Combinatorial solid-state chemistry of inorganic materials

Throughout history, scientists and engineers have relied on the slow and serendipitous trial-and-error process for discovering and developing new materials. In contrast, an emerging theme in modern materials science is the notion of intelligent design of materials. Pioneered by the pharmaceutical industry and adapted for the purposes of materials science and engineering, the combinatorial approach represents a watershed in the process of accelerated discovery, development and optimization of materials. To survey large compositional landscapes rapidly, thousands of compositionally varying samples may be synthesized, processed and screened in a single experiment. Recent developments have been aided by innovative rapid characterization tools, and by advanced materials synthesis techniques such as laser molecular beam epitaxy which can be used to perform parallel-processed design and control of materials down to the atomic scale. Here we review the fast-growing field of combinatorial materials science, with an emphasis on inorganic functional materials.     

From biomedical-engineering research to clinical application and industrialization

The rising costs and aging of the population due to a low birth rate negatively affect the healthcare system in Japan. In 2011, the Council for Science and Technology Policy released the 4th Japan’s Science and Technology Basic Policy Report from 2011 to 2015. This report includes two major innovations, ‘Life Innovation’ and ‘Green Innovation’, to promote economic growth. Biomedical engineering research is part of ‘Life Innovation’ and its outcomes are required to maintain people’s mental and physical health. It has already resulted in numerous biomedical products, and new ones should be developed using nanotechnology-based concepts. The combination of accumulated knowledge and experience, and ‘nanoarchitechtonics’ will result in novel, well-designed functional biomaterials.

This focus issue contains three reviews and 19 original papers on various biomedical opics, including biomaterials, drug-delivery systems, tissue engineering and diagnostics. We hope that it demonstrates the importance of collaboration among scientists, engineers and clinicians, and will contribute to the further development of biomedical engineering.     

Progress of ecomaterials toward a sustainable society

This review paper provides an overview of research activities in Japan in the field of ecomaterials. Ecomaterials are the materials which are used in the life-cycle design of products aimed at reducing environmental impact. Ecomaterials research includes the fields of ‘materials containing less hazardous substances’, ‘materials with green environmental profiles’, ‘materials with a higher potential for recycling’, and ‘materials with higher resource productivity’. They are evolving from being an idealised concept to produce real solutions for materials selection. As part of this trend, multi-performance capability, as required for usage including processability, is becoming an important problem to be solved by materials scientists and engineers.     

Tapping into hidden potential

University departments are going to great lengths to convince potential new recruits that materials science and engineering is for them. In addition to the traditional showcase ‘Open Day’ for pre-university students, outreach staff are facilitating hands-on workshops, problem-solving seminars, and research ‘tasters’ for a far wider audience. High school students are shown how materials science spans traditional subject divides, while teachers receive tips on how to integrate materials-oriented examples into the curriculum. The idea is to show would-be electrical engineers, doctors, and chemists that a degree in materials science could lead to an equally exciting and fulfilling career developing optical materials, biomedical implants, or sensor technology.As the academic year begins, students enrolling at universities worldwide have a treat in store. There is a course on offer that could explain how to cut the cost of street lighting, improve the mobility of an aging population, reduce the amount of waste sent to landfill, speedup electronic communication, and detect the first signs of a biological terrorist attack. No surprises, then, for guessing that this course is materials science and engineering. But teenagers versed in the language of physics, chemistry, biology, and engineering may not have made the connection. And there in lies the root of a possible recruitment problem.     

New semiconductors with new combinations of properties

Tetrahedral semiconductors have so dominated both research and applications that most workers scarcely realise that non-tetrahedral semiconductors even exist, let alone that they are extremely numerous and can show interesting and unusual combinations of properties. It is suggested that chemical bonding arguments can be used to categorise these compounds in terms of energy gap, and even, perhaps, via a new concept: ‘aniso-electronic substitution’ (i.e. of donors or acceptors compensated for by ordered point defects), to optimise the choice of band structure and density of states (the latter being particularly important for improving thermoelectric devices, and not without interest for signal handling and control devices since carrier mobility could be increased). A very wide range of materials is discussed including ‘electron deficient’ boride and aluminide semiconductors.There could be many kinds of application for semiconductors that are rather different to the conventional tetrahedral materials: in lighting, in thermoelectric cooling and power generation, and in sensors, as well as in more familiar logic and control devices. This speculative paper attempts to indicate some of the range of materials and properties that could be on offer with the aim of encouraging academic scientists to work on them; industry is not likely to investigate such unfamiliar territory — yet.     

