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We improved our previous micro-device containing motile micro-algae ( Euglena gracilis ) cells for toxicity monitoring, by introducing micro-trenches between a micro-aquarium and two surrounding channels. Target test solution was introduced from the bypass channel to the micro-aquarium through micro-trenches, with a pulse injection and continuous diffusion. Although the chemical gradient formed in the micro-aquarium was not permanently sustainable but only temporal for a couple of 10 min, the device was simple, easy-to-use, and cost-effective to evaluate the toxicity of the test solution. The cells showed their chemotaxis to the temporal chemical gradients, resulting in the deviated distribution of the cells in the micro-aquarium, whereas metabolic disturbing effects of toxic substances induced the unusual motion of the cells. [ABSTRACT FROM AUTHOR]

Owing to the relatively high conductivity and unique redox behavior, polyaniline (PANI) has been one of the most technologically promising conducting polymers. Although various methodologies have been developed, fabrication of PANI microfibers has been a challenging task owing to the poor solubility in most organic solvents. By taking advantage of a microfluidic technology and organic soluble acid labile t-Boc-protected PANI (t-Boc-PANI) as the conducting polymer precursor, fabrication of PANI microfibers in a size-controlled manner is possible. Introduction of a THF solution containing t-Boc- PANI, and dodecylbenzenesulfonic acid (DBSA) as a core fl ow, and water as a sheath flow into a microfluidic channel with a 3D hydrodynamic focusing effect results in crystallization of the polymer fiber. By changing the flow rate, linear PANI microfibers that range from 16.2 to 39.4 μm in diameter are readily obtained. [ABSTRACT FROM AUTHOR]

We developed and examined a toxicity sensing microchip, where 200-300 cells of flagellated microbes ( Euglena gracilis ) were placed and their movements were monitored with a video camera. The microchip had two microchannels for test sample and reference flow, and the cells were confined completely in a separated closed-space (micro-aquarium). The two microchannels run aside of the micro-aquarium, and molecules of test sample permeated into the micro-aquarium from the microchannels via diffusion through porous polydimethylsiloxane (PDMS) wall. The toxicity of test sample was evaluated real-time from the spatial distribution of the cells and swimming motion. Highly quantitative toxicity monitoring was achieved, owing to the complete confinement of microbial cells and sensitive chemotaxis of the cells. [ABSTRACT FROM AUTHOR]

A microfluidic technique was employed to fabricate polydiacetylene (PDA)-embedded hydrogel microfibers. By taking advantage of calcium ion-induced insoluble hydrogel formation, supramolecularly assembled diacetylene (DA)-surfactant complexes were successfully immobilized in the calcium alginate fibers. Thus, instantaneous microfiber formation was observed when the core flow of DA supramolecules-containing alginate solution met the sheath flow of calcium ions. UV irradiation of the resulting fibers afforded blue colored PDAs, and the formation of a conjugated polymer was confirmed by heat-induced phase transition and by Raman spectroscopy. By adjusting the core and sheath flow rates, PDA-embedded hydrogel fibers of various sizes were obtained. [ABSTRACT FROM AUTHOR]