Department of Mechanical Engineering, York University, 4700 Keele Steet, Toronto, ON, M3J 1P3, Canada.
Soft Matter. 2022 May 4;18(17):3422-3429. doi: 10.1039/d2sm00201a.
Additive manufacturing (AM), in its little more than 40 years of existence, has already established itself as a technology with enormous potential for several fields, especially the ones that require complex, high resolution, small structures, such as tissue engineering. This field has been especially attracted to the most recent AM evolution, 4D printing, due to its ability to create structures responsive to external stimuli. Among the range of materials that are simultaneously suitable for 4D printing and biological uses, poly(-isopropylacrylamide) (pNIPAM) stands out. pNIPAM presents exceptional characteristics such as a low critical solution temperature (LCST) close to the human physiological temperature and biocompatibility with several cell types. However, these characteristics are greatly affected by processing parameters. In this work, pNIPAM hydrogels were manufactured by AM using digital light processing; the printing temperature was varied between 5, 10 and 15 °C to analyze how it affects the hydrogels' final properties. The impact on hydrogels was analyzed by differential scanning calorimetry (DSC), swelling, deswelling and reswelling analyses, scanning electron microscopy (SEM) images, and compression tests. Based on our results increasing the production temperature of the hydrogels by 10 °C led to a decrease of more than 50% in the maximum swelling capacity, approximately 10% increase in water retention, and 6.5 °C variation in the LCST. The justification for such behaviour lies in the increase of the crosslinking rate and thickening of the external layer of hydrogels, which prevents the free movement of water from its interior.
增材制造（AM）在其存在的 40 多年中，已经确立了自己作为一种具有巨大潜力的技术，尤其在需要复杂、高分辨率、小结构的领域，如组织工程。该领域特别吸引了最近的 AM 发展，即 4D 打印，因为它能够创造对外界刺激有响应的结构。在同时适合 4D 打印和生物用途的一系列材料中，聚（异丙基丙烯酰胺）（pNIPAM）脱颖而出。pNIPAM 具有独特的特性，例如接近人体生理温度的低临界溶液温度（LCST）和与多种细胞类型的生物相容性。然而，这些特性受到加工参数的极大影响。在这项工作中，使用数字光处理通过 AM 制造了 pNIPAM 水凝胶；打印温度在 5、10 和 15°C 之间变化，以分析其如何影响水凝胶的最终性能。通过差示扫描量热法（DSC）、溶胀、脱水和再溶胀分析、扫描电子显微镜（SEM）图像和压缩测试分析了水凝胶的影响。根据我们的结果，将水凝胶的生产温度提高 10°C 导致最大溶胀能力下降超过 50%，水保留率增加约 10%，LCST 变化 6.5°C。这种行为的原因在于交联速率的增加和水凝胶外部层的增厚，这阻止了水从内部的自由移动。
