Parameters Governing the Formation of Photopolymerized Silica Sol-Gel Monoliths in PDMS Microfluidic Chips

Although polydimethylsiloxane (PDMS) microfluidic chips provide an alternative to more expensive microfabricated glass chips, formation of monolithic stationary phases in PDMS is not a trivial task. Photopolymerized silica sol-gel monoliths were fabricated in PDMS based microfluidic devices using 3-trimethoxysilylpropylmethacrylate (MPTMOS) and glycidyloxypropyltrimethoxysilane (GPTMOS). The monolith formation was optimized by identifying a suitable porogen, controlling monomer concentration, functional additives, salts, porogen, wall attachment methods, and rinsing procedures. The resulting monoliths were evaluated using scanning electron microscopy, image analysis, differential scanning calorimetry, and separation performance. Monoliths functionalized with boronic acid ligands were used for the separation of cis-diol containing compounds both in batch mode and in the microfluidic chip.