Manufacturing of three-dimensional porous network structures using the laser lamination method of metal-powder sheets

生物技术的最新发展趋势导致需要精确制造可用于高级应用的多孔结构。其中一些例子是组织生长的基质，以及各种各样的植入物。控制毛孔大小对促进血管生长和充足的液体流动很重要。足够的组织生长需要高孔隙度。在本研究中，我们提出了一种三维多孔网络结构的新型制造技术。为了制作二维层，我们采用钛粉带激光烧结技术或钛片激光切割技术。基于快速成型的三维制造技术也与火花等离子烧结（SPS）相结合，以烧结层压带或板。这使我们能够控制多孔结构的内部结构。得到的主要结果如下：(1)使用平均直径为20 μm的纯钛粉，钛粉带的厚度或结构的高度分辨率约为100 μm。(2)激光烧结钛粉带的宽度约为120 μm，激光切割厚度为200 μm或110 μm的钛片的宽度约为200 μm或130 μm。(3)在钛粉层合带的SPS中，NaCl粉更适合作为定速材料。另一方面，利用钛棒抑制层合板在SPS中的运动，使层合板的对准误差减小到±70 μm左右。(4)两种方法均成功制备了孔隙率为45 ~ 50%、孔径为300 μm的三维多孔结构。(5)需要解决的问题是胶带刚度差、厚度波动大、烧结后随机收缩是第一种方法存在的问题。在另一种情况下，需要提高切割钛板的平整度和层合板的放置误差

Recent trends in biotechnology have resulted in the need for accurate fabrication of porous structures which can be used in advanced applications. Some of these examples are substrates for tissue growth, and various kinds of implants. Control of pore size is important for promoting growth of blood vessels and adequate fluid flow. High porosity is required for sufficient tissue in-growth. In this research, we proposed a novel manufacturing technology of three-dimensional (3-D) porous-network structure. For the purpose of fabricating a 2-D layer, we employed the laser sintering technology of titanium powder-tape or laser-cutting technology of titanium sheet. The 3-D manufacturing technology based on rapid prototyping is also combined with spark plasma sintering (SPS) to sinter laminated tapes or sheets. This enables us to control an internal architecture of porous structure.The major results obtained are as follows(1) Thickness of a titanium powder-tape, or height resolution of a structure, was about 100 μm using pure titanium powder with 20 μm in mean diameter.(2) Laser-sintering width of a titanium powder-tape was about 120 μm, and laser-cutting widths of a titanium sheet having 200 μm or 110 μm in thickness, were about 200 μm or 130 μm, respectively.(3) NaCl powder was more suitable as a pace-holding material in the SPS of laminated titanium powder tapes. On the other hand, alignment error of the titanium sheets was reduced to about ±70 μm by utilizing some titanium rods to suppress the movement of the laminated sheets in the SPS.(4) Manufacturing of 3-D porous structures with 45-50% in porosity and 300 μm in pore size was succeeded by the two kinds of approaches.(5) Some issues to be solved are poor stiffness and thickness fluctuation of tapes, and random shrinkage after sintering are problems in the first approach. In the other case, it is necessary to improve flatness of the cut titanium sheet and placement error of the laminated sheets