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