Micro- and nanotextured
surfaces with reconfigurable textures can
enable advancements in the control of wetting and heat transfer, directed
assembly of complex materials, and reconfigurable optics, among many
applications. However, reliable and programmable directional shape
in large scale is significant for prescribed applications. Herein,
we demonstrate the self-directed fabrication and actuation of large-area
elastomer micropillar arrays, using magnetic fields to both program
a shape-directed actuation response and rapidly and reversibly actuate
the arrays. Specifically, alignment of magnetic microparticles during
casting of micropost arrays with hemicylindrical shapes imparts a
deterministic anisotropy that can be exploited to achieve the prescribed,
large-deformation bending or twisting of the pillars. The actuation
coincides with the finite element method, and we demonstrate reversible,
noncontact magnetic actuation of arrays of tens of thousands of pillars
over hundreds of cycles, with the bending and twisting angles of up
to 72 and 61°, respectively. Moreover, we demonstrate the use
of the surfaces to control anisotropic liquid spreading and show that
the capillary self-assembly of actuated micropost arrays enables highly
complex architectures to be fabricated. The present technique could
be scaled to indefinite areas using cost-effective materials and casting
techniques, and the principle of shape-directed pillar actuation can
be applied to other active material systems.
Highlights d CD34 + human thymic progenitors present a spectrum of specification and commitment states d Earliest progenitors are CD7and exhibit stem-cell-like and T-primed transcriptomes d Loss of B-potential precedes that of myeloid and NK potentials during T-commitment d A CD34 + subpopulation of cells is primed for the plasmacytoid dendritic lineage
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