Reversible shape morphing of a neutrally stable shell by untethered local activation of embedded Ni-Ti wires

Daan van der Lans, Ali Amoozandeh Nobaveh, Giuseppe Radaelli*

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

1 Citation (Scopus)
17 Downloads (Pure)


This paper presents a novel shape morphing concept, which exploits neutral stability to achieve reversible shape morphing. The concept is based on actively changing the material stiffness on a local level in order to perturb the neutral stability and thus induce the shell to deform. This concept is realized by embedding Ni-Ti wires in a neutrally stable shell. These wires undergo a significant increase in stiffness upon being heated beyond their Austenite transition temperature. The wires are locally heated by forced convection. The results show that the shape of the shell can be controlled freely along the neutrally stable elastic deformation path by changing the location of the heat stimulus. In contrast to existing shape morphing structures, the presented structure is capable of fully reversible (two-way) shape morphing, while also preserving its shape after removing the stimulus. This allows for positioning without continuous actuation. The shell achieves a significant range of motion and, since the elastic deformation reaction forces do not need to be overcome, it is capable of generating actuation force. Since the actuation concept does not require a complex patterning of active materials to achieve the desired deformation, it can potentially also be applied to other neutrally stable structures.

Original languageEnglish
Pages (from-to)1664-1677
JournalJournal of Intelligent Material Systems and Structures
Issue number14
Publication statusPublished - 2023


  • compliant shells
  • embedded actuation
  • neutral stability
  • Shape morphing
  • variable stiffness


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