The grazing incidence small-angle X-ray scattering (GISAXS) from structures within a thin film on a substrate is generally a superposition of the two scatterings generated by the two X-ray beams (reflected and transmitted beams) converging on the film with a difference of twice the incidence angle (α i) of the X-ray beam in their angular directions; these two scatterings may overlap or may be distinct, depending on α i. The two scatterings are further distorted by the effects of refraction. These reflection and refraction effects mean that GISAXS is complicated to analyze. To quantitatively analyze GISAXS patterns, in this study we derived a GISAXS formula under the distorted wave Born approximation. We applied this formula to the quantitative analysis of the GISAXS patterns obtained for various compositions of polystyrene-b-polyisoprene (PS-b-PI) diblock copolymer thin films on silicon substrates with native oxide layers. This analysis showed that the diblock copolymer thin films consist of hexagonally packed cylinder (HEX) structures, hexagonally perforated layer (HPL) structures, and gyroid structures, all with characteristic preferential orientations, depending on the composition of the copolymer. This is the first report of GISAXS studies of HEX, HPL, and gyroid microdomain structures in block copolymer thin films. Moreover, our study also provides a simple method for understanding GISAXS patterns and for determining the structure factor or interference function from them. Thus, the use of the GISAXS technique with our derived GISAXS formula as a data analysis engine is a very powerful tool for determining the morphologies of polymer thin films on substrates.

Surfaces with physicochemical properties that can be modulated using external stimuli offer great promise for designing responsive or adaptive materials. Here, we describe biocompatible dynamic scaffolds based on thin hydrogel coatings that reversibly hide and display surface chemical patterns in response to temperature changes. At room temperature, the gel absorbs water, triggering an elastic creasing instability that sequesters functionalized regions within tight folds in the surface. Deswelling at approximately 37 degrees C causes the gel surface to unfold, thereby regenerating the biomolecular patterns. Crease positions are directed by topographic features on the underlying substrate, and are translated into two-dimensional micrometre-scale surface chemical patterns through selective deposition of biochemically functionalized polyelectrolytes. We demonstrate specific applications of these dynamic scaffolds--selective capture, sequestration and release of micrometre-sized beads, tunable activity of surface-immobilized enzymes and reversible encapsulation of adherent cells--which offer promise for incorporation within lab-on-a-chip devices or as dynamic substrates for cellular biology.

Thin poly(N-isopropylacrylamide) (PNIPAM) hydrogels were allowed to swell under two conditions: as freestanding layers and as substrate-attached layers. Through a combination of particle tracking and defocusing methods, the positions of beads embedded within the gels were monitored over time via fluorescence microscopy, providing a convenient method to track the kinetics of swelling for layers with thicknesses of the order 100 mm. These data are compared with the predictions of linear poroelastic theory, as specialized for polymer gels. This theory, along with a single set of material properties, accurately describes the observed swelling kinetics for both the freestanding and substrate-attached hydrogels. With the additional measurement of the substrate curvature induced by the swelling of the substrate-attached hydrogels, these experiments provide a simple route to completely characterize the material properties of the gel within the framework of linear poroelasticity, using only an optical microscope.

We introduce a nanoporous membrane suitable for virus filtration with good dimensional stability under high pressures maintaining high selectivity. The membrane consists of a double layer: The upper layer is a nanoporous film with pore size of ∼17 nm and a thickness of ∼160 nm, which was prepared by polystyrene‐block‐poly(methyl methacrylate) copolymer (PS‐b‐PMMA) where PMMA block was removed by ultraviolet irradiation followed by rinsing with acetic acid. The nanoporous block copolymer film was combined with a conventional micro‐filtration membrane to enhance mechanical strength. The membrane employed in this study did not show any damage or crack even at a pressure of 2 bar, while high selectivity was maintained for the filtration of human rhinovirus type 14 which has a diameter of ∼30 nm and is a major pathogen of the common cold in humans. Furthermore, due to crosslinked PS matrix during the UV irradiation, the nanoporous membrane showed excellent resistance to all organic solvents. This could be used under harsh filtration conditions such as high temperature and strong acidic (or basic) solution.

Integrated circuits that have improved functionality and speed in a smaller package and that consume less power are desired by the microelectronics industry as well as by end users, to increase device performance and reduce costs. The fabrication of high-performance integrated circuits requires the availability of materials with low or ultralow dielectric constant (low-k: k