Developing adaptive materials with geometries that change in response to external stimuli provides fundamental insights into the links between the physical forces involved and the resultant morphologies and creates a foundation for technologically relevant dynamic systems. In particular, reconfigurable surface topography as a means to control interfacial properties has recently been explored using responsive gels, shape-memory polymers, liquid crystals and hybrid composites, including magnetically active slippery surfaces. However, these designs exhibit a limited range of topographical changes and thus a restricted scope of function. Here we introduce a hierarchical magneto-responsive composite surface, made by infiltrating a ferrofluid into a microstructured matrix (termed ferrofluid-containing liquid-infused porous surfaces, or FLIPS). We demonstrate various topographical reconfigurations at multiple length scales and a broad range of associated emergent behaviours. An applied magnetic-field gradient induces the movement of magnetic nanoparticles suspended in the ferrofluid, which leads to microscale flow of the ferrofluid first above and then within the microstructured surface. This redistribution changes the initially smooth surface of the ferrofluid (which is immobilized by the porous matrix through capillary forces) into various multiscale hierarchical topographies shaped by the size, arrangement and orientation of the confining microstructures in the magnetic field. We analyse the spatial and temporal dynamics of these reconfigurations theoretically and experimentally as a function of the balance between capillary and magnetic pressures and of the geometric anisotropy of the FLIPS system. Several interesting functions at three different length scales are demonstrated: self-assembly of colloidal particles at the micrometre scale; regulated flow of liquid droplets at the millimetre scale; and switchable adhesion and friction, liquid pumping and removal of biofilms at the centimetre scale. We envision that FLIPS could be used as part of integrated control systems for the manipulation and transport of matter, thermal management, microfluidics and fouling-release materials.

Creative synthetic chemistry has endowed the class of periodic mesoporous organosilica materials, dubbed PMO, with a variety of new and exciting compositions, properties, and functions since its inception a decade ago. Using a handful of recent trendsetting case histories, the multidisciplinary applications of PMO materials in chemistry and physics, materials science and engineering, biology, and medicine are demonstrated in a most powerful way. In doing so, this Review aims to inspire more collaborative and ambitious endeavors in the second decade of PMO research.

We built an out-of-equilibrium material system by designing competing interactions that are both dissipative and programmable.

Mobile microrobots, which can navigate, sense, and interact with their environment, could potentially revolutionize biomedicine and environmental remediation. Many self-organizing microrobotic collectives have been developed to overcome inherent limits in actuation, sensing, and manipulation of individual microrobots; however, reconfigurable collectives with robust transitions between behaviors are rare. Such systems that perform multiple functions are advantageous to operate in complex environments. Here, we present a versatile microrobotic collective system capable of on-demand reconfiguration to adapt to and utilize their environments to perform various functions at the air–water interface. Our system exhibits diverse modes ranging from isotropic to anisotrpic behaviors and transitions between a globally driven and a novel self-propelling behavior. We show the transition between different modes in experiments and simulations, and demonstrate various functions, using the reconfigurability of our system to navigate, explore, and interact with the environment. Such versatile microrobot collectives with globally driven and self-propelled behaviors have great potential in future medical and environmental applications.

Periodic mesoporous organosilica (PMO) with polyhedral oligomeric silsesquioxane (POSS) air pockets integrated into the pore walls has been prepared by a template-directed, evaporation-induced self-assembly spin-coating procedure to create a hybrid POSS-PMO thin film. A 10-fold increase in the porosity of the POSS-PMO film compared to a reference POSS film is achieved by incorporating ∼1.5 nm pores. The increased porosity results in a decrease in the dielectric constant, k, which goes from 2.03 in a reference POSS film to 1.73 in the POSS-PMO film.

Transparent conducting oxides (TCOs) represent a unique class of electrode materials whose hallmark is high electrical conductivity and high optical transparency in the visible spectral range. They are renowned as electrode materials in solar cells, organic light-emitting diodes, and flat-panel displays, on both rigid and flexible substrates. [1,2] A contemporary challenge in materials chemistry is to discover ways of increasing the surface area of TCOs while retaining their conductivity and transparency, a combination of properties that would, for example, enable a new platform for high-efficiency dye-immobilized electrochemiluminescence (ECL) displays, light-emitting diodes (LEDs), lasers, and (bio)chemical sensors.[3]Herein, we report the synthesis of mesoporous antimonydoped tin oxide films dubbed meso-ATOs, interesting candidates for a new type of electrode material that offers the unique combination of high-surface-area ordered mesoscale pores together with high electrical conductivity and high optical transparency, and further we show that it is capable of supporting chemically tethered ruthenium-based dyes, enabling it to function as an efficient and reusable solid-state ECL-based sensor.Why has it taken about two decades of research to achieve this sought after goal? One can trace the difficulty to a number of adverse contributing factors, one of which is the poor affinity between sol-gel precursors of conductive inorganic materials and the organic template-directing mesophase under the nonaqueous evaporation-induced self-assembly (EISA) conditions required to grow conducting mesoporous metal oxide films.[4] Another problem is that high conductivity is usually associated with high crystallinity, and for mesoporous transition metal oxide materials this necessitates crystallization of the as-synthesized amorphous metal oxide framework into a nanocrystalline version, which usually results in strain-induced collapse of channel and/or cavity walls of the mesopores. So far, only mesoporous tin-doped indium oxide (meso-ITO) materials have been reported, but either their conductivity is very low due to low crystallinity [5] or their conductivity is reasonable but the mesostructure can only be templated with a specialty polymer surfactant. [6]

This paper demonstrates for the first time thermally induced gradual hydrophobization, monitored quantitatively by ellipsometric porosimetry, of four prototypical periodic mesoporous organosilicas (PMOs) that are tailored through materials chemistry for use as low-dielectric-constant (low k) materials in microprocessors. Theoretical aspects of this quantification are briefly discussed. A comparison of structural, mechanical, dielectric, and hydrophobic properties of ethane, methane, ethene, and 3-ring PMOs is made. Particularly, ethane, methane, and 3-ring PMOs show impressive water repellency at post-treatment temperatures as low as 350 °C, with corresponding Young's modulus values greater than 10 GPa and k values smaller than 2, a figure of merit that satisfies the technological requirements of future generation microchips.

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