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Highly-stretchable 3D-architected Mechanical Metamaterials

View Article: PubMed Central - PubMed

ABSTRACT

Soft materials featuring both 3D free-form architectures and high stretchability are highly desirable for a number of engineering applications ranging from cushion modulators, soft robots to stretchable electronics; however, both the manufacturing and fundamental mechanics are largely elusive. Here, we overcome the manufacturing difficulties and report a class of mechanical metamaterials that not only features 3D free-form lattice architectures but also poses ultrahigh reversible stretchability (strain > 414%), 4 times higher than that of the existing counterparts with the similar complexity of 3D architectures. The microarchitected metamaterials, made of highly stretchable elastomers, are realized through an additive manufacturing technique, projection microstereolithography, and its postprocessing. With the fabricated metamaterials, we reveal their exotic mechanical behaviors: Under large-strain tension, their moduli follow a linear scaling relationship with their densities regardless of architecture types, in sharp contrast to the architecture-dependent modulus power-law of the existing engineering materials; under large-strain compression, they present tunable negative-stiffness that enables ultrahigh energy absorption efficiencies. To harness their extraordinary stretchability and microstructures, we demonstrate that the metamaterials open a number of application avenues in lightweight and flexible structure connectors, ultraefficient dampers, 3D meshed rehabilitation structures and stretchable electronics with designed 3D anisotropic conductivity.

No MeSH data available.


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Applications of elastomer-lattice structures.(A) An Octet elastomer lattice bonded between two Octet HDDA lattices (i) can sustain bending by 180° (ii) and twisting by 360°. (B) A metal weight (36 g) freely dropped from 100 mm height onto a damper-protected HDDA thin shell (i). The HDDA shell is still intact if the damper is an Octet elastomer lattice (ii, ρ/ρ0 = 26%), but all broken if the damper is an elastomer solid (iii), an Octet HDDA lattice (iv, ρ/ρ0 ~ 26%) or an elastomer foam (v, ρ/ρ0 = 26%). (C) A finger rehabilitation device: (i) A cylindrical lattice with gradient density along the longitudinal direction (marked by the red arrow). The inset shows the calculated relative density along the longitudinal path. (ii) A fabricated elastomer lattice sample with gradient shear modulus along the longitudinal path (shown in the inset). The shear modulus is calculated by μ/μ0 = 0.49 ρ/ρ0 (Octet). (iii) The finger covered with the elastomer lattice can reversibly undergo large-strain bending. (D) A stretchable elastomer-lattice conductor: (i) A schematic to show the stretchable conductor structure. 1–4 denotes the wire connectors that can be connected to the electric circuit shown in Supplementary Fig. 25. (ii) The stretchable conductor under tensile strain ~2.5 is still conductive enough to power a LED light. (iii) The resistances along different conductive paths (e.g., path 1–2 and path 3–4) in functions of increasing tensile strains. All scale bars denote 4 mm.
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f5: Applications of elastomer-lattice structures.(A) An Octet elastomer lattice bonded between two Octet HDDA lattices (i) can sustain bending by 180° (ii) and twisting by 360°. (B) A metal weight (36 g) freely dropped from 100 mm height onto a damper-protected HDDA thin shell (i). The HDDA shell is still intact if the damper is an Octet elastomer lattice (ii, ρ/ρ0 = 26%), but all broken if the damper is an elastomer solid (iii), an Octet HDDA lattice (iv, ρ/ρ0 ~ 26%) or an elastomer foam (v, ρ/ρ0 = 26%). (C) A finger rehabilitation device: (i) A cylindrical lattice with gradient density along the longitudinal direction (marked by the red arrow). The inset shows the calculated relative density along the longitudinal path. (ii) A fabricated elastomer lattice sample with gradient shear modulus along the longitudinal path (shown in the inset). The shear modulus is calculated by μ/μ0 = 0.49 ρ/ρ0 (Octet). (iii) The finger covered with the elastomer lattice can reversibly undergo large-strain bending. (D) A stretchable elastomer-lattice conductor: (i) A schematic to show the stretchable conductor structure. 1–4 denotes the wire connectors that can be connected to the electric circuit shown in Supplementary Fig. 25. (ii) The stretchable conductor under tensile strain ~2.5 is still conductive enough to power a LED light. (iii) The resistances along different conductive paths (e.g., path 1–2 and path 3–4) in functions of increasing tensile strains. All scale bars denote 4 mm.

Mentions: Thanks to the unprecedented combination of high-stretchability, high-complexity in architecture, low density and easy-shapeability, the elastomer metamaterials can facilitate a number of applications. First, in robotic and 4D printing applications, connectors are required to bridge parts to flexibly bend or rotate; however, the existing connectors are either thermoplastics with drawbacks in limited deformability and cyclability, or bulk soft materials short in high density832464748. Here we demonstrate that our elastomer lattices can enable high-flexibility of the structural bridging between 3D printed rigid plastic parts to reversibly sustain large-strain stretching, compression, bending and twisting, yet keeping the whole system at a very low density (Fig. 5A, Supplementary Fig. 21).


