On-Demand Dynamic Chirality Selection in Flower Corolla-like Micropillar Arrays

Abstract

Chiral morphology has been intensively studied in various fields including biology, organic chemistry, pharmaceuticals, and optics. On-demand and dynamic chiral inversion not only cannot be realized in most intrinsically chiral materials but also has mostly been limited to chemical or light-induced methods. Herein, we report reversible real-time magneto-mechanical chiral inversion of a three-dimensional (3D) micropillar array between achiral, clockwise, and counterclockwise chiral arrangements. Inspired by the flower corolla, achiral arrays of five and six radially arranged semicylindrical micropillars were employed as model systems to investigate the dynamic symmetry properties of arrays consisting of odd and even numbers of micropillars, respectively. Each micropillar underwent twisting actuation with a different twisting angle depending on the angle with the magnetic field direction and magnetic flux density, thereby collectively changing the chirality from the achiral to chiral state. Importantly, the morphological handedness of the micropillars was inverted within a few seconds by manipulating the direction of the magnetic field. A chiral morphology consisting of magnetically twisted micropillars was shape-fixed by the introduction of a polymeric binder. This binder could be simply washed off to return the shape-fixed twisted micropillars to their initial straight state. Magnetically programmable and reproducible 3D flower corolla-like micropillar arrays are expected to expand the potential of shape-reconfigurable devices that require real-time chiral manipulation in ambient environments.

Recent Progress on the Development of Magnetically‐Responsive Micropillars: Actuation, Fabrication, and Applications

“…arranged the micropillars with aligned magnetic particles into flower Corolla‐like arrays to achieve on‐demand and reversible chirality selection, which has great potential for applications in biomedical systems. [ 134 ]…”

“…In a later work, Wie et al arranged the micropillars with aligned magnetic particles into flower Corolla-like arrays to achieve on-demand and reversible chirality selection, which has great potential for applications in biomedical systems. [134] The actuated configurations of the programmable micropillar array are determined and fixed once the fabrication is completed. The high heterogeneity of the programmable array limits the versatility of the pillars for practical applications and increases the fabrication cost.…”

Switching Chirality in Arrays of Shape‐Reconfigurable Spindle Microparticles

“…[5] Swelling-induced snap-shut of circular pore arrays leads to symmetry breaking of the square array of pores DOI: 10.1002/adma.202303009 in hydrogel membranes. [6,7] More complexity can be achieved by programming the molecular alignment [2,[8][9][10] or magnetic responsiveness [11] of the micropillars within an array. Nevertheless, the transformation realized in literature, whether by the closure of the pores, contact of the pillars, or twist of pillars, relies on physically constraining the shape-changing units (pores or pillars) by a stiffer matrix.…”

Synergistic Inclusion Effects of Hard Magnetic Nanorods on the Magnetomechanical Actuation of Soft Magnetic Microsphere‐Based Polymer Composites

“…Recently, magnetomehcanical bending actuations have been actively attracted by enabling microtextured surfaces to contactlessly exhibit multiple functionalities such as encoding technique, [1] structural coloration, [2] wetting shape control, [3] droplet transportation, [4][5][6] and directional liquid spreading. [7][8][9] To improve magnitude of magnetic bending actuation of the micropillars, we have suggested several strategies, including the preprogramming of particle arrangement, [1,10] anisotropic stress distribution by designing micropillar geometry, [3] and highly concentrated magnetic composites with soft hinge. [11] In particular, arranging magnetic particles can provide synchronized and directioncontrolled magnetic bending actuation for 3D rectangular micropillars.…”