精密微流控芯片简易制作方法改进

A method for a simpler and more convenient replica
molding of high-performance PDMS chips#
ZHANG Jinling1, YANG Pengyuan2, SUI Guodong1**
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(1. Department of Environmental Science & Engineering, Fudan University, Shanghai 200433;
2. Institute of Biomedical Science, Fudan University, ShangHai 200433)
Abstract: We present a method of an improvement for the standard soft lithography fabrication
process to generate highly reduplicate microfabricated patterns. This method improves the release of
poly (dimethylsiloxane) (PDMS) devices from replica molds with high-density microstructures. During
fabrication, only one extra step was added to prepare a single-spin coating of a thin layer of PDMS,
compared with traditional microfabrication technique. It was validated with silicon wafers containing
arrays of 50 ?m deep SU8 microwells with various densities (a maximum density of 50000/cm2).
Keywords: microfluidics; PDMS; soft lithography


0 Introduction
Briefly introduce the background and object of the research in about 400~600 words, and do
not exceed 800 words. In recent years, soft lithography[1] has become a widely used and mature
fabrication technique for the rapid prototyping of microfluidic circuits because of its applications
in biochemical analysis[2,3], chemical reactions[4] and cell-based micro assays.[5,6] This fabrication
technique imposes restrictions on feature density, fluid handling complexity, and strict design
constraints of channel routing. Assembling of the single and multilayer micro?uidic devices[7-10] as
well as the formation of high-density microwell arrays[11-13] require reliable and efficient
microscale manufacturing techniques. The soft lithography method involves the replica molding
of a master containing lithographically-patterned photoresist structures and poly (dimethylsiloxane)
(PDMS), which is the most widely used elastomeric material for microfluidic chip fabrication.
[14-16]
Casting PDMS elastomers onto molds, and the following release from them, are essential
steps for the practical microscale fabrication, especially for the ones with delicate microstructures.
They are also important for keeping costs low, as the molds can be reused. [17] The adhesion and
friction between micro patterns on the molds and the polymerized elastomer can cause failure of
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the molding process, either by tearing of the device material apart or by damaging photoresist
micro patterns on the mold when casting or removing the device material from the molds. These
issues are more serious when replica molding features have high-density microstructures. To
overcome these defects, alternative treatments, such as a special process of surface modi?cation of
molds, have been taken into consideration to promote mold release process by reducing adhesion
and friction. Some treatment can create a thin layer of deposition on molds to improve the release
of PDMS from silicon and photoresist surfaces. [18] Nevertheless, practical drawbacks of this
approach include the need of advanced coating equipment and special experimental reagents, and
difficulties in achieving reproducible and homogeneous coatings on different substrates. In
addition, the coated layer thickness must be taken in account when preparing devices with very
small delicate features.
Herein we present a simple method to surmount these limitations by adding an extra step into
the soft lithography process. Instead of the direct casting, a single spin coating of PDMS and a
thick flat PDMS layer creates a perfect replication that greatly improves chip releasing and


Foundations: Specialized Research Fund for the Doctoral Program of Higher Edu cation(SRFDP 20090071110006)
and NSFC (20975025)
Brief author introduction:Jinling Zhang, (1985-), Female, Doctor, microfluidics.
Correspondance author: Guodong Sui, (1974-), Male, Professor, Bioanalysis. E-mail: gsui@http://wendang.chazidian.com


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