Membranes fit for a revolution

Within the next few decades we will be driving cars powered by material ‘lumps’ that have no moving parts. Early fuel cell vehicles (FCVs), outriders of the hydrogen economy, are already with us, but only as costly concept prototypes. Affordable family FCVs remain out of reach, largely because a single crucial component at the heart of the ‘alternative engine’ has been exotic, easily damaged and, in common with other fuel cell materials, too expensive. With the emergence of a potential mass market, new answers are needed and it is falling to material scientists to supply them.     

Elasticity, strength and resilience: A comparative study on mechanical signatures of α-Helix, β-sheet and tropocollagen domains

In biology, structural design and materials engineering is unified through formation of hierarchical features with atomic resolution, from nano to macro. Three molecular building blocks are particularly prevalent in all structural protein materials: alpha helices (AHs), beta-sheets (BSs) and tropocollagen (TC). In this article we present a comparative study of these three key building blocks by focusing on their mechanical signatures, based on results from full-atomistic simulation studies. We find that each of the basic structures is associated with a characteristic material behavior: AH protein domains provide resilience at large deformation through energy dissipation at low force levels, BS protein domains provide great strength under shear loading, and tropocollagen molecules provide large elasticity for deformation recovery. This suggests that AHs, BSs, and TC molecules have mutually exclusive mechanical signatures. We correlate each of these basic properties with the molecule’s structure and the associated fundamental rupture mechanisms. Our study may enable the use of abundant protein building blocks in nanoengineered materials, and may provide critical insight into basic biological mechanisms for bio-inspired nanotechnologies. The transfer towards the design of novel nanostructures could lead to new multifunctional and mechanically active, tunable, and changeable materials.     

Selection of composite materials and manufacturing routes for cost-effective performance

A study has been conducted to estimate the costs of manufacture of a simple component in a number of different composite materials and by different manufacturing routes. The materials and routes selected span the range of composites from those appropriate for general engineering applications to aerospace. A simple methodology is introduced for a comparison on the basis of cost-performance efficiency. It is demonstrated that more economic solutions may often be realised by choice of ‘expensive’ carbon rather than ‘cheaper’ E-glass as the reinforcing fibre.     

生物机械工程研究进展

论述了生物机械工程的重要意义、研究现状、发展趋势、存在问题及对策，旨在推动我国生物机械工程的研究和学术地位的确立，推动生物医学工程学的进步，提高人民的健康水平。     

Controlling Cell Behavior Through the Design of Polymer Surfaces

Polymers have gained a remarkable place in the biomedical field as materials for the fabrication of various devices and for tissue engineering applications. The initial acceptance or rejection of an implantable device is dictated by the crosstalk of the material surface with the bioentities present in the physiological environment. Advances in microfabrication and nanotechnology offer new tools to investigate the complex signaling cascade induced by the components of the extracellular matrix and consequently allow cellular responses to be tailored through the mimicking of some elements of the signaling paths. Patterning methods and selective chemical modification schemes at different length scales can provide biocompatible surfaces that control cellular interactions on the micrometer and sub‐micrometer scales on which cells are organized. In this review, the potential of chemically and topographically structured micro‐ and nanopolymer surfaces are discussed in hopes of a better understanding of cell–biomaterial interactions, including the recent use of biomimetic approaches or stimuli‐responsive macromolecules. Additionally, the focus will be on how the knowledge obtained using these surfaces can be incorporated to design biocompatible materials for various biomedical applications, such as tissue engineering, implants, cell‐based biosensors, diagnostic systems, and basic cell biology. The review focusses on the research carried out during the last decade.     

