Patterning Processes for Polymer Brushes to Direct Assembly Christopher K. Ober, Cornell University, DMR 0518785. Brush Schematic. AFM Images.
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Conventionally, high resolution patterning of polymer brushes is done by first producing a patterned initiator layer on the substrate, followed by surface initiated polymerization of a suitable monomer.
We have studied the possibility of directly patterning pre-grown polymer brushes using electron beam lithography. All polymer brushes were grown via surface initiated atom transfer radical polymerization (SI-ATRP).
We have discovered that we can carry out sub-surface patterning of block copolymer brushes. Such types of 3D patterns could be useful in applications such as nanofluidic devices, waveguide materials, and directed nanowire assembly. With a diblock copolymer brush using a negative tone upper block and a positive tone lower block, 3D structures may be written with precise control of size and location using the direct patterning approach.
Figure: a) Illustration of PMMA-b-PS polymer brushes are grown via ATRP. b) Brushes patterned by e-beam and developed. Exposed PMMA is washed away while PS remains due to cross linking. c) PS top layer is etched away by oxygen plasma to prove the existence of nanochannels.