer significant insight for the design and creation of novel underwater antifouling materials.

Organic molecules with donor–acceptor (D–A) structure are an important type of material for nanoelectronics and molecular electronics. The influence of the electron donor and acceptor units on the electrical function of materials is a worthy topic for the development of high-performance data storage. In this work, the effect of different D–A structures (namely D–Π–A–Π–D and A–Π–D–Π–A) on the electronic switching properties of triphenylamine-based molecules is investigated. Devices based on D–Π–A–Π–D molecules exhibit excellent write–read–erase characteristics with a high ON/OFF ratio of up to 10⁶, while that based on A–Π–D–Π–A molecules exhibit irreversible switching behavior with an ON/OFF ratio of about (3.2 × 10¹)–(1 × 10³). Moreover, long retention time of the high conductance state and low threshold voltage are observed for the D–A switching materials. Accordingly, stable and reliable nanoscale data storage is achieved on the thin films of the D–A molecules by scanning tunneling microscopy. The influence of the arrangement of the D and A within the molecular backbone disclosed in this study will be of significance for improving the electronic switching properties (ON/OFF current ratio and reversibility) of new molecular systems, so as to achieve more efficient data storage through appropriate design strategies.

Superhydrophobic surfaces inspired by biological microstructures attract considerable attention from researchers because of their potential applications. In this contribution, two kinds of microscale flower-shaped morphologies with nanometer petals formed from the hierarchical self-assembly of benzothiophene derivatives bearing long alkyl chains have been developed as superhydrophobic surfaces. The intermediate stages of the assemblies demonstrated a new formation mechanism for such flower-shaped morphologies. The hierarchical morphologies of the film exhibited excellent water-repelling characteristics as superhydrophobic surfaces, which were prepared by means of a simple solution process. The transition process from the Cassie state to Wenzel state was easily realized owing to the slight microstructural differences in the two kinds of flowers caused by their different chemical structures. The superhydrophobicity of such functional materials might be beneficial for applications in electrical devices in which the presence of water would influence their performance.

Here, the fabrication of quasi-solid-state TiO₂/dye/poly(3-hexylthiophene) (P3HT) solar cells is reported, in which the dyes with oleophilic thienyl groups were employed and ionic liquid (IL), 1-ethyl-3-methylimidazolium (EMIm) containing lithium bis(trifluromethanesulfone)amide (Li-TFSI) and 4-tert-butylpyridine (t-BP) are assembled with dyed TiO₂ surfaces. One of the devices gave a high conversion efficiency of up to 2.70% under 1 sun illumination. The excellent performance is ascribed to successful molecular self-organization at interface of the dye molecules and P3HT, and to the efficient charge separation and diffusion acquired by introduction of the IL coupled with Li-TFSI and t-BP.

Microcapsule/nanocapsule and encapsulation techniques have great potential for devices of functional materials. Also, electrospinning has attracted great attention for the fabrication of microstructures and nanostructures. The fluidity after melting limits the application of phase-transformation thermochromic materials. In this study, with the melt coaxial electrospinning technique, a phase-transformation thermochromic material was encapsulated in poly(methyl methacrylate) nanofibers. A device of this phase-transformation thermochromic material was realized. With a poly(methyl methacrylate) shell with good optical transmission and a thermoresponsive core made of crystal violet lactone, bisphenol A, and 1-tetradecanol core, the fibers had good thermal energy management, fluorescent thermochromism, and reversibility. The fabrication of thermochromic core–shell nanofibers has further potential in the preparation of temperature sensors with good fluorescence signals and body-temperature calefactive materials with intelligent thermal energy absorption, retention, and release. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

An inverse opal with both superoleophilic (oil contact angle (CA), 5.1° ± 1.2°) and superhydrophobic (water CA, 153.8° ± 1.2°) properties is fabricated using a phenolic resin (PR) as precursor and poly(styrene-methyl methacrylate-acrylic acid) (poly(St-MMA-AA)) colloidal crystals as templates. The stopband of the inverse opal can shift reversibly upon sorption of oils, whereby the peak position is a linear function of the refractive index of the adsorbed oil, e.g., a variation in refractive index of 0.02 will result in a stopband shift of 26 nm. Therefore, the inverse opals show a high sensitivity and selectivity for different petroleum oils. Moreover, as-prepared PR inverse opals show excellent oil-sensing stability in cyclic sorption experiments, which suggests a promising and economical alternative to traditional oil-sensing materials, and will provide a new approach to in situ petroleum monitoring and detection.

BACKGROUND: UV radiation is a potent and ubiquitous carcinogen, which is responsible for most of the skin cancer in the human population. General UV protection materials may produce dangerous degradation products under UV irradiation; therefore, safe, nontoxic and simple UV protection approaches are urgent requirements.

RESULTS: A series of photonic crystals with stopband covering the range 200–400 nm have been fabricated which can shield radiation from the whole UV range. Both UV-visible and ¹H NMR results confirm the effective protection from UV light of 254 nm.

CONCLUSIONS: A facile method for UV protection has been demonstrated by utilizing the unusual optical properties of photonic crystals that can inhibit light propagation at a given frequency without specific requirement of chemical composition. This approach opens a new way to protect from UV damage using safe materials, which is of great significance for extending the practical applications of photonic crystals. Copyright © 2007 Society of Chemical Industry