Two stimuli-responsive polymer brushes, poly(dimethylaminoethyl methacrylate) and poly(methacrylic acid), were grafted from initiator-modified anodized alumina substrates to prepare two pH-responsive surfaces. By regulating the swelling states of the two polymers, water droplets can roll off or adhere onto the textured surface because of different adhesion forces. These forces also strongly affect boundary slippage. To determine the different slippage effects of fluid on our pH-responsive surfaces, a series of rheological experiments are carried out on two kinds of surfaces. A large slip length is obtained and reversibly regulated by changing the fluid pH. These responsive superhydrophobic surfaces with considerable slip length and pH-responsive properties have extensive potential applications in intelligent micro- and nanofluidic devices or biodevices, which can solve fluid flow problems.

•The article describes, with special emphasis, the design and fabrication of structural hydrogels with diversified geometric shapes and dimensions.•The typical applications of such structural hydrogels are introduced.•Some perspectives on future development of structural hydrogel systems are provided.Research on hydrogel systems with structural features has aroused great interests due to its wide range of applications, including actuators, microfluidic units, synthetic adhesives, transplantable tissue organs, and cell scaffolds. This review article describes, with special emphasis, the design and fabrication of structural hydrogels with diversified geometric shapes and dimensions. These hydrogel structures include gradient gel, anisotropic gel, gel patterns, gel wrinkle, gel arrays and gel tubes. Several typical applications of such structural hydrogels are introduced, such as for controlling cell behavior, developing responsive actuators, and designing nature inspired bio-lubrication surface. Some perspectives on future development of structural hydrogel systems are provided.Structural hydrogels by different methods with diversified geometric shapes and dimensions, have been of wide interest over few decades due to great potential applications in tissue engineering, drug release, actuation and sensation.Figure optionsDownload full-size imageDownload as PowerPoint slide

•A surface with robust omniphobicity was prepared.•A variety of liquids with different surface tensions exhibited large slip length.•The viscosity of liquids has a significant effect on boundary slip.Water slips exist over superhydrophobic solid surfaces, but the slip flow of diverse liquids on a single surface has not been deliberately studied to date. Here, we report the slip flow behavior of a variety of liquids with different surface tensions and viscosities on a robust omniphobic surface. This surface displayed a dramatic slippage effect and thus a high drag reduction efficiency of approximately 10–20% for all liquids, depending on both liquid viscosity and surface energy. The observed liquid slip was attributed to the surface dual micro/nanostructure and the low-surface-energy coating.Graphical abstract

Two stimuli-responsive polymer brushes, poly(dimethylaminoethyl methacrylate) and poly(methacrylic acid), were grafted from initiator-modified anodized alumina substrates to prepare two pH-responsive surfaces. By regulating the swelling states of the two polymers, water droplets can roll off or adhere onto the textured surface because of different adhesion forces. These forces also strongly affect boundary slippage. To determine the different slippage effects of fluid on our pH-responsive surfaces, a series of rheological experiments are carried out on two kinds of surfaces. A large slip length is obtained and reversibly regulated by changing the fluid pH. These responsive superhydrophobic surfaces with considerable slip length and pH-responsive properties have extensive potential applications in intelligent micro- and nanofluidic devices or biodevices, which can solve fluid flow problems.

Natural fur with a high density of soft hair fibers was selected as a model hairy surface to study the interaction of microalgae/zoospores with this biomimetic surface covered with “hairs”. The synergistic antifouling (AF)/fouling-release (FR) effect of the hair fibers and the surface chemical composition after grafting polymer brushes onto the hair fibers using surface-initiated atom transfer radical polymerization (SI-ATRP) was also explored. A series of laboratory static and dynamic settlement assays with microalgae and zoospores were carried out to systematically investigate the relationship between the modified poly-sulfopropyl methacrylate (PSPMA) brushes, the density/shape/length of the hair fibers and the AF/FR properties. The results indicate that the polymer brush-modified hairy surface can be effective against the settlement of microalgae/zoospores in different bioassays, especially in dynamic settlement assays. In general, hairy surfaces of higher hair fiber density, and with longer fibers, tend to display lower settlement of microalgae/zoospores, and the surface modification of the hair fibers with PSPMA brushes can strongly improve their AF/FR properties.

Sylgard-184 silicone elastomer negative replica and resorcinol–formaldehyde (RF) positive replica were made by biomimicking the patterns of natural Trifolium and three other kinds of leaves using the micromolding lithography. An effective antifouling (AF) polymer, poly(3-sulfopropyl methacrylate) (PSPMA), was then grafted on these replica surfaces via the surface-initiated atom transfer radical polymerization (SI-ATRP). The AF property of the modified biomimetic surfaces was tested via the settlement assay with two microalgae in different sizes, and their fouling-release (FR) property was evaluated by the removal assay. The results indicate that the structure of microspines on Trifolium leaf can inhibit settlement of microalgae and facilitate the cell release. The AF property was improved by modification with PSPMA brushes.Keywords: antifouling; biomimetic; fouling-release; microalgae settlement; microstructure; polymer brush;

Natural fur with a high density of soft hair fibers was selected as a model hairy surface to study the interaction of microalgae/zoospores with this biomimetic surface covered with “hairs”. The synergistic antifouling (AF)/fouling-release (FR) effect of the hair fibers and the surface chemical composition after grafting polymer brushes onto the hair fibers using surface-initiated atom transfer radical polymerization (SI-ATRP) was also explored. A series of laboratory static and dynamic settlement assays with microalgae and zoospores were carried out to systematically investigate the relationship between the modified poly-sulfopropyl methacrylate (PSPMA) brushes, the density/shape/length of the hair fibers and the AF/FR properties. The results indicate that the polymer brush-modified hairy surface can be effective against the settlement of microalgae/zoospores in different bioassays, especially in dynamic settlement assays. In general, hairy surfaces of higher hair fiber density, and with longer fibers, tend to display lower settlement of microalgae/zoospores, and the surface modification of the hair fibers with PSPMA brushes can strongly improve their AF/FR properties.