Creating biological nanomaterials using synthetic biology

Synthetic biology is a new discipline that combines science and engineering approaches to precisely control biological networks. These signaling networks are especially important in fields such as biomedicine and biochemical engineering. Additionally, biological networks can also be critical to the production of naturally occurring biological nanomaterials, and as a result, synthetic biology holds tremendous potential in creating new materials. This review introduces the field of synthetic biology, discusses how biological systems naturally produce materials, and then presents examples and strategies for incorporating synthetic biology approaches in the development of new materials. In particular, strategies for using synthetic biology to produce both organic and inorganic nanomaterials are discussed. Ultimately, synthetic biology holds the potential to dramatically impact biological materials science with significant potential applications in medical systems.     

Materials aging at the mesoscale: Kinetics of thermal,stress, radiation activations

The complexity of materials aging may be seen as a result of the interplay between several activation processes operating on multiple spatial and temporal scales. Though the disciplines involved may seem disparate at first, material aging fundamentally could be linked by the same set of underlying activations and responses of the system. We examine how recent studies of shear-induced deformation and rheological flow initiated in the soft-matter community can be leveraged to probe the mechanisms of radiation damage in nuclear materials. Bridging these two traditionally separate areas of research demonstrates the emerging notions of mesoscale science as a research frontier concerned with linking macroscale behavior to microscale processes in driven systems. We suggest the combining of microstructure-sensitive measurements with fundamental theories and mechanism-specific simulations is essential to addressing metastable materials responses of strongly activated states.     

Cell responses to physical forces,and how they inform the design of tissue-engineered constructs for bone repair: a review

The fields of biomaterials and bone tissue engineering continue to grow, due in part to new advances in materials science but also to the increasingly broad understanding of how the human body responds to implanted materials. For a long time the goal of the biomaterials scientist was to develop materials that supported healing and were biocompatible, but over time a better understanding of how the body responds to implanted materials has been achieved. The concept of mechanotransduction, which involves mechanical forces applied to the cell, the conversion of those forces into a biochemical signal, the transmission of signals to cells, and the resulting cell response, has blossomed over the past 20 years or so. Here we review how cells, specifically those of the skeletal system, respond to different types of physical forces, how these responses manifest themselves as changes and adaptations within the skeletal system, and how investigators go about evaluating these responses in the laboratory. We also review how these approaches and lessons learned inform the development of novel strategies for bone tissue engineering, toward healing bone defects with biomaterials.     

25th Anniversary Article: Polymer–Particle Composites: Phase Stability and Applications in Electrochemical Energy Storage

Polymer–particle composites are used in virtually every field of technology. When the particles approach nanometer dimensions, large interfacial regions are created. In favorable situations, the spatial distribution of these interfaces can be controlled to create new hybrid materials with physical and transport properties inaccessible in their constituents or poorly prepared mixtures. This review surveys progress in the last decade in understanding phase behavior, structure, and properties of nanoparticle‐polymer composites. The review takes a decidedly polymers perspective and explores how physical and chemical approaches may be employed to create hybrids with controlled distribution of particles. Applications are studied in two contexts of contemporary interest: battery electrolytes and electrodes. In the former, the role of dispersed and aggregated particles on ion‐transport is considered. In the latter, the polymer is employed in such small quantities that it has been historically given titles such as binder and carbon precursor that underscore its perceived secondary role. Considering the myriad functions the binder plays in an electrode, it is surprising that highly filled composites have not received more attention. Opportunities in this and related areas are highlighted where recent advances in synthesis and polymer science are inspiring new approaches, and where newcomers to the field could make important contributions.     

Hybrid nanomaterials through molecular and atomic layer deposition: Top down,bottom up,and in-between approaches to new materials

The ability to produce or alter materials to obtain drastically different or improved properties has been the driving goal of materials science since its inception. Combining multiple elements, compounds, or materials while maintaining the beneficial aspects of each constituent is a complex problem often involving highly interdisciplinary research. Hybrid materials, i.e. materials that incorporate organic and inorganic parts, have become popular in a variety of fields. Though not entirely new, the modern embodiment of hybrid materials has led to a large variety of new materials and techniques to produce them. One of the most recent being combination of atomic layer deposition (ALD), which produces inorganic materials, and molecular layer deposition (MLD), which produces organic materials. Furthermore, a variation on these techniques, commonly referred to as infiltration, has allowed for the modification of a variety of natural and synthetic polymers with surprising results related to their bulk mechanical properties. In this review three approaches are taken. First, hybrid materials through bottom-up combinations of ALD and MLD are reviewed, focusing on the process and properties of the resulting materials. Second, the modification of biomaterials through coating is discussed, and finally the relatively new concept of vapor phase infiltration is considered as a new and unique method to produce hybrid materials from a top down perspective.     

