title: Regioselective patterning of multiple SAMs and applications in surface-guided smart microfluidics.
abstract: A top-down nanofabrication technology is developed to integrate multiple SAMs (self-assembled monolayers) into regioselective patterns. With ultraviolet light exposure through regioselectively hollowed hard mask, an existing SAM at designated microregions can be removed and a dissimilar kind of SAM can be regrown there. By repeating the photolithography-like process cycle, diverse kinds of SAM building blocks can be laid out as a desired pattern in one microfluidic channel. In order to ensure high quality of the surface modifications, the SAMs are vapor-phase deposited before the channel is closed by a bonding process. For the first time the technique makes it possible to integrate three or more kinds of SAMs in one microchannel. The technique is very useful for multiplex surface functionalization of microfluidic chips where different segments of a microfluidic channel need to be individually modified with different SAMs or into arrayed pattern for surface-guided fluidic properties like hydrophobicity/philicity and/or oleophobicity/philicity, etc. The technique has been well validated by experimental demonstration of various surface-directed flow-guiding functions. By modifying a microchannel surface into an arrayed pattern of multi-SAM "two-tone" stripe array, surface-guiding-induced 3D swirling flow is generated in a microfluidic channel that experimentally exhibits quick oil/water mixing and high-efficiency oil-to-water chemical extraction.
authors.affiliation: State Key Lab of Transducer Technology, and, Science Technology on Micro-system Lab, Shanghai Institute of Micro-system and Information Technology, Chinese Academy of Sciences , 865 Changning Road, Shanghai 200050, China.
authors.forename: Chuanzhao
authors.initials: C
authors.lastname: Chen
authors.forename: Pengcheng
authors.initials: P
authors.lastname: Xu
authors.forename: Xinxin
authors.initials: X
authors.lastname: Li
keywords: 3D swirling flow; batch nanofabrication; integration of multiple SAMs; passive mixing extraction; self-assembled monolayer; surface guide microfluidics