报告人: John Biggins（剑桥大学）

时  间：5月22日（周四）16:00-17:30

地  点：北京大学工学院新奥2047

主持人：冯帆

内容简介：

Liquid crystal elastomers (LCEs) are rubbery soft solids that contain the orientational order of a liquid crystal. They exhibit an aligned-isotropic phase transition, which is associated with a very large spontaneous contraction along the alignment (~50%), making LCEs promising artificial muscles. A key idea is that a flat LCE sheet can be fabricated with a pattern of molecular alignment, which turns into a pattern of contraction upon stimulation, morphing the sheet into a (Gauss) curved surface - i.e. LCEs can be used to form programmable shape-shifting devices. For more than a decade now, it has been possible to create an LCE sheet with any pattern of alignment, and much theoretical and computational effort has been expended on designing patterns to produce desired shapes. However, in practice these designs typically do not work well, except for simple high-symmetry shapes such as cones. In contrast, a new experimental technique called direct mechanical programming allows you to create LCEs that can morph into any desired complex shape  without any need for pattern design or complex fabrication. In this talk, I will combine experimental and theoretical results to explain how and why direct mechanical programming works. Critically, such programming depends on alignment rotation within the LCE during fabrication to form complex hierarchical laminate structures. Finally, I will show how a numerical implementation of this idea also provides a new strategy for explicit director design, allowing us to design an LCE sheet that morphs into a whole spherical shell upon stimulation.

报告人简介：

John Biggins a professor of soft matter engineering in Cambridge University Engineering Department, where he leads the soft mechanics group (www.soft.eng.cam.ac.uk) which works on the mechanics of soft solid materials. Research topics include elastic instabilities, such as buckling and wrinkling, morphogenesis, how surface tension deforms soft solids, and a type of artificial muscle known as a liquid crystal elastomer. He currently holds a UKRI “Future Leaders Fellowship,” and has previously held an 1851 Royal Commission Research Fellowship and the Walter Scott Research Fellowship at Trinity Hall.

欢迎广大师生光临！