抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Active motion is intrinsic to all kinds of living organisms from unicellular ones to humans and inspires development of synthetic actively moving materials. Hydrogels, which are three dimensional polymer networks imbibed with aqueous solutions, mimic the swelling/shrinking behavior of plant cells and produce macroscopic actuation upon swelling and shrinking. This Feature Article covers basic principles of design as well as recent advances in the development of hydrogel based actuating systems. It is discussed how simply swelling can be used to generate very complex multistep motion, which can be used to develop new optical devices, sensors, biomaterials, smart surface, etc.

Biomimetic Hydrogel-Based Actuating Systems

Two-dimensional (2D) materials have attracted tremendous research interest since the breakthrough of graphene. Their unique optical, electronic, and mechanical properties hold great potential for harnessing them as key components in novel applications for electronics and optoelectronics. Their atomic thickness and exposed huge surface even make them highly designable and manipulable, leading to the extensive application potentials. What's more, after acquiring the qualification for being the candidate for next-generation devices, the assembly of 2D materials monomers into mass or ordered structure is also of great importance, which will determine their ultimate industrialization. By designing the monomers and regulating their assembling behavior, the exploration of 2D materials toward the next-generation circuits can be spectacularly achieved. In this review, we will first overview the emerging 2D materials and then offer a clear guideline of varied physical and chemical strategies for tuning their properties. Furthermore, assembly strategies of 2D materials will also be included. Finally, challenges and outlooks in this promising field are featured on the basis of its current progress.

Exploring Two-Dimensional Materials toward the Next-Generation Circuits: From Monomer Design to Assembly Control

We investigated the folding of rectangular stimuli-responsive hydrogel-based polymer bilayers with different aspect ratios and relative thicknesses placed on a substrate. It was found that long-side rolling dominates at high aspect ratios (ratio of length to width) when the width is comparable to the circumference of the formed tubes, which corresponds to a small actuation strain. Rolling from all sides occurs for higher actuation, namely when the width and length considerably exceed the deformed circumference. In the case of moderate actuation, when both the width and length are comparable to the deformed circumference, diagonal rolling is observed. Short-side rolling was observed very rarely and in combination with diagonal rolling. On the basis of experimental observations, finite-element modeling and energetic considerations, we argued that bilayers placed on a substrate start to roll from corners due to quicker diffusion of water. Rolling from the long-side starts later but dominates at high aspect r...

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Shape-programmed folding of stimuli-responsive polymer bilayers.

A photoactuator based on a tubular-shaped graphene composite bimorph is fabricated and shows reversible photoactuation with fast response and large deformation (deformation angle of ca. 479° in only 3.6 s), which is mostly attributed to the interfacial thermal stress. Various photoactuator devices based on the tubular bimorph, including a smart box and crawler-type robot that can mimic tank-track motion, are designed.

A Graphene-Based Bimorph Structure for Design of High Performance Photoactuators

Semiconductor micro- and nanotubes can be formed by strain-induced self-rolling of membranes. The effect of geometrical dimensions on the self-rolling behavior of epitaxial mismatch-strained InxGa1−xAs−GaAs membranes are systematically studied both experimentally and theoretically using the finite element method. The final rolling direction depends on the length and width of the membrane as well as the diameter of the rolled-up tube. The energetics of the final states, the history of rolling process, and the kinetic control of the etching anisotropy ultimately determine the rolling behavior. Results reported here provide critical information for precise positioning and uniform large area assembly of semiconducting micro- and nanotubes for applications in photonics, microelectromechanical systems, etc.

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Geometry effect on the strain-induced self-rolling of semiconductor membranes.

Semiconductor micro- and nanotubes can be formed by strain-induced self-rolling of membranes. The geometry effect on the final rolling direction of In x Ga 1−x As-GaAs membranes are systematically studied both experimentally and by the finite element method.

Brad Derickson

Papers

Geometry effect on the strain-induced self-rolling of semiconductor membranes.

Strain-induced self-rolling of semiconductor membranes: Effect of geometry, energetics, and kinetics