Mingjie Liu

Designing Bioinspired Anti-Biofouling Surfaces based on a Superwettability Strategy.

Anti-biofouling surfaces are of high importance owing to their crucial roles in biosensors, biomedical devices, food processing, the marine industry, etc. However, traditional anti-biofouling surfaces based on either the release of biocidal compounds or surface chemical/physical design cannot satisfy the practical demands when meeting real-world complex conditions. The outstanding performances of natural anti-biofouling surfaces motivate the development of new bioinspired anti-biofouling surfaces. Herein, a novel strategy is proposed for rationally designing bioinspired anti-biofouling surfaces based on superwettability. By utilizing the trapped air cushions or liquid layers, Lotus leaf inspired superhydrophobic surfaces, fish scales inspired underwater superoleophobic surfaces, and Nepenthes pitcher plants inspired omniphobic slippery surfaces have been successfully designed as anti-biofouling surfaces to effectively resist proteins, bacteria, cells, and marine organisms. It is believed that these novel superwettability-based anti-biofouling surfaces will bring a new era to both biomedical technology and the marine industry, and will greatly benefit human health and daily life in the near future.

Self-Replenishable Anti-Waxing Organogel Materials.

Abstract Solid deposition, such as the formation of ice on outdoor facilities, the deposition of scale in water reservoirs, the sedimentation of fat, oil, and grease (FOG) in sewer systems, and the precipitation of wax in petroleum pipelines, cause a serious waste of resources and irreversible environmental pollution. Inspired by fish and pitcher plants, we present a self‐replenishable organogel material which shows ultra‐low adhesion to solidified paraffin wax and crude oil by absorption of low‐molar‐mass oil from its crude‐oil environment. Adhesion of wax on the organogel surface was over 500 times lower than adhesion to conventional material surfaces and the wax was found to slide off under the force of gravity. This design concept of a gel with decreased adhesion to wax and oil can be extended to deal with other solid deposition problems.

Adaptive and freeze-tolerant heteronetwork organohydrogels with enhanced mechanical stability over a wide temperature range

Many biological organisms with exceptional freezing tolerance can resist the damages to cells from extra-/intracellular ice crystals and thus maintain their mechanical stability at subzero temperatures. Inspired by the freezing tolerance mechanisms found in nature, here we report a strategy of combining hydrophilic/oleophilic heteronetworks to produce self-adaptive, freeze-tolerant and mechanically stable organohydrogels. The organohydrogels can simultaneously use water and oil as a dispersion medium, and quickly switch between hydrogel- and organogel-like behaviours in response to the nature of the surrounding phase. Accordingly, their surfaces display unusual adaptive dual superlyophobic in oil/water system (that is, they are superhydrophobic under oil and superoleophobic under water). Moreover, the organogel component can inhibit the ice crystallization of the hydrogel component, thus enhancing the mechanical stability of organohydrogel over a wide temperature range (−78 to 80 °C). The organohydrogels may have promising applications in complex and harsh environments.

Anti‐freezing, Conductive Self‐healing Organohydrogels with Stable Strain‐Sensitivity at Subzero Temperatures

Conductive hydrogels are a class of stretchable conductive materials that are important for various applications. However, water-based conductive hydrogels inevitably lose elasticity and conductivity at subzero temperatures, which severely limits their applications at low temperatures. Herein we report anti-freezing conductive organohydrogels by using an H2 O/ethylene glycol binary solvent as dispersion medium. Owing to the freezing tolerance of the binary solvent, our organohydrogels exhibit stable flexibility and strain-sensitivity in the temperature range from -55.0 to 44.6 °C. Meanwhile, the solvent molecules could form hydrogen bonds with polyvinyl alcohol (PVA) chains and induce the crystallization of PVA, greatly improving the mechanical strength of the organohydrogels. Furthermore, the non-covalent crosslinks endow the conductive organohydrogels with intriguing remoldability and self-healing capability, which are important for practical applications.

