Bio-inspired wooden actuators for large scale applications

PLoS One. 2015 Apr 2;10(3):e0120718. doi: 10.1371/journal.pone.0120718. eCollection 2015.


Implementing programmable actuation into materials and structures is a major topic in the field of smart materials. In particular the bilayer principle has been employed to develop actuators that respond to various kinds of stimuli. A multitude of small scale applications down to micrometer size have been developed, but up-scaling remains challenging due to either limitations in mechanical stiffness of the material or in the manufacturing processes. Here, we demonstrate the actuation of wooden bilayers in response to changes in relative humidity, making use of the high material stiffness and a good machinability to reach large scale actuation and application. Amplitude and response time of the actuation were measured and can be predicted and controlled by adapting the geometry and the constitution of the bilayers. Field tests in full weathering conditions revealed long-term stability of the actuation. The potential of the concept is shown by a first demonstrator. With the sensor and actuator intrinsically incorporated in the wooden bilayers, the daily change in relative humidity is exploited for an autonomous and solar powered movement of a tracker for solar modules.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms*
  • Models, Theoretical*

Grant support

MR was funded by the Empa/Marie-Curie COFUND Program and within the framework of the BTA flagship project of the Climate-KIC program. IB receives supportive funding of the Wood Materials Science group at ETH Zürich and Empa by BAFU (Bundesamt für Umwelt) and Lignum, Switzerland. The work also received funding from Climate-KIC in the framework of the flagship project BTA (Building Technology Accelerator). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.