Microfabrication Bonding Process Optimization for a 3D Multi-Layer PDMS Suspended Microfluidics

Microfluidic systems have received increased attention due to their wide variety of applications, from chemical sensing to biological detection to medical analysis. Microfluidics used to be fabricated by using etching techniques that required cleanroom and aggressive chemicals. However, another microfluidic fabrication technique, namely, soft lithography, is less expensive and safer compared to former techniques. Polydimethylsiloxane (PDMS) has been widely employed as a fabrication material in microfluidics by using soft lithography as it is transparent, soft, bio-compatible, and inexpensive. In this study, a 3D multi-layer PDMS suspended microfluidics fabrication process using soft lithography is presented, along with its manufacturing issues that may deteriorate or compromise the microsystem's test results. The main issues considered here are bonding strength and trapped air-bubbles, specifically in multi-layer PDMS microfluidics. In this paper, these two issues have been considered and resolved by optimizing curing temperature and air-vent channel integration to a microfluidic platform. Finally, the suspended microfluidic system has been tested in various experiments to prove its sensitivity to different fluids and flow rates.