Interfacial Engineering of Hierarchically Porous NiTi/Hydrogels Nanocomposites with Exceptional Antibiofouling Surfaces

Seamlessly bridging the hard and the soft, a strategy to fabricate hierarchically porous NiTi/hydrogels nanocomposites is reported. The nanocomposite surface can hold high-content water while keeping its hierarchical nanoscale topography, thus showing exceptional antibiofouling performance. This strategy will lead to antibiofouling alloy (e.g., NiTi)/hydrogel nanocomposites for improved stents and other blood-contacting implants and medical devices.

Highly Stretchable, Shape Memory Organohydrogels Using Phase‐Transition Microinclusions

Shape memory effect in polymer materials has attracted considerable attention due to its promising applications in a variety of fields. However, shape memory polymers prepared by conventional strategy suffer from a common problem, in which high strain capacity and excellent shape memory behavior cannot be simultaneously achieved. This study reports a general and synergistic strategy to fabricate high-strain and tough shape memory organohydrogels that feature binary cooperative phase. The phase- transition micro-organogels and elastic hydrogel framework act synergistically to provide excellent thermomechanical performance and shape memory effect. During shape memory process, the organohydrogels exhibit high strain capacity, featuring fully recoverable stretching deformation by up to 2600% and compression by up to 85% beneath a load ≈20 times the organohydrogels weight. Furthermore, owing to the micro-organogel and hydrogel heterostructures, the interfacial tension derived from heterophases dominates the shape recovery of the organohydrogel material. Simple processing and smart surface patterning of the shape memory behavior and multiple shape memory effects can also be realized. Meanwhile, these organohydrogels are also nonswellable in water and oil, which is important for multimedia applications.

Superhydrophobic Diffusion Barriers for Hydrogels via Confined Interfacial Modification

A ubiquitous strategy to superhydrophobize the surfaces of synthetic hydrogels is reported, creating heterogeneous wettability across the surface and the inner network. Such wetting disparity shows significant influence on preventing immediate diffusion of substances between the hydrogel and the aqueous environment on different scales.

Design and fabrication of functional hydrogels through interfacial engineering

Hydrogels have drawn considerable attention in the past two decades due to their excellent biocompatibility and multi-stimuli responsiveness. They have a wide range of applications in the fields related to tissue engineering, sensors and biomedicine. Their applications are strongly influenced by the surface properties of hydrogels and the interfacial interactions between hydrogels and other substrates. In particular, the surface wettability and adhesion of hydrogels decide their applications as drug carriers and wound dressing materials. Nevertheless, there is a lack of systematic discussion on the surface functionalization strategies of hydrogels. Therefore, this review aims at summarizing the strategies of functionalizing the surfaces of hydrogels and bonding hydrogels with other solid substrates. It also explores the challenges and future perspectives of interfacial engineering of hydrogels.

Superspreading on Immersed Gel Surfaces for the Confined Synthesis of Thin Polymer Films.

Liquid spreading is of significant interest in science and technology. Although surface topography engineering and liquid surface-tension regulating can facilitate spreading, the spreading layers in these strategies are inevitably inhomogeneous or contaminated with surfactants. Herein, we show a general strategy to realize the superspreading of liquids on mutually soluble gel surfaces. The cooperation of the hydraulic pressure under liquid phase and liquid-like property of gel surfaces can dramatically eliminate the local pinning effect and enhance the advancement of three-phase contact line, thus forming stable and homogeneous superspreading liquid layers. Such liquid layers can be converted into various functional thin polymer films with controlled thicknesses (nm- to µm-scale) through one-step polymerization of the reactants. Our strategy offers opportunities for large-scale synthesis of versatile functional thin films for various applications.

Biphasic Synergistic Gel Materials with Switchable Mechanics and Self-Healing Capacity

A fabrication strategy for biphasic gels is reported, which incorporates high-internal-phase emulsions. Closely packed micro-inclusions within the elastic hydrogel matrix greatly improve the mechanical properties of the materials. The materials exhibit excellent switchable mechanics and shape-memory performance because of the switchable micro- inclusions that are incorporated into the hydrogel matrix. The produced materials demonstrated a self-healing capacity that originates from the noncovalent effect of the biphasic heteronetwork. The aforementioned characteristics suggest that the biphasic gels may serve as ideal composite gel materials with validity in a variety of applications, such as soft actuators, flexible devices, and biological materials.