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

Book Reviews Published in "the Hindu": A Study

An attempt has been made to study the reviews published in daily The Hindu. The present article narrates various features and shortcomings of the reviews published in The Hindu

Nanoparticle-Mediated Remote Control of Enzymatic Activity

Nanomaterials have found numerous applications as tunable, remotely controlled platforms for drug delivery, hyperthermia cancer treatment, and various other biomedical applications. The basis for the interest lies in their unique properties achieved at the nanoscale that can be accessed via remote stimuli. These properties could then be exploited to simultaneously activate secondary systems that are not remotely actuatable. In this work, iron oxide nanoparticles are encapsulated in a bisacrylamide-crosslinked polyacrylamide hydrogel network along with a model dehalogenase enzyme, L-2-HAD(ST). This thermophilic enzyme is activated at elevated temperatures and has been shown to have optimal activity at 70 °C. By exposing the Fe(3)O(4) nanoparticles to a remote stimulus, an alternating magnetic field (AMF), enhanced system heating can be achieved, thus remotely activating the enzyme. The internal heating of the nanocomposite hydrogel network in the AMF results in a 2-fold increase in enzymatic activity as compared to the same hydrogel heated externally in a water bath, suggesting that the internal heating of the nanoparticles is more efficient than the diffusion limited heating of the water bath. This system may prove useful for remote actuation of biomedical and environmentally relevant enzymes and find applications in a variety of fields

Effects of Au nanoparticles on thermoresponsive genipin-crosslinked gelatin hydrogels

Gold gelatin hydrogel nanocomposites crosslinked with genipin have been prepared, and the effect of citrate capped Au nanoparticles (NPs) as nanofillers in the crosslinking and swelling of gelatin and release of a model drug (methylene blue) from gelatin nanocomposites have been investigated. The citrate-capped Au NPs prevented the crosslinking reaction between the gelatin and genipin and resulted in less crosslinked hydrogels. Although less crosslinked, the Au gelatin nanocomposites swelled less than the unfilled crosslinked gelatin. The gelatin composites were optically active and thermo-sensitive in a temperature range acceptable for living cells. In vitro release studies demonstrated that the irradiation of the composite gels with monochromatic green light (10532 nm, 100 mW) increases the release of the encapsulated methylene blue, most likely due to the photothermal effect of Au nanoparticles. This opens the possibility to explore the application of these nanocomposites as carriers in remotely controlled light-triggered drug release

A Thermo-electromagnetically Actuated Microrobot for the Targeted Transport of Therapeutic Agents

This work proposes the targeted transport of therapeutic agents using a thermo-electromagnetically actuated microrobot. This microrobot is fabricated via UV polymerization using 2D lithography and is composed of an electromagnetically actuated layer (polyethyleneglycol diacrylate dispersed with iron(II,III) oxide and a thermo-responsive layer (N-isopropylacrylamide). The microrobot can self-fold, driven by temperature changes, and can be steered using an electromagnetic actuation (EMA) system that provides external magnetic fields. In particular, during the EMA, pulling and rolling motions are applied to the unfolded and folded shapes, respectively, of the microrobot. As fundamental tests, the microrobot was characterized in terms of its magnetization curve, swelling properties, travel velocity, and shape changing behavior. In addition, typical polystyrene bead manipulations such as trapping, delivery, and release were performed using the microrobot. Finally, we performed an in vitro test for tumor therapy, in which the robot demonstrated the ability to trap, deliver, and release an anti-cancer drug (docetaxel) encapsulated in microbeads of approximately 300 mm in diameter with an appropriate drug concentration against a mouse mammary tumor cell line (4T1). The outcomes of this research suggest that our thermo-electromagnetically actuated microrobot is suitable for use in biomedical applications. © 2018 Institute of Control, Robotics and Systems and The Korean Institute of Electrical Engineers and Springer-Verlag GmbH Germany, part of Springer Nature1