Fabrication of low-shrinkage microporous 3-D polymer structures through interference lithography

POLY 251

Yongan Xu1, Ali Hayek2, Xuelian Zhu1, Takashi Okada3, Jun Hyuk Moon, junh@seas.upenn.edu1, Stephen Barlow, stephen.barlow@chemistry.gatech.edu3, Seth R. Marder, seth.marder@chemistry.gatech.edu3, and Shu Yang, shuyang@seas.upenn.edu1. (1) Department of Materials Science and Engineering, University of Pennsylvania, 3231 Walnut Street, Philadelphia, PA 19104, (2) Center for Organic Photonics and Electronics and School of Chemistry and Biochemistry, Georgia Institute of Technology, Atlanta, GA GA, 30332-04, (3) School of Chemistry and Biochemistry and Center for Organic Photonics and Electronics, Georgia Institute of Technology, 770 State Street NW, Atlanta, GA 30332-0400
Multi-beam interference lithography offers an efficient route to fabricate various microporous three-dimensional (3D) structures for applications such as micro-optics, microfluidics, microelectro-mechanical systems, and optical data storage. However, the 3D structures fabricated by interference lithography could be distorted by the high refractive index of the photoresist film and the shrinkage of photoresist. For example, we found ~41% shrinkage in the [111] direction when fabricating diamond-like structures from the commercially available negative-tone photoresist, SU8. This large shrinkage together with refraction effect due to large refractive index of SU8 causes structure distortion and residual strain in the 3D porous structures. In order to minimize the structure distortion, we have synthesized narrowly dispersed poly(glycidyl methacrylate) (PGMA) with controlled number of epoxy groups by atom transfer radical polymerization. In contrast to SU8, the 3D structures fabricated from PGMA show a much lower volumetric shrinkage, 5.9%, and fewer cracks in the film.

Aerogels, Foams and Other Nanoporous Materials
9:00 AM-12:00 PM, Tuesday, August 19, 2008 Sheraton Philadelphia City Center -- Freedom Blrm H, Oral

Division of Polymer Chemistry

The 236th ACS National Meeting, Philadelphia, PA, August 17-21, 2008