A review of mechanoluminescence in inorganic solids : compounds, mechanisms, models and applications

Mechanoluminescence (ML) is the non-thermal emission of light as a response to mechanical stimuli on a solid material. While this phenomenon has been observed for a long time when breaking certain materials, it is now being extensively explored, especially since the discovery of non-destructive ML upon elastic deformation. A great number of materials have already been identified as mechanoluminescent, but novel ones with colour tunability and improved sensitivity are still urgently needed. The physical origin of the phenomenon, which mainly involves the release of trapped carriers at defects with the help of stress, still remains unclear. This in turn hinders a deeper research, either theoretically or application oriented. In this review paper, we have tabulated the known ML compounds according to their structure prototypes based on the connectivity of anion polyhedra, highlighting structural features, such as framework distortion, layered structure, elastic anisotropy and microstructures, which are very relevant to the ML process. We then review the various proposed mechanisms and corresponding mathematical models. We comment on their contribution to a clearer understanding of the ML phenomenon and on the derived guidelines for improving properties of ML phosphors. Proven and potential applications of ML in various fields, such as stress field sensing, light sources, and sensing electric (magnetic) fields, are summarized. Finally, we point out the challenges and future directions in this active and emerging field of luminescence research

Super-Flexible Sensors and Advanced 3D Morphing Actuators based on Elastic Instability

Super-flexible devices based on soft materials have the potential to sustain large mechanical deformations, enabling advanced applications such as flexible electronics, soft robots, artificial skin, and biomedical transducers. Subject to a large compression, materials may undergo different types of elastic instabilities such as wrinkles, creases, and folds. Despite recent growing interests in turning this usually unwanted phenomenon into useful engineering applications (e.g. tactile sensing), this topic remains relatively under-researched. Therefore, this thesis focuses on developing the control mechanisms of elastic instabilities, and their applications in sensing and actuation systems. Elastic instabilities induced strain-gated logic sensing technology is developed by research into micro structured metal-elastomer tri-layer system. The test structures are designed to study the deformation behaviour and to exploit the large strain sensing mechanism. The stepwise electrical signals are achieved (from ~1010 to ~120 Ω at first switching stage and then to ~50 Ω at second switching stage) that survived much higher than usual compressive strains of up to 60%. On the other hand, elastic instabilities induced topo-optical sensing strategy is created by patterning microstructure arrays within the tri-layer system. Two unwanted phenomena (creases/folds and oxygen quenching effect) are turned into a responsive and programmable 'fold to glitter' function through micro engineering, which can light up areas of an object or material by creating microscopic creases/folds within its surface. The signal-Noise-Ratio (SNR) contrast in optical pattern generation is improved by 6 folds due to the oxygen quenching effect. The numerical analysis by ABAQUS provides the fundamental theory on the mechanism of generating targeted folding through simulating the in-plane and out-of-plane strain energy localization. Different luminescent optical patterns are demonstrated under in-plane uniaxial or equi-biaxial compression. Apart from the surface deformation, the bulk deformation of heterogeneous layered structures of soft functional hydrogel is also developed to generate the controllable and reconfigurable 3D morphing device. The initial configurations with various shapes (“S”, “W” and “C”) are demonstrated due to the swelling ratio mismatch. The developed sensing and actuation technologies provide opportunities for future applications in flexible electronics, tuneable optics, soft robotics and bio-medical systems

Proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress

Published proceedings of the 2018 Canadian Society for Mechanical Engineering (CSME) International Congress, hosted by York University, 27-30 May 2018

Determining the Fracture Process Zone Length and Mode I Stress Intensity Factor in Concrete Structures via Mechanoluminescent Technology

