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A ferrobotic system for automated microfluidic logistics

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Science Robotics  26 Feb 2020:
Vol. 5, Issue 39, eaba4411
DOI: 10.1126/scirobotics.aba4411
  • Fig. 1 Overview of ferrobotic system concept and mechanism.

    (A) An analogy: Mobility and automation in an AGV system and the devised ferrobotic system. (B) Simulation results depicting the amplification of the actuation capability with the magnetic motor (the x axis is the vertical distance from the center of the magnetic source). (C) Optical image of a representative multifunctional ferrobotic system capable of performing diverse operations, including droplet package transportation, merging, generation, filtration, dispensing, and sensing. Rendered images of the droplets are for illustration purposes only (droplets can form hemisphere or disk-like shapes depending on the channel geometry).

  • Fig. 2 Design and characterization of the navigation floor for package transportation.

    (A) Schematic diagram of the control circuitry. (B) Optical image of the implemented control circuitry and the navigation floor with the close-up view of four neighboring EM coils. (C) Overlaid sequential images (derived from video frames) visualize the commuted path of the ferrobot (programmed with different navigation plans; the durations for commuting “U,” “C,” “L,” and “A” paths were correspondingly 1.4, 1.4, 0.7, and 2.3 s). (D) Characterization of the maximum transportation velocity for two different ferrofluid concentrations. Error bars, SE (n = 3). (E) Characterization of the oscillatory transportation of a package with a ferrobot (sensed with an impedance sensing electrode pair) to evaluate the robustness of the ferrobotic actuation (performed for >24 hours). (F) FFT analysis of the oscillatory profile measured by the impedance sensing electrodes in part (E). Inset shows variation of the fundamental frequency of the 2000-s segmented time windows, depicting near-zero variation.

  • Fig. 3 Demonstration and characterization of advanced operations achieved with functional components.

    (A) Schematic illustration of the droplet dispensing mechanism involving the transportation of the package against a corrugated microfluidic wall. (B) Sequential optical images of the droplet dispensing process. (C) Characterization of the dispensed droplets’ size for different corrugated opening widths. Error bars, SE (n = 10). (D) Schematic illustration of the droplet generation process involving the droplet transportation to a VIA-like orifice. (E) Sequential optical images of the droplet generation process. (F) Characterization of the generated droplets’ volume for different orifice diameters. Error bars, SE (n = 20). (G) Schematic illustration of the filtration mechanism. (H) Optical image of the solution sample before and after filtration. (I) Bead counts before and after filtration (three trials). (J) Schematic illustration of droplet merging and mixing mechanisms. (K) Optical images to visualize the droplet merging (upon applying 2 V) and mixing process (with and without active mixing). (L) Comparison of the progressive mixing index for the two cases of with and without active mixing.

  • Fig. 4 Efficient package sorting with a cross-collaborative network of ferrobots.

    (A) System-level view of the sorting procedure. (B and C) Comparison of the sorting efficiency achieved by (B) a single ferrobot and (C) eight ferrobots tasked with sorting a random sequence of eight packages. State-by-state transitions for both scenarios are illustrated, and the left table details the commuted distance of each ferrobot. The snapshots from the sorting experiment performed with eight ferrobots are shown on the right (captured at the end of each state). (D) The total temporal unit steps required for sorting 2, 4, 8, and 16 packages (based on statistical averaging of all the possible permutations).

  • Fig. 5 Pipelined and automated MMP assay performed by the ferrobotic system.

    (A) General workflow of the MMP assay equipped with a dynamic self-calibration mechanism. (B) Illustration of the ferrobotic tasks in relation to the navigation floor over the processing of a representative sample (performed by three ferrobots). (C) Overview of the navigation plans of the three deployed ferrobots (F1, F2, and F3) with annotated locations of interest. (D) The detailed timeline of the ferrobots’ status (commuting with/without package, standby), with annotated locations of interest. Overlaid sequential video frames illustrating the status at two representative stages. (E) Illustration of the FRET pair from the MMP substrate cleaved by the MMPs present in the sample to yield a fluorescent product that is no longer quenched. (F) The fluorescent readouts [arbitrary fluorescence unit (AFU)] from the calibration and output wells after automated ferrobotic processing and 10 min of incubation. The concentration of MMP in the test sample is estimated with the aid of a real-time calibration standard curve generated from the four calibrator samples [0.0078 U/ml (estimated) versus 0.008 U/ml (expected)]. (G) Estimated MMP concentrations in five tested human plasma samples (performed by the ferrobotic system and manually by a technician; P < 0.01).

Supplementary Materials

  • robotics.sciencemag.org/cgi/content/full/5/39/eaba4411/DC1

    Text

    Fig. S1. EM coil geometry and magnetic field simulation.

    Fig. S2. Multiferrobot transportation.

    Fig. S3. Characterization of the average velocity profile of the droplet.

    Fig. S4. Impedance spectrum measured by the impedance sensing electrode pair.

    Fig. S5. Dispensed droplet characterization.

    Fig. S6. Droplet generation characterization.

    Fig. S7. Collective transportation of nanoliter droplets by a ferrobot.

    Fig. S8. Merge sort algorithm and sorting performance for single versus multiferrobots.

    Fig. S9. Characterization of the MMP assay.

    Movie S1. Ferrobotic commute with different trajectories.

    Movie S2. Ferrobotic droplet dispensing.

    Movie S3. Ferrobotic droplet generation.

    Movie S4. Ferrobotic droplet merging and active mixing.

    Movie S5. Cross-collaborative ferrobotic package sorting for microfluidic logistics.

    Movie S6. Application of the ferrobotic system for the implementation of a pipelined and automated bioassay.

    References (5153)

  • Supplementary Materials

    The PDF file includes:

    • Text
    • Fig. S1. EM coil geometry and magnetic field simulation.
    • Fig. S2. Multiferrobot transportation.
    • Fig. S3. Characterization of the average velocity profile of the droplet.
    • Fig. S4. Impedance spectrum measured by the impedance sensing electrode pair.
    • Fig. S5. Dispensed droplet characterization.
    • Fig. S6. Droplet generation characterization.
    • Fig. S7. Collective transportation of nanoliter droplets by a ferrobot.
    • Fig. S8. Merge sort algorithm and sorting performance for single versus multiferrobots.
    • Fig. S9. Characterization of the MMP assay.
    • Legends for movies S1 to S6
    • References (5153)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). Ferrobotic commute with different trajectories.
    • Movie S2 (.mp4 format). Ferrobotic droplet dispensing.
    • Movie S3 (.mp4 format). Ferrobotic droplet generation.
    • Movie S4 (.mp4 format). Ferrobotic droplet merging and active mixing.
    • Movie S5 (.mp4 format). Cross-collaborative ferrobotic package sorting for microfluidic logistics.
    • Movie S6 (.mp4 format). Application of the ferrobotic system for the implementation of a pipelined and automated bioassay.

    Files in this Data Supplement:

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