• Flexible Macroelectronics
• Microfluidics and Liquid Crystals for Photonics
• Unconventional Techniques for Nanofabrication
• Microstructural Acoustics and Picosecond Ultrasonics

Flexible Macroelectronics:

The field of large area, flexible electronics is interesting partly because it has the potential to enable useful devices - flexible paperlike displays, woven electrotextiles, low cost identification tags, etc - that might be difficult to achieve with established silicon technologies. In addition, many of the materials and processing approaches developed for this area are important for a variety of emerging carbon-based nanoelectronic systems that might have roles in future high density memories or processors. This project focuses on fundamental and applied aspects related to the active organic and inorganic materials and the lithographic methods that are used to pattern circuits out of them. The work involves materials ranging from small molecule semiconductors, to polymeric electroluminescent materials, to single wall carbon nanotubes, to organic self-assembled monolayers to micro/nanostructures of single crystal inorganics. Patterning these materials into active electronic components allows their chemistry and other basic properties to be correlated to device performance.

Recent papers:

E. Menard, K.J. Lee, D.-Y. Khang, R. G. Nuzzo and J.A. Rogers, “A printable form of silicon for high performance thin film transistors on plastic substrates,” Applied Physics Letters, 84(26), 5398-5400 (2004).

Y. Zhou, A. Gaur, S.-H. Hur, C. Kocabas, M. Meitl, M. Shim and J.A. Rogers, "p-channel, n-channel thin film transistors and p-n diodes based on patterned arrays of single wall carbon nanotube percolation network", Nano Letters, 4(10), 2031-2035 (2004).

"V.C. Sundar, J. Zaumseil, V. Podzorov, E. Menard, R. Willett, T. Someya, M. Gershenson and J.A. Rogers, “Elastomeric Transistor Stamps for Reversible Probing of Charge Transport in Molecular Crystals,” Science, 303, 1644-1646 (2004).

J.A. Rogers, Z. Bao, K. Baldwin, A. Dodabalapur, B. Crone, V.R. Raju, V. Kuck, H. Katz, K. Amundson, J. Ewing and P. Drzaic, "Paper-like Electronic Displays: Large Area, Rubber Stamped Plastic Sheets of Electronics and Electrophoretic Inks", Proceedings of the National Academy of Science, 98(9), 4835-4840 (2001).

Microfluidics and Liquid Crystals for Photonics

This project seeks to exploit pumped microfluidics for new classes of tunable photonic devices. It includes basic study and development of (i) means to fabricate microfluidic networks and (ii) phenomena, such as electrowetting, that can be used to pump the fluids. With proper designs, the motion of the fluids can be coupled to the optical properties of basic photonic elements such as planar waveguides and optical fiber. In another approach, it is possible to construct directly these and other elements (e.g. microlenses) out of fluidic structures whose shapes can be dynamically adjusted. These types of t echnologies have capabilities that can complement those of conventional systems. A closely related effort attempts to understand fundamental issues and practical considerations that define upper limits for the operating speed of liquid crystal based modulators and switches. It includes a component that focuses on inventing unusual means to use liquid crystals for tunable fiber and integrated optical devices

Recent papers:

F. Cattaneo, K. Baldwin, S. Yang, T. Krupenkine, S. Ramachandran and J.A. Rogers, "Digitally tunable microfluidic fiber devices", Journal of Microelectromechanical Systems, 12(6), 907-912 (2003).

B.R. Acharya, C. Madsen, L. Moller, K.W. Baldwin, R.A. MacHarrie, C.C. Huang, R. Pindak and J.A. Rogers, "In-Line Liquid Crystal Microcell Polarimeters With Applications in 40 Gb/s Systems", Applied Optics, 42(27), 5407-5412 (2003).

J. Hsieh, P. Mach, F. Cattaneo, S. Yang, T. Krupenkine, K. Baldwin and J.A. Rogers, "Tunable Microfluidic Optical Fiber Devices Based on Molded Plastic Microchannels and Electrowetting Pumps", IEEE Photonics Technology Letters, 15(1), 81-83 (2003).

P. Mach, C. Kerbage, M. Dolinski, K.W. Baldwin, R.S. Windeler, B.J. Eggleton, J.A. Rogers, "Tunable Microfluidic Optical Fiber", Applied Physics Letters, 80(23), 4294-4296 (2002).

Unconventional Techniques for Nanofabrication

New tools for fabricating structures with micron and nanometer dimensions are critical to the progress of nanoscience and nanotechnology. This project seeks to develop soft lithographic methods for nanofabrication, and to use them for building structures that are needed for basic and applied studies. Our recent efforts focus on methods for building 2D and 3D nanophotonic systems and for constructing organic transistors and diodes that have nanometer or molecular scale dimensions.

Recent papers:

J. Zaumseil, M.A. Meitl, J.W.P. Hsu, B. Acharya, K.W. Baldwin, Y.-L. Loo and J.A. Rogers, “Three-dimensional and Multilayer Nanostructures Formed by Nanotransfer Printing”, Nano Letters, 3(9), 1223-1227 (2003).

M.V. Kunnavakkam, F.M. Houlihan, M. Schlax, J.A. Liddle, O. Nalamasu and J.A. Rogers, “Low Cost, Low Loss Microlens Arrays Fabricated by Soft Lithography Replication Process”, Applied Physics Letters, 82(8), 1152-1154 (2003).

S. Jeon, J.-U. Park, R. Cirelli, S. Yang, C.E. Heitzman, P.V. Braun, P.J.A. Kenis, and J.A. Rogers, “Fabricating Complex Three Dimensional Nanostructures With High Resolution Conformable Phase Masks”, Proc. Nat. Acad. Sci. USA, 101(34), 12428-12433 (2004).

Y.-L. Loo, R.W. Willett, K. Baldwin and J.A. Rogers, “Additive, Nanoscale Patterning of Metal Films with a Stamp and a Surface Chemistry Mediated Transfer Process: Applications in Plastic Electronics”, Applied Physics Letters, 81(3), 562-564 (2002).

Microstructural Acoustics and Picosecond Ultrasonics:

Picosecond pulsed lasers provide a convenient source of acoustic waves with frequencies in the GHz range and with wavelengths between one and several hundred microns. This project seeks to develop and use these laser-based tools to study the high frequency acoustic responses of structures with characteristic dimensions that are similar to the acoustic wavelengths: thin films and membranes, multilayer stacks, microfluidic networks, etc. Analysis of these measurements yields intrinsic mechanical and thermal properties on micron length scales. These methods can also be used for basic studies of phononic bandgaps and other interesting acoustic phenomena in micro and nanofabricated structures.

Recent papers:

J.A. Rogers, G.R. Bogart and R.E. Miller, “Quantitative Non-Contact Spatial Mapping of Stress and Flexural Rigidity in Thin Membranes Using a Picosecond Transient Grating Photoacoustic Technique”, Journal of the Acoustical Society of America, 109(2), 547-553 (2001).

J.A. Rogers, “Impulsive Stimulated Thermal Scattering”, McGraw-Hill 2002 Yearbook of Science and Technology, (McGraw-Hill, 2002).

L. Dhar and J.A. Rogers, “High Frequency Phononic Crystals Characterized With a Picosecond Transient Grating Photoacoustic Technique”, Applied Physics Letters, 77(9), 1402-1404 (2000).

J.A. Rogers, A.A. Maznev, M.J. Banet and K.A. Nelson, “Optical Generation and Characterization of Acoustic Waves in Thin Films: Fundamentals and Applications”, Annual Reviews of Materials Science, 30, 117-157 (2000).