Wang Yilei, Weng Can, Sun Huijie, Deng Zijian, Jiang Bingyan
College of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China.
State Key Laboratory of High Performance Complex Manufacturing, Central South University, Changsha 410083, China.
Nanomaterials (Basel). 2022 Sep 29;12(19):3416. doi: 10.3390/nano12193416.
During the demolding process, the interfacial interaction between the polymer and the metal mold insert will lead to the deformation of the micro-structure, which will directly affect the molding quality and performance of injection molded microfluidic chips. In this study, the demolding quality of micro-channels and micro-mixing structures of polycarbonate (PC), polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC), and polystyrene (PS) microfluidic chips for heavy metal detection were investigated by molding experiments. The experimental results showed that the structures of microfluidic chips could be completely replicated. However, tensile deformation and fracture defects were observed at the edges of the micro-structures after demolding. Compared to the Ni mold insert, the calculation of the relative deviation percentages showed that the width of the micro-channel became larger and the depth became smaller, while the dimensions of the micro-mixing structure changes in the opposite direction. Subsequently, a molecular dynamics (MD) simulation model of polymer/nickel (Ni) mold insert for injection molding was established. The changes of adhesion work, demolding resistance and potential energy during demolding were analyzed. The simulation results showed that the polymer structures had some deformations such as necking, molecular chain stretching and voids under the action of adhesion work and demolding resistance. The difference in the contact area with the mold insert directly brought different interfacial interactions. In addition, the potential energy change of the polymer system could be used to quantitatively characterize the demolding deformation of the structure. Overall, the MD method is able to effectively explain the internal mechanisms of interfacial interactions, leading to the demolding deformation of polymer structures from the molecular/atomic scale.
在脱模过程中，聚合物与金属模具镶件之间的界面相互作用会导致微观结构变形，这将直接影响注塑微流控芯片的成型质量和性能。在本研究中，通过成型实验研究了用于重金属检测的聚碳酸酯（PC）、聚甲基丙烯酸甲酯（PMMA）、环烯烃共聚物（COC）和聚苯乙烯（PS）微流控芯片的微通道和微混合结构的脱模质量。实验结果表明，微流控芯片的结构可以被完全复制。然而，脱模后在微观结构的边缘观察到拉伸变形和断裂缺陷。与镍模具镶件相比，相对偏差百分比的计算表明，微通道的宽度变大而深度变小，而微混合结构的尺寸变化方向相反。随后，建立了用于注塑成型的聚合物/镍（Ni）模具镶件的分子动力学（MD）模拟模型。分析了脱模过程中粘附功、脱模阻力和势能的变化。模拟结果表明，在粘附功和脱模阻力的作用下，聚合物结构发生了一些变形，如颈缩、分子链拉伸和空隙。与模具镶件接触面积的差异直接带来了不同的界面相互作用。此外，聚合物体系的势能变化可用于定量表征结构的脱模变形。总体而言，分子动力学方法能够有效地解释界面相互作用的内部机制，从分子/原子尺度上导致聚合物结构的脱模变形。
