A Simple Method To Modify The PDMS Surface Wettability For Biomicrofluidic Applications

Abstract

Polydimethylsiloxane (PDMS) is one of the most used materials for the manufacture of microfluidic devices. Recent studies have combined microfluidic devices and cell cultures to originate a new group of devices, the organs-on-achip (OoC). These devices replicate the microphysiological features that can be found in the human body so that healthy and pathological conditions can be easily studied. PDMS is also one of the materials of choice for the manufacture of the OoC, due to its mechanical and chemical properties, and due to the fact that is a biocompatible and inert material. However, the hydrophobic behavior of PDMS leads to the adsorption of unspecific molecules, hinders cell culture attachment and growth, and decreases the specificity of certain biochemical tests. Additionally, the hydrophobicity of microchannels walls of microfluidic devices difficult the fluid flow, making necessary the use of external sources for the flow control, such as syringe pumps. A common strategy to improve the wettability of the PDMS surface is to apply oxygen plasma. However, the effects of this technique only last a few hours. Another strategy is to alter the bulk of PDMS during manufacture by adding components such as surfactants. In this work, different compounds were combined with PDMS in concentrations of 1 and 2 wt.%. The changes in the wettability were verified on the day of sample manufacturing and one week later. Since the optical properties of PDMS can be important for some microfluidic studies, the changes in the transparency of the samples were also evaluated by measuring the respective transmittance spectrum. The results showed that two tested surfactants can improve the wettability of the PDMS surface to a hydrophilic behavior remaining for at least one week after fabrication. The transparency of the PDMS shows to be affected by one of those two surfactants while the other only led to a small decrease when used the higher concentration.