论文标题

3D可打印应变率依赖机器 -

3D printable strain rate-dependent machine-matter

论文作者

Janbaz, Shahram, Fan, Daniel, Ganjian, Mahya, van Manen, Teunis, Staufer, Urs, Zadpoor, Amir A.

论文摘要

机械材料的机械超材料和元设备是重要的子类别,它是设计高级功能材料的主要范式。最近已经证明了这些概念的各种令人兴奋的应用,从外来的机械性能到类似设备和适应性功能。但是,迄今为止发表的绝大多数研究都集中在此类设备的准静态行为上,忽略了它们丰富的动态行为。最近,我们提出了一类新的应变速率依赖性的机械超材料,该机械超材料由双束(即粘弹性双层束)制成。可以通过施加的应变速率控制此类BI梁的屈曲方向。然而,提出的方法受到了主要限制:具有如此“强”差异差异响应的此类BI梁的3D打印非常具有挑战性。在这里,我们提出了一种替代方法,该方法仅需要“弱”差异响应和合理设计的几何伪影来控制双束束的屈曲方向。我们提出了一个分析模型,该模型描述了几何设计和超弹性以及粘弹性特性的所有可能组合的景观,从而导致屈曲方向的所需应变速率依赖性切换。我们还展示了如何使用多物质和单材料3D打印技术用微观和亚微米分辨率来制造所提出的双束。更重要的是,我们展示了对弱差异响应的需求如何消除对多物质3D打印的需求,因为激光处理参数的变化足以实现有效的差异响应。最后,我们使用相同的3D打印技术来产生应变率依赖的抓地力机制作为潜在应用的展示。

Machine-matter, of which mechanical metamaterials and meta-devices are important sub-categories, is emerging as a major paradigm for designing advanced functional materials. Various exciting applications of these concepts have been recently demonstrated, ranging from exotic mechanical properties to device-like and adaptive functionalities. The vast majority of the studies published to date have, however, focused on the quasi-static behavior of such devices, neglecting their rich dynamic behavior. Recently, we proposed a new class of strain rate-dependent mechanical metamaterials that are made from bi-beams (i.e., viscoelastic bilayer beams). The buckling direction of such bi-beams can be controlled with the applied strain rate. The proposed approach, however, suffers from a major limitation: 3D printing of such bi-beams with such a 'strong' differential strain rate-dependent response is very challenging. Here, we propose an alternative approach that only requires a 'weak' differential response and a rationally designed geometric artifact to control the buckling direction of bi-beams. We present an analytical model that describes the landscape of all possible combinations of geometric designs and hyperelastic as well as viscoelastic properties that lead to the desired strain rate-dependent switching of the buckling direction. We also demonstrate how multi- and single-material 3D printing techniques can be used to fabricate the proposed bi-beams with microscale and submicron resolutions. More importantly, we show how the requirement for a weak differential response eliminates the need for multi-material 3D printing, as the change in the laser processing parameters is sufficient to achieve effective differential responses. Finally, we use the same 3D printing techniques to produce strain rate-dependent gripper mechanisms as showcases of potential applications.

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