The results of a study on a new type of PZT valveless micropump with asymmetric obstacles are presented in this paper. The valveless micropump was made through a MEMS fabrication process by using simply only one photo mask. Asymmetric obstacles are used for the flow directing device instead of the diffuser/nozzle elements used in previous studies. In this study, numerical simulations were also carried out to evaluate the design and the performance of the new micropump. The main feature of the present micropump is that it has a uniform cross-section area across the micro-channel, which gives many advantages. The differential pressure head and the pumping flow rate can be adjusted easily by using obstacles of different shapes and changing the PZT operating frequency without changing the dimensions of the micro-channel. In this experiment, the performance of the micropump was evaluated by measuring the pressure head difference and the flow rate as the input voltage ranged from 20 to 40 V, a range much lower than those in previous studies. The pumping pressure can reach a maximum of 1.2 kPa, and the maximum net volume flow rate is 156 ll/min. These test data indicate that this micropump fulfills the demands for most micro-fluidic systems. Moreover, the present device can be easily applied to complex systems with combinations of several pumps and microchannels in the future.

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We demonstrate a way to transport droplets by an arrowed micropillar array surface with hydrophobic parylene. The lightly hydrophilic parylene surface could be changed to hydrophobic one by treating with fluorine-based plasma ͑CF 4 or SF 6 ͒. The droplet on this hydrophobic parylene surface with arrowed ratchets could be transported by a speaker, and the average measured velocity was 29 mm/ s. Moreover, the authors compared driving performance of the parylene surface ratchets with the ones modified by the hexamethyldisilazane ͑HMDS͒ vapor. Both the results of using hydrophobic parylene and HMDS were better than the previous work.

This study describes experimental results for a multifunctional microfluidic device with fluid pumping, mixing and particle removal. The obstacle-type valveless micropump, micromixer and particle separator are further integrated into the proposed multifunctional device. The process for fabricating this device is simple as only 1 photo mask, 1 inductively coupled plasma (ICP) etching step and anodic glass bonding are required. This novel device was developed utilizing an unsteady flow in a microchannel induced by the piezoelectric zirconium titanate (PZT) membrane oscillation of an obstacle-type valveless micropump. Flow direction is controlled by the amplitude and frequency of power driving the vibrating membrane. The optimal operational frequency for this device is 1.0 kHz. Very high mixing (>95%) and particle removal efficiency (close to 100%) exist at the inlet region and trifurcate zone, respectively. Image processing is utilized to count the number of particles and assess removal efficiency.

A clinical sorting chip integrated with new protein sensing technique has been developed in this work. Antibodycoated nanobeads reacted with antigen was separated from blood plasma based on dielectrophoresis (DEP) forces. MEMS fabrication process was used to produce the bio-chip and only two photo masks were required in the experiment. By using oxygen-plasma direct bonding method, the assembly of an electrode chip and the microchannels will form a set of RBCs and nanobeads separating chip. The original concentration of antigen can be rapidly estimated by nanobeads' Brownian motion measurement in varies of the viscous solutions. During the antibody-antigen reacting, the mean value of the beads diameter increased so that the Brownian velocity decreased with increasing time. The Brownian motion of nanobeads was observed and measured by micro-particle tracking velocimetry (P P-PTV).