Microwell Depth Control on a Polydimethylsiloxane Polymer Using a Simple Colloidal Self Assembly Process

Abstract

The development of soft-lithographic patterning techniques has attracted considerable interest in recent times covering a diverse range of potential applications including microfluidic devices, lab-on chip technologies, micro patterning of biomolecules and micro-optical systems. One of the strategies for producing patterned micro and nano structures is to self-assemble an array of monodispersed spheres. In this study, patterned poly dimethylsiloxane (PDMS) surfaces with hexagonal close-packed microwells were fabricated by the self-assembly of silicon spheres (5 μm and 800 nm) onto the polymer surface. The weight of spheres, in combination with uncompleted curing of the polymer, allows surface deformation. An average depth for microwells after 48 hours curing and a further 48 hours of bead resting time was ~400 nm for 5 μm beads and ~100 nm for 800 nm beads. An increased curing time pre bead placement on the polymer surface was found to show a decrease in the depth of the microwells (for 5 μm spheres, a 400 to 45 nm well depth decrease, at 2 to 9 days curing, respectively). Young's Modulus values measured on the polymer over this period increased from ca. 650 kPa to ca. 750 kPa. Microwell depth was found to increase from 400 to over 500 nm for resting times of 3 and 15 days (an increase of ca. 28% for this period).