Search

We present a simple synthetic approach for the preparation of monodisperse thermosensitive gelatin microspheres in a microfluidic system. Based on the mechanism of shear force-driven break-off, aqueous droplets of a gelatin solution were continuously produced in an immiscible continuous fluid. Under cooling conditions, the gelatin droplets solidified into hydrogel microspheres, which resulted from the aggregation or crystallization of collagen folds. The produced gelatin microspheres possess a high monodispersity and fast response to environmental temperature. In addition, the size of the prepared microspheres can be manipulated by altering the flow rate of the continuous phase or aqueous phase, and the physical strength of the gelatin microspheres can be controlled by simply changing the gelatin concentration. Furthermore, this approach enables the preparation of monodisperse microspheres with the ability to exhibit different thermosensitivities and encapsulate colloidal particles under mild conditions, which demonstrate sequential release of the desired encapsulants according to the responsive temperature.

We described a simple and facile method to generate uniform agarose microwells on a polyelectrolyte (PEL) multilayer functionalized surface for efficient and reliable cell patterning. The PEL multilayers, composed of polyallylamine hydrochloride (PAH) and polystyrene sulfonate ammonium (PSS), provide an adhesive environment, which promotes cell proliferation in live cell-based assays. Agarose microwells, which are able to selectively isolate cells into individual compartments, are fabricated by micromolding the agarose solution in capillaries (MIMIC). Moreover, the fabricated agarose microwells are able to effectively form different shapes (e.g., circles, triangles, squares, and stars) and can isolate multiple cell types (e.g., HEK 293, NIH3T3, and HepG2). We also demonstrated how this technique can be used for the real-time monitoring of communication between primary neuronal cells in the agarose microwells. Open image in new window

This study presents simple method for surface modification of hydrophobic poly(dimethylsiloxane) (PDMS) microchannel using combination of silane coupling and photopolymerization. The method spatially modulates the wettability and can fabricate high contrast spatial patterning of microfluidic device wettability. The physical and chemical characteristics are investigated with contact angle, Fourier-transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), change of meniscus of water fluid, and spatially selective immobilization of fluorescent dyes. We successfully use our method to selectively modify the surface properties in certain areas of assembled microchannel. Furthermore, our approach allows for the generation of highly monodisperse double emulsions and multiple emulsions containing various numbers of inner droplets. Open image in new window

This paper reports a simple method for creating a functionalized surface for the efficient micro/nanopatterning of proteins by micromolding in capillaries (MIMIC) of poly(ethylene glycol)-poly(lactide) diblock copolymer (PEG-PLA) and self-assembled polyelectrolyte multilayers (PEL). The fabricated surface consisted of two distinct regions: a PEL region to promote protein immobilization and a PEG-PLA background as a biological barrier to prevent the nonspecific binding of proteins. When the ability of anti-biofouling of PEG-PLA was compared with the most widely used blocking agents, such as bovine serum albumin (BSA) and skim milk, the PEG-PLA prevents the nonspecific adsorption of several proteins. The properties of a functionalized surface were characterized by the water contact angle and atomic force microscopy (AFM). Topological analysis clearly indicated that the MIMIC method provides a reliable surface regardless of the micro- and nanopattern size. Two different functionalities of the fabricated surface produce uniform protein patterns from the micro- to nanoscale with a high signal to noise ratio. The proposed method allows for flexibility in forming shapes, such as lines, squares, circles, triangles and stars, and can control the pattern size from 400 nm to 90 μm. Finally, the antigen-antibody assay showed good linearity over the range of 10 ng/mL to 25 μg/mL, indicating its feasibility for a quantitative measurement of the concentration of target proteins in a sample.

This study reports a simple but efficient method for create bacteria microarrays on a predesigned functional surface consisting of two distinctive regions; a bacterial immobilizing area and a nonimmobilizing region. The functionalized surface was fabricated by a combination of self-assembled polyelectrolyte multilayers (PEL) and micromolding in the capillaries (MIMIC) of poly(ethylene glycol)-poly(d,l-lactide) diblock copolymer (PEGPLA). The PEL region provides bacterial immobilization, and the nonspecific binding of bacteria was prevented using PEG-PLA as passivation molecules. The topological change in the functionalized surface was characterized by atomic force microscopy (AFM), which suggested the occurrence of a laterally homogeneous and well defined surface modification. An analysis of the fluorescence signals from the bacteria microarray indicates that the bacteria are viable and grow after immobilization on patterned surface features. The rapid fabrication of two different functionalities on the surface results in a uniform bacteria pattern with a high signal to noise ratio and shape flexibility, such as lines, squares, and circles. Moreover, the pattern size could be controlled from 20 to 100 μm.

This paper describes the simple nanopatterning of proteins on polyelectrolyte surfaces using microcontact printing with a nanopatternable, hydrophilic composite nanomold. The composite nanomold was easily fabricated by blending two UV-curable materials composed of Norland Optical Adhesives (NOA) 63 and poly(ethylene glycol) dimethacrylate (PEG-DMA). NOA 63 provided stable nanostructure formation and PEG-DMA induced high wettability of proteins in the nanomold. Using the composite mold and functionalized surface with polyelectrolytes, the fluorescent, isothiocyanate-tagged, bovine serum albumin (FITC-BSA) was successfully patterned with 8 nm height and 500 nm width. To confirm the feasibility of the protein assay on a nanoscale, a glycoprotein-lectin assay was successfully demonstrated as a model system. As expected, the lectins correctly recognized the nano-patterned glycoproteins such as chicken ovalbumin. The simple preparation of composite nanomold and functionalized surface with a universal platform can be applied to various biomolecules such as DNA, proteins, carbohydrates, and other biomolecules on a nanoscale.

This study presents a microfluidic method for the production of monodisperse poly(ethylene glycol) (PEG) microspheres using continuous droplet formation and in situ photopolymerization in microfluidic devices. We investigated the flow patterns for the stable formation of droplets using capillary number and the flow rate of the hexadecane phase. Under the stable region, the resulting microspheres showed narrow size distribution having a coefficient of variation (CV) of below 1.8%. The size of microspheres (45∼95 ώm) could be easily controlled by changing the interfacial tension between the two immiscible phases and the flow rates of the dispersed or continuous phase.