Session: 13-01-01: Design and Fabrication, Analysis, Processes, and Technology for Micro and Nano Devices and Systems

Paper Number: 95734

95734 - Thermal Fusion Bonding With a Pressure-Assisted Boiling Point High Pressure System for Solid Phase Extraction Microfluidic Devices 

Nucleic acids (NAs) such as cell-free DNA (cfDNA) from plasma can be mixed with an immobilization buffer, and then the mixture can be used to extract and pre-concentrate DNA in the format of the solid phase extraction (SPE) microfluidic devices. Our group has fabricated a polymer SPE device using an array of diamond micropillars (5 µm side length, 5 µm spacing, 10 ~ 20 µm height) using SU8 lithography, electroforming of NiCo, and polymer hot embossing. However, thermal fusion bonding of the hot embossed SPE devices with coversheets showed inconsistent bonding results, which required development of a more robust bonding process.

 

A reliable bonding process for hot embossed SPE devices with coversheets using the pressure-assisted boiling point (PABP) high pressure system was developed to obtain more consistent bonding results. The bonding system utilizes boiling water to set both the temperature and pressure boundary conditions for bonding. Thermal fusion bonding (TFB) of the SPE devices made in polycarbonate (PC, Lexan 9034, T_g: 147^oC) and cyclic olefin copolymer (COC, Topas 6013, T_g: 138^oC) was done using the PABP high pressure system. The coversheets of PC and COC used for TFB were 250 µm thick in the same materials as the embossed SPE devices.

 

The bonding temperature for PC was 150^oC and that for COC was 140^oC. A differential bonding pressure of 10 or 20 kPa and bonding times from 5 min to 15 min were used for PC, while a differential bonding pressure of 20 kPa and bonding times of 15 min were used for COC. Microscope inspection revealed that the PC SPE device bonded at differential pressure of 10 kPa and bonding time of 5 min had a partial collapse of the coversheet to the bottom of the inlet and outlets. In contrast, the COC SPE device bonded at differential pressure of 20 kPa and bonding time of 15 min showed no collapse of the cover sheet at the same locations. After microscopic inspection, the same SPE device was tested with dye at a flow rate of 50 µL/min to confirm the passage of fluid from the one inlet to two outlets. There was complete fluid flow of dye from the one inlet to the two outlets without any leakage. The volumes observed at the two outlets looked similar, which indicated that the pressure drop at both sides of the columns were comparable to each other.

 

Further bonding process optimization using the PABP high pressure system is still underway. The bonded SPE devices will allow for isolation of cfDNA from plasma with high recovery efficiency.

Presenting Author: Daniel Park Louisiana State Univ

Presenting Author Biography: Daniel S. Park received his B.S. degree in Physics from Sung Kyun Kwan University, Seoul, Korea, in 1990, his M.S. degree in Electrical Engineering from Louisiana State University in 1999, and his Ph. D. degree in Electrical Engineering from the University of Texas at Dallas in 2004. He is currently a research associate at the Mechanical and Industrial Engineering and the Center for BioModular Multi-scale Systems (CBMM) in Louisiana State University, working on micromodel devices for enhanced oil recovery applications and BioMEMS devices/systems for biomedical applications. His research interests include micro/nano fabrication techniques and their applications to micromodels, BioMEMS, and nano-scale devices/systems.

Authors:

Daniel Park Louisiana State Univ
S Cho Kyungnam University
Taehyun Park Kyungnam University
Steven Soper University Kansas
Michael Murphy Louisiana State Univ