3D列印輕量化結構的可光固化泡沫製程技術

Abstract

在現代的社會中，泡沫構造的材料越來越常被作為填料使用，使在同一體積下，耗材較少且質量較輕，又由於其孔洞的構造，可以作為隔熱、保冷，抑或是抗噪的材料。如此特殊的性質卻因為其複雜的構造，難以精確製造出所要的形狀、孔隙度及機械強度，為了讓泡沫構造得以更加被廣泛應用，我們發展出了一套能夠3D列印、快速成型並且可以輕易控制的泡沫構造製程方法。 在此研究中，引進了DLP技術以快速將稍縱即逝的泡沫光固化形成我們所要的構造。添加光敏感的單體(PEGDA)、起始劑(TPO)以及交聯劑(TiO2)使容易能夠在UV光的照射下進行反應，於泡沫之間的薄膜交聯固化成型。為了讓調製的墨水能夠有效起泡，我們將水與界面活性劑(CTAB)均勻混合，降低表面張力並使溶液中的顆粒均勻懸浮，另外再添加奈米顆粒(SiO2)使泡沫更加穩定。將上述溶液配製完成後，使用設計改良後的裝置讓溶液與空氣混合形成穩定均一的泡沫構造，其孔隙大小、孔隙度可經由裝置中海綿的孔洞大小、流體的流速、裝置循環次數以及調整氣液比例來控制。由於溶液中顆粒與氣泡會對UV光固化反應造成阻礙，必須加入加速劑(NVP)來降低氧氣對自由基聚合反應的抑制並加速光固化程序，顆粒與氣泡造成的散射與反射能夠透過UV吸收劑的添加幫助提升列印的品質，而光固化造成嚴重的體積收縮則能夠藉由添加網絡中的填充物(PEG)作支撐使泡沫構造不致崩塌。3D列印(DLP)的製程方法使簡單或繁雜構造都能夠輕易地製作出來，泡沫孔洞大小於30µm以下，列印時的精細度小於200µm，器具能夠輕量化的同時(密度低於0.35 g/cm3)，緻密的固化泡沫在經過固化之後提供一定程度的支撐力(壓縮強度大於400 kPa)及彈性(彈性模數為5.93 kPa)。這項技術最大的優點在於能夠直接印製出所需的器具形狀，不須經過切割、拼裝等等後處理來獲取所需產品，減少了原料的使用與浪費，在擁有相近成效的情況下，將原料、時間成本減至最低。

In modern society, foam-based materials are increasingly being used as fillers due to their ability to reduce material consumption and weight while providing thermal insulation, cooling, noise reduction, and other benefits. However, the complex structure of foam makes it difficult to manufacture precisely, with the desired shape, porosity, and mechanical strength. To enable wider applications of foam structures, we have developed a 3D printing process that allows for rapid manufacturing and easy control of foam structures. In this study, we introduced direct light processing (DLP) technology to quickly solidify fleeting foam into the desired structure. We added photosensitive monomers (PEGDA), initiators (TPO), and crosslinking agents (TiO2) to enable reaction under UV light, which crosslinked and solidified the thin films between the foam. To effectively foam the ink, we mixed water and a surfactant (CTAB) to reduce surface tension and uniformly suspend particles in the solution, and added nanoparticles (SiO2) to stabilize the foam. After preparing the ink solution, we used a modified device to mix the solution with air to form stable and small-pored foam structures. The pore size and porosity of the resulting product can be controlled by adjusting the pore size of the sponge in the device, the fluid flow rate, the number of cycles, and the gas-liquid ratio. Since the particles and bubbles in the solution obstruct the radical polymerization, an accelerator (NVP) was added to reduce the oxygen inhibition and maintain the rapid UV curing process. An addition of a UV absorber assists in increasing the printing quality restricted by the scattering and reflection of particles. The serious volume shrinkage caused by UV curing was supported by adding fillers (PEG) in the network to prevent the foam structure from collapsing. The 3D printing (DLP) process allows for easy manufacturing of simple or complex structures, with foam pore sizes below 30 μm and printing precision below 200 μm. The lightweight and dense solidified foam (density lower than 0.35 g/cm3) provides a certain degree of support (above 400 kPa) and elasticity (the elasticity modulus is at 5.93 kPa). The biggest advantage of this technology is that it can directly print the desired tool shape, eliminating the need for cutting, assembly, and other post-processing steps to obtain the desired product. This reduces material usage and waste while minimizing material and time costs, achieving similar results.