Acousto-optic tunable filter sidelobe analysis and reduction with telecentric confocal optics

The acousto-optic tunable filter (AOTF) has optical sidelobes that are due to the acoustic field produced by the transducer. These sidelobes were analyzed by wave-vector phase matching between the optical and acoustic fields, which correlated with measurements made with a TeO2 AOTF. A white-light point source was filtered and imaged, showing reasonably large and slowly decreasing sidelobes covering a large spectral range. This effect reduces the image quality of an AOTF system by producing faint secondary images of bright objects. The image quality can be improved with a telecentric confocal optical arrangement in which the angular shift of the sidelobes is greatly reduced, producing a much sharper image. This effect was also demonstrated experimentally with the point source.     

高分子科学中的计算机模拟

综述了计算机模拟在高分子科学中的发展和现状,介绍了它的研究方法及研究领域,并指出了它的发展方向。     

Microfluidic Templating of Spatially Inhomogeneous Protein Microgels

3D scaffolds in the form of hydrogels and microgels have allowed for more native cell‐culture systems to be developed relative to flat substrates. Native biological tissues are, however, usually spatially inhomogeneous and anisotropic, but regulating the spatial density of hydrogels at the microscale to mimic this inhomogeneity has been challenging to achieve. Moreover, the development of biocompatible synthesis approaches for protein‐based microgels remains challenging, and typical gelation conditions include UV light, extreme pH, extreme temperature, or organic solvents, factors which can compromise the viability of cells. This study addresses these challenges by demonstrating an approach to fabricate protein microgels with controllable radial density through microfluidic mixing and physical and enzymatic crosslinking of gelatin precursor molecules. Microgels with a higher density in their cores and microgels with a higher density in their shells are demonstrated. The microgels have robust stability at 37 °C and different dissolution rates through enzymolysis, which can be further used for gradient scaffolds for 3D cell culture, enabling controlled degradability, and the release of biomolecules. The design principles of the microgels could also be exploited to generate other soft materials for applications ranging from novel protein‐only micro reactors to soft robots.     

Controlled photonic manipulation of proteins and other nanomaterials

The ability to controllably handle the smallest materials is a fundamental enabling technology for nanoscience. Conventional optical tweezers have proven useful for manipulating microscale objects but cannot exert enough force to manipulate dielectric materials smaller than about 100 nm. Recently, several near-field optical trapping techniques have been developed that can provide higher trapping stiffness, but they tend to be limited in their ability to reversibly trap and release smaller materials due to a combination of the extremely high electromagnetic fields and the resulting local temperature rise. Here, we have developed a new form of photonic crystal "nanotweezer" that can trap and release on-command Wilson disease proteins, quantum dots, and 22 nm polymer particles with a temperature rise less than ~0.3 K, which is below the point where unwanted fluid mechanical effects will prevent trapping or damage biological targets.     

A review of additive manufacturing of metamaterials and developing trends

The concept of metamaterials originates from the proposal of left-hand materials with negative refractive index, followed by which, varieties of metamaterials with kinds of fantastic properties that cannot be found in natural materials, such as zero/negative Poisson’s ratio, electromagnetic/acoustic/thermal cloaking effect, etc., were come up with. According to their application fields, the metamaterials are roughly classified into four categories, electromagnetic metamaterials, acoustic metamaterials, thermal metamaterials, and mechanical metamaterials. By designing structures and arranging the distribution of materials with different physical parameters, the function of metamaterials can be realized in theory. Additive manufacturing (AM) technology provides a more direct and efficient way to achieve a sample of metamaterial and experiment verification due to the great advantages in fabricating complex structures. In this review, we introduce the typical metamaterials in different application situations and their design methods. In particular, we are focused on the fabrication of metamaterials and the application status of AM technology in them. Furthermore, we discuss the limits of present metamaterials in the aspect of design method and the disadvantages of existing AM technology, as well as the development tendency of metamaterials.     

