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Proceedings Paper

Wood as inspiration for new stimuli-responsive structures and materials
Author(s): Joseph E. Jakes; Nayomi Plaza; Samuel L. Zelinka; Donald S. Stone; Sophie-Charlotte Gleber; Stefan Vogt
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Paper Abstract

Nature has often provided inspiration for new smart structures and materials. Recently, we showed a bundle of a few wood cells are moisture-activated torsional actuators that can reversibly twist multiple revolutions per centimeter of length. The bundles produce specific torque higher than that produced by electric motors and possess shape memory twist capabilities. Here we also report that ion diffusion through wood cell walls is a stimuli-responsive phenomenon. Using the high spatial resolution and sensitivity of synchrotron-based x-ray fluorescence microscopy (XFM), metal ions deposited into individual wood cell walls were mapped. Then, using a custom-built relative humidity (RH) chamber, diffusion of the metal ions was observed in situ first at low RH and then at increasingly higher RH. We found that ions did not diffuse through wood cell walls at low RH, but diffusion occurred at high RH. We propose that both the shape memory twist effect and the moisture content threshold for ionic diffusion are controlled by the hemicelluloses passing through a moisture-dependent glass transition in the 60-80% RH range at room temperature. An advantage of wood over other stimuli-responsive polymers is that wood lacks bulk mechanical softening at the transition that controls the stimuliresponsive behavior. We demonstrate using a custom-built torque sensor that the torque generation in wood cell bundles actually continues to increase over the RH range that hemicelluloses soften. The hierarchical structure of wood provides the inspiration to engineer stimuli-responsive polymers and actuators with increased mechanical strength and higher recovery stresses.

Paper Details

Date Published: 8 March 2014
PDF: 13 pages
Proc. SPIE 9055, Bioinspiration, Biomimetics, and Bioreplication 2014, 90550K (8 March 2014); doi: 10.1117/12.2045163
Show Author Affiliations
Joseph E. Jakes, U.S. Forest Service (United States)
Nayomi Plaza, U.S. Forest Service (United States)
Univ. of Wisconsin-Madison (United States)
Samuel L. Zelinka, U.S. Forest Service (United States)
Donald S. Stone, Univ. of Wisconsin-Madison (United States)
Sophie-Charlotte Gleber, Argonne National Lab. (United States)
Stefan Vogt, Argonne National Lab. (United States)


Published in SPIE Proceedings Vol. 9055:
Bioinspiration, Biomimetics, and Bioreplication 2014
Akhlesh Lakhtakia, Editor(s)

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