This thesis reports the results of projects I have participated in during the period of my masters’ thesis. The first project reports a new fluidic micro-plasma chip with an Al-coated spherical surface. This device is designed to efficiently capture the glowing microdischarge signal. The detection of nutrients in water using this chip has been demonstrated. The detailed explanations of the basic principle of glowing microdischarge signal, the fluidic microplasma chip, the operating optical system, the concentration testes and result data analysis will be introduced in the following chapters. We detected the nitrate and phosphate in water sample successfully with our device. The second project reports an optimized microfluidic droplet device for fabricating 3D microtissues and studying the cell behaviors in 3D microtissues. It has been found by properly selecting the size of the microchambers on the microfluidic device and choosing an optimal concentration of collagen to fabricate microtissues. The behaviors of cells in the microtissues can be essentially the same as those of cells in a conventional cell culture system. Furthermore, this optimized microfluidic droplet device for fabricating 3D collagen-based microtissues can also be used to study breast cancer cell proliferation and motility. This is additional work that I did for my master’s thesis and is included in the appendix.