3D‐Printed Silicone Soft Architectures with Programmed Magneto‐Capillary Reconfiguration

Abstract

Soft intelligent structures that are programmed to reshape and reconfigure under magnetic field can find applications such as in soft robotics and biomedical devices. Here, a new class of smart elastomeric architectures that undergo complex reconfiguration and shape change in applied magnetic fields, while floating on the surface of water, is reported. These magnetoactive soft actuators are fabricated by 3D printing with homocomposite silicone capillary ink. The ultrasoft actuators easily deform by the magnetic force exerted on carbonyl iron particles embedded in the silicone, as well as lateral capillary forces. The tensile and compressive moduli of the actuators are easily determined by their topological design through 3D printing. As a result, their responses can be engineered by the interplay of the intensity of the magnetic field gradient and the programmable moduli. 3D printing allows us to fabricate soft architectures with different actuation modes, such as isotropic/anisotropic contraction and multiple shape changes, as well as functional reconfiguration. Meshes that reconfigure in magnetic fields and respond to external stimuli by reshaping could serve as active tissue scaffolds for cell cultures and soft robots mimicking creatures that live on the surface of water.

Multifunctional magnetic soft composites: a review

“…Direct ink writing (DIW) printing is an extrusion-based additive manufacturing method by which materials with shear-thinning properties are extruded from printing nozzles. It is a flexible filament-by-filament printing method that serves as a tool for fabricating single or multi-material geometries, including magnetic hydrogels [ 105 ], elastomers [ 49 , 106 ], and SMPs [ 78 , 107 ] with complex structures and programmed magnetization distributions. Recent work develops a customized DIW printing system with in-situ magnetization programming capability, where the magnetizations of NdFeB particles are aligned along the extrusion direction under a localized magnetic field.…”

“…The properties and functionalities of the soft material systems are related to the configurations and deformations of the structures. With the ability to undergo large deformations as programmed, the mechanical [ 46 , 80 , 107 , 121 ], optical [ 112 , 122 ], and acoustic properties [ 120 , 123 – 127 ], or wettability [ 106 , 119 ] of magnetic soft composites are actively tunable under the applied magnetic field. For instance, an array of microplates embedded with aligned Fe microparticles possess a superhydrophobic or hydrophilic surface on each side of the plates ( figure 5(d) [ 119 ]).…”

Smart composites with tunable stress–strain curves

“…Consequently, they are suitable for application in tunable mechanical and structural components such as actuators under cyclic loading [21][22][23]. Indeed, tunable materials and smart composites can provide alternative means of achieving actuation in robotics and aerospace where there is a need for tunable stiffness [24,25] with the magnetic field as a particularly suitable method for inducing actutation in the presence of intricate geometries [26,27], which further highlights the underlying motivation of this work from a broad perspective.…”

Composite Reinforcement Architectures: A Review of Field-Assisted Additive Manufacturing for Polymers

“…The process of printing such structures also involved extrusion of an ink with neodymium-iron-boron particles through conical micro-nozzles with a 50 mT magnetic field applied at the point of exit using an electromagnet or a permanent magnet. Printed magnetic actuators with carbonyl iron beads have also shown the potential to behave as soft intelligent structures that can be programmed to reshape and reconfigure when exposed to a magnetic field and are capable of floating on water [100]. However, such materials [100,101] are primarily used for shape-memory applications and can be categorized as 4D printing rather than improved mechanical properties in AM.…”

“…Printed magnetic actuators with carbonyl iron beads have also shown the potential to behave as soft intelligent structures that can be programmed to reshape and reconfigure when exposed to a magnetic field and are capable of floating on water [100]. However, such materials [100,101] are primarily used for shape-memory applications and can be categorized as 4D printing rather than improved mechanical properties in AM. Although magnetic particles are typically used for prints in the millimeter to micrometer range, the Oakridge National Lab has implemented a composite material with 65 vol.% of NdFeB in Nylon-12 to manufacture large magnets using their Big Area Additive Manufacturing (BAAM) system and compared results with traditional injection-molded magnets to prove that BAAM is capable of producing a better hysteresis loop and higher intrinsic coercivity and remanence values [102].…”