Department of Chemical Engineering , McMaster University , 1280 Main Street West , Hamilton , ON L8S 4L8 , Canada.
Department of Chemistry and Chemical Biology , McMaster University , 1280 Main Street West , Hamilton , ON L8S 4M1 , Canada.
ACS Appl Mater Interfaces. 2019 Feb 13;11(6):6325-6335. doi: 10.1021/acsami.8b16232. Epub 2019 Jan 30.
Although two-dimensional hydrogel thin films have been applied across many biomedical applications, creating higher dimensionality structured hydrogel interfaces would enable potentially improved and more biomimetic hydrogel performance in biosensing, bioseparations, tissue engineering, drug delivery, and wound healing applications. Herein, we present a new and simple approach to control the structure of hydrogel thin films in 2.5D. Hybrid suspensions containing cellulose nanocrystals (CNCs) and aldehyde- or hydrazide-functionalized poly(oligoethylene glycol methacrylate) (POEGMA) were spin-coated onto prestressed polystyrene substrates to form cross-linked hydrogel thin films. The films were then structured via thermal shrinking, with control over the direction of shrinking leading to the formation of biaxial, uniaxial, or hierarchical wrinkles. Notably, POEGMA-only hydrogel thin films (without CNCs) did not form uniform wrinkles due to partial dewetting from the substrate during shrinking. Topographical feature sizes of CNC-POEGMA films could be tuned across 2 orders of magnitude (from ∼300 nm to 20 μm) by varying the POEGMA concentration, the length of poly(ethylene glycol) side chains in the polymer, and/or the overall film thickness. Furthermore, by employing adhesive masks during the spin-coating process, structured films with gradient wrinkle sizes can be fabricated. This precise control over both wrinkle size and wrinkle topography adds a level of functionality that to date has been lacking in conventional hydrogel networks.
虽然二维水凝胶薄膜已应用于许多生物医学应用中，但创建更高维度的结构化水凝胶界面将使生物传感、生物分离、组织工程、药物输送和伤口愈合应用中的水凝胶性能得到潜在改善和更仿生。在此，我们提出了一种新的简单方法来控制 2.5D 中水凝胶薄膜的结构。含有纤维素纳米晶体 (CNC) 和醛基或酰肼基功能化聚(聚乙二醇甲基丙烯酸酯) (POEGMA) 的混合悬浮液被旋涂到预加应力的聚苯乙烯基底上，形成交联水凝胶薄膜。然后通过热收缩对薄膜进行结构化，控制收缩方向导致形成双轴、单轴或分级皱纹。值得注意的是，由于收缩过程中与基底的部分去湿，仅含 POEGMA 的水凝胶薄膜（不含 CNC）无法形成均匀的皱纹。通过改变 POEGMA 浓度、聚合物中聚乙二醇侧链的长度和/或薄膜的总厚度，可以将 CNC-POEGMA 薄膜的形貌特征尺寸调谐 2 个数量级（从约 300nm 到 20μm）。此外，通过在旋涂过程中使用粘性掩模，可以制造具有梯度皱纹尺寸的结构化薄膜。这种对皱纹尺寸和皱纹形貌的精确控制增加了一个功能水平，迄今为止，这在传统水凝胶网络中是缺乏的。
