Papers by Author: Kai Yuan Cheng

Abstract: Biochip is an emerging technology and has evoked great research interests in recent years. In this paper, a novel air-driven loop-type microfluidic biochip was investigated. Differing from conventional micro channels, this chip has a micro loop-channel and 3 sets of driving conduits with valveless design in their intersections so that the microfluid can be driven smoothly in unidirectional circular movements. The driving efficiency reaches the highest if the entry angle of driving conduits is in the tangent direction of the loop-channel. However, the smaller the included angle, the impact area the larger, leading to comparatively serious reflow phenomenon. Furthermore, the microfluid can be controlled to stop almost instantaneously in the loop segment. Therefore, this loop-type biochip is suitable for biochemical reactions under repeated multiple temperature operations such as polymerase chain reaction. A full circular movement completes a cycle of PCR amplification. Besides, this biochip has its merits including simpler chip design, shorter channel length, and flexible controllability for biochemical reactions.

Abstract: This investigation presents a fibre-optic Fabry-Perot interferometer as a displacement sensor in an atomic force microsope (AFM). A simple model of light wave transmission between two fibres with the same core diameter is proposed to determine the theoretical equation of light intensity of interference fringes from the fibre-optic Fabry-Perot interferometer. By replacing an AFM cantilever with a movable reflective mirror, the variations of relative light intensity of the interference fringes with the spacing between the fibre and the mirror were recorded. The theoretical equation for the light intensity of interference fringes was close to those obtained experimentally. Finally, a fibre-optic Fabry-Perot interferometer was operated in an AFM to image a two-dimensional phase array with a pitch of 4 µm and a depth of 150 nm.