Self-assemblies of linearly aligned diamond fillers in polysiloxane/diamond composite films with enhanced thermal conductivity

The relocation of diamond fillers was performed in polysiloxane-based composite films under different electric fields. The microscale diamond filler particles were dispersed by sonication in a prepolymer mixture of polysiloxane, followed by high-speed mixing. The homogeneous suspension was cast onto a polyamide spacer of microscale thickness and subjected to three different electric fields: AC, DC, and switched DC, before the mixture became cross-linked. Analysis revealed that self-assemblies of linearly aligned diamond fillers (LADFs) were fabricated in the composite film, connecting the film planes as bridges with different thicknesses depending on the applied electric field. Composites with assemblies of LADFs exhibited enhanced thermal conductivity and electrical insulation, and are attractive for application as thermal interface materials in the semiconductor industry.     

Acoustic methods for obtaining the pressure reflection coefficient from a buffer rod based measurement cell

The known acoustic methods for obtaining the pressure reflection coefficient from a buffer rod based measurement cell are presented, along with 2 new generic approaches for measuring the pressure reflection coefficient using 2 buffer rods enclosing the liquid to be characterized in a symmetrical arrangement. An acoustic transducer is connected to each of the buffer rods. The generic approaches are divided into a relative amplitude approach and a mixed amplitude approach. For the relative amplitude approach, families of 4, 5, or 6 echo signals can be used to obtain the pressure reflection coefficient. The mixed amplitude approach uses specific information about the transducers and/or the electronics sensitivities in receive mode to obtain the pressure reflection coefficient using families of 3, 4, 5, or 6 echo signals. Some of the new methods from the relative amplitude approach imply a reduced uncertainty relative to the previously known ABC method. The effect of the liquid attenuation, digitizer bit resolution, and the signal-to-noise ratio on the uncertainty characteristics of the pressure reflection coefficient are discussed, along with a discussion of the suitability of the various methods for different buffer materials.     

Kirigami-enabled self-folding origami

Self-folding of complex origami-inspired structures from flat states allows for the incorporation of a multitude of surface-related functionalities into the final 3D device. Several self-folding techniques have therefore been developed during the last few years to fabricate such multi-functional devices. The vast majority of such approaches are, however, limited to simple folding sequences, specific materials, or large length scales, rendering them inapplicable to microscale (meta)materials and devices with complex geometries, which are often made from materials other than the ones for which these approaches are developed. Here, we propose a mechanical self-folding technique that only requires global stretching for activation, is applicable to a wide range of materials, allows for sequential self-folding of multi-storey constructs, and can be downscaled to microscale dimensions. We combined two types of permanently deforming kirigami elements, working on the basis of either multi-stability or plastic deformation, with an elastic layer to create self-folding basic elements. The folding angles of these elements could be controlled using the kirigami cut patterns as well as the dimensions of the elastic layer and be accurately predicted using our computational models. We then assembled these basic elements in a modular manner to create multiple complex 3D structures (e.g., multi-storey origami lattices) in different sizes including some with microscale feature sizes. Moreover, starting from a flat state enabled us to incorporate not only precisely controlled, arbitrarily complex, and spatially varied micropatterns but also flexible electronics into the self-folded 3D structures. In all cases, our computational models could capture the self-folding behavior of the assemblies and the strains in the connectors of the flexible electronic devices, thereby guiding the rational design of our specimens. This approach has numerous potential applications including fabrication of multi-functional and instrumented implantable medical devices, steerable medical instruments, and microrobots.     

