Shape Change Through Programmable Stiffness

  • Michael McEvoy
  • Nikolaus CorrellEmail author
Part of the Springer Tracts in Advanced Robotics book series (STAR, volume 109)


We present a composite material with embedded sensing and actuation that can perform permanent shape changes by temporarily varying its stiffness and applying an external moment. Varying stiffness is a complementary approach to actuator-chain based approaches that can be accomplished using a large variety of means ranging from heat, electric field or vacuum. A polycaprolactone (PCL) bar provides stiffness at room temperature. Heating elements and thermistors are distributed along the bar so that local regions can be tuned to a specific temperature/stiffness. Applying an external moment using two tendon actuators then lets the material snap into a desired shape. We describe the composite structure, the principles behind shape change using variable stiffness control, and forward and inverse kinematics of the system. We present experimental results using a 5-element bar that can assume different global conformations using two simple actuators.


Multi-functional materials Embedded computation Variable stiffness 



This work has been supported by the Airforce Office of Scientific Research under grant number FA9550-12-1-0145, the National Science Foundation under grants number #1150223 and #1153158, and a Beverly Sear’s Graduate Student Research Grant. We are grateful for this support.


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Copyright information

© Springer International Publishing Switzerland 2016

Authors and Affiliations

  1. 1.Department of Computer ScienceUniversity of Colorado at BoulderBoulderUSA

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