Hydrogels consist of hydrophilic polymer networks dispersed in water. Many applications of hydrogels rely on their unique combination of solid‐like mechanical behavior and water‐like transport ...properties. If the temperature is lowered below 0 °C, however, hydrogels freeze and become rigid, brittle, and non‐conductive. Here, a general class of hydrogels that do not freeze at temperatures far below 0 °C, while retaining high stretchability and fracture toughness, is demonstrated. These hydrogels are synthesized by adding a suitable amount of an ionic compound to the hydrogel. The present study focuses on tough polyacrylamide‐alginate double network hydrogels equilibrated with aqueous solutions of calcium chloride. The resulting hydrogels can be cooled to temperatures as low as −57 °C without freezing. In this temperature range, the hydrogels can still be stretched more than four times their initial length and have a fracture toughness of 5000 J m−2. It is anticipated that this new class of hydrogels will prove useful in developing new applications operating under a broad range of environmental and atmospheric conditions.
The present study demonstrates a general class of hydrogels that do not freeze at temperatures far below 0 °C, while retaining high stretchability and fracture toughness. The resulting hydrogels can be cooled to −57 °C without fully freezing, and can still be stretched more than four times their initial length, with a fracture toughness of 5000 J m−2.
Functional devices that use hydrogels as ionic conductors and elastomers as dielectrics have the advantage of being soft, stretchable, transparent, and biocompatible, making them ideal for biomedical ...applications. These devices are typically fabricated by manual assembly. Techniques for the manufacturing of soft materials have generally not looked at integrating multiple dissimilar materials. Silane coupling agents have recently shown promise for creating strong bonds between hydrogels and elastomers but have yet to be used in the extrusion printing of complex devices that integrate both hydrogels and elastomers. Here, we demonstrate the viability of silane coupling agents in a system with the rheology and functional composition necessary for three-dimensional (3D) extrusion printing of hydrogel–elastomer materials, specifically polyacrylamide (PAAm) hydrogel and poly(dimethylsiloxane) (PDMS) hydrophobic elastomer. By introducing a charge-neutral surfactant in the PDMS and adjusting silane concentrations in the PAAm, cast material samples demonstrate strong adhesion. We were also able to achieve an interfacial toughness of up to Γ = 193 ± 6.3 J/m2 for a fully extrusion printed PAAm hydrogel-on-PDMS bilayer. This result demonstrates that an integration strategy based on silane coupling agents makes it possible for extrusion printing of a wide variety of hydrogel and silicone elastomers.
The environmental awareness and concerns (plastic pollution) worldwide have driven the development of sustainable and environmentally friendly biopolymer derived from renewable materials. ...Biopolymers, especially L-lactic acid (L-LA) have played a crucial role in manufacturing polylactic acid, a biodegradable thermoplastic. Recently, L-LA production from non-edible macroalgal biomass has gained immense attraction due to it offers the simplest saccharification process for the biorefinery route. However, the commercialization of macroalgal-based L-LA is still limited due to high production costs. This paper has comprehensively reviewed the potential and development of third-generation feedstock for L-LA production, including significant technological barriers to be overcome for potential commercialization purposes. Then, an insight into the state-of-the-art hydrolysis and fermentation technologies using macroalgae as feedstock are also deliberated in detail. Furthermore, this review provides a conceivable picture of macroalgae-based L-LA biorefinery and future research directions that can be served as an important guideline for scientists, policymakers, and industrial players.
