Soman Pranav, Fozdar David Y, Lee Jin Woo, Phadke Ameya, Varghese Shyni, Chen Shaochen
Department of NanoEngineering, University of California, San Diego, 9500 Gilman Drive, Atkinson Hall, MC-0448, La Jolla, CA 92093.
Soft Matter. 2012 May 14;8(18):4946-4951. doi: 10.1039/C2SM07354D.
Poisson's ratio describes the degree to which a material contracts (expands) transversally when axially strained. A material with a zero Poisson's ratio does not transversally deform in response to an axial strain (stretching). In tissue engineering applications, scaffolding having a zero Poisson's ratio (ZPR) may be more suitable for emulating the behavior of native tissues and accommodating and transmitting forces to the host tissue site during wound healing (or tissue regrowth). For example, scaffolding with a zero Poisson's ratio may be beneficial in the engineering of cartilage, ligament, corneal, and brain tissues, which are known to possess Poisson's ratios of nearly zero. Here, we report a 3D biomaterial constructed from polyethylene glycol (PEG) exhibiting in-plane Poisson's ratios of zero for large values of axial strain. We use digital micro-mirror device projection printing (DMD-PP) to create single- and double-layer scaffolds composed of semi re-entrant pores whose arrangement and deformation mechanisms contribute the zero Poisson's ratio. Strain experiments prove the zero Poisson's behavior of the scaffolds and that the addition of layers does not change the Poisson's ratio. Human mesenchymal stem cells (hMSCs) cultured on biomaterials with zero Poisson's ratio demonstrate the feasibility of utilizing these novel materials for biological applications which require little to no transverse deformations resulting from axial strains. Techniques used in this work allow Poisson's ratio to be both scale-independent and independent of the choice of strut material for strains in the elastic regime, and therefore ZPR behavior can be imparted to a variety of photocurable biomaterial.
泊松比描述了材料在轴向应变时横向收缩（膨胀）的程度。泊松比为零的材料在轴向应变（拉伸）时不会发生横向变形。在组织工程应用中，具有零泊松比（ZPR）的支架可能更适合模拟天然组织的行为，并在伤口愈合（或组织再生）过程中适应并向宿主组织部位传递力。例如，零泊松比的支架在软骨、韧带、角膜和脑组织工程中可能有益，因为已知这些组织的泊松比接近零。在此，我们报告了一种由聚乙二醇（PEG）构建的三维生物材料，在较大轴向应变值下表现出平面内泊松比为零。我们使用数字微镜器件投影打印（DMD-PP）来创建由半重入孔组成的单层和双层支架，其排列和变形机制导致了零泊松比。应变实验证明了支架的零泊松行为，并且添加层数不会改变泊松比。在具有零泊松比的生物材料上培养的人间充质干细胞（hMSCs）证明了利用这些新型材料进行生物应用的可行性，这些应用要求轴向应变几乎不产生横向变形。这项工作中使用的技术使得泊松比在弹性范围内与尺度无关，并且与支柱材料的选择无关，因此零泊松比行为可以赋予各种光固化生物材料。
