| Popis: |
This work reports design, device fabrication, modeling and experimental results on new sampling and separation principles in which liquid is transported in a droplet form on a planner hydrophobic surface with no moving parts. The presented particle sampler and separator constitute core units for the handheld lab-on-a-chip-based airborne particle monitoring system. For the airborne particle sampling, a novel method is developed by which the particles on the solid surface are swept and sampled by electrowetting-actuated moving droplets. Theoretical analysis and experimental works along with microfabricated testing devices are carried out to investigate the underlying physics and to optimize the sampling conditions. The sampling concepts are examined and proved on a solid surface and perforated filter membrane showing high sampling efficiencies. For the particle separation, a new separation scheme is developed in which the mixed particles are separated within a mother droplet by traveling-wave dielectrophoresis (tw-DEP). Using the subsequent operation of droplet splitting by way of electrowetting, the separated particles can be isolated into each split droplet according to the DEP properties of the particles. This in-droplet separation is examined with many combinations of particles in microfabricated devices. By investigating the particle behavior as function of the frequency of the traveling wave DEP signal, the separation efficiencies are optimized. The above microfluidic units constitute key components for upstream particle sampling and downstream sample processing in the lab on a chip system, providing the following advantages: extremely small amount use of samples/reagents (2) no external pressure source required for fluidic operations, (3) simple design and fabrication since no mechanical moving structure. |
