A Versatile Bonding Method for PDMS and SU-8 and Its Application towards a Multifunctional Microfluidic Device.

Zhen Zhu,Carlos Escobedo,Kegang Liu,Pan Chen

doi:10.3390/mi7120230

Abstract

This paper reports a versatile and irreversible bonding method for poly(dimethylsiloxane) (PDMS) and SU-8. The method is based on epoxide opening and dehydration reactions between surface-modified PDMS and SU-8. A PDMS replica is first activated via the low-cost lab equipment, i.e., the oxygen plasma cleaner or the corona treater. Then both SU-8 and plasma-treated PDMS samples are functionalized using hydrolyzed (3-aminopropyl)triethoxysilane (APTES). Ultimately, the samples are simply brought into contact and heated to enable covalent bonding. The molecular coupling and chemical reactions behind the bonding occurring at the surfaces were characterized by water contact angle measurement and X-ray photoelectron spectroscopy (XPS) analysis. The reliability of bonded PDMS-SU-8 samples was examined by using tensile strength and leakage tests, which revealed a bonding strength of over 1.4 MPa. The presented bonding method was also applied to create a metal-SU-8-PDMS hybrid device, which integrated SU-8 microfluidic structures and microelectrodes. This hybrid system was used for the effective trapping of microparticles on-chip, and the selective releasing and identification of predefined trapped microparticles. The hybrid fabrication approach presented here, based on the PDMS-SU-8 bonding, enables multifunctional integration in complex microfluidic devices.

Highlights

In microfluidics, poly(dimethylsiloxane) (PDMS) is the most commonly used material to fabricate micro channels [1,2]
We present a reliable, biocompatible and versatile bonding method for PDMS and SU-8 based on the surface activation of PDMS with oxygen plasma and APTES-involved epoxide opening and dehydration reactions
We have presented a facile, versatile and reliable bonding method for poly(dimethylsiloxane) (PDMS) and SU-8 based on the surface modification with (3-aminopropyl)triethoxysilane (APTES) hydrolysate

Summary

Introduction

Poly(dimethylsiloxane) (PDMS) is the most commonly used material to fabricate micro channels [1,2]. PDMS elastomer offers advantages in the fabrication of microfluidic devices, such as ease of use and rapid prototyping, the elasticity of PDMS may cause geometric deformation during the replication, bonding, and fluidic operation at high pressures [7,8,9,10,11]. SU-8 enables wafer-level processes and allows for the precise alignment with pre-patterned functional structures on wafer [18,19]. For these reasons, SU-8 renders microfluidic devices with the potential to integrate multiple functions, such as microelectrodes and actuators, which can be applied in important biological applications, including single-cell studies and biosensing [20,21,22,23]

Methods

Results

Conclusion