Surface micromachining of polydimethylsiloxane (PDMS) for microfluidic biomedical applications

A major technical hurdle in microfluidics is the difficulty in achieving high fidelity lithographic patterning on polydimethylsiloxane (PDMS). Here, we report a simple yet highly precise and repeatable PDMS surface micromachining method using direct photolithography followed by reactive ion etching (RIE). Our method to achieve surface patterning of PDMS applied an O2 plasma treatment to PDMS to activate its surface to overcome the challenge of poor photoresist adhesion on PDMS for photolithography. Our photolithographic PDMS surface micromachining technique is compatible with conventional soft lithography and other silicon-based surface and bulk micromachining techniques. To illustrate the general application of our method, we demonstrated fabrications of large microfiltration membranes and free-standing beam structures in PDMS for different biological applications.