A research team including the School of Engineering and Applied Sciences at the University of Virginia has developed for the first time an organ building module that can be "printed on demand" and is compatible with the human body. This will greatly assist in researching the progression of various diseases and corresponding therapies. The research results were published in the latest issue of the journal Nature Communications. The key to this achievement is a biomaterial with controllable mechanical properties that can be matched with various human tissues. Compared to existing bioprinting technologies, this is a huge leap forward. This unique bioprinting method is called Spherical Particle Digital Assembly (DASP). The technology can deposit biomaterial particles in the matrix: these particles are polymer hydrogels, which simulate human tissues by adjusting the arrangement of monomer and chemical bond; And what is wrapped in the particles are real human cells; Water based substrates can be used to construct 3D structures and provide a suitable environment for cell growth. Compared with the previous hydrogel bio ink, this new particle is less toxic, more biocompatible to cells, and has a unique "double network" structure - formed by two intertwined molecular networks, with strong mechanical strength, but can imitate the physical characteristics of human tissue. The research team has designed a multi-channel nozzle that can mix hydrogel ingredients as needed. Moreover, the forming process of this "double network" hydrogel bio ink is very fast, and it can change from a liquid drop to an elastic gel in 60 seconds. Through this state-of-the-art material and control technology, the team has achieved "on-demand printing" of organoids, which can be used as 3D cell models based on human tissue for studying various diseases, tissue modeling, and developing novel therapies. The team added that if this bioprinting is further optimized, it has the potential to be used for artificial organ transplantation, screening candidate new drugs, and so on. Hydrogel bio ink is a new material specially developed for printing human organs. However, limited by current technological processes, we can only print smaller human organs. Therefore, various research teams are trying to use new printing materials and improve manufacturing accuracy. Scientists at the University of Virginia have developed a new set of materials and methods that tightly combine growable biological "seeds" with printing substrates to obtain artificial tissues that can grow and automatically adhere to requirements. This scheme provides the possibility for precise manufacturing of multi-scale organs and opens up new paths for future research in human tissue engineering and artificial organ transplantation. (New Society)