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Title: Wood as inspiration for new stimuli-responsive structures and materials

Source: Proceedings of SPIE Volume 9055, 90550K 2014 SPIE. 13 p.

Author(s)Jakes, Joseph E.; Plaza-Rodriguez, Nayomi; Zelinka, Samuel L.; Stone, Donald S.; Gleber, Sophie-Charlotte; Vogt, Stefan

Publication Year: 2014  View PDF »

Category: Conference Proceedings
Associated Research Project(s):   FPL-4707-2B  FPL-4723-1B

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 stimuli- responsive 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.

Keywords: shape memory; torsional actuator; wood; stimuli-responsive diffusion

Publication Review Process: Informally Refereed (Peer-Reviewed)

File size: 562 kb(s)

Date posted: 05/14/2014

This publication is also viewable on Treesearch:  view
RITS Product ID: 67701
Current FPL Scientists associated with this product (listed alphabetically)
Jakes, Joseph
Research Materials Engineer
Plaza Rodriguez, Nayomi
Research Materials Engineer
Zelinka, Samuel L.
Materials Research Engineer

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