Title: Three-dimensional Cell Structure Assembly by On-chip Fabrication and Manipulation

Lost or damage of an organ due to disease or injury is a serious problem for human body. The typical therapy is to get an artificial organ or a transplant. Unfortunately, artificial organs and other implanted abiotic devices often fail over time. Transplantation of organs to replace the incurable ones, such as heart, liver, or kidney, is a highly successful therapy. A successful transplant requires a compatible and willing donor. However, the need for donor organs far exceeds the supply. This donor scarcity problem has resulted in new technique which is to build artificial organs by cells and organic materials, which is defined as tissue engineering. Traditionally, many useful and important in vitro methods for tissue engineering are contributed by two-dimensional (2D) cell structures. However, an increasing number of researchers have questioned the validity of studying cells in an environment that is so far removed from the in vivo state. Three-dimensional (3D) cell structure assembly in tissue engineering provides a promising way to build artificial organs. A specific 3D multi-cellular structure is often critical for proper cellular function. Besides, if an artificial organ is to assemble and work properly, specific cells must be directed to specific locations at a specific time, forming patterns of cells with a defined function. This is a fundamental feature of tissue and organ assembly in all living organisms. 3D cellular structures provide a similar environment for cells as in the real tissues, which enhance the cell proliferation and cell-cell interaction during building artificial tissues. The ability to build such 3D structures would be useful for tissue engineering.