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Nature produces materials using available molecular building blocks following a bottom-up approach. These materials are formed with great precision and flexibility in a controlled manner. This approach offers the inspiration for manufacturing new artificial materials and devices. Synthetic artificial materials can find many important applications ranging from personalized therapeutics to solutions for environmental problems. Among these materials, responsive synthetic materials are capable of changing their structure and/or properties in response to external stimuli, and hence are termed "smart" materials. Herein, this review focuses on alginate-based smart materials and their stimuli-responsive preparation, fragmentation, and applications in diverse fields from drug delivery and tissue engineering to water purification and environmental remediation. In the first part of this report, we review stimuli-induced preparation of alginate-based materials. Stimuli-triggered decomposition of alginate materials in a controlled fashion is documented in the second part, followed by the application of smart alginate materials in diverse fields. Because of their biocompatibility, easy accessibility, and simple techniques of material formation, alginates can provide solutions for several present and future problems of humankind. However, new research is needed for novel alginate-based materials with new functionalities and well-defined properties for targeted applications.

The rapid development of biophotonics and biomedical sciences makes a high demand on photonic structures to be interfaced with biological systems that are capable of manipulating light at small scales for sensitive detection of biological signals and precise imaging of cellular structures. However, conventional photonic structures based on artificial materials (either inorganic or toxic organic) inevitably show incompatibility and invasiveness when interfacing with biological systems. The design of biophotonic probes from the abundant natural materials, particularly biological entities such as virus, cells and tissues, with the capability of multifunctional light manipulation at target sites greatly increases the biocompatibility and minimizes the invasiveness to biological microenvironment. In this review, advances in biophotonic probes for bio-detection and imaging are reviewed. We emphatically and systematically describe biological entities-based photonic probes that offer appropriate optical properties, biocompatibility, and biodegradability with different optical functions from light generation, to light transportation and light modulation. Three representative biophotonic probes, i.e., biological lasers, cell-based biophotonic waveguides and bio-microlenses, are reviewed with applications for bio-detection and imaging. Finally, perspectives on future opportunities and potential improvements of biophotonic probes are also provided., The emerging biological entities-based biophotonic probes, such as biological lasers, biophotonic waveguides, and bio-microlenses, have opened up an entirely new window for bio-detection and imaging with high biocompatibility.

Japanese cedar (Cryptomeria japonica) wood is widely used as a traditional construction material in Japan. The relationship between an individual’s perceived comfort level and a preference for Japanese cedar wood interiors is of interest. We compared volunteers’ physiological responses and subjective evaluations of wooden dwelling spaces with different wood materials: planed Japanese cedar lumber, or printed grain resin sheet overlay boards. Eighty-three subjects were asked to stay in each room for 30 min. We evaluated salivary stress markers, blood pressure, the profile of mood states-brief form (POMS), and a questionnaire that used the semantic differential method to evaluate the subjects’ feeling state for both rooms. The concentrations of the volatile organic compounds in both rooms were also quantified after the experiment. The results demonstrated that the subjects’ evaluation of each room was highly dependent on their preference; each room was evaluated more positively by subjects who preferred it. Although the subjects’ feelings were also influenced by their preference, the room with Japanese cedar did not elicit negative feelings, even from the subjects who disliked it. The subjects’ physiological responses were totally independent of their preferences. Their blood pressure decreased in the Japanese cedar room, and their salivary alpha-amylase activity was repressed in both rooms. These results indicated that the subjective evaluations were influenced in part by the subjects’ preferences, while their physiological responses were not affected. Regardless of which room the subjects preferred, the Japanese cedar room reduced the subjects’ blood pressure compared to the room with artificial materials.

Penrose-like tilings with higher-order rotational symmetry are discussed. Two new examples of recursive rhombic tilings with 7-fold symmetry are derived. The entangled inflation/deflation rules cyclically permute the characteristic 7-fold patches and provide a possibility of expanding the tilings up to infinity without additional ad hoc rearrangements. The derived tilings are self-similar and fully coincide with themselves after inflations and deflations. The main structural motif is presented by repeatedly appearing seven-pointed stars surrounded by similar seven-pointed stars. Characteristic patches demonstrate mutual metamorphoses. The patches cyclically morph each into another while the tilings as a whole remain self-consistent. The results of the study can be used for the development of new artificial materials with heptagonal symmetry.

