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Bio-inspired wooden actuators for large scale applications.

Rüggeberg M, Burgert I - PLoS ONE (2015)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Building Materials, Swiss Federal Institute of Technology Zürich (ETH Zürich), Zürich, Switzerland; Applied Wood Materials, Swiss Federal Laoratories of Materials Science and Technology (EMPA), Dübendorf, Switzerland.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus

Configuration of beech strips, spruce strips and bilayers and their response to drying.a) Cutting direction of single layers of beech and spruce and their dimensional changes after a decrease in wood moisture content of 10%. L = longitudinal direction, R = radial direction, T = tangential direction; WMC = wood moisture content; rH = relative humidity; green arrows indicate fibre direction and cellulose microfibril orientation (as the microfibrils are oriented almost parallel to the fibre axis). The relative dimensional changes along the long axis of the strips are given in red (specific values for the strips shown). b) Bending of a corresponding bilayer following the change in wood moisture content.
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pone.0120718.g001: Configuration of beech strips, spruce strips and bilayers and their response to drying.a) Cutting direction of single layers of beech and spruce and their dimensional changes after a decrease in wood moisture content of 10%. L = longitudinal direction, R = radial direction, T = tangential direction; WMC = wood moisture content; rH = relative humidity; green arrows indicate fibre direction and cellulose microfibril orientation (as the microfibrils are oriented almost parallel to the fibre axis). The relative dimensional changes along the long axis of the strips are given in red (specific values for the strips shown). b) Bending of a corresponding bilayer following the change in wood moisture content.

Mentions: Strips of 120mm length, 20mm width and various thicknesses between 1-4mm were cut from boards of spruce and beech which were obtained from a local wood supplier (Paul Aecherli AG, Regensdorf, Switzerland). Spruce strips with a thickness of 0.2mm and 0.8mm were cut from commercially available sliced veneers (Hess & Co. AG, Döttingen, Switzerland). The beech strips were used as active layer with swelling and shrinking along the long axis of the strip. They were cut with the fibre direction perpendicular to the long axis of the strips with an inclination of the annual rings of 20–25°. This is close to the tangential orientation (Fig. 1a) which is subjected to the largest dimensional changes [15]. The spruce strips were used as resistive layer and cut with the fibre direction parallel to the long axis of the samples and with an inclination of the annual rings of 90° (longitudinal–radial orientation). The strips were stored at 65% relative humidity and 20°C. Prior to gluing and to any experiment the strips and bilayers were equilibrated at the required initial experimental condition for at least 72 hours. Bilayers were prepared (Fig. 1b) by gluing together a beech and a spruce strip with the polyurethane glue HB-S309 (Purbond, Switzerland). The strips and bilayers were weighed immediately before and after gluing and curing to determine the weight of the added glue.


Bio-inspired wooden actuators for large scale applications.

Rüggeberg M, Burgert I - PLoS ONE (2015)

Configuration of beech strips, spruce strips and bilayers and their response to drying.a) Cutting direction of single layers of beech and spruce and their dimensional changes after a decrease in wood moisture content of 10%. L = longitudinal direction, R = radial direction, T = tangential direction; WMC = wood moisture content; rH = relative humidity; green arrows indicate fibre direction and cellulose microfibril orientation (as the microfibrils are oriented almost parallel to the fibre axis). The relative dimensional changes along the long axis of the strips are given in red (specific values for the strips shown). b) Bending of a corresponding bilayer following the change in wood moisture content.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4383548&req=5

pone.0120718.g001: Configuration of beech strips, spruce strips and bilayers and their response to drying.a) Cutting direction of single layers of beech and spruce and their dimensional changes after a decrease in wood moisture content of 10%. L = longitudinal direction, R = radial direction, T = tangential direction; WMC = wood moisture content; rH = relative humidity; green arrows indicate fibre direction and cellulose microfibril orientation (as the microfibrils are oriented almost parallel to the fibre axis). The relative dimensional changes along the long axis of the strips are given in red (specific values for the strips shown). b) Bending of a corresponding bilayer following the change in wood moisture content.
Mentions: Strips of 120mm length, 20mm width and various thicknesses between 1-4mm were cut from boards of spruce and beech which were obtained from a local wood supplier (Paul Aecherli AG, Regensdorf, Switzerland). Spruce strips with a thickness of 0.2mm and 0.8mm were cut from commercially available sliced veneers (Hess & Co. AG, Döttingen, Switzerland). The beech strips were used as active layer with swelling and shrinking along the long axis of the strip. They were cut with the fibre direction perpendicular to the long axis of the strips with an inclination of the annual rings of 20–25°. This is close to the tangential orientation (Fig. 1a) which is subjected to the largest dimensional changes [15]. The spruce strips were used as resistive layer and cut with the fibre direction parallel to the long axis of the samples and with an inclination of the annual rings of 90° (longitudinal–radial orientation). The strips were stored at 65% relative humidity and 20°C. Prior to gluing and to any experiment the strips and bilayers were equilibrated at the required initial experimental condition for at least 72 hours. Bilayers were prepared (Fig. 1b) by gluing together a beech and a spruce strip with the polyurethane glue HB-S309 (Purbond, Switzerland). The strips and bilayers were weighed immediately before and after gluing and curing to determine the weight of the added glue.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Institute for Building Materials, Swiss Federal Institute of Technology Zürich (ETH Zürich), Zürich, Switzerland; Applied Wood Materials, Swiss Federal Laoratories of Materials Science and Technology (EMPA), Dübendorf, Switzerland.

ABSTRACT
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.

No MeSH data available.


Related in: MedlinePlus