| Speaker : |
Dr. Peigang DENG (Department of Mechanical Engineering, The Hong Kong University of Science and Technology) |
| Subject : |
Micro Bubble Actuator for DNA Hybridization Enhancement |
| Date : |
December 13, 2004 (Conference room 226, Faculty of Engineering bldg.8, Hongo campus)
December 15, 2004 (Conference room 1, Institute of Industrial Science, Komaba campus) |
| Abstract : |
DNA-based biosensors usually use DNA probes to detect the presence of target DNA molecules from a specific pathogen. The underlying principle in these biosensors relies on DNA hybridization in which one strand of DNA (say DNA probe) matches up with its complementary strand (target DNA) to form a double-stranded molecule. The hybridization process is often limited by a passive diffusion process of the large DNA molecules in a static hybridization solution. To improve the performance of the micro DNA biosensor, we propose to introduce distributed active bubble perturbations in the hybridization solution for the purpose of enhancing the molecular diffusion and consequently the DNA hybridization process.
A novel micro bubble actuator of specially designed micro heater (10×3µm2) and single bubble system was developed based on MEMS technology for bubble generation with high controllability and reliability. Under pulse heating, this actuator can generate highly localized near homogeneous boiling and produce single bubbles periodically in DI water and two common DNA buffers. Due to the asymmetric cycle of the bubble growth and collapse periods, the flow field can be effectively perturbed.
Fundamental investigation of effects of scaling of heater size on micro transient boiling was studied on a series of thin film planar Pt heaters, which had various feature sizes ranging from 0.5 µm up to 70 µm. It was found that there existed a critical feature size of the heater (10 µm), for which the boiling phenomena on heaters with feature size below or above this critical value were quite different.
Micro vapor bubble generation in ssDNA solutions was experimentally and theoretically investigated. A distinct retardation effect on the motion of the micro bubble was observed at high ssDNA concentrations, due to the dissipation effect of the ssDNA macromolecules on bubble kinetics. Measurements of bubble nucleation temperature indicated that an increase in the DNA concentration or a higher heat flux from the heater could lead to a higher heating rate, a faster bubble nucleation process and a higher nucleation temperature.
The hybridization between molecular beacon and its complement was investigated firstly in a 96-well plate following a conventional way. Thereafter, the assay was transferred to a PDMS based reaction chamber, where various 2-D micro heater arrays were distributed on the bottom for micro bubble generation. Compared to the hybridization time for the hybridization without bubble agitation, it is distinctively shorten by 18% with 10 cycles of micro bubble agitation from a 2×1 heater array, and by 43% with 10 cycles of micro bubble agitation from a 2×2, and 3×3 heater array. |
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