An Alternative Solution for Microfluidic Chip Fabrication

Abstract

This paper focuses on microfluidic devices, widely used in bioengineering. Their fabrication for research is almost entirely made of PDMS (a silicone), using photolithography and replica molding technologies, which involve many processing steps, sealed with a glass layer by plasma bonding. Our solution fabricates devices in just two steps, laser ablation of a glass layer, technology already extensively tested, and sealing with a commercial silicone layer by plasma bonding, drastically reducing skilled human operations and lead time. The paper describes the technologies with PDMS and with our solution, the design of a microfluidic test chip, the laser ablation and assessment by a confocal microscope of the microfluidic circuit in the glass layer of the chip, the plasma bonding of glass layers with PDMS and two other commercial silicones utilizing a grid of different plasma parameters, the qualitative assessment of the plasma bonding and choosing of a silicone as PDMS substitute, the extensive test on the bonding quality by two different pressure circuits on a batch of microfluidic chips realized with our proposed technology.

UV picosecond laser processing for microfluidic applications

“…In this way, micrometer-sized geometries can be processed with a scan speed of millimeters per second, reaching time resolutions of microseconds, removing the effects of accelerations, and optimizing the processing time. The laser parameters were chosen based on our previous work [11], optimizing them to achieve the accuracy and depths imposed by the device design. For the main channels the laser parameters chosen are 100 kHz of repetition rate, a pulse energy of 7 µJ, a scan strategy made of parallel longitudinal lines 3 µm spaced, and a scan speed of 300 mm/s to equally distribute the energy along and between the scanlines, all repeated for 11 passes.…”

“…A more consolidated approach is to create the 2.5D structures on the surface of the glass and seal it with a silicon cover, to create a closed channel [8,11]. By allowing the depth and width of each channel to vary, this approach offers a straightforward method to increase the precision of the generated geometries [12].…”