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Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers.

Mao Y, Yu K, Isakov MS, Wu J, Dunn ML, Jerry Qi H - Sci Rep (2015)

Bottom Line: A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics.An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding.A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

View Article: PubMed Central - PubMed

Affiliation: The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.

ABSTRACT
Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging of solar cells and space structures, deployable biomedical devices, and self-assembling robots and airbags. Here we demonstrate sequential self-folding structures realized by thermal activation of spatially-variable patterns that are 3D printed with digital shape memory polymers, which are digital materials with different shape memory behaviors. The time-dependent behavior of each polymer allows the temporal sequencing of activation when the structure is subjected to a uniform temperature. This is demonstrated via a series of 3D printed structures that respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. Measurements of the spatial and temporal nature of self-folding structures are in good agreement with the companion finite element simulations. A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics. An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding. A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

No MeSH data available.


3D folding structures mimicking the USPS mailbox.(a) A USPS mailbox is folded into a box by following a sequence of folding. (b) A programmed 3D printed sheet with different materials assigned at different hinges. (c–f) The design of the folding box with some details at the hinges. (g–j) Upon heating, the sheet folds into a box with self-locking mechanism.
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f6: 3D folding structures mimicking the USPS mailbox.(a) A USPS mailbox is folded into a box by following a sequence of folding. (b) A programmed 3D printed sheet with different materials assigned at different hinges. (c–f) The design of the folding box with some details at the hinges. (g–j) Upon heating, the sheet folds into a box with self-locking mechanism.

Mentions: Folding boxes are notable folding structures in daily life and widely used in packaging. They normally require a folding sequence in order to form a stable and fully packed structure. Taking a USPS mailbox (Fig. 6a) as an example, one can have a sheet of hard board paper cut into a specific shape. At the time of usage, one folds the box in a sequential manner; the red lines represent the first group of folds, where some lips are folded to form supports; the blue lines represents the second group of folds to partially close the box; the final folds (black lines) insert the two small lids (on the left top and bottom) into the holes formed by the long blue line folds to increase the stability of the box; also the white color patch represents glue that will seal the structure to from a final strong and stable box. Inspired by this, we design a 3D folding box with an internal locking mechanism, as shown in Fig. 6b. Three types of hinges are used. Hinge H-3 is used on the smaller lips to enable fast folding of these lips (red lines). Hinge H-5 is used in the location indicated by the green line, to enable intermediate folding speeds such that some self-support and self-locking mechanism can be formed. Hinge H-6 (black lines) has the slowest folding speed and is used to form the final structure. The original shape of the box is shown in Fig 6c. Since curved portions of the hinges are not in the printing plane, these hinges are suspect to damage during unfolding. To improve the damage tolerance, hinges are specially designed (Fig. 6d–f). A periodic step profile is employed along the surface contour of the hinge (Fig. 6d). Thinner stepwise sections require lower bending stress and have higher thermal conductivity, making it both easier and faster to unfold complex assemblies. Additionally, the periodic profile allows for a wider range of bending motion since the hinge is not subject to restrictive compressive strains. Thicker stepwise sections serve to maintain part rigidity through higher average modulus than a thin hinge alone. To secure the interface between hinges and structural faces, the hinges are embedded within the structural faces and reinforced with a triangular interface to maximize axial strength (Fig. 6e). Longer hinges are equipped with slots cut along the length of the jagged contours to isolate fracture points such that the assembly would not be compromised should a fracture occur (Fig. 6f). Figure 6g–j show the folding sequence. The whole structure folds back in about 11 seconds.


Sequential Self-Folding Structures by 3D Printed Digital Shape Memory Polymers.

Mao Y, Yu K, Isakov MS, Wu J, Dunn ML, Jerry Qi H - Sci Rep (2015)

3D folding structures mimicking the USPS mailbox.(a) A USPS mailbox is folded into a box by following a sequence of folding. (b) A programmed 3D printed sheet with different materials assigned at different hinges. (c–f) The design of the folding box with some details at the hinges. (g–j) Upon heating, the sheet folds into a box with self-locking mechanism.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562068&req=5

f6: 3D folding structures mimicking the USPS mailbox.(a) A USPS mailbox is folded into a box by following a sequence of folding. (b) A programmed 3D printed sheet with different materials assigned at different hinges. (c–f) The design of the folding box with some details at the hinges. (g–j) Upon heating, the sheet folds into a box with self-locking mechanism.
Mentions: Folding boxes are notable folding structures in daily life and widely used in packaging. They normally require a folding sequence in order to form a stable and fully packed structure. Taking a USPS mailbox (Fig. 6a) as an example, one can have a sheet of hard board paper cut into a specific shape. At the time of usage, one folds the box in a sequential manner; the red lines represent the first group of folds, where some lips are folded to form supports; the blue lines represents the second group of folds to partially close the box; the final folds (black lines) insert the two small lids (on the left top and bottom) into the holes formed by the long blue line folds to increase the stability of the box; also the white color patch represents glue that will seal the structure to from a final strong and stable box. Inspired by this, we design a 3D folding box with an internal locking mechanism, as shown in Fig. 6b. Three types of hinges are used. Hinge H-3 is used on the smaller lips to enable fast folding of these lips (red lines). Hinge H-5 is used in the location indicated by the green line, to enable intermediate folding speeds such that some self-support and self-locking mechanism can be formed. Hinge H-6 (black lines) has the slowest folding speed and is used to form the final structure. The original shape of the box is shown in Fig 6c. Since curved portions of the hinges are not in the printing plane, these hinges are suspect to damage during unfolding. To improve the damage tolerance, hinges are specially designed (Fig. 6d–f). A periodic step profile is employed along the surface contour of the hinge (Fig. 6d). Thinner stepwise sections require lower bending stress and have higher thermal conductivity, making it both easier and faster to unfold complex assemblies. Additionally, the periodic profile allows for a wider range of bending motion since the hinge is not subject to restrictive compressive strains. Thicker stepwise sections serve to maintain part rigidity through higher average modulus than a thin hinge alone. To secure the interface between hinges and structural faces, the hinges are embedded within the structural faces and reinforced with a triangular interface to maximize axial strength (Fig. 6e). Longer hinges are equipped with slots cut along the length of the jagged contours to isolate fracture points such that the assembly would not be compromised should a fracture occur (Fig. 6f). Figure 6g–j show the folding sequence. The whole structure folds back in about 11 seconds.

Bottom Line: A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics.An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding.A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

View Article: PubMed Central - PubMed

Affiliation: The George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332, USA.

ABSTRACT
Folding is ubiquitous in nature with examples ranging from the formation of cellular components to winged insects. It finds technological applications including packaging of solar cells and space structures, deployable biomedical devices, and self-assembling robots and airbags. Here we demonstrate sequential self-folding structures realized by thermal activation of spatially-variable patterns that are 3D printed with digital shape memory polymers, which are digital materials with different shape memory behaviors. The time-dependent behavior of each polymer allows the temporal sequencing of activation when the structure is subjected to a uniform temperature. This is demonstrated via a series of 3D printed structures that respond rapidly to a thermal stimulus, and self-fold to specified shapes in controlled shape changing sequences. Measurements of the spatial and temporal nature of self-folding structures are in good agreement with the companion finite element simulations. A simplified reduced-order model is also developed to rapidly and accurately describe the self-folding physics. An important aspect of self-folding is the management of self-collisions, where different portions of the folding structure contact and then block further folding. A metric is developed to predict collisions and is used together with the reduced-order model to design self-folding structures that lock themselves into stable desired configurations.

No MeSH data available.