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Microfluidic devices, which consist of networks of channels with micrometer dimensions, have attracted considerable attention in a wide range of applications including analytical systems, biomedical devices, and as tools for chemistry and biochemistry based experiments 1 5 . These devices can produce monodisperse droplets with exceptional precision, which are useful as individual compartments for chemical reactions and templates for preparation of monodisperse functional particles 6 11 . To date, several types of microfluidic devices have been developed. For example, capillary microfluidic devices consist of coaxial assemblies of tapered glass capillaries on glass slides 12,13 .Although the device can be fabricated at low cost, it is cumbersome to set the positions and sizes of the capillaries precisely. There are also polydimethylsiloxane PDMS devices, which consist of patterned microchannels in a silicone elastomer of PDMS fabricated by soft lithography techniques 14 16 . Although using soft lithography facilitates accurate control of the positions and sizes of the channels in the device through the design of mask patterns, it is difficult to fabricate flow channels in three dimensions, which would limit the utility of the device for many applications. 21 , could be prepared by polymerization of a gelation reagent dissolved in the monodisperse water droplets. Although stereolithography is a promising method for fabricating three-dimensional microfluidic devices, the default properties of the resin are inappropriate for many applications. For example, the device cannot produce oilin-water O/W emulsions and double emulsions, consisting of drops of oil and water assembled into a core-shell structure, owing to the hydrophobic surface properties of the flow channels 22,23 . To broaden the applicability of the devices, control of the wetting characteristics of the surface of channels is necessary. In this paper, we report on the surface treatment of the NOTE Abstract: A microfluidic device with three-dimensional flow channels was fabricated by stereolithography, and hydrophilic surface treatment of the flow channel was performed by coating the wall of the channel with a silica layer. After the treatment, the device produced monodisperse oil-in-water (O/W) emulsions. The silica layer on the channel surface was then coated with a fluorinated silane coupling agent to make it hydrophobic, thus enabling the treated device to produce monodisperse inverted water-in-oil (W/O) emulsions.

Novel calcium ion (Ca 2 þ )-responsive hydrogels composed of designed b-sheet peptides were constructed. As the novel designed peptide, E1Y9, has a Glu residue to interact with Ca 2 þ , the peptide in the sol-state self-assembled into hydrogels in the presence of Ca 2 þ . The hydrogelation did not occur in the absence of Ca 2 þ ; therefore, Ca 2 þ -dependent hydrogelation was achieved by the molecular design. The hydrogelation from the viscous sol-state solution can be induced by a slower self-assembly process of the b-sheet peptide involving a rapid process of Ca 2 þ binding. When the sol-state peptide solution was injected with Ca 2 þ , gel drops and strings with desired shapes could be constructed. Different cell lines can be cultured on the hydrogel, demonstrating its low toxicity, which is comparable to commercially available microtiter plate surfaces for cell culture. Furthermore, the hydrogels showed a high cell-adhesive ability that was similar in magnitude to fibronectin, which is a native cell-adhesive protein. The Ca 2 þ -responsive peptide nanofiber-based hydrogelation system will facilitate novel studies exploiting self-assembling peptide nanomaterials that will lead to cell-based technology, such as three-dimensional cell culturing.

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