Shirman E, Shirman T, Shneidman AV, Grinthal A, Phillips KR, Whelan H, Bulger E, Abramovitch M, Patil J, Nevarez R, et al. Modular Design of Advanced Catalytic Materials Using Hybrid Organic–Inorganic Raspberry Particles. Adv. Func. Mater. 2017 :1704559.
Publisher's VersionAbstractCatalysis is one of the most sophisticated areas of materials research that encompasses a diverse set of materials and phenomena occurring on multiple length and time scales. Designing catalysts that can be broadly applied toward global energy and environmental challenges requires the development of universal frameworks for complex catalytic systems through rational and independent (or quasi-independent) optimization of multiple structural and compositional features. Toward addressing this goal, a modular platform is presented in which sacrificial organic colloids bearing catalytic nanoparticles on their surfaces self-assemble with matrix precursors, simultaneously structuring the resulting porous networks and fine-tuning the locations of catalyst particles. This strategy allows combinatorial variations of the material building blocks and their organization, in turn providing numerous degrees of freedom for optimizing the material’s functional properties, from the nanoscale to the macroscale. The platform enables systematic studies and rational design of efficient and robust systems for a wide range of catalytic and photocatalytic reactions, as well as their integration into industrial and other real-life environments.
Aizenberg M, Okeyoshi K, Aizenberg J.
Inverting the Swelling Trends in Modular Self-Oscillating Gels Crosslinked by Redox-Active Metal Bipyridine Complexes. Adv. Func. Mater. 2017 :1704205.
Publisher's VersionAbstractThe developing field of active, stimuli-responsive materials is in need for new dynamic architectures that may offer unprecedented chemomechanical switching mechanisms. Toward this goal, syntheses of polymerizable bipyridine ligands, bis(4-vinylbenzyl)[2,2′-bipyridine]-4,4′-dicarboxylate and N4,N4′-bis(4-vinylphenyl)-2,2′-bipyridine-4,4′-dicarboxamide, and a number of redox-active Ruthenium(II) and Iron(II) complexes with them are reported. Detailed characterizations by NMR, Fourier transform infrared spectroscopy, high-resolution mass-spectrometry, X-ray, and cyclic voltammetry show that the topology of these molecules allows them to serve as both comonomers and crosslinkers in polymerization reactions. Electronic properties of the ligands are tunable by choosing carboxylate- or carboxamido-linkages between the core and the vinylaryl moieties, leading to a library of Ru and Fe complexes with the M(III)/M(II) standard redox potentials suitable for catalyzing self-oscillating Belousov–Zhabotinskii (BZ) reaction. New poly(N-isopropylacrylamide)-based redox-responsive functional gels containing hydrophilic comonomers, which have been prepared using representative Ru bpy complexes as both a crosslinker and redox-active catalyst, exhibit a unique feature: their swelling/contraction mode switches its dependence on the oxidation state of the Ru center, upon changing the ratio of comonomers in the hybrid gel network. The BZ self-oscillations of such crosslinked hydrogels have been observed and quantified for both supported film and free-standing gel samples, demonstrating their potential as chemomechanically active modules for new functional materials.
Kumar K, Liu J, Christianson C, Ali M, Tolley MT, Aizenberg J, Ingber DE, Weaver JC, Bertoldi K.
A Biologically Inspired, Functionally Graded End Effector for Soft Robotics Applications. Soft Robotics. 2017;4 (4) :317-323.
Publisher's VersionAbstractSoft robotic actuators offer many advantages over their rigid counterparts, but they often are unable to apply highly localized point loads. In contrast, many invertebrates have not only evolved extremely strong ‘‘hybrid appendages’’ that are composed of rigid ends that can grasp, puncture, and anchor into solid substrates, but they also are compliant and resilient, owing to the functionally graded architecture that integrates rigid termini with their flexible and highly extensible soft musculatures. Inspired by the design principles of these natural hybrid appendages, we demonstrate a synthetic hybrid end effector for soft-bodied robots that exhibits excellent piercing abilities. Through the incorporation of functionally graded interfaces, this design strategy minimizes stress concentrations at the junctions adjoining the fully rigid and soft components and optimizes the bending stiffness to effectively penetrate objects without interfacial failure under shear and compressive loading re- gimes. In this composite architecture, the radially aligned tooth-like elements apply balanced loads to maximize puncturing ability, resulting in the coordinated fracture of an object of interest.