The deformation and mechanical responses of rocks are prime concern in development of varieties of civil and mining engineering structures. The deformation and mechanical properties of both natural and artificial materials are strongly depend on mineral constituents and their arrangements, temperatures and pressures, stress rates and structural anisotropy. This study elaborates an understanding of structural anisotropy, compression rates and mechanical attributes relationship in rocks with specific examples of deformed rocksalt. The cubical samples (5X5X5 cm3) with three kinds of structural anisotropy were subjected to quasistatic compressive stress at rates 0.00035 MPa/min, 0.0035 MPa/min, 0.035 MPa/min, 0.35 MPa/min, 3.5MPa/min, 5 MPa/ min, 7MPa/min and 9 MPa/min on servo-controlled Material Testing System (MTS). The stress-strain curves prepared from deformation of rocksalt’s samples under different rates of compressions are used to determine major mechanical parameters viz., strengths, strains, and modulus of elasticity. A micromechanical en-echelon crack array model is proposed to explain the influence of structural anisotropy on deformation patterns and mechanical properties of rocksalt.According to the proposed model the deformation progresses due to different proportional contributions of tensile and shear crack arrays under the influence of structural anisotropy. The control of structural anisotropy loses with respect to increment in rate of compression with enhance contribution of shear crack arrays in comparison to tensile crack arrays and ultimately fails in shear where the structurally anisotropic rock show isotropic behaviour.

Metamaterials are artificial materials with emerging physical properties that go well beyond those of their individual constituents, providing interesting opportunities to tailor interactions between waves and matter. This article provides an overview of recent research activity in electromagnetics, nano-optics, acoustics and mechanics, showing how suitably tailored meta-elements and their arrangements open exciting venues to manipulate and control waves in unprecedented ways. Theoretical and experimental efforts to realize metamaterials for scattering suppression, nanostructures and metasurfaces to control wave propagation and radiation, large nonreciprocity in bulk materials without magnetism, giant nonlinear responses in properly tailored metasurfaces, and metasurfaces with balanced loss and gain are discussed. Physical insights into the exotic phenomena behind the metamaterial responses, new devices based on these concepts, and their impact on technology are also discussed.

Cranioplasty for recovering skull defects carries the risk for a number of complications. Various materials are used, including autologous bone graft, metallic materials, and non-metallic materials, each of which has advantages and disadvantages. If the use of autologous bone is not feasible, those artificial materials also have constraints in the case of complex anatomy and/or irregular defects. This study used metal 3D-printing technology to overcome these existing drawbacks and analyze the clinical and mechanical performance requirements. To find an optimal structure that satisfied the structural and mechanical stability requirements, we evaluated biomechanical stability using finite element analysis (FEA) and mechanical testing. To ensure clinical applicability, the model was subjected to histological evaluation. Each specimen was implanted in the femur of a rabbit and was evaluated using histological measurements and push-out test. We believe that our data will provide the basis for future applications of a variety of unit structures and further clinical trials and research, as well as the direction for the study of other patient-specific implants.

Salt weathering is one of the most aggressive worldwide weathering processes severely affecting natural and artificial materials to unlimited weathering grades. This impact is highly considered for the highly ranked archeological sites. So, this paper aims to examine the durability of the huge quarries of the Eocene nummulitic limestone that had been widely used for construction and/or carving of the Pharaonic archeological sites in Egypt, e.g., the Giza Pyramids and the Great Sphinx. The durability had been examined for this limestone before and after applying three resins prepared in single or combined states and at variable limits of concentration. These resins are namely ethyl silicate, Premal-AC33, and Paraloid 80. Petrographic, mineralogical, physical, and mechanical properties and durability investigations had been conducted for this limestone before treatment with such resins. Treatment has been conducted through two regimes, namely repeated brushing and total immersion using each resin at each level of concentration. Examining samples’ surface color after treatment and resin’s penetration depth, as well as rock’s geotechnical properties’, limits using ultrasonic waves, and sample’s salt susceptibility index (SSI) using Mercury intrusion porosimetry (MIP) has been considered for each resin at each level of concentration. The data had been discussed indicating that Paraloid B-80 used in a single state dissolved in 300 ml acetone or in combination with ethyl silicate dissolved in ethyl alcohol are the best for increasing durability of such nummulitic limestone.

