Phillips KR, Shirman T, Aizenberg M, England GT, Vogel N, Aizenberg J. Silica–titania hybrids for structurally robust inverse opals with controllable refractive index. Journal of Materials Chemistry C. 2020;8 (1) :109 - 116. Publisher's VersionAbstract
Templated from sacrificial colloidal assemblies, inverse opals are comprised of an interconnected periodic network of pores, forming a photonic crystal. They are used in a variety of applications, most of which, especially those in optics and photocatalysis, require a high degree of control over the long-range order, composition and refractive index. It has been shown that hybrid materials combining different components can yield materials with properties that are superior to the individual components. Here, we describe the assembly of hybrid titania/silica inverse opals using sol–gel chemistry, resulting in a mixed oxide with well-dispersed titanium and silicon. Titania has a high refractive index (2.4–2.9), but cracks typically form in the inverse opal structure; conversely, silica can produce highly ordered crack-free inverse opals, but it has a lower refractive index (∼1.4). By adjusting the ratio of titania and silica, the refractive index can be tailored while minimizing the crack density and maintaining structural order, allowing for control over the optical properties of this hybrid nanoporous material.
Korevaar PA, Kaplan CN, Grinthal A, Rust RM, Aizenberg J. Non-equilibrium signal integration in hydrogels. 2020;11 (1) :386. Publisher's VersionAbstract
Materials that perform complex chemical signal processing are ubiquitous in living systems. Their synthetic analogs would transform developments in biomedicine, catalysis, and many other areas. By drawing inspiration from biological signaling dynamics, we show how simple hydrogels have a previously untapped capacity for non-equilibrium chemical signal processing and integration. Using a common polyacrylic acid hydrogel, with divalent cations and acid as representative stimuli, we demonstrate the emergence of non-monotonic osmosis-driven spikes and waves of expansion/contraction, as well as traveling color waves. These distinct responses emerge from different combinations of rates and sequences of arriving stimuli. A non-equilibrium continuum theory we developed quantitatively captures the non-monotonic osmosis-driven deformation waves and determines the onset of their emergence in terms of the input parameters. These results suggest that simple hydrogels, already built into numerous systems, have a much larger sensing space than currently employed.
Magnabosco G, Papiano I, Aizenberg M, Aizenberg J, Falini G. Beyond biotemplating: multiscale porous inorganic materials with high catalytic efficiency. Chemical Communications. 2020;56 (23) :3389 - 3392. Publisher's VersionAbstract
Biotemplating makes it possible to prepare materials with complex structures by taking advantage of nature's ability to generate unique morphologies. In this work, we designed and produced a multi-scale porosity (MSP) scaffold starting from sea urchin spines by adding an additional nano-porosity to its native micro-porosity. The final replica shows porosity in both length scales and is an effective high-performing photocatalytic material.
Luneau M, Guan E, Chen W, Foucher AC, Marcella N, Shirman T, Verbart DMA, Aizenberg J, Aizenberg M, Stach EA, et al. Enhancing catalytic performance of dilute metal alloy nanomaterials. 2020;3 (1) :46. Publisher's VersionAbstract
Dilute alloys are promising materials for sustainable chemical production; however, their composition and structure affect their performance. Herein, a comprehensive study of the effects of pretreatment conditions on the materials properties of Pd0.04Au0.96 nanoparticles partially embedded in porous silica is related to the activity for catalytic hydrogenation of 1-hexyne to 1-hexene. A combination of in situ characterization and theoretical calculations provide evidence that changes in palladium surface content are induced by treatment in oxygen, hydrogen and carbon monoxide at various temperatures. In turn, there are changes in hydrogenation activity because surface palladium is necessary for H2 dissociation. These Pd0.04Au0.96 nanoparticles in the porous silica remain structurally intact under many cycles of activation and deactivation and are remarkably resistant to sintering, demonstrating that dilute alloy catalysts are highly dynamic systems that can be tuned and maintained in a active state.
Luneau M, Shirman T, Filie A, Timoshenko J, Chen W, Trimpalis A, Flytzani-Stephanopoulos M, Kaxiras E, Frenkel AI, Aizenberg J, et al. Dilute Pd/Au Alloy Nanoparticles Embedded in Colloid-Templated Porous SiO2: Stable Au-Based Oxidation Catalysts. Chemistry of MaterialsChemistry of Materials. 2019;31 (15) :5759 - 5768. Publisher's Version
McCoy DE, McCoy VE, Mandsberg NK, Shneidman AV, Aizenberg J, Prum RO, Haig D. Structurally assisted super black in colourful peacock spiders. Proceedings of the Royal Society B: Biological SciencesProceedings of the Royal Society B: Biological Sciences. 2019;286 (1902) :20190589. Publisher's Version
Magnabosco G, Polishchuk I, Palomba F, Rampazzo E, Prodi L, Aizenberg J, Pokroy B, Falini G. Effect of Surface Chemistry on Incorporation of Nanoparticles within Calcite Single Crystals. Crystal Growth & DesignCrystal Growth & Design. 2019;19 (8) :4429 - 4435. Publisher's Version
Shahsafi A, Joe G, Brandt S, Shneidman AV, Stanisic N, Xiao Y, Wambold R, Yu Z, Salman J, Aizenberg J, et al. Wide-Angle Spectrally Selective Absorbers and Thermal Emitters Based on Inverse Opals. ACS PhotonicsACS Photonics. 2019;6 (11) :2607 - 2611. Publisher's Version
Phillips KR, Zhang CT, Yang T, Kay T, Gao C, Brandt S, Liu L, Yang H, Li Y, Aizenberg J, et al. Fabrication of Photonic Microbricks via Crack Engineering of Colloidal Crystals. Advanced Functional MaterialsAdvanced Functional MaterialsAdv. Funct. Mater. 2019;n/a (n/a) :1908242. Publisher's VersionAbstract
