Enclosed casting of epoxy resin for rapid fabrication of rigid microfluidic chips

- Epoxy resin was demonstrated for rapidly fabricating rigid microfluidic devices.
- Enclosed casting enabled by PDMS intermediate molds can produce ready-to-use devices.
- A series of bonding methods were developed for epoxy resin with most common materials.
- Multilayer microvalve, PCR, and high-speed flow cytometry imaging were tested.

A commercially available epoxy resin from Hexion was demonstrated as a complementary material to PDMS (polydimethylsiloxane) for rapidly fabricating rigid microfluidic devices. The fabrication process was streamlined to include the master mold fabrication, one or two times of the PDMS casting, and an enclosed casting of epoxy resin. The use of PDMS as intermediate molds not only guaranteed the easy demolding, but also enabled the novel enclosed casting. This process can produce epoxy resin microdevices in suitable shapes with even surfaces and preformed via holes, eliminating the inconvenient device preparations, such as cutting and drilling. A series of facile bonding methods were developed for epoxy resin with most of common materials used in microfluidics, yielding improved bonding strengths of 261 kPa for epoxy-PDMS, 1185 kPa for epoxy-glass, and 1516 kPa for epoxy-epoxy. To further demonstrate the material versatility, we performed three critical microfluidic applications on epoxy resin-based microdevices, including multilayer pneumatic microvalves, on-chip PCR with improved efficiencies, and ultra-high-speed flow cytometry imaging of microbeads at a flow rate of 8.3 m/s. This study validated the feasibility of utilizing epoxy resin as a routine material for rapidly testing out new designs, for which PDMS may not work, in a laboratory setting.