Fabrication of an integrated microfluidic and surface acoustic wave device for fluid analysis

A technique is presented for the fabrication of an integrated microfluidic surface acoustic wave (SAW) sensor suitable for a wide range of fluidic analyses. The device was fabricated in Microchem SU8-25, on a PMMA substrate, employing a modified SU8 process. Standard SU8 procedures are sufficiently close to the glass transition temperature for PMMA to cause significant warping. PMMA is advantageous as a substrate material as it is cheap, easily machined, hydrophobic, and exhibits superior adhesion with SU8. A novel die bonding technique was explored to join the SU-8 fluidic structures to a lithium niobate SAW sensor. This involved additional fluidic structures, and the optical adhesive, NOA-73. A device with a 1cm by 1.5cm by 25um chamber was fabricated with these techniques, and was used to explore fundamental properties of flow at the microscale, in particular at the surface of the SAW device.