We have proposed a micromachined system with the aim of controlling injection of DNA into cells. The injection system is composed of two components: hollow microcapillaries for injection and microchambers for trapping cells. The hollow microcapillary array, the most important part of the system has been fabricated. In this paper, we present a micromachined DNA injection system and the fabrication of hollow microcapillary array. Bosch deep reactive ion etching (RIE) etching was used to etch small, deep holes, approximately 5 mu m in diameter and 100 mu m in depth, on a silicon substrate, and enabled the fabrication of microcapillaries with microchannels inside. The fabricated hollow microcapillaries are 1 mu m in thickness, 30 mu m in length and 5 mu m in diameter and are made of SiO2. The height of the microcapillaries can be easily controlled. Silicon substrate with microcapillaries is bonded anodically with a processed glass substrate, and enables the silicon membrane to endure pressure from outside during DNA injection. By back-side silicon etching in TMAH solution and making holes on tips of microcapillaries, the fabrication of hollow microcapillaries is completed. Hollow microcapillary arrays can also be used in some applications other than DNA injection, such as microchannels in fluid delivery systems.
