Mengjiao Cheng

A functionally integrated device for effective and facile oil spill cleanup.

In this Letter, we have fabricated a multifunctional device for highly efficient and inexpensive oil spill cleanup by combining electroless metal deposition with self-assembled monolayers, which has integrated the functions of oil containment booms, oil-sorption materials, oil skimmers, and water-oil separating devices. This functionally integrated device has a lower density than that of water, which leads to a potential application as oil containment booms; it can take up oil that is 3.5 times its own weight, which shows excellent oil-sorption properties, with the water-oil separating yield of the as-prepared device being up to 92%. The device has the advantages of high efficiency, capacity of antiwave, and reproducibility, which is suitable for many types of organic solvents or oils, even for emulsion of petroleum and water, and thus is a proof-of-principle idea to be applied in marine spilt oil cleanup and other water-oil separating systems.

Extraordinary drag-reducing effect of a superhydrophobic coating on a macroscopic model ship at high speed

We have fabricated a self-cleaning coating on a model ship with a large and curved surface by electroless deposition of gold aggregates, and the superhydrophobic model ship exhibited a remarkable drag reduction of 38.5% at a velocity of 0.46 m s−1. The as-prepared coating exhibits excellent superhydrophobic properties, with a contact angle as high as 159.7°. To rule out the influence of wetting area differences between superhydrophobic coated materials and normal materials, we modified the large curved surface of a model ship with the self-cleaning coating and investigated its drag reducing properties at high speed. The results showed that the superhydrophobic coating took effect in reducing drag; the mechanism of the drag reduction is discussed based on the plastron effect and Newtons law of viscosity.

Bell‐Shaped Superhydrophilic–Superhydrophobic–Superhydrophilic Double Transformation on a pH‐Responsive Smart Surface

Superhydrophobic to neutral water droplets, superhydrophilic to acidic or basic. This double transition of surface wettability in response to a single stimulus - pH - is demonstrated for the first time. The smart surface is composed of a rough gold surface modified with a self-assembled monolayer (SAM) containing three thiols, HS(CH2 )11 CH3 , HS(CH2 )10 COOH, and HS(CH2 )11 NH2 . A ternary diagram is generated that describes wettability as a function of the SAM composition and the pH of the surrounding solution.

Surface Adhesive Forces: A Metric Describing the Drag‐Reducing Effects of Superhydrophobic Coatings

Nanomaterials with superhydrophobic properties are promising as drag-reducing coatings. However, debates regarding whether superhydrophobic surfaces are favorable for drag reduction require further clarification. A quantified water adhesive force measurement is proposed as a metric and its effectiveness demonstrated using three typical superhydrophobic coatings on model ships with in situ sailing tests.

Macroscopic Supramolecular Assembly of Rigid Building Blocks Through a Flexible Spacing Coating

Macroscopic supramolecular assembly is a promising method for manufacturing macroscopic, ordered structures for tissue-engineering scaffolds. A flexible spacing coating is shown to overcome undesired surface and size effects and to enable assembly of macroscopic cubes with host/guest groups. The assembled pairs disassembled upon introduction of competitive guest molecules, thereby demonstrating a multivalent assembly mechanism.

pH‐Responsive On‐Off Motion of a Superhydrophobic Boat: Towards the Design of a Minirobot

Combining chemical reactions and stimuli-responsive surfaces as clutch system, a functional cooperating minirobot with on-off locomotion that is responsive to pH changes is fabricated. Its locomotion can be switched on by changing pH value of the solution from 1 to 13, turned off by adjusting the pH back to acidic, and restarted by transforming the solution to basic.

Diving–Surfacing Cycle Within a Stimulus‐responsive Smart Device Towards Developing Functionally Cooperating Systems

DOI: 10.1002/adma.201001577 Recently, functionally cooperating systems, which are defi ned as the integration of two or more smart materials or surfaces into one device which then act in an orderly manner for a complex function or a given intention, have gained increasing attention. Since nanomaterials were fi rst demonstrated by Feynmann in 1959, various functional materials have been created, particularly since the 1980s. [ 1 ] Nanomaterials not only lead to signifi cant progress in fundamental research but have also revolutionized technology and the economy. However, most of the research into nanomaterials is focused on passive fi elds. In order to promote materials science from the present passive level to active level materials, a great emphasis has been placed on the area of smart materials. Smart materials, [ 2 ] which respond to a stimulus or a change of environment to produce a dynamic and reversible transition in chemical or physical properties, have been well investigated in many fi elds, [ 3 , 4 ] including cantilever sensors, gene delivery, micropumps, and artifi cial muscles. Based on the above concept, various stimulus for smart materials have been introduced, such as humidity, [ 5 , 6 ] solvent composition, [ 7 ] light, [ 8–11 ] electric fi eld, [ 12 , 13 ] magnetic fi eld, [ 14–17 ] pH value, [ 18 , 19 ] and temperature. [ 20 , 21 ] Ichimura et al. [ 11 ] prepared a photo-responsive surface to realize a light-driven liquid motion. Langer and coworkers [ 12 ]

Layer-by-layer self-assembly under high gravity field.

In the present article, we have developed a facile and rapid method to fabricate a polyelectrolyte multilayer under high gravity field and investigated the difference of mass transfer in the diffusing process between LbL self-assembled technique under high gravity field (HG-LbL) and dipping assembly. Herein, we have employed polyethyleneimine and zinc oxide nanoparticles, which is a well-known UV blocking material with typical absorption properties in the range of 300-400 nm, as building blocks and applied hydrogen bonding as the driving force to construct the multilayer under HG-LbL and dipping assembly. The results show that, compared with dipping assembly, HG-LbL can highly improve the utilization and adsorption efficiency of building blocks by hastening the diffusing process, and meanwhile the resulting multilayer films still achieve comparable quality as those prepared from dipping assembly.

Converting Chemical Energy Into Electricity through a Functionally Cooperating Device with Diving–Surfacing Cycles

A smart device that can dive or surface in aqueous medium has been developed by combining a pH-responsive surface with acid-responsive magnesium. The diving-surfacing cycles can be used to convert chemical energy into electricity. During the diving-surfacing motion, the smart device cuts magnetic flux lines and produces a current, demonstrating that motional energy can be realized by consuming chemical energy of magnesium, thus producing electricity.

Programmable macroscopic supramolecular assembly through combined molecular recognition and magnetic field-assisted localization.

Macroscopic supramolecular assembly is a promising bottom-up method to construct ordered three-dimensional structures in a programmable way because of its flexible tailoring features. To handle the challenges of precisely aligning the building blocks, we proposed the combination of magnetic field-assisted localization for the locomotion of building blocks and host/guest supramolecular recognition for their immobilization. By applying this strategy, we have realized the stepwise construction of microscale glass fibers into an ordered complex pattern. Furthermore, through the introduction of a competitive guest molecule to disassemble the assembled structure, we demonstrated that the interaction between the fibers and the substrate was supramolecular rather than nonselective stickiness. Multivalent theory was used to interpret the mechanism for the interaction process.