Self-Assembly of Microstructures

Four areas are investigated in this research: erecting microstructures normal to the substrate plane without direct human intervention (self-assembled), providing low resistance electrical connections to the erected microstructure, realizing circular motion normal to the substrate plane, and implementing a micro-robot. The designs in this research concentrate on erecting and providing power to a leg designed for use with the micro-robot. The leg and the attached low resistance electrical connectors were not self-assembled because the accompanying actuators were not powerful enough. However, the novel connectors provide the most practical, versatile, and lowest possible resistance connections for the MUMPs fabrication process. The micro-robot was a 1 cm by 1 cm by 0.125 mm thick silicon chip with 96 legs micro-machined on one side. The legs were able to support the weight of the chip but could not move the chip. The gold wires used to remotely power the legs, restricted the chip\u27s movement. The chip was turned over, and used as a micro-position to transport a 1 cm by 1 cm by 0.023 mm piece of kapton film. A vertically deflecting actuator was used to bump the edge of a 222 mm diameter wheel, causing circular motion normal to the substrate

Nanoindentation Technique for Characterizing Cantilever Beam Style RF Microelectromechanical Systems (MEMS) Switches

A nanoindentation technique was used to mechanically actuate a radio frequency micro-switch along with the measurement of contact resistance to investigate its applicability to characterize deflection and contact resistance behaviors of micro-sized cantilever beam switches. The resulting load–displacement relationship showed a discontinuity in slope when the micro-switch closed. The measured spring constants reasonably agreed with theoretical values obtained from the simple beam models. The change in contact resistance during test clearly indicated micro-switch closure but it did not coincide exactly with the physical contact between two electric contacts due to a resistive contaminated film

Selecting Metal Alloy Electric Contact Materials for MEMS Switches

This paper presents a method for selecting metal alloys as the electric contact materials for microelectromechanical systems (MEMS) metal contact switches. This procedure consists of reviewing macro-switch lessons learned, utilizing equilibrium binary alloy phase diagrams, obtaining thin film material properties and, based on a suitable model, predicting contact resistance performance. After determining a candidate alloy material, MEMS switches were designed, fabricated and tested to validate the alloy selection methodology. Minimum average contact resistance values of 1.17 and 1.87 Ω were measured for micro-switches with gold (Au) and gold–platinum (Au–(6.3%)Pt) alloy electric contacts, respectively. In addition, \u27hot-switched\u27 life cycle test results of 1.02 × 108 and 2.70 × 108 cycles were collected for micro-switches with Au and Au–(6.3%)Pt contacts, respectively. These results indicate increased wear with a small increase in contact resistance for MEMS switches with metal alloy electric contacts

Molecular Layer Deposition on Carbon Nanotubes

Molecular layer deposition (MLD) techniques were used to deposit conformal coatings on bulk quantities of carbon nanotubes (CNTs). Several metalcone MLD chemistries were employed, including alucone (trimethylaluminum/glycerol and trimethylaluminum/ethylene glycol), titanicone (TiCl₄/glycerol), and zincone (diethyl zinc/glycerol). The metalcone MLD films grew directly on the CNTs and MLD initiation did not require atomic layer deposition (ALD) of an adhesion layer. Transmission electron microscopy revealed that MLD formed three-dimensional conformal deposits throughout a CNT scaffold. Mechanical testing was also performed on sheets of CNT networks coated by MLD. Young’s Modulus values improved from an initial value of 510 MPa for uncoated CNT sheet to values that ranged from 2.2 GPa, for 10 nm of glycerol alucone (AlGL), to 8.7 GPa for a composite 5 nm AlGL + 5 nm Al₂O₃ coating