Abstract Evaporation-induced self-assembly of colloidal particles is one of the most versatile fabrication routes to obtain large-area colloidal crystals; however, the formation of uncontrolled ?drying cracks? due to gradual solvent evaporation represents a significant challenge of this process. While several methods are reported to minimize crack formation during evaporation-induced colloidal assembly, here an approach is reported to take advantage of the crack formation as a patterning tool to fabricate microscopic photonic structures with controlled sizes and geometries. This is achieved through a mechanistic understanding of the fracture behavior of three different types of opal structures, namely, direct opals (colloidal crystals with no matrix material), compound opals (colloidal crystals with matrix material), and inverse opals (matrix material templated by a sacrificial colloidal crystal). This work explains why, while direct and inverse opals tend to fracture along the expected {111} planes, the compound opals exhibit a different cracking behavior along the nonclose-packed {110} planes, which is facilitated by the formation of cleavage-like fracture surfaces. The discovered principles are utilized to fabricate photonic microbricks by programming the crack initiation at specific locations and by guiding propagation along predefined orientations during the self-assembly process, resulting in photonic microbricks with controlled sizes and geometries.
Howell C, Grinthal A, Sunny S, Aizenberg M, Aizenberg J. Designing Liquid-Infused Surfaces for Medical Applications: A Review. Advanced MaterialsAdvanced MaterialsAdv. Mater. 2018;30 (50) :1802724. Publisher's VersionAbstract
Abstract The development of new technologies is key to the continued improvement of medicine, relying on comprehensive materials design strategies that can integrate advanced therapeutic and diagnostic functions with a variety of surface properties such as selective adhesion, dynamic responsiveness, and optical/mechanical tunability. Liquid-infused surfaces have recently come to the forefront as a unique approach to surface coatings that can resist adhesion of a wide range of contaminants on medical devices. Furthermore, these surfaces are proving highly versatile in enabling the integration of established medical surface treatments alongside the antifouling capabilities, such as drug release or biomolecule organization. Here, the range of research being conducted on liquid-infused surfaces for medical applications is presented, from an understanding of the basics behind the interactions of physiological fluids, microbes, and mammalian cells with liquid layers to current applications of these materials in point-of-care diagnostics, medical tubing, instruments, implants, and tissue engineering. Throughout this exploration, the design parameters of liquid-infused surfaces and how they can be adapted and tuned to particular applications are discussed, while identifying how the range of controllable factors offered by liquid-infused surfaces can be used to enable completely new and dynamic approaches to materials and devices for human health.
Alvarenga J, Ainge Y, Williams C, Maltz A, Blough T, Khan M, Aizenberg J. Research Update: Liquid gated membrane filtration performance with inorganic particle suspensions. APL MaterialsAPL Materials. 2018;6 (10) :100703. Publisher's Version
Yao Y, Waters JT, Shneidman AV, Cui J, Wang X, Mandsberg NK, Li S, Balazs AC, Aizenberg J. Multiresponsive polymeric microstructures with encoded predetermined and self-regulated deformability. Proceedings of the National Academy of Sciences. 2018;115 (51) :12950. Publisher's VersionAbstract
The range of allowed deformation modes currently described for the actuation of microstructures is limited. In this work we introduce magnetic-field–guided encoding of highly controlled molecular anisotropy into 3D liquid-crystalline elastomer microstructures capable of displaying unique multiresponsive, shape-changing behaviors. The richness of the predetermined and self-regulated deformations and region-specific motions in these microstructural arrays gives rise to physicochemical insights, as well as potential applications in controlled adhesion, information encryption, soft robotics, and self-regulated light–material interactions.Dynamic functions of biological organisms often rely on arrays of actively deformable microstructures undergoing a nearly unlimited repertoire of predetermined and self-regulated reconfigurations and motions, most of which are difficult or not yet possible to achieve in synthetic systems. Here, we introduce stimuli-responsive microstructures based on liquid-crystalline elastomers (LCEs) that display a broad range of hierarchical, even mechanically unfavored deformation behaviors. By polymerizing molded prepolymer in patterned magnetic fields, we encode any desired uniform mesogen orientation into the resulting LCE microstructures, which is then read out upon heating above the nematic–isotropic transition temperature (TN–I) as a specific prescribed deformation, such as twisting, in- and out-of-plane tilting, stretching, or contraction. By further introducing light-responsive moieties, we demonstrate unique multifunctionality of the LCEs capable of three actuation modes: self-regulated bending toward the light source at T < TN–I, magnetic-field–encoded predetermined deformation at T > TN–I, and direction-dependent self-regulated motion toward the light at T > TN–I. We develop approaches to create patterned arrays of microstructures with encoded multiple area-specific deformation modes and show their functions in responsive release of cargo, image concealment, and light-controlled reflectivity. We foresee that this platform can be widely applied in switchable adhesion, information encryption, autonomous antennae, energy harvesting, soft robotics, and smart buildings.
Yao Y, Waters J, Shneidman AV, Cui J, Wang X, Mandsberg NK, Li S, Balazs AC, Aizenberg J. Multi-responsive polymeric microstructures with encoded pre-determined and self-regulated deformability. Proceedings of the National Academy of Sciences. 2018;115 (51) :12950-12955. Publisher's Version
Timoshenko J, Wrasman C, Luneau M, Shirman T, Cargnello M, Bare S, Aizenberg J, Friend C, Frenkel A. Probing atomic distributions in mono- and bimetallic nanoparticles by supervised machine learning. Nano Letters. 2018. acs.nanolett.8b04461.pdf
Kreder MJ, Daniel D, Tetreault A, Cao Z, Lemaire B, Timonen JVI, Aizenberg J. Film Dynamics and Lubricant Depletion by Droplets Moving on Lubricated Surfaces. PHYSICAL REVIEW. 2018;8 (031053).Abstract

