IRG 2: Guided Self-Assembly

Main photo, left to right: Steve Chou, Doug Adamson, Dudley Saville, Bill Russel, Thanos Panagiotopoulos (co-leader), Rick Register (co-leader), Ilhan Aksay Not Pictured: Pablo Debenedetti Below: Paul Chaikin

We seek to understand the fabrication, science, and technology of large-scale ordered, patterned, addressable, and interconnected structures with features on the nanometer to micron scale. Substrates of square centimeters in area covered with trillions of organic or inorganic structures have applications in biology, chemistry, physics, and engineering, such as nanofilters, sensors, nanofluidic devices, catalytic supports, quantum dots, optical devices, and ultradense memories. Dense large-scale arrays with features less than 100 nm are beyond the capabilities of conventional lithography, but our group has helped pioneer organic-based self-assembly of ordered nanometer patterns and their transfer into inorganic substrates. For many applications high density and short-range order suffice but an even larger class requires fully aligned and ordered patterns, mandating a more controlled approach to large-scale order than self-assembly alone offers.

We use external fields (electric, magnetic, thermal, stress) and physical boundaries, as appropriate for each material system investigated, to create registered periodic structures with long-range order. Surfactants, diblock copolymers, and immiscible fluids share a common set of principles and driving forces in their self-assembly and the guidance mechanisms, especially that governing the motion of material interfaces in applied fields, which allows us to guide the self-assembly process. Current approaches to guided self-assembly being pursued by our IRG include single-nanodomain-thick block copolymers aligned by stress; highly-regular micron-scale pattern formation guided by fluid instabilities coupled with the charge distribution on confining plates; and the simultaneous synthesis and alignment of nanoporous silicates using applied electric fields. A close coupling with theory spanning from the molecular to the mesoscopic level aids in interpreting and guiding the experiments.

Selected Publications:

• G. Arya, J. Rottler, A.Z. Panagiotopoulos, D.J. Srolovitz, and P.M. Chaikin, “Shear Ordering in Thin Films of Spherical Block Copolymer,” Langmuir, 21, 11518 (2005).
• D.E. Angelescu, J.H. Waller, D.H. Adamson, P. Deshpande, S.Y. Chou, R.A. Register, and P.M. Chaikin, “Macroscopic Orientation of Block Copolymer Cylinders in Single-Layer Films by Shearing”, Adv. Mater., 16, 1736 (2004).
• W. D. Ristenpart, I. A. Aksay, and D. A. Saville, “Electrically Guided Assembly of Planar Superlattices in Binary Colloidal Suspensions,” Phys. Rev. Lett., 90, 128303 (2003).