Papers by Author: Chih Hsin Shih

Abstract: The stabilities of the burst frequencies of the capillary valves have a strong impact on the robustness of sequential flow controls on the centrifugal platform. In this study, factors which influence the burst frequencies of the capillary valves were investigated. It was found that the burst frequencies of the capillary valves were affected by the flow retardation effects. Hydrophobic treatment on the surface of the capillary valve is necessary in order to reduce the retention time of the liquid. In addition, by increasing the depth of the reservoir and conducting hydrophilic treatment on the surface of the reservoir, variations in burst frequencies of the capillary valves can be greatly reduced.

Abstract: In this study, mixing efficiencies of oscillating micromixers based on a compact disc under various operating conditions and geometric parameters were analyzed. By alternating the direction of rotation, stirring of liquids inside the chamber can be used for mixing. The experimental results showed that under the same operating conditions, deeper chamber and lower liquid filling ratio resulted in better mixing efficiency. Under the same distance of motion, oscillating frequency had more impact on the mixing efficiency than the oscillating amplitude. In addition, the experimental results also demonstrated that this batch mixing mechanism can also be utilized to achieve satisfactory mixing of liquids with viscosity of 100 cp within 10 seconds.

Abstract: This work reports a novel mixing design that can do fast, batch-typed liquid mixing on a centrifugal platform. Mixing is an important procedure for many applications related to chemical reactors and biological assays, especially in the field of microfluidics. The extremely small sizes of microchannels make it difficult to achieve turbulence to assist mixing. To overcome this problem, a meandering fluidic design on the centrifugal platform is proposed. Centrifual force promotes mixing by inducing lateral flow movement in the circular section and flow focusing effect in the bending section. The degree of mixing was studied for solutions with various viscosities under different rotational speeds. The experimental results showed that this mixer can mix microliter or nanoliter volumes of aqueous solutions within one second.

Abstract: This work presents a novel approach to decant and meter supernatant on a centrifugal platform. Supernatant decanting, such as decanting plasma from the centrifuged whole blood, is an important sample preparation procedure for the whole blood bioassays. By manipulating the centrifugally induced pressure and the elastic deformation of the chamber’s plastic lid, fixed amounts of the supernatant can be decanted into the detection chamber. This approach has the advantages of low manufacturing cost and ease of operation.