Figure 4 Microstructure of stitching interface. SEM images of the interfaces of two PAAm hydrogels with (A) or without (B) stitching. Scale bar=100 µm. Sequence of fluorescent microscopic images show that the FITC labeled CS-MA diffuses from the interface of PAAm hydrogels in coating (C) and integrative (D) periods. Scale bar=300 µm.
3.4 Construction of 3D architectures and microfluidic chips via layer-by-layer adhesion
Using layer-by-layer adhesion, various architectures can be constructed from different hydrogels. Here we provide some examples that are unable to be fabricated by sacrificial templates. Firstly, we obtained a 3D architecture by stitching PAAm and F127-DA hydrogel strips with CS-MA. As shown in Figure 5A, the strips were superimposed on each other and after stitching, the strips well bonded together, which can be pulled without detachment (Supplementary Movie 2). Furthermore, a microfluidic chip was assembled by three hydrogels of PAAm, F127-DA and PEG-DA, providing an inner vascular-like channel (Figure 5B). The hydrogel chip endured a sharp twist without cracking (Supplementary Movie 3), indicating strong adhesion among the hydrogels.