Research ArticleAPPLIED SCIENCES AND ENGINEERING

Reprogrammable shape morphing of magnetic soft machines

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Science Advances  18 Sep 2020:
Vol. 6, no. 38, eabc6414
DOI: 10.1126/sciadv.abc6414
  • Fig. 1 Heat-assisted 3D magnetic programming of magnetic soft machines.

    (A) A magnetic soft elastomer, composed of magnetic CrO2 particles embedded in PDMS, is locally heated above the Curie temperature of the particles via a laser. Above the Curie temperature, the particles lose their permanent magnetization, and their magnetization direction is reoriented by applying an external magnetic field during cooling. R.T., room temperature. (B) The magnetic soft elastomer is heated above the Curie temperature of the CrO2 particles (118°C) in 1.7 s and cooled down to half of this temperature in 4 s. (C) The magnetic soft elastomer is magnetized with 90% efficiency by heat-assisted magnetization and demagnetized by only heating above the Curie temperature without any external magnetic field. Error bars represent the SD of the mean. (D to G) Examples of the magnetic soft elastomer cut into the shapes of a body with a tail and wings (D) and a six-legged body (E) with corresponding magnetization directions (indicated by red arrows) and out-of-plane magnetic flux profile measurements. Color bars indicate magnetic flux density strength. (F and G) Upon magnetic actuation, individual parts underwent shape change in accordance with their programmed magnetization directions. Scale bars, 2 mm. Insets show the initial shape of the structures in the absence of magnetic fields. (H and I) Bodies with wings and legs are stacked to generate a 3D hierarchical dragonfly structure upon magnetic actuation. Scale bar, 2 mm. Actuation of the structures is performed by applying magnetic fields of 60 mT in the directions indicated with the black arrows.

  • Fig. 2 Discrete and 3D magnetization of magnetic soft structures.

    (A to D) Distributed 3D magnetizations, out-of-plane magnetic flux density profile measurements, finite element simulations, and experimental shape changes upon magnetic actuation of a four-segment ring (A), eight-segment ring (B), a half-sphere (C), and a cube structure (D). Scale bars, 1 mm. Actuation was performed by applying a magnetic field of 60 mT in the directions indicated with the black arrows.

  • Fig. 3 Reprogrammable magnetization of 2D magnetic soft machines.

    (A) Distributed 3D magnetizations, out-of-plane magnetic flux density profile measurements, finite element simulations, and experimental shape changes upon magnetic actuation of a stickman structure. (B and C) Reprogramming the distributed magnetization directions in the stickman structure enables reconfiguring the shape changes. Red arrows indicate local magnetization directions. Color bars indicate magnetic flux density strength and total deformation, respectively. Scale bar, 1 mm. (D to J) Tuning mechanical behavior of an auxetic metamaterial by reprogramming the distributed magnetization profile of individual units. The length and width of the whole structure are denoted with a and b, respectively. (E to G) The flexible auxetic structure expands and compresses both in length and width depending on the magnetic actuation direction, displaying a negative Poisson’s ratio. (H to J) Reprogramming the magnetization profile of three units in the middle results in an expansion in width with minimal change in length irrespective of the magnetic actuation direction. Red arrows indicate local magnetization directions. Green solid lines show the reprogrammed regions. Scale bar, 5 mm. Actuation of the structures is performed by applying uniform magnetic fields of 60 mT in the directions indicated with the black arrows. (K to P) Reprogramming magnetization profile of a quadrupedal soft robot enables tunable locomotion patterns. (K and N) Magnetization directions of the legs are programmed to generate different deformation configurations. Red arrows indicate local magnetization directions. (L and O) Upon magnetic actuation (20 mT) indicated with the black arrows, the legs deform in accordance with their magnetization directions. Scale bar, 1 mm. (M and P) Flexible robots with different magnetization profiles generate different locomotion patterns with rotational magnetic actuation. Scale bar, 5 mm.

  • Fig. 4 Reprogrammable magnetization of 3D-configured magnetic soft machines.

    (A to D) Reprogrammable magnetization of flexible 2D magnetic leaves distributed on a 3D-printed nonmagnetic body. (B and C) Magnetization direction of individual leaves is programmed by local laser heating. (D) Magnetization direction of half of the leaves, indicated by the red dashed line, is reprogrammed in the reverse direction. Scale bar, 5 mm. (E to H) A four-finger adaptive soft gripper, enabled by reprogramming magnetization profile of the fingers. (F to H) Shape deformation of the fingers is reprogrammed to grasp objects with different morphologies, including a sphere (3-mm diameter) (F), a rod (4-mm diameter and 4-mm height) (G), and a car representing complex morphology (10.6-mm length, 3-mm width, and 1.75-mm height) (H). Red arrows indicate local magnetization directions. Scale bar, 2 mm. Actuation of the structures is performed by applying uniform magnetic fields of 60 mT in the directions indicated with the black arrows.

  • Fig. 5 Heat-assisted magnetic programming of soft materials at the microscale.

    (A) Scanning a focused laser spot on a magnetic soft elastomer (MSE), which creates a precisely controlled local heating, in a desired pattern is used to program the magnetization profile on that material. (B and C) An example soft structure with six petals (150-μm width, 500-μm length, and 30-μm thickness) is placed on a micropost. Red arrows indicate the magnetization directions of the petals. Magnetic actuation (60 mT) resulted in deformation of petals in reverse directions. (D) A collimated laser can heat a desired shape on a target magnetic soft elastomer in one shot through a mask containing the micropattern of this desired shape. (E and F) Magnetic flux density measurements of example magnetically programmed samples by this micropatterned laser heating. The smallest magnetic pattern is 80 μm in width. Scale bars, 250 μm. (G) Contact transfer of desired magnetic profiles in one shot via global heating. The magnetic soft elastomer is placed in direct contact with NdFeB magnets, with a greater Curie temperature, arranged in different configurations and heated above the Curie temperature of the CrO2. Magnetization directions of the NdFeB magnets are transferred to the magnetic soft elastomer during cooling. (H and I) Magnetic flux density measurements of the NdFeB masters of different example shapes and configurations and the magnetic soft elastomer slaves. Scale bars, 500 μm and 1 mm, respectively. (J) Contact transfer of a complex magnetization profile in the geometric pattern of Minerva. Insets show close up views of the magnetic flux density profile of the magnetic soft elastomer slave. The smallest magnetic pattern is 38 μm in width. Color bars indicate magnetic flux density strength. Scale bars, 1 mm and 250 μm, respectively.

Supplementary Materials

  • Supplementary Materials

    Reprogrammable shape morphing of magnetic soft machines

    Yunus Alapan, Alp C. Karacakol, Seyda N. Guzelhan, Irem Isik, Metin Sitti

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    • Computational modeling of the magnetic soft elastomers
    • Figs. S1 to S11
    • Legends movies S1 to S4

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