Szu I. Yeh

Development of a millimetrically scaled biodiesel transesterification device that relies on droplet-based co-axial fluidics

In this study, we investigated a fluidic system that adheres to new concepts of energy production. To improve efficiency, cost, and ease of manufacture, a millimetrically scaled device that employs a droplet-based co-axial fluidic system was devised to complete alkali-catalyzed transesterification for biodiesel production. The large surface-to-volume ratio of the droplet-based system, and the internal circulation induced inside the moving droplets, significantly enhanced the reaction rate of immiscible liquids used here – soybean oil and methanol. This device also decreased the molar ratio between methanol and oil to near the stoichiometric coefficients of a balanced chemical equation, which enhanced the total biodiesel volume produced, and decreased the costs of purification and recovery of excess methanol. In this work, the droplet-based co-axial fluidic system performed better than other methods of continuous-flow production. We achieved an efficiency that is much greater than that of reported systems. This study demonstrated the high potential of droplet-based fluidic chips for energy production. The small energy consumption and low cost of the highly purified biodiesel transesterification system described conforms to the requirements of distributed energy (inexpensive production on a moderate scale) in the world.

The visual colorimetric detection of multi-nucleotide polymorphisms on a pneumatic droplet manipulation platform

A simple and visual method to detect multi-nucleotide polymorphism (MNP) was performed on a pneumatic droplet manipulation platform on an open surface. This approach to colorimetric DNA detection was based on the hybridization-mediated growth of gold nanoparticle probes (AuNP probes). The growth size and configuration of the AuNP are dominated by the number of DNA samples hybridized with the probes. Based on the specific size- and shape-dependent optical properties of the nanoparticles, the number of mismatches in a sample DNA fragment to the probes is able to be discriminated. The tests were conducted via droplets containing reagents and DNA samples respectively, and were transported and mixed on the pneumatic platform with the controlled pneumatic suction of the flexible PDMS-based superhydrophobic membrane. Droplets can be delivered simultaneously and precisely on an open-surface on the proposed pneumatic platform that is highly biocompatible with no side effect of DNA samples inside the droplets. Combining the two proposed methods, the multi-nucleotide polymorphism can be detected at sight on the pneumatic droplet manipulation platform; no additional instrument is required. The procedure from installing the droplets on the platform to the final result takes less than 5 min, much less than with existing methods. Moreover, this combined MNP detection approach requires a sample volume of only 10 µl in each operation, which is remarkably less than that of a macro system.

Development of an active micromixer by dielectrophrosis particle manipulating

A particle manipulating micromixer was developed successfully in this study. The present device was fabricated by simply MEMS process. Only two photomasks, one for electrode array chip and another for micro-channel, were needed to manufacture the micromixer. Dielectrophoresis (DEP) force was used to manipulate the particles in the micro-channel. In this experience, polymer particles with diameter of 1 n m were tested in the fluid with conductivity of 0.10mS/cm. The results show that the symmetrical vortices were observed at frequency of 100 kHz. The traveling wave DEP (twDEP) occurred when the input frequency was 10MHz. Micro-mixer chip which can stir fluid to achieve mixing was fabricated successfully by combining an electro array chip and Y-type micro-channel. The mixing performance depends on the voltage input. The flow phenomena were obtained and analyzed by micro-PIV technology. In the future, different cells can be manipulated by the present micromixer to achieve the rapid mixing with different driving frequency. It is useful in the biological or biomedical application.