The history and science of the artificial

This is the concluding chapter from a new book, The Evolution of Designs; Biological Analogy in Architecture and the Applied Arts, recently published by Cambridge University Press©. The book reviews the history of analogies made between the design of artefacts and the ‘design’ of organisms, since the beginnings of biology as a scientific subject around 1800. The analogies are shown to be conducive to a functionalist fallacy — the idea that the utilitarian functions of artefacts serve to define their forms in a deterministic way — and conducive to a historicist fallacy — that the ‘evolution’ of artefacts follows some necessary historical sequence of development, which is not under the control of men. The book ends by asking ‘What remains that is useful and true, in biological analogies with design?’     

Assembling DNA into Advanced Materials: From Nanostructured Films to Biosensing and Delivery Systems

The past decade has witnessed a rapid expansion in the design and assembly of engineered materials for biological applications. However, such applications place limitations on the molecular building blocks that can be used. Requirements for polymer‐based building blocks include biocompatibility, biodegradability, and stimuli‐responsive behavior. Many traditional polymers used in materials science are limited in at least one of these areas, so new polymers need to be explored. As we outline here, DNA is one such polymer that shows promise in developing the next generation of ‘smart’ materials for biomedical and diagnostic applications.     

A sequential approximation method using neural networks for engineering design optimization problems

There are three characteristics in engineering design optimization problems: (1) the design variables are often discrete physical quantities; (2) the constraint functions often cannot be expressed analytically in terms of design variables; (3) in many engineering design applications, critical constraints are often ‘pass–fail’, ‘0–1’ type binary constraints. This paper presents a sequential approximation method specifically for engineering optimization problems with the three characteristics. In this method a back-propagation neural network is trained to simulate a rough map of the feasible domain formed by the constraints using a few representative training data. A training data point consists of a discrete design point and whether this design point is feasible or infeasible. Function values of the constraints are not required. A search algorithm then searches for the optimal point in the feasible domain simulated by the neural network. This new design point is checked against the true constraints to see whether it is feasible, and is then added to the training set. The neural network is trained again with this added information, in the hope that the network will better simulate the boundary of the feasible domain of the true optimization problem. Then a further search is made for the optimal point in this new approximated feasible domain. This process continues in an iterative manner until the approximate model locates the same optimal point in consecutive iterations. A restart strategy is also employed so that the method may have a better chance to reach a global optimum. Design examples with large discrete design spaces and implicit constraints are solved to demonstrate the practicality of this method.     

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.     

Novel Deposition System Designs for Thin Film Materials Research

Modern thin film deposition systems must be designed for maximum flexibility with respect to their physical footprint as well as the range of processes and materials they can support. Increasingly disciplines that have not traditionally utilized thin film deposition, such as biology and medicine, are demanding that materials never intended for vacuum be applied on a molecular level. Multi‐user nanofabrication facilities are tasked to adapt and accommodate new requirements while also making room for new tools in environments which may already be over crowded. New system designs, mindful of these challenges, are discussed.     

Wave packet engineering using a phase-programmable femtosecond optical source

Abstract

A new optical telecommunication method combining time and frequency domain multiplexing is proposed using phase-controlled femtosecond pulses. Each pulse in a pulse train can be used as a data packet with data bits in the frequency domain. We call the new principle ‘wave packet engineering’, which adjusts the amplitude and phase of the wave function in device materials arbitrarily by controlling the spectral phase of femtosecond pulses. The optical phase-to-amplitude converter is demonstrated with organic dye molecules, in which the phase information in the phase-modulated pulses can be demodulated into the luminescence intensity. The luminescence intensity from cyanine dye molecules is observed to be chirp dependent, and is explained quantum mechanically in terms of coherent population transfer. The design principle of the device using semiconductor coupled quantum nanostructures is also discussed in terms of wave packet engineering.     

