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Dissertation Defense

Eric J. Wilhelm:
"Printed Electronics and Micro-electromechanical Systems"

Friday, May 7, 2004, 4:30 PM EST

Bartos Theatre, MIT Media Lab (E15)

Joseph Jacobson, Chair
Associate Professor of Media Arts and Sciences
MIT Media Laboratory

George Barbastathis
Esther and Harold E. Edgerton Assistant Professor
Department of Mechanical Engineering

Carol Livermore
Assistant Professor of Mechanical Engineering
Department of Mechanical Engineering

Alexander H. Slocum
Professor of Mechancial Engineering, MacVicar Faculty Fellow
Department of Mechanical Engineering

Current electronics and micro-electromechanical systems (MEMS) manufacture is optimized for the production of very high-volume parts on a limited range of substrates. These processes are long, consume large amounts of resources, and require expensive machines and facilities, but yield excellent products. Cheaper, faster printing processes are beginning to emerge with the ability to economically produce low or high-volume electronics and MEMS on flexible substrates.

This thesis describes the theoretical and practical design of a suite of printing processes, including liquid embossing and offset liquid embossing (OLE). These printing techniques have created resistors, capacitors, and thin-film transistors without etching, vacuum deposition, or high temperatures. Here, the fabrication of all-printed electrostatic actuators is described.

In liquid embossing, a polydimethylsiloxane (PDMS) stamp with bas-relief features is brought into intimate contact with a thin liquid film such as a metal or semi-conductor nanoparticle colloid, spin-on-glass, or polymer to create patterns as small as 100 nm. A simulation of liquid embossing was developed by coupling fluid flow in a thin liquid film to the diffusion of solvent into a PDMS stamp. The model accurately predicts real aspects of the printing process including the time required to stamp and usable stamp geometries.

OLE was designed to address some of the limitations of liquid embossing. In OLE the patterned liquid film is transferred to a different substrate, allowing finer control over geometry and material placement and leaving behind excess material trapped during stamping. All-printed electrostatic actuators were fabricated using OLE by patterning gold on flexible polyimide and then under-etching with oxygen plasma. The polyimide acts as a sacrificial material, dielectric layer, and mechanical substrate. Square electrostatic actuators 50 microns on a side can modulate light up to approximately 1 kHz with fields of 1-2 volts per micron. These actuators also show a sharp non-linear response to driving voltage that could be used as part of a passive row column addressing scheme.

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