Highly-stretchable 3D-architected Mechanical Metamaterials
Applications of elastomer-lattice structures.(A) An Octet elastomer lattice bonded between two Octet HDDA lattices (i) can sustain bending by 180° (ii) and twisting by 360°. (B) A metal weight (36 g) freely dropped from 100 mm height onto a damper-protected HDDA thin shell (i). The HDDA shell is still intact if the damper is an Octet elastomer lattice (ii, ρ/ρ0 = 26%), but all broken if the damper is an elastomer solid (iii), an Octet HDDA lattice (iv, ρ/ρ0 ~ 26%) or an elastomer foam (v, ρ/ρ0 = 26%). (C) A finger rehabilitation device: (i) A cylindrical lattice with gradient density along the longitudinal direction (marked by the red arrow). The inset shows the calculated relative density along the longitudinal path. (ii) A fabricated elastomer lattice sample with gradient shear modulus along the longitudinal path (shown in the inset). The shear modulus is calculated by μ/μ0 = 0.49 ρ/ρ0 (Octet). (iii) The finger covered with the elastomer lattice can reversibly undergo large-strain bending. (D) A stretchable elastomer-lattice conductor: (i) A schematic to show the stretchable conductor structure. 1–4 denotes the wire connectors that can be connected to the electric circuit shown in Supplementary Fig. 25. (ii) The stretchable conductor under tensile strain ~2.5 is still conductive enough to power a LED light. (iii) The resistances along different conductive paths (e.g., path 1–2 and path 3–4) in functions of increasing tensile strains. All scale bars denote 4 mm.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5035992&req=5

f5: Applications of elastomer-lattice structures.(A) An Octet elastomer lattice bonded between two Octet HDDA lattices (i) can sustain bending by 180° (ii) and twisting by 360°. (B) A metal weight (36 g) freely dropped from 100 mm height onto a damper-protected HDDA thin shell (i). The HDDA shell is still intact if the damper is an Octet elastomer lattice (ii, ρ/ρ0 = 26%), but all broken if the damper is an elastomer solid (iii), an Octet HDDA lattice (iv, ρ/ρ0 ~ 26%) or an elastomer foam (v, ρ/ρ0 = 26%). (C) A finger rehabilitation device: (i) A cylindrical lattice with gradient density along the longitudinal direction (marked by the red arrow). The inset shows the calculated relative density along the longitudinal path. (ii) A fabricated elastomer lattice sample with gradient shear modulus along the longitudinal path (shown in the inset). The shear modulus is calculated by μ/μ0 = 0.49 ρ/ρ0 (Octet). (iii) The finger covered with the elastomer lattice can reversibly undergo large-strain bending. (D) A stretchable elastomer-lattice conductor: (i) A schematic to show the stretchable conductor structure. 1–4 denotes the wire connectors that can be connected to the electric circuit shown in Supplementary Fig. 25. (ii) The stretchable conductor under tensile strain ~2.5 is still conductive enough to power a LED light. (iii) The resistances along different conductive paths (e.g., path 1–2 and path 3–4) in functions of increasing tensile strains. All scale bars denote 4 mm.
Mentions: Thanks to the unprecedented combination of high-stretchability, high-complexity in architecture, low density and easy-shapeability, the elastomer metamaterials can facilitate a number of applications. First, in robotic and 4D printing applications, connectors are required to bridge parts to flexibly bend or rotate; however, the existing connectors are either thermoplastics with drawbacks in limited deformability and cyclability, or bulk soft materials short in high density832464748. Here we demonstrate that our elastomer lattices can enable high-flexibility of the structural bridging between 3D printed rigid plastic parts to reversibly sustain large-strain stretching, compression, bending and twisting, yet keeping the whole system at a very low density (Fig. 5A, Supplementary Fig. 21).

View Article: PubMed Central - PubMed

ABSTRACT

Soft materials featuring both 3D free-form architectures and high stretchability are highly desirable for a number of engineering applications ranging from cushion modulators, soft robots to stretchable electronics; however, both the manufacturing and fundamental mechanics are largely elusive. Here, we overcome the manufacturing difficulties and report a class of mechanical metamaterials that not only features 3D free-form lattice architectures but also poses ultrahigh reversible stretchability (strain > 414%), 4 times higher than that of the existing counterparts with the similar complexity of 3D architectures. The microarchitected metamaterials, made of highly stretchable elastomers, are realized through an additive manufacturing technique, projection microstereolithography, and its postprocessing. With the fabricated metamaterials, we reveal their exotic mechanical behaviors: Under large-strain tension, their moduli follow a linear scaling relationship with their densities regardless of architecture types, in sharp contrast to the architecture-dependent modulus power-law of the existing engineering materials; under large-strain compression, they present tunable negative-stiffness that enables ultrahigh energy absorption efficiencies. To harness their extraordinary stretchability and microstructures, we demonstrate that the metamaterials open a number of application avenues in lightweight and flexible structure connectors, ultraefficient dampers, 3D meshed rehabilitation structures and stretchable electronics with designed 3D anisotropic conductivity.

No MeSH data available.


Related in: MedlinePlus