Anti‐Icing Superhydrophobic Surfaces Based on Core‐Shell Fossil Particles

A novel approach for the design of functional coatings using fossil diatomaceous earth particles decorated by a thin layer of grafted polymer chains is reported. The polymer‐modified diatomaceous earth particles are able to form liquid marbles, superhydrophobic surfaces, and are highly promising for the design of anti‐icing coatings.     

Stimuli‐Responsive Polymeric Systems for Biomedical Applications

Smart polymeric‐based devices and surfaces that reversibly alter their physico‐chemical characteristics in response to their environment are the center of many studies related to the development of materials and concepts in a broad‐range of biomedical fields. Although the initial interests were more focused in systems for the delivery of therapeutic molecules, other applications have been raised in topics ranging from actuators to biomaterials for tissue engineering and regenerative medicine. The general aspects of the different types of stimuli that can be used to modulate the response are reviewed mainly for the case of hydrogels and surfaces, based on natural‐origin or biodegradable macromolecules. Thermosensitive or light responsive surfaces that can modulate cell adhesion or protein adsorption are addressed as well as less conventional smart surfaces, such as substrates onto which biomineralization may be triggered. Injectable liquids that turn to gels by the action of heating (sol‐gel thermo‐reversible hydrogels) or by changing pH or the ionic milieu (bioinspired self‐assembling systems) may find great applicability as temporary scaffolds in non invasive procedures to deliver drugs or cells to particular places in the body. Examples of systems that recognize independently or simultaneously more than one stimulus will also be presented. Besides the typical response to temperature and pH, recent developments on materials that react to biochemical stimuli, including specific enzymes, antibodies or cells, are also highlighted.     

Bioinspired Surfaces with Superwettability for Anti‐Icing and Ice‐Phobic Application: Concept,Mechanism, and Design

Ice accumulation poses a series of severe issues in daily life. Inspired by the nature, superwettability surfaces have attracted great interests from fundamental research to anti‐icing and ice‐phobic applications. Here, recently published literature about the mechanism of ice prevention is reviewed, with a focus on the anti‐icing and ice‐phobic mechanisms, encompassing the behavior of condensate microdrops on the surface, wetting, ice nucleation, and freezing. Then, a detailed account of the innovative fabrication and fundamental research of anti‐icing materials with special wettability is summarized with a focus on recent progresses including low‐surface energy coatings and liquid‐infused layered coatings. Finally, special attention is paid to a discussion about advantages and disadvantages of the technologies, as well as factors that affect the anti‐icing and ice‐phobic efficiency. Outlooks and the challenges for future development of the anti‐icing and ice‐phobic technology are presented and discussed.     

Self‐Folded Gripper‐Like Architectures from Stimuli‐Responsive Bilayers

Self‐folding microgrippers are an emerging class of smart structures that have widespread applications in medicine and micro/nanomanipulation. To achieve their functionalities, these architectures rely on spatially patterned hinges to transform into 3D configurations in response to an external stimulus. Incorporating hinges into the devices requires the processing of multiple layers which eventually increases the fabrication costs and actuation complexities. The goal of this work is to demonstrate that it is possible to achieve gripper‐like configurations in an on‐demand manner from simple planar bilayers that do not require hinges for their actuation. Finite element modeling of bilayers is performed to understand the mechanics behind their stimuli‐responsive shape transformation behavior. The model predictions are then experimentally validated and axisymmetric gripper‐like shapes are realized using millimeter‐scale poly(dimethylsiloxane) bilayers that undergo differential swelling in organic solvents. Owing to the nature of the computational scheme which is independent of length scales and material properties, the guidelines reported here would be applicable to a diverse array of gripping systems and functional devices. Thus, this work not only demonstrates a simple route to fabricate functional microgrippers but also contributes to self‐assembly in general.     

Nano/Micro‐Manufacturing of Bioinspired Materials: a Review of Methods to Mimic Natural Structures

Through billions of years of evolution and natural selection, biological systems have developed strategies to achieve advantageous unification between structure and bulk properties. The discovery of these fascinating properties and phenomena has triggered increasing interest in identifying characteristics of biological materials, through modern characterization and modeling techniques. In an effort to produce better engineered materials, scientists and engineers have developed new methods and approaches to construct artificial advanced materials that resemble natural architecture and function. A brief review of typical naturally occurring materials is presented here, with a focus on chemical composition, nano‐structure, and architecture. The critical mechanisms underlying their properties are summarized, with a particular emphasis on the role of material architecture. A review of recent progress on the nano/micro‐manufacturing of bio‐inspired hybrid materials is then presented in detail. In this case, the focus is on nacre and bone‐inspired structural materials, petals and gecko foot‐inspired adhesive films, lotus and mosquito eye inspired superhydrophobic materials, brittlestar and Morpho butterfly‐inspired photonic structured coatings. Finally, some applications, current challenges and future directions with regard to manufacturing bio‐inspired hybrid materials are provided.     

Near‐Infrared Light Responsive Multi‐Compartmental Hydrogel Particles Synthesized Through Droplets Assembly Induced by Superhydrophobic Surface

Light‐responsive hydrogel particles with multi‐compartmental structure are useful for applications in microreactors, drug delivery and tissue engineering because of their remotely‐triggerable releasing ability and combinational functionalities. The current methods of synthesizing multi‐compartmental hydrogel particles typically involve multi‐step interrupted gelation of polysaccharides or complicated microfluidic procedures with limited throughput. In this study, a two‐step sequential gelation process is developed to produce agarose/alginate double network multi‐compartmental hydrogel particles using droplets assemblies induced by superhydrophobic surface as templates. The agarose/alginate double network multi‐compartmental hydrogel particles can be formed with diverse hierarchical structures showing combinational functionalities. The synthesized hydrogel particles, when loaded with polypyrrole (PPy) nanoparticles that act as photothermal nanotransducers, are demonstrated to function as near‐infrared (NIR) light triggerable and deformation‐free hydrogel materials. Periodic NIR laser switching is applied to stimulate these hydrogel particles, and pulsatile release profiles are collected. Compared with massive reagents released from single‐compartmental hydrogel particles, more regulated release profiles of the multi‐compartmental hydrogel particles are observed.