Research ArticleMICROROBOTS

Floating magnetic microrobots for fiber functionalization

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Science Robotics  25 Sep 2019:
Vol. 4, Issue 34, eaax8336
DOI: 10.1126/scirobotics.aax8336
  • Fig. 1 Setup of the microrobot-assisted high-precision wet transfer.

    (A) Magnetically controlled microrobots via an external magnet to align a floating 2D device on a target substrate (e.g., optical fiber and 3D microdevice). (B) View of the microrobot structure in which iron lines trapped in an elastomer matrix are used to store a preferred magnetization direction. (C) Final assembled devices featuring the functional pattern aligned with a 5-μm and 0.4° precision.

  • Fig. 2 Floating microrobots with different preferred magnetization directions: Fabrication and control principles.

    (A) Fabrication of microrobots. Different magnetization directions were programmed in the material with a ring magnet. (B) Clamping mechanism used in this study. Microrobots were moved together or apart depending on the vertical position of the magnet, allowing effective clamping of the pattern to be transferred, followed by rotational and orientation control.

  • Fig. 3 Iron line orientation inside the PDMS matrix.

    (A) Micro-CT reconstruction of the polymer/iron mix. The iron lines aligned with the magnetic field direction during the polymer curing. (B) Iron line direction versus position. The direction of the iron lines followed the curing magnetic field direction.

  • Fig. 4 Magnetic control of the microrobot pair.

    (A) Different equilibrium positions of the microrobot pair as influenced by the vertical position of the magnet. Left: Experimental results. Right: Simulation results acquired using finite element modeling of the magnetic field. (B) Optical images showing the microrobot pair manipulating a floating pattern (for animation, see movie S1).

  • Fig. 5 Force characterization of a single microrobot.

    (A) Schematic illustration of how force characterization was performed. The microrobot pushed a 120-μm-diameter glass fiber; the deformation of the fiber is linked to the applied force. (B) Microrobot stiffness versus iron mass concentration with a 20-mm distant magnet. Microrobots with α = 0 were characterized. The stiffness was assumed to be linear and 1 mm away from the equilibrium position of the robot. The error bars show the differences between loading and unloading force measurement at 1 mm. By assuming no remnant magnetization, the magnetic susceptibility was also deduced.

  • Fig. 6 Fiber patterning using microrobot-assisted wet transfer.

    (A) Side view of the transfer pool with the microrobot pair holding a pattern to be transferred. (B) Fabrication workflow for patterning Au microdevices on the fiber using the proposed microrobot-assisted wet transfer. Steps 3 to 6 are recorded in movie S3. (C) Floating pattern (grid structures) transferred onto a 200-μm-diameter optical fiber as viewed from the microscope. (D) Scanning electron microscopy (SEM) (Tescan SEM/FIB LYRA3 XM) images of two successive transfer position markers for assessing the achievable transfer accuracy of the proposed system.

  • Fig. 7 Example applications of microrobot-assisted wet transfer for fiber functionalization.

    (A) Top: Interface between fiber-supported electrodes and a dedicated PCB. Bottom: Impedance characterization of a two-electrode device with and without electrodeposition of Pt black. (B) Fiber-based 2D graphene devices. Sequential wet transfers were made to successively pattern the Au track and then the graphene film. The presence of graphene was assessed with Raman spectrometry and a plasma destructive test. (C) SEM picture of a functionalized microtool 3D printed to the tip of a fiber. The Au track was aligned and transferred onto the 3D structure with good conformity. The transfer steps on this microtool are available in movie S4. (D) Fiber-based strain gauge designed for measuring fiber deformation based on its resistivity change. SEM picture of the device, picture of the experience, and resulting signal.

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/4/34/eaax8336/DC1

    Text

    Fig. S1. Magnet magnetic field measurement.

    Fig. S2. Schematics of the microrobot cutter.

    Fig. S3. Water surface deformation due to the microrobot.

    Fig. S4. Clamping hysteresis for thick microrobot.

    Fig. S5. Simulation of the magnetic horizontal force on the floating.

    Fig. S6. Stable robot position simulation using the measured magnetic field from the magnet.

    Fig. S7. Comparison between magnetic force and surface tension force.

    Fig. S8. Evolution of the lateral magnetic force over surface tension force (γ) with magnet altitude.

    Fig. S9. Microrobot force characterization.

    Fig. S10. Position of the pattern grasped by two microrobots at different microscope stage positions.

    Fig. S11. Airflow cover impact on precision.

    Fig. S12. Microrobot drag force measurement.

    Fig. S13. Drying of a pattern on the fiber.

    Fig. S14. Transfer on different fiber diameters.

    Fig. S15. Raman spectrum of graphene transferred onto fiber at different positions.

    References (37, 38)

    Movie S1. Summary.

    Movie S2. Pattern manipulation.

    Movie S3. Transfer example.

    Movie S4. Microtool patterning.

  • Supplementary Materials

    The PDF file includes:

    • Text
    • Fig. S1. Magnet magnetic field measurement.
    • Fig. S2. Schematics of the microrobot cutter.
    • Fig. S3. Water surface deformation due to the microrobot.
    • Fig. S4. Clamping hysteresis for thick microrobot.
    • Fig. S5. Simulation of the magnetic horizontal force on the floating.
    • Fig. S6. Stable robot position simulation using the measured magnetic field from the magnet.
    • Fig. S7. Comparison between magnetic force and surface tension force.
    • Fig. S8. Evolution of the lateral magnetic force over surface tension force (γ) with magnet altitude.
    • Fig. S9. Microrobot force characterization.
    • Fig. S10. Position of the pattern grasped by two microrobots at different microscope stage positions.
    • Fig. S11. Airflow cover impact on precision.
    • Fig. S12. Microrobot drag force measurement.
    • Fig. S13. Drying of a pattern on the fiber.
    • Fig. S14. Transfer on different fiber diameters.
    • Fig. S15. Raman spectrum of graphene transferred onto fiber at different positions.
    • Legends for movies S1 to S4
    • References (37, 38)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Summary.
    • Movie S2 (.mp4 format). Pattern manipulation.
    • Movie S3 (.mp4 format). Transfer example.
    • Movie S4 (.mp4 format). Microtool patterning.

    Files in this Data Supplement:

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