Peihong Xue

Janus Si Micropillar Arrays with Thermal-Responsive Anisotropic Wettability for Manipulation of Microfluid Motions

In this paper, Janus micropillar array (MPA) with fore-aft controllable wettability difference was demonstrated. With two-step modification process, we successfully decorate the Janus pillar skeletons with wettability-switchable polymer brush on one side and hydrophilic self-assembled monolayer on the other. Owing to the switchable wettability of the polymer brush, the patterned surface could switch between anisotropic wetting and isotropic wetting at different temperatures, which gives the possibility of coupling the well-designed surface with microfluidic channel to manipulate the microfluid motion. Additionally, a further photothermal control of microfluid was also established based on the thermal-responsive Janus MPA through introducing infrared light to adjust the temperature of the microfluidic system. We believe that the thermal-responsive Janus micropillar arrays would provide a new strategy to control the flow and motion of fluids in microfluidic channels and show potential applications in the future microfluidic chips.

Morphology-Patterned Anisotropic Wetting Surface for Fluid Control and Gas–Liquid Separation in Microfluidics

This article shows morphology-patterned stripes as a new platform for directing flow guidance of the fluid in microfluidic devices. Anisotropic (even unidirectional) spreading behavior due to anisotropic wetting of the underlying surface is observed after integrating morphology-patterned stripes with a Y-shaped microchannel. The anisotropic wetting flow of the fluid is influenced by the applied pressure, dimensions of the patterns, including the period and depth of the structure, and size of the channels. Fluids with different surface tensions show different flowing anisotropy in our microdevice. Moreover, the morphology-patterned surfaces could be used as a microvalve, and gas-water separation in the microchannel was realized using the unidirectional flow of water. Therefore, benefiting from their good performance and simple fabrication process, morphology-patterned surfaces are good candidates to be applied in controlling the fluid behavior in microfluidics.

Nanotransfer printing of gold disk, ring and crescent arrays and their IR range optical properties

We demonstrate a facile method to fabricate gold plasmonic microstructures based on the combination of colloidal lithography and a nanotransfer printing method. Poly(dimethylsiloxane) PDMS hemisphere arrays were fabricated through colloidal lithography and used as a “stamp” for the nanotransfer printing. Three kinds of plasmonic microstructures, gold disk, ring and crescent arrays, were fabricated by transferring gold “ink” onto the PDMS stamp, then to the substrate based on covalent “glue”. By adjusting the pressure applied during the printing process, the diameter of the as-prepared gold disks and gold rings can be precisely controlled, and these plasmonic arrays all exhibited significant diameter dependent LSPR properties in the NIR or Mid-IR range. In addition, by obliquely depositing gold ink onto the PDMS stamp, a gold crescent array with asymmetrical geometry was also prepared on the substrate. Owing to the asymmetric structure of the gold crescents, the gold crescent array showed significant polarization dependent LSPR properties in the Mid-IR range. We believe that these as-prepared gold plasmonic microstructures could show promising potential for application as real-time, label-free plasmonic sensing platforms in the IR range.

Morphology-controlled fabrication of elliptical nanoring arrays based on facile colloidal lithography

In this paper, we demonstrate a facile modified colloidal lithography (CL) method for the fabrication of morphology-controlled elliptical nanoring arrays (ERAs), which combines template-guided dewetting of polymer film and oxygen reactive ion etching. The elliptical templates were fabricated via a modified micromolding method using colloidal nanosphere arrays as the original templates, which were used to guide the dewetting of the polymer film to form ERAs. The height, aspect ratio and size of the resulting arrays could be controlled exactly. Moreover, through etching the underlying functional materials or mixing functional materials into the polymer film, elliptical ring arrays of different functional materials could also be fabricated, such as gold ERAs, silicon ERAs, ferromagnetic Fe–Ni composite ERAs, Fe3O4 ERAs and fluorescent ERAs. A potential application of the as-prepared functional ERAs is to provide a model for the fundamental research of anisotropic properties of the asymmetric patterned surface arrays and the fabrication of anisotropic surface pattern based devices for potential applications of shape-dependent optical and magnetic devices.