Division of Electrical and Computer Engineering, Louisiana State University, Baton Rouge, LA 70809, USA.
Soft Matter. 2017 Jun 14;13(23):4224-4230. doi: 10.1039/c6sm02637k.
Self-folding or micro-origami technologies are actively investigated as a novel manufacturing process to fabricate three-dimensional macro/micro-structures. In this paper, we present a simple process to produce a self-folding structure with a biaxially oriented polystyrene sheet (BOPS) or Shrinky Dinks. A BOPS sheet is known to shrink to one-third of its original size in plane, when it is heated above 160 °C. A grid pattern is engraved on one side of the BOPS film with a laser engraver to decrease the thermal shrinkage of the engraved side. The thermal shrinkage of the non-engraved side remains the same and this unbalanced thermal shrinkage causes folding of the structure as the structure shrinks at high temperature. We investigated the self-folding mechanism and characterized how the grid geometry, the grid size, and the power of the laser engraver affect the bending curvature. The developed fabrication process to locally modulate thermomechanical properties of the material by engraving the grid pattern and the demonstrated design methodology to harness the unbalanced thermal shrinkage can be applied to develop complicated self-folding macro/micro structures.
自折叠或微折纸技术作为一种新颖的制造工艺，可用于制造三维宏观/微观结构，受到了广泛的研究。本文提出了一种使用双轴取向聚苯乙烯片（BOPS）或 Shrinky Dinks 生产自折叠结构的简单工艺。当 BOPS 片加热到 160°C 以上时，其在平面上的收缩率可达原始尺寸的三分之一。我们使用激光雕刻机在 BOPS 薄膜的一侧刻蚀网格图案，以减小刻蚀侧的热收缩。未刻蚀侧的热收缩保持不变，这种不平衡的热收缩导致结构在高温下收缩时发生折叠。我们研究了自折叠的机制，并分析了网格几何形状、网格尺寸和激光雕刻机功率如何影响弯曲曲率。通过刻蚀网格图案来局部调节材料的热机械性能的开发制造工艺，以及利用不平衡热收缩的设计方法，可以应用于开发复杂的自折叠宏观/微观结构。
