Energy conversion from a mechanical form to electricity is one of the most important research advancements to come from the horizontal locomotion of small objects. Until now, the Marangoni effect has been the only propulsion method to produce the horizontal locomotion to induce an electromotive force, which is limited to a short duration because of the specific property of surfactants. To solve this issue, in this article we utilized the decomposition of hydrogen peroxide to provide the propulsion for a sustainable energy conversion from a mechanical form to electricity. We fabricated a mini-generator consisting of three parts: a superhydrophobic rotator with three jaws, three motors to produce a jet of oxygen bubbles to propel the rotation of the rotator, and three magnets integrated into the upper surface of the rotator to produce the magnet flux. Once the mini-generator was placed on the solution surface, the motor catalyzed the decomposition of hydrogen peroxide. This generated a large amount of oxygen bubbles that caused the generator and integrated magnets to rotate at the air/water interface. Thus, the magnets passed under the coil area and induced a change in the magnet flux, thus generating electromotive forces. We also investigated experimental factors, that is, the concentration of hydrogen peroxide and the turns of the solenoid coil, and found that the mini-generator gave the highest output in a hydrogen peroxide solution with a concentration of 10 wt % and under a coil with 9000 turns. Through combining the stable superhydrophobicity and catalyst, we realized electricity generation for a long duration, which could last for 26 000 s after adding H2O2 only once. We believe this work provides a simple process for the development of horizontal motion and provides a new path for energy reutilization.

A “post-infiltration and subsequent photo-cross-linking layer-by-layer assembly” strategy was, for the first time, introduced to fabricate carboxylated chitosan (CCS) based antibacterial multilayer films with improved stability under alkaline conditions. Precursory polyelectrolyte multilayers were assembled from CCS and poly­(allylamine hydrochloride) (PAH). 4,4′-Diazostilbene-2,2′-disulfonic acid disodium salt was then infiltrated to cross-link the multilayers under UV irradiation. Analysis by UV–vis spectra showed that absorbance at characteristic wavelengths of the multilayers increased almost linearly with number of CCS/PAH bilayers. AFM images indicated that surfaces of the cross-linked multilayers were rather uniform and stable against basic treatments. Surface wettability of the multilayers was determined by water contact angle measurements. The multilayers exhibited reasonable antibacterial properties against Gram-negative E. coli, demonstrating that the multilayers were active in preventing bacterial growth and represented a novel type of antibacterial films with improved stability under alkaline conditions. These results open new possibilities for building functionalized architectures onto polyelectrolyte multilayer films.

A post-photochemical cross-linking strategy was successfully demonstrated to enhance the stability of polyelectrolyte poly(allylamine hydrochloride)(PAH)/poly(vinylsulfonic acid sodium salt)(PVS) multilayers. Conventional polyelectrolyte multilayers of PAH/PVS are usually fabricated through electrostatic layer-by-layer(LbL) assembly, resulting in poor stability, especially in basic solutions, which leads to the urgent demand for converting weak electrostatic interactions into covalent bonds to enhance the stability of the multilayers. This stability problem has been ultimately addressed by post-infiltrating a photosensitive cross-linking agent, 4,4′-diazostilbene-2,2′-disulfonic acid disodium salt(DAS), into the LbL assembled films to initiate the photochemical reaction to cross-link the multilayers. The obviously improved stability of the photo-cross-linked multilayers was demonstrated through experiments with basic solution treatments. Compared to the complete decomposition of uncross-linked multilayers in basic solution, over 74.4% of the covalently cross-linked multilayers were retained under the same conditions, even after a longer duration of basic solution treatment.