Fu-Qiang Nie

Directional water collection on wetted spider silk.

Many biological surfaces in both the plant and animal kingdom possess unusual structural features at the micro- and nanometre-scale that control their interaction with water and hence wettability. An intriguing example is provided by desert beetles, which use micrometre-sized patterns of hydrophobic and hydrophilic regions on their backs to capture water from humid air. As anyone who has admired spider webs adorned with dew drops will appreciate, spider silk is also capable of efficiently collecting water from air. Here we show that the water-collecting ability of the capture silk of the cribellate spider Uloborus walckenaerius is the result of a unique fibre structure that forms after wetting, with the ‘wet-rebuilt’ fibres characterized by periodic spindle-knots made of random nanofibrils and separated by joints made of aligned nanofibrils. These structural features result in a surface energy gradient between the spindle-knots and the joints and also in a difference in Laplace pressure, with both factors acting together to achieve continuous condensation and directional collection of water drops around spindle-knots. Submillimetre-sized liquid drops have been driven by surface energy gradients or a difference in Laplace pressure, but until now neither force on its own has been used to overcome the larger hysteresis effects that make the movement of micrometre-sized drops more difficult. By tapping into both driving forces, spider silk achieves this task. Inspired by this finding, we designed artificial fibres that mimic the structural features of silk and exhibit its directional water-collecting ability.

A Biomimetic Potassium Responsive Nanochannel: G-Quadruplex DNA Conformational Switching in a Synthetic Nanopore

Potassium is especially crucial in modulating the activity of muscles and nerves whose cells have specialized ion channels for transporting potassium. Normal body function extremely depends on the regulation of potassium concentrations inside the ion channels within a certain range. For life science, undoubtedly, it is significant and challenging to study and imitate these processes happening in living organisms with a convenient artificial system. Here we report a novel biomimetic nanochannel system which has an ion concentration effect that provides a nonlinear response to potassium ion at the concentration ranging from 0 to 1500 microM. This new phenomenon is caused by the G-quadruplex DNA conformational change with a positive correlation with ion concentration. In this work, G-quadruplex DNA was immobilized onto a synthetic nanopore, which undergoes a potassium-responsive conformational change and then induces the change in the effective pore size. The responsive ability of this system can be regulated by the stability of G-quadruplex structure through adjusting potassium concentration. The situation of the grafting G-quadruplex DNA on a single nanopore can closely imitate the in vivo condition because the G-rich telomere overhang is attached to the chromosome. Therefore, this artificial system could promote a potential to conveniently study biomolecule conformational change in confined space by the current measurement, which is significantly different from the nanopore sequencing. Moreover, such a system may also potentially spark further experimental and theoretical efforts to simulate the process of ion transport in living organisms and can be further generalized to other more complicated functional molecules for the exploitation of novel bioinspired intelligent nanopore machines.

Bioinspired Smart Gating of Nanochannels Toward Photoelectric-Conversion Systems

Learning from nature has inspired the creation of intelligent materials to better understand and imitate biology. Recent studies on bioinspired responsive surfaces that can switch between different states are shown, which open up new avenues for the development of smart materials in two dimensions. Based on this strategy, biomimetic nanochannel systems have been produced by introducing responsive molecules, which closely mimic the gating mechanism of biological nanochannels and show potential applications in many fields such as photoelectric-conversion systems demonstrated in this paper.

In situ electrochemical switching of wetting state of oil droplet on conducting polymer films.

Switching of wettability is achieved in situ, which is a challenge of materials science. Generally, changing liquid droplet is required to ex situ study the wettability response before and after the surface given a treatment, in the sense that the liquid impregnation in the surface structures is irreversible. Herein, an in situ wettability switch is achieved by utilizing the same liquid droplet to characterize the dynamic wettability when the conducting polymer is being stimulated. The oil droplet is facilitated to escape from the nanoscale traps through electrochemically tuning surface composition and surface micro/nanostructures, permitting a reversible and rapid transition between partly wetting and superantiwetting state. This in situ switch is promising for integration into a microfluidic system for the control of the liquid droplets motion.

Scab-Inspired Cytophilic Membrane of Anisotropic Nanofibers for Rapid Wound Healing

This work investigates the influence of cytophilic and anisotropic nanomaterials on accelerated cell attachment and directional migration toward rapid wound healing. Inspired by the anisotropic protein nanofibers in scab, a polyurethane (PU) nanofibrous membrane with an aligned structure was fabricated. The membrane showed good affinity for wound-healing-related cells and could guide cell migration in the direction of PU nanofibers. Also, the morphology and distribution of F-actin and paxillin of attached cells were influenced by the underlying nanofibers. The randomly distributed PU nanofibers and planar PU membrane did not show a distinct impact on cell migration. This scab-inspired cytophilic membrane is promising in applications as functional interfacial biomaterials for rapid wound healing, bone repair, and construction of neural networks.

Precise control of wettability from LCST tunable surface

In this study, we demonstrated precise control of wettability from a thermally-responsive surface and investigated the effects of chemical composition and surface roughness. By altering feeding manners of initiators during surface grafting process of poly(N-isopropylacrylamide-co-N-isopropylmethylacrylamide) [poly(NIPAAm-co-NIPMAM)], two thermally-responsive wettability transitions were achieved and could be precisely controlled. Only using initiators grafted on surface for grafting copolymerization, surface wettability exhibited a gradual even linear transition between hydrophilic and hydrophobic within 25–45 °C, whereas for initiators both grafted on surface and dissolved in solution, surface wettability sharply switched within 2 °C and their lower critical solution temperature (LCST) can be tuned with every step of about 3 °C in the range 32–45 °C by adjusting the ratios of comonomers. The underlying mechanism was proposed to clarify the relations between different thermally-responsive behaviors of surface wettability and surface chemical composition induced by different feeding manners of initiators. Furthermore, the introduction of surface roughness could not only enlarge the changing range of water contact angle (CA) by 60–100°, but also affect the thermally-responsive behaviors of surface wettability from the gradual changing to sharp switching in partial region of temperature.

Air Bubble Bursting Effect of Lotus Leaf

Superhydrophobic surfaces, especially lotus leaf surface, have been largely explored due to their great importance in fundamental research and abundant potential applications. However, many efforts have been focused on investigating the superhydrophobic surfaces in air instead of in water environment, which are rather crucial to industrial separation progress. A novel air bubble bursting effect on lotus leaf surface was firstly discovered and the underlying mechanism was believed to be related to the micro/nano-hierarchical rough structures. Inspired by air bubble bursting effect on lotus leaf, a superhydrophobic “artificial lotus leaf” with similar micro/nano-hierarchical rough structures was successfully constructed by photolithography and wet etching and also achieved air bubble bursting effect. Smooth and rough silicon surface with the ordered nano-structure or patterned micro-structure were utilized to study the contribution of the micro/nano-hierarchical structures to air bubble bursting, and it was found that air bubble could burst on the superhydrophobic surfaces with micro-structure, but more time was required, while nano-structure could accelerate air bubble bursting. Moreover, the height, width, and spacing of hierarchical structures also affected air bubble bursting, and the effect of the height was more obvious. When the height of hierarchical structures was around the height of lotus papillae, the width and spacing were significant for air bubble bursting. Eventually, an original model was proposed to further evaluate the reason that the micro/nano-hierarchical rough structures had an excellent air bubble bursting effect, and its validity was theoretically demonstrated. It was believed that these findings should spark further theoretical study of some bubble-related interfacial phenomena and find its wide applications in the industrial separation process without any accessional energy and other additives, such as mineral flotation, food processing, textile dyeing, and fermentation.Copyright