Recent developments in PDMS surface modification for microfluidic devices

Abstract

PDMS is enjoying continued and ever increasing popularity as the material of choice for microfluidic devices due to its low cost, ease of fabrication, oxygen permeability and optical transparency. However, PDMS's hydrophobicity and fast hydrophobic recovery after surface hydrophilization, attributed to its low glass transition temperature of less than -120 degrees C, negatively impacts on the performance of PDMS-based microfluidic device components. This issue has spawned a flurry of research to devise longer lasting surface modifications of PDMS, with particular emphasis on microfluidic applications. This review will present recent research on surface modifications of PDMS using techniques ranging from metal layer coatings and layer-by-layer depositions to dynamic surfactant treatments and the adsorption of amphipathic proteins. We will also discuss significant advances that have been made with a broad palette of gas-phase processing methods including plasma processing, sol-gel coatings and chemical vapor deposition. Finally, we will present examples of applications and future prospects of modified PDMS surfaces in microfluidics, in areas such as molecular separations, cell culture in microchannels and biomolecular detection via immunoassays.

Universal hydrophilic coating of thermoplastic polymers currently used in microfluidics

“…The hydrophobic nature of disposable plastic and PDMS devices presents a considerable drawback to microfluidics applications (6,7). For instance, the introduction of aqueous solutions into narrow channels is complicated by the low wettability of these materials.…”

“…It is generally recognized that proteins, which are attracted to hydrophobic and electrostatic 3 interactions, irreversibly adsorb onto the surface of plastic microdevices, which leads to poor analytical performance. Much effort has been devoted to modifying the surface of polymeric materials to adjust their wettability, adhesion and biocompatibility (8).…”

“…(PVP-g-GMA) and poly(vinyl alcohol)-g-glycidyl methacrylate (PVA-g-GMA) have been covalently grafted onto APTES modified PDMS surfaces (31). These polymers are attached to the surface owing to the reactivity of surface functionalities to the chemically reactive polymer groups.…”

PDMS microfluidics developed for polymer based photonic biosensors

“…[31] The influence of the modification has been also studied and is found in literature [10,11,12,32,33]. Modified surface characteristics of our device were analyzed by contact angle measurement.…”

“…protein) adsorption are key issues as regards reliability of microfluidic part of a PDMS-based sensor [5,6,7,9]. On the other hand, the addition of surfactants can beneficially change the above properties [10]. Materials like TX-100 [11] and PDMS-PEO (poly(dimethylsiloxane-ethylene oxide polymer)) [12] has been successfully introduced to the fabrication of microfluidics for analytical purposes, however, the effect of their integration into a complex microsystem was not described so far.…”