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Nanoscale Lamb wave–driven motors in nonliquid environments

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Science Advances  08 Mar 2019:
Vol. 5, no. 3, eaau8271
DOI: 10.1126/sciadv.aau8271
  • Fig. 1 Light-actuated rotation of a motor in air and vacuum.

    (A) Schematic of experimental configuration showing that a pulsed supercontinuum light (pulse duration, 2.6 ns; repetition rate, 5 kHz; wavelength, 450 to 2400 nm) is delivered into a microfiber and light power is measured by a power meter at the output end. The microfiber is suspended in air or vacuum, and the gold plate is placed on it and then rotates around it due to the actuation of the pulsed light. (B) False-color scanning electron micrograph of a gold plate (side length, 11 μm; thickness, 30 nm) below a microfiber with a radius of 880 nm. Note that the plate-microfiber system is placed on a silicon substrate after rotation experiments. (C) Sequencing optical microscopy images of the anticlockwise revolving gold plate around the microfiber in air (sample A, 5 kHz) (see movie S1). The measured average light power is 0.6 mW. (D) Sequencing SEM images of a clockwise revolving gold plate (long side length, 10.5 μm; short side length, 3.7 μm; thickness, 30 nm) around a microfiber (radius, 2 μm) in vacuum (see movie S2). The measured average light power is 1.5 mW. Arrows in (C) and (D) represent the direction of light propagation. Gray circles and yellow lines below (C) and (D) denote the microfiber and plate, respectively. Red curve arrows indicate the rotation direction of the plate.

  • Fig. 2 Relationship between rotation speed and repetition rate.

    (A) Effective width (Weff) of the plate obtained from every frame of experimental videos (sample A, 1 kHz). For convenience, the effective width of the plate is presented with pixel length (see also fig. S6). (B) Fourier transformation of the effective width to obtain its variation frequency (i.e., rotation speed of the plate). (C) Light-actuated rotation speed of the motor increases linearly with repetition rate of light pulses, and different samples give similar results (see movie S1 for sample A and movie S6 for sample B). The power for every light pulse remains the same when the repetition rate is changed. Error bars are the variance of rotation speed.

  • Fig. 3 A stepping rotary motor.

    (A) Schematic showing that a specific number (n) of light pulses are emitted at a 1-kHz repetition rate when the light source senses a positive edge on every trigger input. The 1-Hz electric trigger signal is generated by a waveform generator. (B) Step angle of the motor increasing linearly with the light pulse number (n) for one of the trigger inputs (see also movie S3). The motor rotates about 0.1° for every single light pulse. (C) Stepping rotation of the motor when the light pulse numbers (n) are 500 and 200.

  • Fig. 4 Lamb wave–driven mechanism of the motor.

    (A) Schematic diagram showing a Lamb wave generated on the surface of a gold plate by line-shaped evanescent field outside a microfiber. (B and C) Schematic diagram (side view) showing (B) anticlockwise locomotion in the right-shifted case and (C) clockwise locomotion in the left-shifted case of the plate on the microfiber surface driven by the Lamb wave. Black ellipses in zoomed-in part represent collective motion pattern of surface gold atoms during the Lamb wave propagation. (D) Decomposition of movements showing synergic crawling and turning of the gold plate during one light pulse in the right-shifted case. Gray circle and yellow rectangle indicate the microfiber surface and plate, respectively. A, B, and O (O′) represent the head, end, and contact point of the plate, respectively. Note that the contact point represents the center point of the contact area. The plate crawls leftward (shown from top to middle), and the contact point of the plate changes from O to O′ (AOOB<AOOB). The plate turns at a slight angle (Δϕ) (shown from middle to bottom). The plate locomotes a distance (Δϕ ⋅ r) after this series of movements, and the contact point of the plate remains unchanged.

  • Fig. 5 One example application, demonstrating a micromirror for laser scanning.

