Research ArticlePHYSICS

Emergent stereoselective interactions and self-recognition in polar chiral active ellipsoids

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Science Advances  26 Feb 2021:
Vol. 7, no. 9, eabd0331
DOI: 10.1126/sciadv.abd0331
  • Fig. 1 Realizing tunable chiral active motion.

    (A to F) Left: Snapshots of 3D-printed chiral active ellipsoids for three different left-right mass asymmetries ΔmLR. The red dashed lines show the hollowed-out portion of the particle. Right: Superimposed snapshots showing a nearly circular path traced by the ellipsoids under vertical agitation. The snapshot of the ellipsoid at t = 0 s is shown in white. The blue arrows indicate the handedness of the orbit. Scale bars, 3 mm. (G) Probability distribution of angular displacements. Graph showing probability distribution of angular displacements Δθ between successive time instances (Δt = 0.03 s) of C1 (blue □), C2 (orange ○), C3 (green △), C4 (violet ▽), C5 (red ◊), and C6 (purple ⊲). Photo credit: [(A) to (F), left panels] Pragya Arora, JNCASR.

  • Fig. 2 Emergent stereoselective interactions in polar chiral active ellipsoids.

    (A and B) Superimposed snapshots of a representative active mover and spinner, respectively. The mover is composed of a dextrogyre (+) and levogyre (−) monomer [top left in (A)], while the spinner is made of two (+) monomers (B). Note that the spinner has a net clockwise (+) motion (blue dashed arrow), same as that of its components, and is localized in space. (C) Translational mean squared displacement (MSD) of mover (black squares) and orientational MSD of spinner (red circles) versus lag time t. (D) Fraction of dimers that existed as movers and spinners in liquids of C1 as well as C2 ellipsoids at ϕ = 1%. The error bars represent the SD of the mean and were obtained from multiple statistically independent realizations of an experiment. (E to G) Pathways of mover and spinner formation. The panels depict the sequence of steps aiding in the dimer formation. A mover bond is typically mediated by two reaction mechanisms. (E) Collision followed by realignment. (F) Trimer disintegration into a mover and monomer. (G) A spinner bond mediated by collision of two aligned particles. All these moves generally last 1 s. Photo credit: (E to G) Pragya Arora, JNCASR.

  • Fig. 3 Self-recognition in polar chiral active ellipsoids.

    (A) Probability distribution of mover lifetimes for the three possible configurations shown in the inset. (i) C2C2 (hollow blue squares), (ii) C4C4 (red triangles), and (iii) C2C4 (brown circles). Both the radius (represented by the arrows in the inset) and the angular velocities of C2 and C4 are different. (B) Superimposed snapshots of representative active mover trajectory for each of the three configurations. The average lifetime τmov [shown by dashed vertical lines in (A)] of C2C2 mover is 14.8 s, that of C4C4 mover is 3.1 s, and that of C2C4 mover is 1.4 s. Photo credit: (A) Pragya Arora, JNCASR.

  • Fig. 4 Relaxation dynamics of polar chiral active liquids depends on their net chirality, χ.

    (A and B) Relaxation dynamics phase diagram in the (χ, ϕ) plane for orientational and translational degrees of freedom (DOF), respectively. The circles represent the χ and ϕ at which experiments were performed. In (A) and (B), the isochrones at intermediate ϕ are shown by white dashed lines. The color bar indicates the value of ταR and ταT. τα for ϕ’s in between experimental data points were obtained from linear interpolation. (C and D) ταR versus χ and ταT versus χ, respectively, at ϕ = 0.72. (E) Top 20% translationally least mobile particles (red filled circles) in a time interval of 5t* across various χ at ϕ = 0.72. (F) Probability distribution of cluster size P(Nc) at ϕ = 0.72 across various χ. (G) 〈Nc〉 versus χ for ϕ = 0.72. In (C), (D), and (G), the error bars represent the SD of the mean and were obtained from multiple statistically independent realizations of an experiment. Photo credit: (E) Pragya Arora, JNCASR.

  • Fig. 5 Chirality-dependent cooperative dynamics.

    (A to C) Particle displacement maps over 7t* for ϕ = 0.85. (A) χ = 0 (racemic mixture). (B) χ = 0.5 (enantiomeric excess). (C) χ = 1 (enantiopure). The color bar shows the magnitude of scaled particle displacement Δr/β over 7t*.

  • Table 1 Details of various 3D-printed polar chiral active ellipsoids.

    LabelαβγΔmLRωRDimer state
    observed
    (mm)(mm)(mm)(g)(rad/s)(mm)
    C1632.16.91 × 10−312.21.3Spinners, movers
    C2632.15.85 × 10−311.91.4Spinners, movers
    C3632.14.78 × 10−38.52.2Movers
    C4632.13.13 × 10−35.14.1Movers
    C5632.11.97 × 10−32.56.1Movers
    C6632.11.04 × 10−32.110Movers

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