Eric Wilhelm

Ink-jet printed nanoparticle microelectromechanical systems

Reports a method to additively build three-dimensional (3-D) microelectromechanical systems (MEMS) and electrical circuitry by ink-jet printing nanoparticle metal colloids. Fabricating metallic structures from nanoparticles avoids the extreme processing conditions required for standard lithographic fabrication and molten-metal-droplet deposition. Nanoparticles typically measure 1 to 100 nm in diameter and can be sintered at plastic-compatible temperatures as low as 300/spl deg/C to form material nearly indistinguishable from the bulk material. Multiple ink-jet print heads mounted to a computer-controlled 3-axis gantry deposit the 10% by weight metal colloid ink layer-by-layer onto a heated substrate to make two-dimensional (2-D) and 3-D structures. We report a high-Q resonant inductive coil, linear and rotary electrostatic-drive motors, and in-plane and vertical electrothermal actuators. The devices, printed in minutes with a 100 /spl mu/m feature size, were made out of silver and gold material with high conductivity,and feature as many as 400 layers, insulators, 10:1 vertical aspect ratios, and etch-released mechanical structure. These results suggest a route to a desktop or large-area MEMS fabrication system characterized by many layers, low cost, and data-driven fabrication for rapid turn-around time, and represent the first use of ink-jet printing to build active MEMS.

All-additive fabrication of inorganic logic elements by liquid embossing

We report an all-additive patterning technique, liquid embossing, in which a thin liquid film is embossed by an elastomeric stamp. We show that, for sufficiently thin films, isolated features are produced as the stamp contacts the underlying substrate, and that the liquid remains patterned even after removal of the stamp. Such an approach enables the rapid patterning of inorganic nanocrystal solutions, as capping groups and solvents can volatilize efficiently at the exposed liquid surface. Using this technique, we have fabricated all-printed all-inorganic transistors, photodetectors, and resistors, as well as multilayer structures with sacrificial layers and vias. Such an approach may enable a route to all-printed inorganic semiconductor logic and machines.

Experimental Validation of Physics-Based Planning and Control Algorithms for Planetary Robotic Rovers

Robotic planetary exploration is a major component of the United States’ NASA space science program. The focus of our research is to develop rover planning and control algorithms for high-performance robotic planetary explorers based on the physics of these systems. Experimental evaluation is essential to ensure that unmodeled effects do not degrade algorithm performance. To perform this evaluation a low-cost rover test-bed has been developed. It consists of a rocker-bogie type rover with an on-board manipulator operating in a rough-terrain environment. In this paper the design and fabrication of an experimental rover system is described, and the experimental validation of several rover control algorithms is presented. The experimental results obtained are key to the evaluation and validation of our research.

Nanoparticle-based microelectromechanical systems fabricated on plastic

In this letter, we demonstrate the additive fabrication of electrostatic actuators on polyimide plastic by offset liquid embossing. They are formed by printing a nanoparticle colloid of gold on a polyimide substrate and then under-etching the polyimide through patterned etch holes. Residual stresses in the released gold films cause the films to bend away from the substrate. These films can then be electrostatically attracted toward the substrate and used to modulate light. The actuators range in size from 45to100μm and are controlled by electric fields of approximately 2V∕μm, allowing switching at several hundred cycles per second.

Direct printing of nanoparticles and spin-on-glasses by offset liquid embossing

We describe offset liquid embossing (OLE), a method for additively printing nanoparticles and spin-on-glasses. OLE utilizes the transfer of patterned material from a polydimethylsiloxane surface of tuned wettability to a rigid or flexible substrate. Multiple layers can be aligned and printed without the need for planarization. The printing is fast (10 s transfer to substrate) and can be done at ambient conditions. Bridge-like structures were printed in spin-on-glass without etching.

Nanotectonics: Direct Fabrication of All-Inorganic Logic Elements and Micro-Electro-Mechanical Systems from Nanoparticle Precursors

The reduced melting point and high solubility of inorganic nanoparticles have been shown to be useful in the low-temperature solution-based fabrication of semiconductor devices. These inks have been patterned using various techniques to form inorganic logic elements, multi-layer structures, and MEMS. Here we report a new technique known as offset liquid embossing that is used to print the nanoparticle inks. Structures created include multiple layers of gold and spin-on-glass printed without the need for etching or planarization, and 100 nm resolution.