Amini S, Kolle S, Petrone L, Ahanotu O, Sunny S, Sutanto CN, Hoon S, Cohen L, Weaver JC, Aizenberg J, et al. Preventing mussel adhesion using lubricant-infused materials. Science. 2017;357 (6352) :668-673.
Publisher's VersionAbstractMussels are opportunistic macrofouling organisms that can attach to most immersed solid surfaces, leading to serious economic and ecological consequences for the maritime and aquaculture industries. We demonstrate that lubricant-infused coatings exhibit very low preferential mussel attachment and ultralow adhesive strengths under both controlled laboratory conditions and in marine field studies. Detailed investigations across multiple length scales—from the molecular-scale characterization of deposited adhesive proteins to nanoscale contact mechanics to macroscale live observations—suggest that lubricant infusion considerably reduces fouling by deceiving the mechanosensing ability of mussels, deterring secretion of adhesive threads, and decreasing the molecular work of adhesion. Our study demonstrates that lubricant infusion represents an effective strategy to mitigate marine biofouling and provides insights into the physical mechanisms underlying adhesion prevention.
Daniel D, Timonen JVI, Li R, Velling SJ, Aizenberg J.
Oleoplaning droplets on lubricated surfaces. Nat. Phys. 2017;13 (10) :1020-1025.
Full TextAbstractRecently, there has been much interest in using lubricated surfaces to achieve extreme liquid repellency: a foreign droplet immiscible with the underlying lubricant layer was shown to slide o at a small tilt angle <5◦ . This behaviour was hypothesized to arise from a thin lubricant overlayer film sandwiched between the droplet and solid substrate, but this has not been observed experimentally. Here, using thin-film interference, we are able to visualize the intercalated film under both static and dynamic conditions. We further demonstrate that for a moving droplet, the film thickness follows the Landau–Levich–Derjaguin law. The droplet is therefore oleoplaning—akin to tyres hydroplaning on a wet road—with minimal dissipative force and no contact line pinning. The techniques and insights presented in this study will inform future work on the fundamentals of wetting for lubricated surfaces and enable their rational design.
England GT, Russell C, Shirman E, Kay T, Vogel N, Aizenberg J.
The Optical Janus Effect: Asymmetric Structural Color Reflection Materials. Adv. Mater. 2017;29 (29) :1606876.
Publisher's VersionAbstractStructurally colored materials are often used for their resistance to photobleaching and their complex viewing-direction-dependent optical properties. Frequently, absorption has been added to these types of materials in order to improve the color saturation by mitigating the effects of nonspecific scattering that is present in most samples due to imperfect manufacturing procedures. The combination of absorbing elements and structural coloration often yields emergent optical properties. Here, a new hybrid architecture is introduced that leads to an interesting, highly directional optical effect. By localizing absorption in a thin layer within a transparent, structurally colored multilayer material, an optical Janus effect is created, wherein the observed reflected color is different on one side of the sample than on the other. A systematic characterization of the optical properties of these structures as a function of their geometry and composition is performed. The experimental studies are coupled with a theoretical analysis that enables a precise, rational design of various optical Janus structures with highly controlled color, pattern, and fabrication approaches. These asymmetrically colored materials will open applications in art, architecture, semitransparent solar cells, and security features in anticounterfeiting materials.
Alvarez MM, Aizenberg J, Analoui M, Andrews AM, Bisker G, Boyden ES, Kamm RD, Karp JM, Mooney DJ, Oklu R, et al. Emerging Trends in Micro- and Nanoscale Technologies in Medicine: From Basic Discoveries to Translation. ACS Nano. 2017;11 (6) :5195-5214.
