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A micro-pillar chip is proposed and developed to separate the amino acids, phenylalanine and tryptophan, through the aqueous two-phase system (ATPS). The surface properties of micro-pillars, specifically hydrophobicity and hydrophilicity for separation are also investigated. Because their isoelectic points (pl values) are similar, these amino acids are difficult to separate by general extraction techniques; the ATPS is thus adopted in a micro-system to separate these amino acids and only a few micro liters of sample are required. The results reveal that the various surface properties of micro-pillars distinguish the separation mechanisms and efficiency. When the micro-pillar array is constructed in the ATPS, the separation efficiency is improved. Furthermore, the surface of micro-pillars becomes activated from hydrophobic to hydrophilic, and micro-pillars with a hydrophilic surface increase the separation ability without sample residues. Hence separation is improved on incorporating hydrophilic micro-pillars in the ATPS.

In this work we present an asymmetric microfluidics oscillator of innovative design and systematically investigated it with both numerical and experimental methods. The design of both entrance nozzle and asymmetric feedback channels enable the oscillator to stably oscillate in very small range of Reynolds number 1~100, whereas the Strouhal number remained as 1 × 10−3. The results reveal that improvement of the performance was resulted from the augmented periodic impingement of the flows from the feedback channels. The analysis also indicates that dynamic phenomena in the working fluid of this novel oscillator were distinctive and appropriately appraised.