A review of computational phononics: the bulk,interfaces, and surfaces

Broad-based interest in microscale heat transport in novel materials, engineered phononic materials, metamaterials, and their relevant systems has created significant demand for computational approaches to aid in investigation and design of materials that support phonons. This review describes the significant improvements that have been made and new needs that have emerged for capabilities associated with the computability of phonons. The technical scope encompasses issues, especially relevant to bulk, interface, and surface effects. Traditional approaches such as molecular dynamics, lattice dynamics, and Boltzmann transport equation continue to advance the field but are frequently extended to the limits of their physical or numerical validity. New materials beyond traditional group-IV, III–V, and II–VI semiconductors, phenomena that critically depend on scattering, such as in low-dimensional nanostructures, materials with interior surfaces and defects, and in high-temperature environments, continue to push these limits. The basis for the traditional calculation methods shares their origins with the earliest theories for thermal transport, acoustic waves in solids, spectroscopy and dynamical crystal lattices. These will remain in wide use in the future. But computing methods and the accompanying advances in microprocessor technologies have enabled growth of phonon computing models and methods in sophistication, accuracy, fidelity and complexity that will lead to fundamental impacts beyond the classic types of problems for which they were developed. With their increasingly integrated use for design and research, the myriad developments that presently exist must be understood for their suitability for certain applications and their ability to aid in the pursuit of new technologies.     

Point Estimation of the Central Orientation of Random Rotations

Data as three-dimensional rotations have application in computer science, kinematics, and materials sciences, among other areas. Estimating the central orientation from a sample of such data is an important problem, which is complicated by the fact that several different approaches exist for this, motivated by various geometrical and decision-theoretical considerations. However, little is known about how such estimators compare, especially on common distributions for location models with random rotations. We examine four location estimators, three of which are commonly found in different literatures and the fourth estimator (a projected median) is newly introduced. Our study unifies existing literature and provides a detailed numerical investigation of location estimators for three commonly used rotation distributions in statistics and materials science. While the data-generating model influences the best choice of an estimator, the proposed projected median emerges as an overall good performer, which can be suggested without particular distributional assumptions. We illustrate the estimators and our findings with data from a materials science study by approximating the central orientation of cubic crystals on the microsurface of a metal. Accompanying supplementary materials are available online.     

Exploration and Exploitation of Water in Colloidal Crystals

Water on solid surfaces is ubiquitously found in nature, in most cases due to mere adsorption from ambient moisture. Because porous structures have large surfaces, water may significantly affect their characteristics. This is particularly obvious in systems formed by separate particles, whose interactions are strongly influenced by small amounts of liquid. Water/solid phenomena, like adsorption, condensation, capillary forces, or interparticle cohesion, have typically been studied at relatively large scales down to the microscale, like in wet granular media. However, much less is known about how water is confined and acts at the nanoscale, for example, in the interstices of divided systems, something of utmost importance in many areas of materials science nowadays. With novel approaches, in‐depth investigations as to where and how water is placed in the nanometer‐sized pores of self‐assembled colloidal crystals have been made, which are employed as a well‐defined, versatile model system with useful optical properties. In this Progress Report, knowledge gained in the last few years about water distribution in such nanoconfinements is gathered, along with how it can be controlled and the consequences it brings about to extract new or enhance existing material functionalities. New methods developed and new capabilities of standard techniques are described, and the water interplay with the optical, chemical, and mechanical properties of the ensemble are discussed. Some lines for applicability are also highlighted and aspects to be addressed in the near future are critically summarized.     

Combinatorial growth of multinary nanostructured thin functional films

The rapid generation of material libraries with multidimensional gradients is important for the discovery of new functional materials. Here we report an integrated fabrication scheme, based on glancing angle physical vapor deposition, to form a thin-film materials library with controlled variations in nanoshape, multinary composition, and oxidation state on a single large area substrate. We demonstrate the versatility of the method by growing an octonary materials system, which we characterize with high-throughput methods, and reveal variations in several physico-chemical properties. Among others, we examine the materials library in the frame of the oxygen evolution reaction and show that nanostructuring leads to NiO clusters that are active towards such a reaction. Our scheme can be readily extended to include more starting elements, and can be transferred to other deposition methods, making this an adaptable and versatile platform for combinatorial materials science.     

声学超构材料技术实用化的进展

声学超构材料是当前声学和材料学一个热门的研究领域.声学超构材料可定义为:通过对材料在特征物理尺度上进行人工设计制备,使其具有超越常规材料的声学性能的一种人工序构的复合材料.其亚波长特性、超常声学性能以及颠覆性应用的可能吸引了学界和工程界的关注.21世纪以来,随着增材制造技术的发展,声学超构材料的实验室加工与制备问题得以...