Composite Slow-Release Fouling Release Coating Inspired by Synergistic Anti-Fouling Effect of Scaly Fish.

Inspired by the antifouling properties of scaly fish, the conventional silicone coating with phenylmethylsilicone oil (PSO/PDMS) composite coating was fabricated and modified with single layer polystyrene (PS) microsphere (PSO/PDMS-PS) arrays. The fish scale like micro-nano structures were fabricated on the surface of bio-inspired coating, which can reduce the contact area with the secreted protein membrane of fouling organisms effectively and prevent further adhesion between fouling organisms and bio-inspired coating. Meanwhile, PSO exuded to the coating surface has the similar function with mucus secreted by fish epidermis, which make the coating surface slithery and will be polished with the fouling organisms in turbulent waters. Compared to PSO/PDMS coating without any structure and conventional silicone coating, PSO/PDMS-PS showed better antiadhesion activity against both marine bacteria and benthic diatom (Navicula sp.). Additionally, the existence of PS microspheres can reduce the release rate of PSO greatly, which will extend the service life of coating. Compared to PSO/PDMS coating, the sustained release efficiency of PSO/PDMS-PS coating can reach 23.2%. This facile method for fabricating the bio-inspired composite slow-release antifouling coating shows a widely fabricating path for the development of synergistic anti-fouling coating.

Graded Protein/PEG Nanopattern Arrays: Well-Defined Gradient Biomaterials to Induce Basic Cellular Behaviors.

Gradient biomaterials have shown enormous potential in high-throughput screening of biomaterials and material-induced cell migration. To make the screening process more rapid and precise, improving the regularity of morphological structure and chemical modification on gradient biomaterials have attracted much attention. In this paper, we present a novel fabrication strategy to introduce ordered nanopattern arrays into gradient biomaterials, through combining surface-initiated atom transfer radical polymerization and inclined reactive-ion etching based on colloidal lithography. Graded protein/poly(ethylene glycol) (PEG) nanopattern arrays on a quartz substrate were fabricated and applied to affect the behaviors of cells. Owing to the continuously changed ratio of two different components, the corresponding cell adhesion density along the substrate showed obvious graded distribution after culturing for 24 h. Meanwhile, the cytoskeleton showed obvious polarization after culturing for 7 days, which is parallel with the direction of gradient. Additionally, oriented migration was generated when mouse MC3T3-E1 cells were cultured on the graded protein/PEG nanopattern arrays. On the basis of the ordered and well-defined nanopatterns, the correlation between the extracellular matrix and corresponding expressions generated by different stimuli can be investigated.

Graded nanowell arrays: a fine plasmonic "library" with an adjustable spectral range.

We present an effective approach for fabricating graded plasmonic arrays based on ordered micro-/nanostructures with a geometric gradient. Ag nanowell arrays with graded geometric parameters were fabricated and systematically investigated. The order of the graded plasmonic arrays is generated by colloidal lithography, while the geometric gradient is the result of inclined reactive ion etching. The surface plasmon resonance (SPR) peaks were measured at different positions, which move gradually along the Ag nanowell arrays with a geometric gradient. Such micro-/nanostructure arrays with graded and integrated SPR peaks can work as a fine plasmonic "library" (FPL), and the spectral range can be controlled using a "coarse adjustment knob" (lattice constant) and a "fine adjustment knob" (pore diameter). Additionally, the spectral resolution of the FPL is high, which benefits from the high value of the full height/full width at half-maximum and the small step size of the wavelength shift (0.5 nm). Meanwhile, the FPL could be effectively applied as a well-defined model to verify the plasmonic enhancement in surface enhanced Raman scattering. As the FPL is an integrated optical material with graded individual SPR peaks, it can not only be a theoretical model for fundamental research, but also has great potential in high-throughput screening of optical materials, multiplex sensors, etc.

Thermal-Responsive Anisotropic Wetting Microstructures for Manipulation of Fluids in Microfluidics.

We show morphology-patterned stripes modified by thermal-responsive polymer for smartly guiding flow motion of fluid in chips. With a two-step modification process, we fabricated PNIPAAm-modified Si stripes on silicon slides, which were employed as substrates for fluid manipulation in microchannels. When the system temperature switches between above and below the lower critical solution temperature (LCST) of PNIPAAm, the wettability of the substrates also switches between strong anisotropy and weak anisotropy, which resulted in anisotropic (even unidirectional) flow and isotropic flow behavior of liquid in microchannels. The thermal-responsive flow motion of fluid in the chip is influenced by the applied pressure, the thickness of PNIPAAm, and dimension of the microchannels. Moreover, we measured the feasible applied pressure scopes under different structure factors. Because of the excellent reversibility and quick switching speed, the chip could be used as a thermal-responsive microvalve. Through tuning the system temperature and adding the assistant gas, we realized successive "valve" function. We believe that the practical and simple chip could be widely utilized in medical detection, immunodetection, protein analysis, and cell cultures.

Ordered Micro/Nanostructures with Geometric Gradient: From Integrated Wettability "Library" to Anisotropic Wetting Surface.

