Abstract Reconfigurable micromachines that are highly conscious of changing environments have significant potential for use in biomedical applications, such as minimally invasive surgery, cell manipulation, and tissue engineering. Current nanofabrication approaches with sophisticated designs appear to enhance the controllability of shape transformations, such as bending, folding, and twisting, while minimizing the response time. However, the construction of three-dimensional (3D) structures at a small scale with a high shape-morphing freedom poses challenges because of the lack of applicable materials and effective fabrication techniques. Here, we develop an advanced four-dimensional microprinting strategy for constructing 3D-to-3D shape-morphing micromachines in a single-material-single-step mode. Using direct laser writing, heterogeneous stimulus-responsive hydrogels can be distributed spatially into arbitrary 3D shapes with sub-micrometer features. The material crosslinking densities, stiffnesses, and swelling/shrinking degrees can be modulated by programming the exposure dosage of femtosecond laser pulses and characterized to predict the shape-morphing behaviors via finite-element methods. With our proposed approach, complex 3D reconfigurable compound micromachines with mechanical advantages, which exhibit an excellent deformation-amplifying effectiveness, can be constructed to achieve a rapid, precise, and reversible 3D-to-3D shape transformation in response to multiple external stimuli, and they emerge as promising smart and multifunctional micromachine candidates for various engineering applications.

中文翻译：

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可重构复合微机械的四维直接激光写入

摘要 高度感知环境变化的可重构微型机器在生物医学应用中具有巨大的潜力，例如微创手术、细胞操作和组织工程。当前具有复杂设计的纳米制造方法似乎增强了弯曲、折叠和扭曲等形状变换的可控性，同时最大限度地减少了响应时间。然而，由于缺乏适用的材料和有效的制造技术，在小尺度上构建具有高形状变形自由度的三维 (3D) 结构带来了挑战。在这里，我们开发了一种先进的四维微打印策略，用于以单材料单步模式构建 3D 到 3D 形状变形微机器。使用直接激光写入，异质刺激响应水凝胶可以在空间上分布成具有亚微米特征的任意 3D 形状。材料交联密度、刚度和膨胀/收缩度可以通过编程飞秒激光脉冲的曝光剂量来调节，并通过有限元方法表征以预测形状变形行为。使用我们提出的方法，可以构建具有机械优势的复杂 3D 可重构复合微机械，具有出色的变形放大效果，可实现快速、精确和可逆的 3D 到 3D 形状转换，以响应多种外部刺激，以及它们成为各种工程应用的有前途的智能和多功能微型机器候选者。