Publisher's VersionAbstractWe discuss the state of the art and innovative micro- and nanoscale technologies that are finding niches and opening up new opportunities in medicine, particularly in diagnostic and therapeutic applications. We take the design of point-of-care applications and the capture of circulating tumor cells as illustrative examples of the integration of micro- and nanotechnologies into solutions of diagnostic challenges. We describe several novel nanotechnologies that enable imaging cellular structures and molecular events. In therapeutics, we describe the utilization of micro- and nanotechnologies in applications including drug delivery, tissue engineering, and pharmaceutical development/testing. In addition, we discuss relevant challenges that micro- and nanotechnologies face in achieving cost-effective and widespread clinical implementation as well as forecasted applications of micro- and nanotechnologies in medicine.
Hou X, Zhang YS, Trujillo-de Santiago G, Alvarez MM, Ribas J, Jonas SJ, Weiss PS, Andrews AM, Aizenberg J, Khademhosseini A.
Interplay between materials and microfluidics. Nat. Rev. Mater. 2017;2 (5) :17016.
Publisher's VersionAbstractDevelopments in the field of microfluidics have triggered technological revolutions in many disciplines, including chemical synthesis, electronics, diagnostics, single-cell analysis, micro- and nanofabrication, and pharmaceutics. In many of these areas, rapid growth is driven by the increasing synergy between fundamental materials development and new microfluidic capabilities. In this Review, we critically evaluate both how recent advances in materials fabrication have expanded the frontiers of microfluidic platforms and how the improved microfluidic capabilities are, in turn, furthering materials design. We discuss how various inorganic and organic materials enable the fabrication of systems with advanced mechanical, optical, chemical, electrical and biointerfacial properties — in particular, when these materials are combined into new hybrids and modular configurations. The increasing sophistication of microfluidic techniques has also expanded the range of resources available for the fabrication of new materials, including particles and fibres with specific functionalities, 3D (bio)printed composites and organoids. Together, these advances lead to complex, multifunctional systems, which have many interesting potential applications, especially in the biomedical and bioengineering domains. Future exploration of the interactions between materials science and microfluidics will continue to enrich the diversity of applications across engineering as well as the physical and biomedical sciences.
Kaplan CN, Noorduin WL, Li L, Sadza R, Folkertsma L, Aizenberg J, Mahadevan L.
Controlled growth and form of precipitating microstructures. Science. 2017;355 (6332) :1395-1399.
Publisher's VersionAbstractControlled self-assembly of three-dimensional shapes holds great potential for fabrication of functional materials. Their practical realization requires a theoretical framework to quantify and guide the dynamic sculpting of the curved structures that often arise in accretive mineralization. Motivated by a variety of bioinspired coprecipitation patterns of carbonate and silica, we develop a geometrical theory for the kinetics of the growth front that leaves behind thin-walled complex structures. Our theory explains the range of previously observed experimental patterns and, in addition, predicts unexplored assembly pathways. This allows us to design a number of functional base shapes of optical microstructures, which we synthesize to demonstrate their light-guiding capabilities. Overall, our framework provides a way to understand and control the growth and form of functional precipitating microsculptures.
Sutton A, Shirman T, Timonen JVI, England GT, Kim P, Kolle M, Ferrante T, Zarzar LD, Strong E, Aizenberg J.
Photothermally triggered actuation of hybrid materials as a new platform for in vitro cell manipulation. Nat. Commun. 2017;8 :14700.
Full TextAbstractMechanical forces in the cell’s natural environment have a crucial impact on growth,
differentiation and behaviour. Few areas of biology can be understood without taking into account how both individual cells and cell networks sense and transduce physical stresses. However, the field is currently held back by the limitations of the available methods to apply physiologically relevant stress profiles on cells, particularly with sub-cellular resolution, in controlled in vitro experiments. Here we report a new type of active cell culture material that allows highly localized, directional and reversible deformation of the cell growth substrate, with control at scales ranging from the entire surface to the subcellular, and response times on the order of seconds. These capabilities are not matched by any other method, and this versatile material has the potential to bridge the performance gap between the existing single cell micro-manipulation and 2D cell sheet mechanical stimulation techniques.