The mechanoluminescent (ML) technology that is being developed as a new and substitutive technology for structural health monitoring systems (SHMS) comprises stress/strain sensing micro-/nanoparticles embedded in a suitable binder, digital imaging system, and digital image processing techniques. The potential of ML technology to reveal the fracture process zone (FPZ) that is commonly found in structural materials like concrete and to calculate the stress intensity factor (SIF) of concrete, which are crucial for SHMS, has never been done before. Therefore, the potential of ML technology to measure the length of the FPZ and to calculate the SIF has been demonstrated in this work by considering a single-edge notched bend (SENB) test of the concrete structures. The image segmentation approach based on the histogram of an ML image as well the skeletonization of an ML image have been introduced in this work to facilitate the measurement of the length of ML pattern, crack, and FPZ. The results show ML technology has the potential to determine fracture toughness, to visualize FPZ and cracks, and to measure their lengths in structural material like concrete, which makes it applicable to structural health monitoring systems (SHMS) to characterize the structural integrity of structures

Technical, Economic and Societal Effects of Manufacturing 4.0

This open access book is among the first cross-disciplinary works about Manufacturing 4.0. It includes chapters about the technical, the economic, and the social aspects of this important phenomenon. Together the material presented allows the reader to develop a holistic picture of where the manufacturing industry and the parts of the society that depend on it may be going in the future. Manufacturing 4.0 is not only a technical change, nor is it a purely technically driven change, but it is a societal change that has the potential to disrupt the way societies are constructed both in the positive and in the negative. This book will be of interest to scholars researching manufacturing, technological innovation, innovation management and industry 4.0

Technical, Economic and Societal Effects of Manufacturing 4.0

This open access book is among the first cross-disciplinary works about Manufacturing 4.0. It includes chapters about the technical, the economic, and the social aspects of this important phenomenon. Together the material presented allows the reader to develop a holistic picture of where the manufacturing industry and the parts of the society that depend on it may be going in the future. Manufacturing 4.0 is not only a technical change, nor is it a purely technically driven change, but it is a societal change that has the potential to disrupt the way societies are constructed both in the positive and in the negative. This book will be of interest to scholars researching manufacturing, technological innovation, innovation management and industry 4.0

Street Furniture and the Nation State: A Global Process

In the popular imagination, street furniture has traditionally been understood as evoking a sense of national or local identity. From Paris’ metro entrances, DDR lampposts in Berlin, and London’s york stone pavements, the designed environment has been able to contribute to the unique qualities of a place. In some instances this was deliberate. In postwar Britain for instance, the Council of Industrial Design – a state-funded design organization - often appeared to measure the quality of street furniture on the basis of its national characteristics. On other occasions, the relationship between such objects and identity emerged accidentally. In Britain during the 1980s, for example, the replacement of Gilbert Scott's red telephone box with an alternative BT model provoked considerable debate. For many people, this act was not just a Conservative attack on nationalization and state-ownership, but also on the very fabric of British identity. This understanding of street furniture has retained its currency for many years, and cities across the world have used street furniture to provide a sense of visual coherency for neighbourhoods in need of new identities, strengthening their character and improving the public's relationship to them. In this way, street furniture has been employed as a cipher for the narrative of regeneration, in which - as a means of altering the identity of a space - street furniture can project a new face upon the street. Increasingly however, advertising companies are able to lever themselves into the street furniture market by offering to provide the service to the local authorities for free in return for advertising space. In offering this service, global companies like JC Decaux, Wall and Clear Channel command a huge amount of commercial power within the city. The excessive homogenization of street furniture coupled with the overwhelming presence of advertising which is increasingly sanctioned by local authorities keen to reduce costs, has resulted in the perception of poorer quality streets. Thus, the irony of regeneration is that by seeking to promote the unique identity of a city, many places often end up looking more and more alike. This paper will examine recent developments in the process by which the street is furnished and the agents responsible. It will specifically look at how these changes have affected the relationship between street furniture and identity, and equally the effect this process has had on understandings of national design histories. Clearly, evaluating contemporary street furniture through the lens of the nation-state is of very little value, since the international differences between street furniture are considerably less marked than they used to be. This extraordinary aesthetic convergence is partly linked to economies of scale - after all, just how many different kinds of bus stop can Europe afford to have? Yet it also reflects some of the challenges posed by globalization and privatization of public space. This paper will reflect upon that process, and how these bigger narratives increasingly affect the landscape of the street