Fully stressed frame structures unobtainable by conventional design methodology

A structure is said to be fully stressed if every member of the structure is stressed to its maximum allowable limit for at least one of the loading conditions. Fully stressed design is most commonly used for small and medium size frames where drift is not a primary concern. There are several potential methods available to the engineer to proportion a fully stressed frame structure. The most commonly used methods are those taught to all structural engineering students and are very easy to understand and to implement. These conventional methods are based on the intuitive idea that if a member is overstressed, it should be made larger. If a member is understressed, it can be made smaller, saving valuable material. It has been found that a large number of distinct fully stressed designs can exist for a single frame structure subjected to multiple loading conditions. This study will demonstrate that conventional methods are unable to converge to many, if not most, of these designs. These unobtainable designs are referred to as ‘repellers’ under the action of conventional methods. Other, more complicated methods can be used to locate these repelling fully stressed designs. For example, Newton's method can be used to solve a non‐linear system of equations that defines the fully stressed state. However, Newton's method can be plagued by divergence and also by convergence to physically meaningless solutions. This study will propose a new fully stressed design technique that does not have these problems. Copyright © 2001 John Wiley & Sons, Ltd.     

Change in cell adhesion property on cytocompatible interface using phospholipid polymer grafted with poly( , -lactic acid) segment for tissue engineering

Tissue engineering is a multi-disciplinary science that utilizes basic principles from materials engineering and molecular biology to reconstruct tissues from polymer matrices and cellular components. Artificial skins were well known as one of the concrete examples. Technological innovation of the tissue engineering must be contributed to improve quality of life. From the viewpoint, design of cytocompatible materials for tissue engineering would be the most important candidate to reconstruct tissue. 2-Methacryloyloxyethyl phosphorylcholine (MPC), n-butyl methacrylate, and polylactic acid (PLA) macromonomer were polymerized for the preparation of cytocompatible interface. The polymer may involve following novel properties: (i) cytocompatibility by phospholipid groups, and (ii) enhancement of cell adhesion by PLA segment. The results of X-ray photoelectron spectroscopy showed the MPC unit and PLA segment on the membrane, which was prepared by dip coating. The surface mobility by contacting water was estimated with static contact angle measurement. The contact angle by water decreased after contact with water due to the chain rearrangement of hydrophilic MPC unit. Fibroblast cells adhesion and protein adsorption on the membranes were studied. The number of cell adhesion and cell proliferation on the membrane was well correlated with each other. Furthermore, the number of cell adhesion was proportional to the PLA macromonomer (MaPLA) composition. The adherent cell morphology showed round shape, because of the existence of MPC unit. However, the cell morphology would be spread after the cell proliferation. These findings suggest that the change in the polymer composition by combination of MPC and MaPLA could regulate the number of cell adhesion and the morphology.     

Continuous Taguchi—a model-based approach to Taguchi's ‘quality by design’ with arbitrary distributions

Statistical experimental design has been used in ‘off-line’ quality control to determine the optimal settings for a system even when the mathematical model is known. Taguchi demonstrated how signal-to-noise ratios could be used to improve the performance of a system through variance minimization. However, these statistical methods often do not use the full distribution information that may be available. Proposed in this paper is an extension and complement to Taguchi's use of experimental design and signal-to-noise ratios for known system models. The use of a probability transformation method with the mathematical system model will allow designers to perform parameter and tolerance design simultaneously using a method of ‘fast integration’. The result is a new method in the field of ‘quality by design’, which we call continuous Taguchi, that can handle both linear and non-linear systems, with components of any distribution type, with or without correlation of the variables. In addition, an interpretation of Taguchi's classification of factors is given in the context of our full distribution method. © 1998 John Wiley & Sons, Ltd.     

Aleatory architectures

We discuss new approaches and concepts at the intersection of granular materials research and architecture/structural engineering that are based on stochastic (re-) configuration of individual structural elements. These approaches, which we term aleatory architectures, suggest that building materials and components can have their own ‘agency’—that they can be designed to adapt and to find their own responses to structural or spatial contexts. Here we introduce some of the key ideas and ask: Can there be design by disorder? What are the possibilities of material agency? Can we develop a vocabulary of concepts to interpret various orderings of chance? Several papers in this Topical Collection then investigate these questions in more detail from a range of different scientific and architectural perspectives.