Lubricated surfaces have shown promise in numerous applications where impinging foreign droplets
must be removed easily; however, before they can be widely adopted, the problem of lubricant depletion,
which eventually leads to decreased performance, must be solved. Despite recent progress, a quantitative
mechanistic explanation for lubricant depletion is still lacking. Here, we first explain the shape of a droplet
on a lubricated surface by balancing the Laplace pressures across interfaces. We then show that the
lubricant film thicknesses beneath, behind, and wrapping around a moving droplet change dynamically

with the droplet’s speed—analogous to the classical Landau-Levich-Derjaguin problem. The intercon-
nected lubricant dynamics results in the growth of the wetting ridge around the droplet, which is the

dominant source of lubricant depletion. We then develop an analytic expression for the maximum amount
of lubricant that can be depleted by a single droplet. Counterintuitively, faster-moving droplets subjected to
higher driving forces deplete less lubricant than their slower-moving counterparts. The insights developed
in this work will inform future work and the design of longer-lasting lubricated surfaces.

Daniel D, Timonen JVI, Li R, Velling SJ, Kreder MJ, Tetreault A, Aizenberg J. Origins of liquid-repellency on structured, flat, and lubricated surfaces . Phys. Rev. Lett. 2018.Abstract
There are currently three main classes of liquid-repellent surfaces: micro-/nano-structured superhydrophobic surfaces, flat surfaces grafted with `liquid-like' polymer brushes, and lubricated surfaces. Despite recent progress, the mechanistic explanation for the differences in droplet behavior on such surfaces is still under debate. Here, we measured the dissipative force acting on a droplet moving on representatives of these surfaces at different velocities U = 0.01--1 mm/s using a cantilever force sensor with sub-μN accuracy, and correlated it to the contact line dynamics observed using optical interferometry at high spatial (micron) and temporal (lessthan 0.1s) resolutions. We find that the dissipative force---due to very different physical mechanisms at the contact line---is independent of velocity on superhydrophobic surfaces, but depends non-linearly on velocity for flat and lubricated surfaces. The techniques and insights presented here will inform future work on liquid-repellent surfaces and enable their rational design.
Hinz K, Alvarenga J, Kim P, Park D, Aizenberg J, Bechthold M. Pneumatically adaptive light modulation system (PALMS) for buildings. Materials & Design. 2018;152 :156-167. Publisher's VersionAbstract

This research introduces a novel approach to control light transmittance based on flexible polydimethylsiloxane (PDMS) films that have been plasma-treated such that micro-scale surface features have a visual effect as the film responds to applied strain. The effect is continuously tunable from optically clear (71.5% Transmittance over a 400–900 nm wavelength) to completely diffuse (18.1% T). Changes in the film's optical properties are triggered by bi-axial strains applied using a pneumatic system to form pressurized envelopes. This paper reports on a series of experimental studies and provides system integration research using prototypes, simulations and geometric models to correlate measured optical properties, strain, and global surface curvatures. In conclusion, a design is proposed to integrate PDMS light control within existing building envelopes.