Hu Y, Kim P, Aizenberg J.
Harnessing structural instability and material instability in the hydrogel-actuated integrated responsive structures (HAIRS). Extreme Mechanics Letters. 2017;13 :84-90.
AbstractWe describe the behavior of a temperature-responsive hydrogel actuated integrated responsive structure (HAIRS). The structure is constructed by embedding a rigid high-aspect-ratio post in a layer of poly(Nisopropylacrylamide) (PNIPAM) hydrogel which is bonded to a rigid substrate. As the hydrogel contracts, the post abruptly tilts. The HAIRS has demonstrated its broad applications in generating reversible micropattern formation, active optics, tunable wettability, and artificial homeostasis. To quantitatively describe and predict the system behavior, we construct an analytical model combining the structural instability, i.e. buckling of the post, and the material instability, i.e. the volume phase transition of PNIPAM hydrogel. The two instabilities of the system result in a large hysteresis in response to heating and cooling processes. Experimental results validate the predicted phenomenon of the abrupt tilting as temperature and large hysteresis in a heating-and-cooling cycle in the PNIPAM actuated HAIRS. Based on this model, we further discuss the influence of the material properties on the actuation of the structure.
Kovalenko Y, Sotiri I, Timonen JVI, Overton JC, Homes G, Aizenberg J, Howell C.
Bacterial Interactions with Immobilized Liquid Layer. Adv. Healthcare Mater. 2017;6 (15) :1600948.
Publisher's VersionAbstractBacterial interactions with surfaces are at the heart of many infection-related problems in healthcare. In this work, the interactions of clinically relevant bacteria with immobilized liquid (IL) layers on oil-infused polymers are investigated. Although oil-infused polymers reduce bacterial adhesion in all cases, complex interactions of the bacteria and liquid layer under orbital flow conditions are uncovered. The number of adherent Escherichia coli cells over multiple removal cycles increases in flow compared to static growth conditions, likely due to a disruption of the liquid layer continuity. Surprisingly, however, biofilm formation appears to remain low regardless of growth conditions. No incorporation of the bacteria into the layer is observed. Bacterial type is also found to affect the number of adherent cells, with more E. coli remaining attached under dynamic orbital flow than Staphylococcus aureus, Pseudomonas aeruginosa under identical conditions. Tests with mutant E. coli lacking flagella confirm that flagella play an important role in adhesion to these surfaces. The results presented here shed new light on the interaction of bacteria with IL layers, highlighting the fundamental differences between oil-infused and traditional solid interfaces, as well as providing important information for their eventual translation into materials that reduce bacterial adhesion in medical applications.
Chen J, Howell C, Haller CA, Patel MS, Ayala P, Moravec KA, Dai E, Liu L, Sotiri I, Aizenberg M, et al. An immobilized liquid interface prevents device associated bacterial infection in vivo. Biomaterials. 2017;113 :80-92.
AbstractVirtually all biomaterials are susceptible to biofilm formation and, as a consequence, device-associated infection. The concept of an immobilized liquid surface, termed slippery liquid-infused porous surfaces (SLIPS), represents a new framework for creating a stable, dynamic, omniphobic surface that displays ultralow adhesion and limits bacterial biofilm formation. A widely used biomaterial in clinical care, expanded polytetrafluoroethylene (ePTFE), infused with various perfluorocarbon liquids generated SLIPS surfaces that exhibited a 99% reduction in S. aureus adhesion with preservation of macrophage viability, phagocytosis, and bactericidal function. Notably, SLIPS modification of ePTFE prevents device infection after S. aureus challenge in vivo, while eliciting a significantly attenuated innate immune response. SLIPS-modified implants also decrease macrophage inflammatory cytokine expression in vitro, which likely contributed to the presence of a thinner fibrous capsule in the absence of bacterial challenge. SLIPS is an easily implementable technology that provides a promising approach to substantially reduce the risk of device infection and associated patient morbidity, as well as health care costs.