Localized Self‐Growth of Reconfigurable Architectures Induced by a Femtosecond Laser on a Shape‐Memory Polymer

Abstract

natural behavior, many works have been done to realize reconfigurable shape transformation with artificial soft materials in a controlled manner. [8][9][10][11] Heterogeneous structures composited of hydrogel constituents with different swelling/shrinkage ratio [12][13][14][15][16] or anisotropic swelling behavior [17,18] have been constructed to accomplish dynamic tunable morphologies. Large shape deformation is shown in photodeformable crosslinked liquid crystal polymer through the orientation change of liquid crystal molecules, [19][20][21][22] and thus light-driven movable microarchitecture can be obtained. Inflation of elastic polymers constrained by relative stiff materials are applied to realize reconfigurable shape transformation. [23][24][25] These aforementioned shape reconfigurable materials are highly desired for many applications in soft robotics, [23,24] smart textiles, [26] drug delivery, [27] self-shaping devices, [28] and actuators. [22,29] Although nature-inspired artificial dynamic architectures have been widely studied as referred above, so far most of the shape transformation are dependent on the whole material deformation due to the technical challenge to locally induce shape change in a bulk material. Efforts have been taken to achieve dynamic structural behavior such as self-folding through modification of the localized properties of active materials, but these can only be done in macroscale by embedding Architectures of natural organisms especially plants largely determine their response to varying external conditions. Nature-inspired shape transformation of artificial materials has motivated academic research for decades due to wide applications in smart textiles, actuators, soft robotics, and drug delivery. A "self-growth" method of controlling femtosecond laser scanning on the surface of a prestretched shape-memory polymer to realize microscale localized reconfigurable architectures transformation is introduced. It is discovered that microstructures can grow out of the original surface by intentional control of localized laser heating and ablation, and resultant structures can be further tuned by adopting an asymmetric laser scanning strategy. A distinguished paradigm of reconfigurable architectures is demonstrated by combining the flexible and programmable laser technique with a smart shape-memory polymer. Proof-of-concept experiments are performed respectively in information encryption/decryption, and microtarget capturing/ release. The findings reveal new capacities of architectures with smart surfaces in various interdisciplinary fields including anti-counterfeiting, microstructure printing, and ultrasensitive detection.

A Review of Shape Memory Polymers and Composites: Mechanisms, Materials, and Applications

“…Shape memory arrays that consist of repeat units such as cylinders, cuboids, prisms, cones, and polyhedral can be fabricated by silica molding, nanoindentation, or localized laser [ 208 ] ( Figure a). Altering the arrangement and intervals of the repeat SMP units will significantly affect SMP topography.…”

Fabricating 3D Metastructures by Simultaneous Modulation of Flexible Resist Stencils and Basal Molds

“…Layer‐by‐layer stacking [ 8,16,17 ] and hybrid self‐assembly [ 18,19 ] show high lateral resolutions but are compromised by the complicated alignments and the lack of addressability. Direct writing technologies, such as laser writing, [ 20,21 ] and 3D printing [ 9,22,23 ] are currently only true 3D fabrication techniques but available for the very limited choice of materials and its resolution is optical‐diffraction limited. Focused ion beam [ 24,25 ] combines the high‐resolution and addressability together but is in short of controllability on 3D metastructures.…”

The Fabrication of Micro/Nano Structures by Laser Machining

“…The In 2018, Y. Zhang et al reported a microscale local morphology with a reversible structure was produced by using a uniform, low-cost shape memory polystyrene film, which assisted a sensible controlled femtosecond laser scanning strategy to achieve symmetric and asymmetric growth. The structure had potential applications in particle capture/release and information encryption [114]. Shrinkage properties of polystyrene film was showed in Figure 8d.…”

“…(e,f) SEM of polystyrene film after laser machining. (a-c) reproduced with permission from[113], Nature, 2017; and (d-f) reproduced with permission from[114],Wiley, 2018.…”