Improving the actuation speed and multi-cyclic actuation characteristics of silicone/ethanol soft actuators

Boxi Xia, Aslan Miriyev, Cesar Trujillo, Neil Chen, Mark Cartolano, Shivaniprashant Vartak, Hod Lipson

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The actuation of silicone/ethanol soft composite material-actuators is based on the phase change of ethanol upon heating, followed by the expansion of the whole composite, exhibiting high actuation stress and strain. However, the low thermal conductivity of silicone rubber hinders uniform heating throughout the material, creating overheated damaged areas in the silicone matrix and accelerating ethanol evaporation. This limits the actuation speed and the total number of operation cycles of these thermally-driven soft actuators. In this paper, we showed that adding 8 wt.% of diamond nanoparticle-based thermally conductive filler increases the thermal conductivity (from 0.190 W/mK to 0.212 W/mK), actuation speed and amount of operation cycles of silicone/ethanol actuators, while not affecting the mechanical properties. We performed multi-cyclic actuation tests and showed that the faster and longer operation of 8 wt.% filler material-actuators allows collecting enough reliable data for computational methods to model further actuation behavior. We successfully implemented a long short-term memory (LSTM) neural network model to predict the actuation force exerted in a uniform multi-cyclic actuation experiment. This work paves the way for a broader implementation of soft thermally-driven actuators in various robotic applications.

Original languageEnglish
Article number62
Issue number3
StatePublished - 1 Sep 2020
Externally publishedYes


  • Actuation speed
  • Machine learning
  • Mechanical properties
  • Multi-cyclic actuation
  • Neural networks
  • Performance prediction
  • Silicone/ethanol
  • Soft actuator
  • Thermal conductivity

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Control and Optimization


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