In this paper we provide faster algorithms for approximately solving ℓ_∞ regression, a fundamental problem prevalent in both combinatorial and continuous optimization. In particular we provide an ...accelerated coordinate descent method which converges in k iterations at a O(1/k) rate independent of the dimension of the problem, and whose iterations can be implemented cheaply for many structured matrices. Our algorithm can be viewed as an alternative approach to the recent breakthrough result of Sherman She17 which achieves a similar running time improvement over classic algorithmic approaches, i.e. smoothing and gradient descent, which either converge at a O(1/√k) rate or have running times with a worse dependence on problem parameters. Our running times match those of She17 across a broad range of parameters and in certain cases, improves upon it. We demonstrate the efficacy of our result by providing faster algorithms for the well-studied maximum flow problem. We show how to leverage our algorithm to achieve a runtime of Õ(m + √ns/ε) to compute an ε-approximate maximum flow, for an undirected graph with m edges, n vertices, and where s is the squared ℓ_2 norm of the congestion of any optimal flow. As s = O(m) this yields a running time of Õ(m + √nm/ε), generically improving upon the previous best known runtime of Õ(m/ε) in She17 whenever the graph is slightly dense. Moreover, we show how to leverage this result to achieve improved exact algorithms for maximum flow on a variety of unit capacity graphs. We achieve these results by providing an accelerated coordinate descent method capable of provably exploiting dynamic measures of coordinate smoothness for smoothed versions of ℓ_∞ regression. Our analysis leverages the structure of the Hessian of the smoothed problem via a simple bound on its trace, as well as techniques for exploiting column sparsity of the constraint matrix for faster sampling and improved smoothness estimates. We hope that the work of this paper can serve as an important step towards achieving even faster maximum flow algorithms.
The extensive growth of energy and plastic demand has raised concerns over the depletion of fossil fuels. Moreover, the environmental conundrums worldwide integrated with global warming and improper ...plastic waste management have led to the development of sustainable and environmentally friendly biofuel (bioethanol) and biopolymer (lactic acid, LA) derived from biomass for fossil fuels replacement and biodegradable plastic production, respectively. However, the high production cost of bioethanol and LA had limited its industrial-scale production. This paper has comprehensively reviewed the potential and development of third-generation feedstock for bioethanol and LA production, including significant technological barriers to be overcome for potential commercialization purposes. Then, an insight into the state-of-the-art hydrolysis and fermentation technologies using macroalgae as feedstock is also deliberated in detail. Lastly, the sustainability aspect and perspective of macroalgae biomass are evaluated economically and environmentally using a developed cascading system associated with techno-economic analysis and life cycle assessment, which represent the highlights of this review paper. Furthermore, this review provides a conceivable picture of macroalgae-based bioethanol and lactic acid biorefinery and future research directions that can be served as an important guideline for scientists, policymakers, and industrial players.
Graphical abstract
Haah codes on general three-manifolds Tian, Kevin T.; Samperton, Eric; Wang, Zhenghan
Annals of physics,
January 2020, 2020-01-00, Letnik:
412
Journal Article
Recenzirano
Odprti dostop
Haah codes represent a singularly interesting gapped Hamiltonian schema that has resisted a natural generalization, although recent work shows that the closely related type I fracton models are more ...commonplace. These type I siblings of Haah codes are better understood, and a generalized topological quantum field theory framework has been proposed. Following the same conceptual framework, we outline a program to generalize Haah codes to all 3-manifolds using Hastings’ LR stabilizer codes for finite groups.
•Error correction codes on finite groups.•Fracton models on all three manifolds.•Profinite completion of three manifold groups.
The presence of highly modifiable chemical functional groups, abundance of functional groups, and their biological origin make proteins an important class of biomaterials from a fundamental science ...and applied engineering perspective. Hence, the utilization of proteins from the animal rendering industry (animal protein, AP) for high-value, nonfeed, and nonfertilizer applications is intensely pursued. Although this leads to the exploration of protein-derived plastics as a plausible alternative, the proposed methods are energy-intensive and not based on protein in its native form, which leads to high processing and production costs. Here, we propose, for the first time, novel pathways to develop engineered hybrid systems utilizing AP in its native form and epoxy resins with mechanical properties ranging from toughened thermosets to elastic epoxy-based systems. Furthermore, we demonstrate the capability to engineer the properties of epoxy–AP hybrids from high-strength hybrids to elastic films through controlling the interaction, hydrophilicity, as well as the extent of cross-linking and network density. Through the facile introduction of cochemicals, a sevenfold increase in the mechanical properties of the conventional epoxy–AP hybrid is achieved. Similarly, because of better compatibility afforded by the similar hydrophilicity, AP demonstrated higher cross-linking capability with a water-soluble epoxy (WEP) matrix, resulting in an elastic WEP–AP hybrid without any external aid.
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