The field of rock mechanics is concerned with the response of rocks to the forces acting on them, characterizing this behaviour in specific environments and under varying loading conditions. This review discusses the suitability of current mechanical testing methods for inhomogeneous rock bodies, with a specific focus on the use of artificial samples in place of real rocks in these tests. The use of artificial materials such as cement, resins and sand-based mixtures is reviewed, as is the manufacture of three-dimensionally printed samples. The benefits and drawbacks of using such specimens in mechanical tests are discussed, and the validity of their simulation of real rock discussed. There is evidence that 3D printed samples have the advantage of overcoming the problems of specimen reproducibility and also make possible the ability to test the response of specific defects to loading. There is thus great potential for the use of 3D printing in this field. However, the review concludes that further post-processing and careful thought about the materials used must be carried out to ensure that printed samples are of adequate strength and brittleness to accurately simulate real rocks.

The authors discuss the testing of periodic materials and structures via noise spectroscopy as an alternative to frequency sweep spectral analyzers, and the presented procedure employs the various advantages offered by a wide spectrum signal a Generally, noise spectroscopy tests are carried out to verify the behaviour of the response of periodic structures, and the related objective consists in recording the properties of microscopic structures in natural and artificial materials. The aim is to propose and verify a high-precision metrological method utilizable for the investigation of structures and materials in the frequency range between 100 MHz and 10 GHz; this paper therefore characterizes the design of a suitable measuring technique based on noise spectroscopy. In this context, the applied equipment is also shown to complement the underlying theoretical analysis.

Mechanical responsiveness in many plants is produced by helical organizations of cellulose microfibrils. However, simple mimicry of these naturally occurring helical structures does not produce artificial materials with the desired tunable actuations. Here, we show that actuating fibres that respond to solvent and vapour stimuli can be created through the hierarchical and helical assembly of aligned carbon nanotubes. Primary fibres consisting of helical assemblies of multiwalled carbon nanotubes are twisted together to form the helical actuating fibres. The nanoscale gaps between the nanotubes and micrometre-scale gaps among the primary fibres contribute to the rapid response and large actuation stroke of the actuating fibres. The compact coils allow the actuating fibre to rotate reversibly. We show that these fibres, which are lightweight, flexible and strong, are suitable for a variety of applications such as energy-harvesting generators, deformable sensing springs and smart textiles.

In the past decade, artificial materials with unusual wave interactions have significantly evolved and matured. In honour of the tenth anniversary of the premiere metamaterials conference, we look at the directions in which this field is evolving, and its impact on technology.

The remarkable processes that characterize living organisms, such as motility, self-healing and reproduction, are fuelled by a continuous injection of energy at the microscale. The field of active matter focuses on understanding how the collective behaviours of internally driven components can give rise to these biological phenomena, while also striving to produce synthetic materials composed of active energy-consuming components. The synergistic approach of studying active matter in both living cells and reconstituted systems assembled from biochemical building blocks has the potential to transform our understanding of both cell biology and materials science. This methodology can provide insight into the fundamental principles that govern the dynamical behaviours of self-organizing subcellular structures, and can lead to the design of artificial materials and machines that operate away from equilibrium and can thus attain life-like properties. In this Review, we focus on active materials made of cytoskeletal components, highlighting the role of active stresses and how they drive self-organization of both cellular structures and macroscale materials, which are machines powered by nanomachines. The field of active matter studies how internally driven motile components self-organize into large-scale dynamical states and patterns. This Review discusses how active matter concepts are important for understanding cell biology, and how the use of biochemical components enables the creation of new inherently non-equilibrium materials with unique properties that have so far been mostly restricted to living organisms.

