Facile Methods to Make PDMS Hydrophilic: A Time Evolution Study for Microfluidic Devices

Flexible microfluidics have found extensive utility in the biological and biomedical fields. A leading substrate material for compliant devices is polydimethylsiloxane (PDMS). Despite its many advantages, PDMS is inherently hydrophobic, limiting its use in passive (pumpless) microfluidics. To this end, many physical and chemical modifications to PDMS have been introduced, ranging from amphiphilic molecule additions to surface plasma treatments. When transitioning from lab benchtop to realized medical devices, these modifications must exhibit long-term stability. We have investigated an array of PDMS modifications, utilizing contact angle goniometry to study surface energy over a 30-day evolution study. Samples were stored in air and water, and Fourier Transform Infrared-Attenuated Total Reflectance (FTIR-ATR) analysis was used to confirm surface functional group uniformity. We have identified preferred modification techniques for long-lasting PDMS devices and characterized often overlooked material stability.