由蜡和聚氨酯泡沫制备的相变材料可能使机器人从固态向湿软状态转变，并且又可以恢复到固态。这种材料由MIT和Stony Brook University开发，期望未来机器人能实现软硬状态的互相转变，这种特点的机器人在外科手术中将大有作为，比如软机器人在进行手术时，将不会破坏组织和血管。软硬互变材料的机器人，由于其可压缩性、灵活性和柔韧性，或许可以用于一些救灾中，制备这种机器人最初的想法是来自软体动物章鱼。
图片来源MIT。
研究人员将PU泡沫材料浸泡在热蜡油中使蜡油渗透完全充满泡沫材料中即可获得类似性质的材料，详情请阅读文献：
Thermally Tunable, Self-Healing Composites for Soft Robotic Applications（Macromolecular Materials and Engineering，DOI: 10.1002/mame.201400017）
摘要：The field of soft robotics has inspired recent mechanical engineering and materials science innovations to enable shape-shifting systems to be developed. This paper presents the design and analysis of a novel thermally tunable composite, namely, a flexible open-cell foam coated in wax that can achieve significant ranges of stiffness, strength, and volume. Experimental results were compared to a proposed model for predicting the bulk compression modulus of the composites. Additionally, preliminary studies indicate that the composites exhibit self-healing properties, in which heating between loading cycles can mend wax that has been plastically deformed, for example, by cracking or delaminating from the foam.
作者：Nadia G. Cheng1,†,*, Arvind Gopinath2, Lifeng Wang3, Karl Iagnemma1 andAnette E. Hosoi1