An approach to create new artificial materials with hierarchical structures and tailored properties using a layer-by-layer assembly of two-dimensional (2D) oxide nanosheets is demonstrated. 2D nanosheets have remarkable potential as building blocks for tailoring fusion materials combined with a range of foreign materials such as organic molecules, gels, polymers, and inorganic and metal nanoparticles. The ability to create functionalized, 2D hierarchical systems will lead to various applications in optoelectronics, spinelectronics, energy and environment technologies.

Bone defect caused by injury, infection, tumor and congenital diseases is one of the most common diseases in clinical orthopaedics. Bone grafts are necessary when self-healing is not effective during the recovery. Preparation of ideal bone substitutes with good biocompatibility and biodegradability to repair bone defects has become the focus. So far artificial materials used in hard tissue repair and reconstruction most notably are metals and their alloys, then the ceramic materials and their composite materials. From the perspective of mechanical properties, metals have some advantages, but corrosion issue and stress shielding of metal have baffled scientists through the age and have been long searched for solution. The elastic modulus of ceramic is more close to the natural bone compared to metal while the improvement of brittleness has been always the emphasis for clinical use. Therefore, development of materials of proper mechanical properties without affecting biological compatibility has become a significant subject.

Recent research on manipulating the speed of light has established the possibility of bringing down the speed of light to a value that can be challenged by a humble bullock cart. The processes that influence the speed of light in natural and artificial materials have been investigated in depth, leading to the design of specific techniques to slow down and even store light in appropriate medium at room temperature. We introduce here the basic science of slow-light propagation in materials and artificial structures such as photonic crystals and highlight the important milestones in research on this fascinating frontier. � 2013 Indian Academy of Sciences.

Bioinspired surfaces with special wettability have rapidly emerged at the forefront of materials research. What is behind biological surfaces with special wettability, and how can we realize special wettability properties for artificial materials? This article describes how the interplay between unique multiscale (micro- and nanoscale) structures of biological surfaces and intrinsic material properties plays a crucial role in achieving the desired wettability and functionalities. Taking inspiration from natural surfaces, researchers have designed and created novel interfacial materials with versatile special wettability, such as superantiwetting surfaces (superhydrophobic and superoleophobic), smart switchable surfaces, and water collecting surfaces.

This article is devoted to thermophysical studies of a multifunctional cover consisting of natural and artificial materials of a 2.8 m thick near-surface repository. The objectives were to determine the maximum depth of the frost zone and to evaluate the changes of the thermophysical properties of natural materials comprising the cover. The analysis showed that the depth of the frost zone does not drop below 0.6 m. The change of the thermophysical properties of the building materials used for a multifunctional cover is manifested as a decrease in the rate of advance of the temperature field. The thermal insulation properties of the repository are more than adequate – for total cover thickness 2.8 m the depth of the frost zone is 0.6 m.

We report two cases of successful use of negative pressure wound therapy (NPWT) to control of left ventricular assist device (LVAD)-related mediastinitis. It is difficult to treat mediastinitis in patients who have undergone LVAD implantation, because it is impossible to remove the infected artificial materials from the mediastinal space. This report indicates that NPWT might become the preferred therapeutic option for control of mediastinitis in patients who have undergone LVAD implantation.

This study investigates the performance of artificial materials used for erosion control on steep slopes under high rainfall intensity. Soil samples were laid on a 300 × 100 cm platform inclined at either 35° or 45°, after which the soil was covered with various materials and subjected to a rainfall intensity of 130 mm/h for an hour. A wooden-block net covered with a jute net resulted in the greatest erosion resistance, providing 83% resistance at 35° and 76% at 45°. On the 35° slope, the artificial materials showed relatively good erosion resistance. As the slope was raised to 45°, some of the materials did not attach effectively to the soil surface. Thus, the runoff velocity increased and erosion became severe. For optimum erosion resistance, the material used to protect soil must attach to the soil surface well and have structural properties, such as a high coverage ratio to reduce the impact of rainfall on the soil and uniformly distributed transverse structures to reduce runoff energy and trap soil.

