Biological cells on microchips: new technologies and applications.

Integration of various chemical devices and complex operations onto a microchip, which is often referred to as a micro total analysis system (mu-TAS) or lab-on-a-chip, creates extremely efficient devices that exploit the advantages of a microspace. Furthermore, as the scale of the fluidic microvolume is roughly proportional to living cell sizes and processing capabilities, cells and micro chemical systems can be combined to develop practical prototypical microdevices. This approach has led to development of tools for investigating cellular functions, biochemical reactors and bioassay systems, as well as hybrid bio/artificial tissue engineered organs. Recently, bio-microactuators exploiting mechanical properties of cells powered without external energy sources have also been reported. This review focuses on new technologies involving cell-based devices on microchips, with a special emphasis on bio-microactuators. Firstly, we review systems to place and handle cells on a microchip. Secondly, we review bio-microactuators developed using single or a few driving cells. Finally, we review bio-microactuators developed using numerous cells or tissue to generate stronger forces. Understanding fundamental concepts behind the distinct features and performance characteristics of these cell-based micro-systems will lead to development of new devices that will be exploited in various fields in the future.