Inching its way forward: A DNA nanodevice is presented which can autonomously and processively move on a well‐defined track with a 7‐nm step size. The moving principle integrates DNAzyme activity and a strand‐displacement strategy, which resembles the behavior of a caterpillar eating its way through a row of plants (see picture).

We report on two types of poly(methacrylic acid) (PMAA)-based hydrogel microcontainers (capsules) of cubical shape with distinctly different shape responses upon pH variations. The microcontainers were prepared as replicas of cubical inorganic templates through chemical cross-linking of hydrogenbonded layer-by-layer (LbL) films. The two types of hollow hydrogels, a single-component (PMAA) and PMAA-poly(N-vinylpyrrolidone) (PMAA-PVPON), showed drastic differences in their shape response to pH variations. Cubical (PMAA) 20 capsules turned into bulged sphere-like structures of the same size when transitioned from pH 3 to pH 8. In contrast, cubical (PMAA-PVPON) 5 capsules retained their cubical shape at pH 3 while increasing in size at pH 8. The pH-triggered size change of cubical capsules was completely reversible. The difference in pH-triggered shape responses was rationalized through the difference in hydrogel rigidity expressed as the ratio of the polymer contour length between the neighboring cross-links to the persistence polymer length. The ratios of 22.7 and 2 for (PMAA) and (PMAA-PVPON) systems, respectively, suggested that the dual-component system is more rigid and therefore expands uniformly in all directions. We believe that the results provide new prospects for developing polymeric materials with predictable shape and size-changing properties for controlled drug delivery, cellular uptake, and pH-regulating transport behavior in microfluidic devices.

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The difficulty in dyeing microfiber synthetic leather filled with ordinary polyurethane presents a significant challenge in maintaining the uniformity and highly realistic appearance of the resulting products. In the present study, a type of acid-dyeable polyurethane (PU-MDEA; MDEA=N-methyldiethanolamine) was synthesized, and its chemical structure and dyeing properties were investigated. Nuclear magnetic resonance analysis indicated that cationic groups were successfully incorporated into the PU-MDEA backbone via chain extension using MDEA. The amorphous nature of PU-MDEA was determined by differential scanning calorimetry, X-ray diffraction, and polarizing optical microscopy. Owing to the strong binding between these cationic groups and acid dye, as well as the reduced resistance to dye penetration, PU-MDEA showed better dyeability toward the acid dyes studied herein when compared with the control sample (microfiber synthetic leather filled with ordinary polyurethane). The adsorption isotherm experiment revealed that the dyeing process conformed to the Langmuir model, thereby indicating that the acid dyes attached to PU-MDEA via strong ionic bonding rather than van der Waals forces or hydrogen bonding. Additionally, it was found that the wastewater resulting from the dyeing of the microfiber synthetic leather filled with PU-MDEA exhibited environmentally friendly characteristics when compared with that displayed by the control sample (microfiber synthetic leather filled with ordinary polyurethane). Thus, the current results show the potential of PU-MDEA, as a filler, in the manufacture of microfiber synthetic leather to achieve fast dyeing rate, high dye uptake, and good color fastness, thereby improving the uniformity and highly realistic appearance of the resulting products.

The utilization of organoantimony and organobismuth complexes in CO2fixation is reviewed in this article.