A variable stiffness joint with electrospun P(VDF-TrFE-CTFE) variable stiffness springs

Raffaella Carloni*, Valerie I. Lapp, Andrea Cremonese, Juri Belcari, Andrea Zucchelli

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

9 Citations (Scopus)
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This letter presents a novel rotational variable stiffness joint that relies on one motor and a set of variable stiffness springs. The variable stiffness springs are leaf springs with a layered design, i.e., an electro-active layer of electrospun aligned nanofibers of poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) [P(VDF-TrFE-CTFE)] surrounded by two electrodes of aluminum and held together by inactive material. To achieve a variable stiffness, different voltages and, therefore, different electric fields, are applied to the springs. The variable stiffness springs are electromechanically analyzed to highlight the voltage-deflection and force-deflection characteristics. Finally, the springs are used in the design of a proof-of-concept variable stiffness joint prototype. Experimental results on the variable stiffness joint confirm the viability of the proposed solution.

Original languageEnglish
Pages (from-to)973-978
Number of pages6
JournalIEEE Robotics and Automation Letters
Issue number2
Early online date15-Jan-2018
Publication statusPublished - Apr-2018


  • Soft material robotics
  • compliant joint/mechanism

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