This study examined the effects of contact with wood on the living human body using a physiological index and subjective evaluation. Consecutive blood pressure measurements were used as the physiological index, and sensory evaluation using the semantic differential (SD) method was used for subjective evaluation. Consideration was also given to cases in which materials were cooled and heated as well as kept at room temperature, to eliminate the effects of heat flux due to differences in thermal conductivity between wood and other materials. It was found that contact with wood produced coarse/natural sensations, with no associated increase in systolic blood pressure. Contact with cold wood created subjectively dangerous/uncomfortable but still coarse/natural sensations, also with no associated increase in blood pressure; therefore, there was no correspondence between subjective evaluation and physiological responses. Contact with aluminum kept at room temperature and cold acrylic plastic created flat/artificial and dangerous/uncomfortable sensations, with an associated significant increase in blood pressure; thus, there was a close correlation between subjective evaluation and physiological responses. It was therefore concluded that contact with wood, unlike artificial materials such as aluminum, induces no physiological stress even when kept at room temperature or cooled.

This article celebrating Arthur von Hippel's career considers the expanding frontiers in the field of biomaterials, a subject that intrigued him given his interests in the molecular engineering of materials. The interface of materials science and biology started to develop decades ago when synthetic materials were first used to repair parts of the human body. An exciting transformation is now occurring in the field, as advances in biology are used to engineer bioactive materials at the molecular level. The transformation is going further to other frontiers that include the use of sophisticated materials to obtain biological information and learn biology, the creation of materials that imitate biological microstructures and functions, and the manipulation of organisms to create artificial materials.

Three experimental tasks are of primary interest in biomechanics: determination of the mechanical properties of biomaterials, including tissues and artificial materials; validation of the mechanical reliability of implantable devices; assessment of the compatibility of the mechanical properties of such devices with the surrounding biological environment. Due to the complexity of the in vivo conditions, most of these studies are performed on in vitro models. This contribution presents a review of some methods that are currently utilised at the Laboratory of Biological Structure Mechanics at the Politecnico of Milan.

Since humans first walked the Earth they have used structural materials derived from Nature to make tools, weapons, textiles, and dwellings. Even in ancient times there was recognition that Nature offered more than just an abundant source of materials; it offered ideas. Looking at how Nature solved a problem may have helped early inventors solve countless problems related, for instance, to building a boat, making a shield, or constructing a house. One of history’s great inventors, Leonardo da Vinci, is famous for his studies of living forms and for his inventions, which were often based on ideas derived from Nature.1 The lessons learned by da Vinci and others were, of course, not always successful, as seen in the countless efforts throughout the ages by humans to fly like a bird. Nonetheless, these are the origins of human’s seeking to solve problems by mimicking Nature. In modern terms we tend to call this field “biomimetics,” which essentially means we are seeking to replicate some or all of the features of a biological system. This is of huge importance in medicine where biomimetic solutions are used to treat a range of diseases and conditions. It is known, for instance, that various materials (often derived from Nature) have been used to mimic the form and function of teeth for millennia.2 In medicine our understanding of the human body’s anatomy and physiology has greatly improved over the past 100 years. This has led to dramatic improvements in our ability to replicate the form and function of human tissues using artificial materials. In the latter half of the 20th century, this ability to replicate human tissue has been the most striking advance in biomimetics. The approximate development of biomimetics over the course of human history is shown schematically in Fig. 1.

Postoperative empyema associated with artificial material infection involves several treatment problems. We report the successful treatment of a case of post-bullectomy empyema with a small alveolar fistula that was associated with artificial material infection by Streptococcus viridans. In this case, complete empyema space sterilization was obtained by tube drainage and daily pleural irrigation using 0.1% gentian violet solution. This treatment circumvented the need for invasive surgery, including removal of the infected artificial materials and space-filling and/or collapse procedures. Consequently, gentian violet irrigation may be a useful treatment option in selected cases with complicated thoracic empyema.

Although Nature has always been a common source of inspiration in the development of artificial materials, only recently has the ability of man-made materials to produce complex three-dimensional (3D) structures from two-dimensional sheets been explored. Here we present a new approach to the self-shaping of soft matter that mimics fibrous plant tissues by exploiting small-scale variations in the internal stresses to form three-dimensional morphologies. We design single-layer hydrogel sheets with chemically distinct, fibre-like regions that exhibit differential shrinkage and elastic moduli under the application of external stimulus. Using a planar-to-helical three-dimensional shape transformation as an example, we explore the relation between the internal architecture of the sheets and their transition to cylindrical and conical helices with specific structural characteristics. The ability to engineer multiple three-dimensional shape transformations determined by small-scale patterns in a hydrogel sheet represents a promising step in the development of programmable soft matter.

