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"Stephen, Craig"
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Cephalopod-inspired design of electro-mechano-chemically responsive elastomers for on-demand fluorescent patterning
Cephalopods can display dazzling patterns of colours by selectively contracting muscles to reversibly activate chromatophores – pigment-containing cells under their skins. Inspired by this novel colouring strategy found in nature, we design an electro-mechano-chemically responsive elastomer system that can exhibit a wide variety of fluorescent patterns under the control of electric fields. We covalently couple a stretchable elastomer with mechanochromic molecules, which emit strong fluorescent signals if sufficiently deformed. We then use electric fields to induce various patterns of large deformation on the elastomer surface, which displays versatile fluorescent patterns including lines, circles and letters on demand. Theoretical models are further constructed to predict the electrically induced fluorescent patterns and to guide the design of this class of elastomers and devices. The material and method open promising avenues for creating flexible devices in soft/wet environments that combine deformation, colorimetric and fluorescent response with topological and chemical changes in response to a single remote signal.
Cephalopods change colour by mechanically activating chromatophores via muscle contraction. Here, the authors use a similar concept for flexible displays, where electric field control over elastomer strain allows activation of mechanophores and provides on-demand and variable fluorescent patterns.
Journal Article
Mechanical gating of a mechanochemical reaction cascade
Covalent polymer mechanochemistry offers promising opportunities for the control and engineering of reactivity. To date, covalent mechanochemistry has largely been limited to individual reactions, but it also presents potential for intricate reaction systems and feedback loops. Here we report a molecular architecture, in which a cyclobutane mechanophore functions as a gate to regulate the activation of a second mechanophore, dichlorocyclopropane, resulting in a mechanochemical cascade reaction. Single-molecule force spectroscopy, pulsed ultrasonication experiments and DFT-level calculations support gating and indicate that extra force of >0.5 nN needs to be applied to a polymer of gated
g
DCC than of free
g
DCC for the mechanochemical isomerization
g
DCC to proceed at equal rate. The gating concept provides a mechanism by which to regulate stress-responsive behaviours, such as load-strengthening and mechanochromism, in future materials designs.
Polymer mechanochemistry offers opportunities to control and engineer desired chemical transformations. Here, Craig and co-workers present a mechanical gating system whereby one mechanophore modulates the reactivity of another, resulting in a mechanochemical cascade reaction.
Journal Article
Enhanced polymer mechanical degradation through mechanochemically unveiled lactonization
The mechanical degradation of polymers is typically limited to a single chain scission per triggering chain stretching event, and the loss of stress transfer that results from the scission limits the extent of degradation that can be achieved. Here, we report that the mechanically triggered ring-opening of a [4.2.0]bicyclooctene (BCOE) mechanophore sets up a delayed, force-free cascade lactonization that results in chain scission. Delayed chain scission allows many eventual scission events to be initiated within a single polymer chain. Ultrasonication of a 120 kDa BCOE copolymer mechanically remodels the polymer backbone, and subsequent lactonization slowly (~days) degrades the molecular weight to 4.4 kDa, > 10× smaller than control polymers in which lactonization is blocked. The force-coupled kinetics of ring-opening are probed by single molecule force spectroscopy, and mechanical degradation in the bulk is demonstrated. Delayed scission offers a strategy to enhanced mechanical degradation and programmed obsolescence in structural polymeric materials.
The mechanical degradation of polymers is typically limited to a single chain scission event and the loss of stress transfer during the scission process limits the extent of degradation achieved. Here, the authors report a mechanically triggered, delayed scission strategy that allows many eventual scission events to be initiated within a single polymer chain.
Journal Article
Urban allies : ten brand-new collaborative stories
These collaborative stories unite two beloved characters from two different urban fantasy series in each of ten electrifying new stories.
Book
The role of polymer mechanochemistry in responsive materials and additive manufacturing
The use of mechanical forces to chemically transform polymers dates back decades. In recent years, the use of mechanochemistry to direct constructive transformations in polymers has resulted in a range of engineered molecular responses that span optical, mechanical, electronic and thermal properties. The chemistry that has been developed is now well positioned for use in materials science, polymer physics, mechanics and additive manufacturing. Here, we review the historical backdrop of polymer mechanochemistry, give an overview of the existing toolbox of mechanophores and associated theoretical methods, and speculate as to emerging opportunities in materials science for which current capabilities are seemingly well suited. Non-linear mechanical responses and internal, amplifying stimulus–response feedback loops, including those enabled by, or coupled to, microstructured metamaterial architectures, are seen as particularly promising.
Polymer mechanochemistry converts mechanical forces in materials to chemical reactions through the response of functional groups known as mechanophores. This Review discusses the colorimetric, mechanical, chemical and electronic responses of mechanophores that may be useful in materials for strain sensing and strengthening, soft devices and additive manufacturing.
Journal Article
One Health most often has people as the primary beneficiary. How must One Health policies and practice change to make animal, plant and ecosystem health a primary focus that is influenced by human and environmental factors?
The bulk of One Heath’s investment and research focuses on how animal or environmental threats impact human health or well-being. One Health has been less attentive to how human and environmental dimensions interact to impact animal health or on the environmental implications of health management at the human-animal interface. There has also been comparatively little investigation on how to create One Health programmes that promote reciprocal care that is neither human first, nor animal first nor environment first, but rather concurrently protects the health of all three. With this question, we invite authors to explore if or how current policies, practices and perspectives have shaped the primacy of human health as a benefactor of One Health and examine what changes need to be made, if any, to broaden the application of One Health approaches and perspectives. We encourage the use of implementation science methods and strategies to develop evidence-based policies and practice and to promote their regular use by researchers, practitioners and policymakers.
Journal Article
How do the practical and pragmatic limitations in the design or implementation of wildlife disease surveillance systems bias our understanding of the drivers, epidemiology, and impact of pathogen traffic between wildlife and people or domestic species, or within wildlife host populations?
Decision makers want more information on the presence, distribution, movement, and impacts of pathogens in wild animals to anticipate or assess the risk of pathogen spillover from wildlife to people or domestic animals or to better understand the conservation implications of contagious diseases in wildlife. There are many impediments to designing and implementing a wildlife health surveillance system that fulfils all the expectations for ‘good’ surveillance. There are well-known pragmatic limitations such as the inability to sample targeted populations consistently and regularly in a representative manner, lack of validated tests, and funding limitations that restrict surveillance to periodic surveys. The nature and impact of the biases on data collection, generation, management, quality, analysis, interpretations, and information sharing are poorly studied. We invite authors to address the question in the title.
Journal Article