Assembly of Cellular Microstructures into Lobule-Like 3D Microtissues Based on Microrobotic Manipulation* Research supported by the Beijing Natural Science Foundation under Grant 4164099and the National Natural Science Foundation of China under grants 61603044and 61520106011.

Fabrication of cellular microtissues in vitro that reproduce physiology of human liver has shown great potential and demand in clinical and biomedical research. However, creating tissue-engineered constructs in vitro with both organ-like geometry and biological functions presents unique challenge attribute to complex structure and function of human liver. Here, we have developed photopattern and microrobotic manipulation for fabrication of cellular microtissue in vitro as a substitution of liver lobule as well as liver functions. Poly (ethylene) glycol diacrylate (PEGDA) hydrogel containing hepatocytes are introduced into microfluidic channel to produce cell encapsulated 2D microstructures with lobule-like pattern by photocrosslinking. Microrobotic manipulation is developed for 3D assembly of 2D microstructures into 3D microtissues based on liquid force. To form an integration with lobule-like structure, randomly oriented 2D microstructures are aligned into regular shape by self-alignment process based on hydrophilic-hydrophobic interactions. After the 2D fabrication and 3D assembly process, cells can proliferate and spread in PEGDA hydrogel. During long-term culture, cells perform high viability in both 2D microstructures and 3D microtissues. Albumin secretion of hepatocytes encapsulating in microtissues maintain during the culture period. It indicates that hepatocytes can keep high viability and some liver functions in these microtissues which providing a potential demonstration for biomedical research in the future.