Geometric gradients within ordered micro/nanostructures exhibit unique wetting properties. Well-defined and ordered microsphere arrays with geometric gradient (OMAGG) are successfully fabricated through combining colloidal lithography and inclined reactive ion etching (RIE). During the inclined RIE, the graded etching rates in vertical direction of etcher chamber are the key to generating a geometric gradient. The OMAGG can be used as an effective mask for the preparation of micro/nanostructure arrays with geometric gradient by selective RIE. Through this strategy, a well-defined wettability "library" with graded silicon cone arrays is fabricated, and the possibility of screening one desired "book" from the designated wettability "library" is demonstrated. Meanwhile, the silicon cone arrays with geometric gradient (SCAGG) can be applied to control the wetting behavior of water after being modified by hydrophilic or hydrophobic chemical groups. Based on this result, a temperature-responsive wetting substrate is fabricated by modifying poly n-isopropyl acrylamide (PNIPAM) on the SCAGG. These wettability gradients have great potential in tissue engineering, microfluidic devices, and integrated sensors.

Morphology-Patterned Anisotropic Wetting Surface for Fluid Control and Gas-Liquid Separation in Microfluidics.

This article shows morphology-patterned stripes as a new platform for directing flow guidance of the fluid in microfluidic devices. Anisotropic (even unidirectional) spreading behavior due to anisotropic wetting of the underlying surface is observed after integrating morphology-patterned stripes with a Y-shaped microchannel. The anisotropic wetting flow of the fluid is influenced by the applied pressure, dimensions of the patterns, including the period and depth of the structure, and size of the channels. Fluids with different surface tensions show different flowing anisotropy in our microdevice. Moreover, the morphology-patterned surfaces could be used as a microvalve, and gas-water separation in the microchannel was realized using the unidirectional flow of water. Therefore, benefiting from their good performance and simple fabrication process, morphology-patterned surfaces are good candidates to be applied in controlling the fluid behavior in microfluidics.

Controlling flow behavior of water in microfluidics with a chemically patterned anisotropic wetting surface.

We report the flow behavior of water in microfluidic systems based on a chemically patterned anisotropic wetting surface. When water flows inside a microchannel on top of a micropatterned surface with alternating hydrophilic/hydrophobic stripes, it exhibits an anisotropic flowing characteristic owing to the anisotropic wettability; thus, the patterned surface acts as a microvalve for the microfluidic system. The anisotropic flow of water is influenced by the microscale features of the patterns and the dimensions of the microchannels. Furthermore, by reasonably combining the patterned surface and microchannel together, we realize the transportation of water in a microchannel along a "virtual" wall, which is the boundary of the hydrophilic and hydrophobic area. We believe that the chemically patterned surfaces could be an alternative strategy to control the flow behavior of water in microfluidic channels.

Quantitative assay for the colonization ability of heterogeneous bacteria on controlled nanopillar structures.

The colonization ability of bacteria on biomaterial surfaces is influenced by the morphology of the bacteria and the nanotopography of the biomaterial. However, interactions between the bacterial morphology and nanotopography of biomaterials have not yet been completely elucidated. In this article, we quantitatively characterized the bacterial morphology to illuminate the integrated effects of polyethylene terephthalate (PET) nanopillar arrays on the colonization of bacteria cells with different shapes. Our results demonstrated that the interaction between interpillar spacing and the diameter of the bacterial cells impacted the number of bacterial cells that adhered to different PET substrates. The interpillar spacing of nanopillar arrays promotes bacterial adhesion in a definite range (<50 nm). However, further increasing the interpillar spacing inhibited the adhesion of bacteria to the nanopillar arrays. Moreover, the interpillar spacing also influenced the morphologies of adherent bacterial cells on the PET nanopillar arrays, which consequently facilitated bacterial adhesion to the nanopillar arrays. Our findings enhance the understanding of interactions between controlled nanotopography and bacterial colonization and provide an appropriate parameter for the design of antibacterial materials with nanotopography.

Janus Si micropillar arrays with thermal-responsive anisotropic wettability for manipulation of microfluid motions.

In this paper, Janus micropillar array (MPA) with fore-aft controllable wettability difference was demonstrated. With two-step modification process, we successfully decorate the Janus pillar skeletons with wettability-switchable polymer brush on one side and hydrophilic self-assembled monolayer on the other. Owing to the switchable wettability of the polymer brush, the patterned surface could switch between anisotropic wetting and isotropic wetting at different temperatures, which gives the possibility of coupling the well-designed surface with microfluidic channel to manipulate the microfluid motion. Additionally, a further photothermal control of microfluid was also established based on the thermal-responsive Janus MPA through introducing infrared light to adjust the temperature of the microfluidic system. We believe that the thermal-responsive Janus micropillar arrays would provide a new strategy to control the flow and motion of fluids in microfluidic channels and show potential applications in the future microfluidic chips.

Anisotropic Janus Si nanopillar arrays as a microfluidic one-way valve for gas-liquid separation.

In this paper, we demonstrate a facile strategy for the fabrication of a one-way valve for microfluidic (MF) systems. The micro-valve was fabricated by embedding arrays of Janus Si elliptical pillars (Si-EPAs) with anisotropic wettability into a MF channel fabricated in poly(dimethylsiloxane) (PDMS). Two sides of the Janus pillar are functionalized with molecules with distinct surface energies. The ability of the Janus pillar array to act as a valve was proved by investigating the flow behaviour of water in a T-shaped microchannel at different flow rates and pressures. In addition, the one-way valve was used to achieve gas-liquid separation. We believe that the Janus Si-EPAs modified by specific surface functionalization provide a new strategy to control the flow and motion of fluids in MF channels.