Fig. 4: Active forces organized by boundary layer defects.
a Fluorescence micrograph of an active nematic confined in a disk. The orange triangle indicates the location of a wall defect. Scale bar, 100 μm. b Corresponding director field overlaid on top of the fluorescence image. c Map with the magnitude of the active force per unit area, f = ∣∇ ⋅ Q∣, overlaid (in magenta) on top of the fluorescence image. Arrows indicate the direction of the force, while the color intensity maps the magnitude of the force. d Fluorescence micrograph of the system with two neighboring wall defects. e Magnitude of the active force per unit area overlaid (in magenta) on top of the fluorescence micrograph . f Projection of f in the azimuthal (θ) direction. The color code is green for counter-clockwise (CCW) and magenta for clockwise (CW) force. g Sketch of the orientational field and the force map in the vicinity of the two neighboring wall defects prior to annihilation. h Spatially-integrated azimuthal component of the active force, Fθ = ∫(eθ ⋅ ∇ ⋅ Q)dr as a function of time for the single defect situation (a–c). Nucleation events are marked with red disks. i Spatially integrated active force as a function of time corresponding to a video from Opathalage et al.28. A snapshot from that video and the magnitude of the computed active force is shown as an inset. Scale bar, 50 μm.