    (A) Schematic representation of a rotary plate used as a micromirror to deflect the light beam. The reflected beam rotates 2θ when the plate rotates θ. The distance between the plate and the far field white screen is L (6.4 cm). The relationship between the position of the laser spot on the white screen (y) and the rotation angle of the reflected light (2θ) is y = L × tan(2θ). (B) Sequencing optical images of the laser spot (the center of which is marked with red circles) on the screen in the far field (see also movie S9). (C) Experimentally measured and theoretically expected position of the laser spot on the white screen. The rotational speed of the plate, actuated by light pulses at a repetition rate of 5 kHz in the experiment, is 0.95 rpm (0.1 rad/s). The preconceived relationship between y and t is y = L × tan(2ωt + θ0) = 6.4tan(0.2t + θ0). θ0 is the initial angle.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/5/3/eaau8271/DC1

    Section S1. Measurements of the adhesion force between gold plates and microfibers

    Section S2. Extraction of the angle between gold plates and microfibers

    Section S3. Ruling out the optical force and the photophoretic force as driving forces

    Section S4. A theoretical model of locomotion resolution

    Section S5. Numerical simulations of the Lamb wave in an asymmetrically configured plate

    Fig. S1. Experimental procedures.

    Fig. S2. Experimental configuration of the locomotor system in vacuum.

    Fig. S3. Numerical calculation of plasmonic heating in the gold plate.

    Fig. S4. Measurements of the adhesion force between gold plates and microfibers.

    Fig. S5. Calculations of the angle between the gold plate and the microfiber using the projection method.

    Fig. S6. Rotation of the locomotor actuated by light pulses with different repetition rates.

    Fig. S7. Experimental system of a micromirror for optical sweeping.

    Fig. S8. Numerical results of the Lamb wave generated in a gold plate.

    Fig. S9. Wave motion patterns for the right-shifted and left-shifted asymmetric configurations.

    Fig. S10. Lamb wave propagating in a larger gold plate.

    Movie S1. A motor that is driven by a pulsed supercontinuum light with different repetition rates in air (sample A).

    Movie S2. A motor that is driven by a pulsed supercontinuum light in vacuum.

    Movie S3. A pulsed light–actuated stepping motor.

    Movie S4. A lower power of the light pulse and a smaller rotation step for the locomotor.

    Movie S5. A motor that is driven by a 1064-nm pulsed light in air.

    Movie S6. A motor that is driven by a pulsed supercontinuum light with different repetition rates in air (sample B).

    Movie S7. Deforming the microfiber to measure the adhesion force.

    Movie S8. An animation to illustrate the rotary locomotion of the motor.

    Movie S9. A light-actuated rotary micromirror.

    Movie S10. Rotation direction of the motor controlled by different asymmetric configurations.

    References (3241)

  • Supplementary Materials

    The PDF file includes:

    • Section S1. Measurements of the adhesion force between gold plates and microfibers
    • Section S2. Extraction of the angle between gold plates and microfibers
    • Section S3. Ruling out the optical force and the photophoretic force as driving forces
    • Section S4. A theoretical model of locomotion resolution
    • Section S5. Numerical simulations of the Lamb wave in an asymmetrically configured
    • Fig. S1. Experimental procedures.
    • Fig. S2. Experimental configuration of the locomotor system in vacuum.
    • Fig. S3. Numerical calculation of plasmonic heating in the gold plate.
    • Fig. S4. Measurements of the adhesion force between gold plates and microfibers.
    • Fig. S5. Calculations of the angle between the gold plate and the microfiber using the projection method.
    • Fig. S6. Rotation of the locomotor actuated by light pulses with different repetition rates.
    • Fig. S7. Experimental system of a micromirror for optical sweeping.
    • Fig. S8. Numerical results of the Lamb wave generated in a gold plate.
    • Fig. S9. Wave motion patterns for the right-shifted and left-shifted asymmetric configurations.
    • Fig. S10. Lamb wave propagating in a larger gold plate.
    • Legends for movies S1 to S10
    • References (3241)

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mp4 format). A motor that is driven by a pulsed supercontinuum light with different repetition rates in air (sample A).
    • Movie S2 (.mp4 format). A motor that is driven by a pulsed supercontinuum light in vacuum.
    • Movie S3 (.mp4 format). A pulsed light–actuated stepping motor.
    • Movie S4 (.mp4 format). A lower power of the light pulse and a smaller rotation step for the locomotor.
    • Movie S5 (.mp4 format). A motor that is driven by a 1064-nm pulsed light in air.
    • Movie S6 (.mp4 format). A motor that is driven by a pulsed supercontinuum light with different repetition rates in air (sample B).
    • Movie S7 (.mp4 format). Deforming the microfiber to measure the adhesion force.
    • Movie S8 (.mp4 format). An animation to illustrate the rotary locomotion of the motor.
    • Movie S9 (.mp4 format). A light-actuated rotary micromirror.
    • Movie S10 (.mp4 format). Rotation direction of the motor controlled by different asymmetric configurations.

    Files in this Data Supplement:

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