Morphing in nature and beyond: a review of natural and synthetic shape-changing materials and mechanisms

Shape-changing materials open an entirely new solution space for a wide range of disciplines: from architecture that responds to the environment and medical devices that unpack inside the body, to passive sensors and novel robotic actuators. While synthetic shape-changing materials are still in their infancy, studies of biological morphing materials have revealed key paradigms and features which underlie efficient natural shape-change. Here, we review some of these insights and how they have been, or may be, translated to artificial solutions. We focus on soft matter due to its prevalence in nature, compatibility with users and potential for novel design. Initially, we review examples of natural shape-changing materials—skeletal muscle, tendons and plant tissues—and compare with synthetic examples with similar methods of operation. Stimuli to motion are outlined in general principle, with examples of their use and potential in manufactured systems. Anisotropy is identified as a crucial element in directing shape-change to fulfil designed tasks, and some manufacturing routes to its achievement are highlighted. We conclude with potential directions for future work, including the simultaneous development of materials and manufacturing techniques and the hierarchical combination of effects at multiple length scales.</p

Highly Active Absorbent for SO₂ Removal Prepared from Coal Ash (Part 2)

This paper is a sequel of previous study (Part 1) on the preparation of highly active absorbents for SO₂ removal from coal ash and limestone. The prepared absorbent from coal fly ash was tested for its desulfurization activity at varying conditions using the experimental SO₂ absorption analyzer. Simulated flue gas moisture used was composed SO₂, NO, CO₂, O₂ and H₂O. The activity of the produced absorbent closely depends on the method of preparation taking into account the effect of time and temperature for curing and drying. The effects of particle size, surface area and % glass content were correlated with the SO₂ removal efficiency. The produced absorbent exhibited high efficiency not only SO₂ but also for NO removal at temperatures ranging from 100-165⁰C of the gas mixture. NO serves as catalyst in the oxidation of SO₂ to SO, forming ettringite [Ca₆A1₂ (SO₁)₃(OH)₁₂25H₂O or 6CaOA1₂O₃3SO₃31H₂O) and CaSO₄ in the spent absorbent