Eric J Wilhelm's
Research



I am developing an additive microfabrication technique based on liquid embossing nanoparticle colloids. The potential applications include truly 3-dimensional MEMS and logic, biological scaffolding, and photonic band gaps.

Publications and awards:

Fuller, S. B., E. J. Wilhelm, et al. (2002). "Ink-jet printed nanoparticle microelectromechanical systems." Journal of Microelectromechanical Systems 11(1): 54-60.
We report 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 I to 100 nm in diameter and can be sintered at plastic-compatible temperatures as low as 300 degreesC 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 mum 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.

Bulthaup, C. A., E. J. Wilhelm, et al. (2001). "All-additive fabrication of inorganic logic elements by liquid embossing." Applied Physics Letters 79(10): 1525-1527.
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.

Mihm, S. (2000). "Print your next PC." Technology Review 103(6): 66-70.

Winner of the 2000 Collegiate Inventors Competition (with Colin Bulthaup)

C. Bulthaup, E.J. Wilhelm, B.N. Hubert, B.A. Ridley, and J.M. Jacobson, "Direct Fabrication of All-Inorganic Logic Elements and Microelectromechanical Systems from Nanoparticle Precursors", Material Research Society symposium on Non-lithographic and lithographic methods for nanofabrication, 2000.

Perez, J. M., E. J. Wilhelm, et al. (2000). "The use of power ultrasound coupled with magnetic separation for the solid phase synthesis of compound libraries." Bioorganic & Medicinal Chemistry Letters 10(2): 171-174.
Enhanced reaction rates are observed when power ultrasound is utilized as a substitute for mixing during solid phase organic chemical reactions on a paramagnetic support. Power ultrasound is also used to facilitate the washing of the paramagnetic support as it is magnetically separated from the reaction mixture. Selective examples from a library targeting the kappa-opioid receptor are presented.

Iagnemma, K., R. Burn, et al. (2000). "Experimental validation of physics-based planning and control algorithms for planetary robotic rovers." Experimental Robotics Vi 250: 319-328.
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.

B.A. Ridley, B. Nivi, B.N. Hubert, C. Bulthaup, E.J. Wilhelm, and J.M. Jacobson ,"Solution Processed Inorganic Transistors and Sub-Micron Non-Lithographic Patterning Using Nanoparticle Inks", Nanophase and Nanocomposite Materials III, Mater. Res. Soc. Proc. 581, pp 115-120, 1999.