When trying to identify the beginnings of “tissue engineering” as a defined scientific field, the first major scientific meeting devoted to “tissue engineering” comes to mind. This meeting took place in 1988 at Granlibakken, Lake Tahoe, California. When looking through the proceedings of this meeting, one can see that many of the fundamental challenges of tissue engineering, still unresolved today, were articulated back at that time. As practiced today, the field of tissue engineering is based on a blending of engineering principles in the materials sciences with the principles of cell and tissue biology to create functional replacements for aged, traumadamaged, or diseased human tissues and organs.The driving force behind the field of “tissue engineering” is the desire to replace defective human tissue with artificial substitutes to improve the quality of human life. This desire is not unique to our times but can be traced back several thousand years. The earliest reports of the use of artificial materials in wound healing are contained in the Edgar Smith papyrus. This historic document mentions the use of sutures and woundclosure devices around 4000 B.C. and the use of metals in bone repair around 2000 B.C. In ancient times, Native Americans apparently used silk and hair as suture materials.In 1900 natural tissues like amnion and placenta were suggested as skin replacements, an approach that was obviously doomed to fail due to immunological reactions. The general lack of understanding of the immune response at the beginning of this century forced researchers and clinicians to abandon attempts to use natural tissues as medical implants and contributed to a focus on synthetic materials. Advances in metallurgy facilitated the introduction of metals for bone reconstruction and dental prosthesis, and the large number of casualties during World War I resulted in the establishment of stainless steel and other metals as the preferred orthopedic implant materials.

Moving beyond mimicry, biologically inspired artificial materials can be simpler in design yet more powerful in function than their natural analogues. A tropical fruit seed serves as a guide to making new photonic elements.

Science and engineering of biorelated polymers and materials are becoming increasingly important for development of artificial organs, drug delivery systems, regenerative medicine, diagnostics and biominetics. It is essential for these materials to adequately design new polymers with on-demand shape, structures, properties and functionality, and to fully understand and control the interactions of the materials with biological molecules, which include protein adsorption, blood coagulation, immune reactions, tissue regeneration, biodegradability and biomineralization. Such effort clearly realizes excellent diagnostic and therapeutic values of the materials due to valuable biocompatibility. The key ambition of this field is to widely focus and investigate the interface between artificial materials and biological systems.

Artificial materials composed of either structured or random subunits far below the wavelength of light can be designed to display fascinating physical properties. Recent advances in fabrication technology have established the great potential of such metamaterials for applications.

The new artificial materials characterized as layered ultrathin coherent structures (LUCS) have attracted a great deal of research interest. They are important not only for the novel physical properties they exhibit, but also for possible additional phenomena, such as excitonic superconductivity. In previous publications, we developed a tight-binding theory for the electronic structures of these materials. The present paper studies the phonon structures of LUCSs for a special lattice model, including nearest- and next-nearest-neighbor harmonic interactions.

For a long time the lignin-sulfonic acids, obtained in very large quantities in the manufacture of sulphitepulp, have engaged the interest of chemical research workers for economic and scientific reasons. for both fields the determination of the constitution of the lignin-sulfonic acids and the knowledge of the processes taking place between lignin and sulfonic acid are of basic importance. During the last years our institute was able to gain a broader conception of the whole problem by means of model experiments, For the first time it was possible to achieve progress in this direction through a combination of oxidative and hydrolytic decomposition and the complete elimination of the sulfonic acid radical. Although researchers of the whole world have been working on this problem for years, no progress of any greater importance in the utilization of lignin-sulfonic acid has been made. Nevertheless experiments on the production of artificial materials from lignin-sulfonic acid as a base are very promising. By high pressure hydrogenation valuable products are obtained, although at high costs. The production of vanillin is far advanced (especially in the United States) and yields a new success of by-products which may be used with much success in combination with artificial materials, e.g. press plates.