Carbon nanotubes are manipulated in three dimensions inside a scanning electron microscope (SEM). A custom piezoelectric vacuum manipulator achieves positional resolutions comparable to scanning probe microscopes, with the ability to manipulate objects along one rotational and three linear degrees of freedom. This prototypical device can probe, select and handle nanometre-scale objects such as carbon nanotubes in order to explore and correlate their mechanical and electrical properties. Under real-time SEM inspection, carbon nanotubes are stressed while monitoring their conductivity, and nanotubes are attached to commercial atomic force microscope (AFM) tips such that the forces applied to the tubes can be measured from the cantilevers' deflections. The manipulator functions both as a research tool for investigating properties of carbon nanotubes and other nanoscale objects without surface restrictions, and as a rudimentary building device for larger nanotube assemblies. This capability to select and manipulate nanoscale components and to examine directly their suitability as construction materials during various phases of the construction process will play an important role in enabling the technology of assembling mechanical and electronic devices from prefabricated components.
This work addresses a range of issues on modeling electrothermal microactuators, including the physics of temperature dependent material properties and Finite Element Analysis modeling techniques. Electrical and thermal conductivity are a nonlinear function of temperature that can be explained with electron and phonon transport models, respectively. Parametric forms of these equations are developed for polysilicon and a technique to extract these parameters from experimental data is given. A modeling technique to capture the convective and conductive cooling effects on a thermal actuator in air is then presented. Using this modeling technique and the established polysilicon material properties, simulation results are compared with measured actuator responses. Both static and transient analyzes have been performed on two styles of actuators and the results compare well with measured data.[946]Index Terms-Electrothermal microactuator, modeling thermal actuator, polysilicon material properties.
A micromachined end-effector along with techniques in micromanipulation for directed micro-electro-mechanical systems (MEMS) assembly is presented. A passive end-effector, fabricated in a 50 µm thick single crystal silicon (SCS) deep reactive ion etched (DRIE) process, is compared with a microgripper made with the same process. With this passive tool, pick and place assembly of MEMS components can be accomplished reliably, since the end-effector is more mechanically robust than comparable microgrippers. This end-effector can withstand an order of magnitude more force than conventional MEMS based microgrippers used for microassembly. In addition, the elimination of any actuation reduces packaging complexity and allows easier integration of sensing mechanisms for feedback control. This simplified passive end-effector with an integrated electrical contact sensor is also presented, along with assembly techniques and designs used for directed pick and place MEMS assembly. Both mechanical and electrical MEMS interconnects are demonstrated.
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