Two alternatives are investigated and compared: System A uses positive pressure featuring an exterior grid to restrain and shape the inflated film during expansion; System B uses negative pressure where the films are shaped according to the geometry of an interstitial grid that serves as a spacer between two film surfaces. Both systems can provide effective control of opacity levels using pneumatic pressure and may be suitable for use with existing glazing systems or ethylene tetrafluoroethylene (ETFE) pneumatic envelopes.

Yao Y, Aizenberg J, Park K-C. Dropwise Condensation on Hydrophobic Bumps and Dimples. Appl. Phys. Lett. 2018;112 (15) :151605. Full TextAbstract
Surface topography plays an important role in promoting or suppressing localized condensation. In this work, we study the growth of water droplets on hydrophobic convex surface textures such as bumps and concave surface textures such as dimples with a millimeter scale radius of curvature. We analyze the spatio-temporal droplet size distribution under a supersaturation condition created by keeping the uniform surface temperature below the dew point and show its relationship with the sign and magnitude of the surface curvature. In particular, in contrast to the well-known capillary condensation effect, we report an unexpectedly less favorable condensation on smaller, millimeter-scale dimples where the capillary condensation effect is negligible. To explain these experimental results, we numerically calculated the diffusion flux of water vapor around the surface textures, showing that its magnitude is higher on bumps and lower on dimples compared to a flat surface. We envision that our understanding of millimetric surface topography can be applied to improve the energy efficiency of condensation in applications such as water harvesting, heating, ventilation, and air conditioning systems for buildings and transportation, heat exchangers, thermal desalination plants, and fuel processing systems.
Li L, Fijneman AJ, Kaandorp JA, Aizenberg J, Noorduin WL. Directed nucleation and growth by balancing local supersaturation and substrate/nucleus lattice mismatch. PNAS. 2018;14 :3573-3580. Publisher's VersionAbstract
Controlling nucleation and growth is crucial in biological and artificial mineralization and self-assembly processes. The nucleation barrier is determined by the chemistry of the interfaces at which crystallization occurs and local supersaturation. Although chemically tailored substrates and lattice mismatches are routinely used to modify energy landscape at the substrate/nucleus interface and thereby steer heterogeneous nucleation, strategies to combine this with control over local supersaturations have remained virtually unexplored. Here we demonstrate simultaneous control over both parameters to direct the positioning and growth direction of mineralizing compounds on preselected polymorphic substrates. We exploit the polymorphic nature of calcium carbonate (CaCO3) to locally manipulate the carbonate concentration and lattice mismatch between the nucleus and substrate, such that barium carbonate (BaCO3) and strontium carbonate (SrCO3) nucleate only on specific CaCO3 polymorphs. Based on this approach we position different materials and shapes on predetermined CaCO3 polymorphs in sequential steps, and guide the growth direction using locally created supersaturations. These results shed light on nature’s remarkable mineralization capabilities and outline fabrication strategies for advanced materials, such as ceramics, photonic structures, and semiconductors.
Hou X, Li J, Tesler AB, Yao Y, Wang M, Min L, Sheng Z, Aizenberg J. Dynamic air/liquid pockets for guiding microscale flow. Nat. Commun. 2018;9 :733. Full TextAbstract

Microscale flows of fluids are mainly guided either by solid matrices or by liquid–liquid interfaces. However, the solid matrices are plagued with persistent fouling problems, while liquid–liquid interfaces are limited to low-pressure applications. Here we report a dynamic liquid/solid/gas material containing both air and liquid pockets, which are formed by partially infiltrating a porous matrix with a functional liquid. Using detailed theoretical and experimental data, we show that the distribution of the air- and liquid-filled pores is responsive to pressure and enables the formation and instantaneous recovery of stable liquid–liquid interfaces that sustain a wide range of pressures and prevent channel contamination. This adaptive design is demonstrated for polymeric materials and extended to metal-based systems that can achieve unmatched mechanical and thermal stability. Our platform with its unique adaptive pressure and antifouling capabilities may offer potential solutions to flow control in microfluidics, medical devices, microscale synthesis, and biological assays.