Innovative design, assembling and actuation of arrays of nanoelectromechanical system (NEMS) devices using nanoscale building blocks

Kim, Kwanoh
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Rotary nanomotors, a type of nanoelectromechanical system (NEMS) device that converts electric energy into mechanical motions, are critical for advancing NEMS technology in various fields but have been difficult to obtain using traditional techniques. As a consequence, it is highly desirable to investigate new mechanisms to develop large arrays of rotary NEMS devices with high efficiency, small size, and reliable performance at a low cost. In this dissertation, we report innovative designs and mechanisms for assembling and actuating arrays of rotary NEMS devices based on the electric tweezers and unique magnetic interactions among components. NEMS oscillators and motors were assembled from nanoscale building blocks including nanowires working as rotors, patterned nanomagnets as bearings, and quadrupole electrodes as stators. Multiple devices could be assembled in an ordered array and rotated either between two designated angles reciprocally or the full cycles continuously with controlled angle, speed (over 18,000 rpm) and chirality. Their fundamental electric, magnetic, and mechanical interactions were investigated, which provided an understanding of nanoscale dynamics critical to designing and actuating various metallic NEMS devices. We could reduce the size of the device with all its characteristic dimensions below 1 micron and continuously rotate a nanomotor for up to 15 hours, which is equivalent to more than 240,000 cycles in total. As an application, NEMS devices were used for controlled biochemical release and demonstrated the releasing rate of biochemical from the devices could be precisely tuned by mechanical rotation. Various magnetic configurations were purposely designed and successfully implemented, which resulted in distinct rotation behaviors including repeatable wobbling and self-rolling in addition to in-plane rotation. With the understandings of these rotation characteristics, high-performance micromotors have been rationally designed and successfully achieved, where the micromotors rotate at uniform speeds and position at desired angles, resembling step motors. Bioinspired micromotors comprised of three-dimensional porous diatom frustule rotors and patterned micromagnets were assembled and rotated in a microfluidic channel. Simulation results showed that they could stir and agitate liquid in a microchannel more efficiently than simple one-dimensional nanoentities and would be promising for microfluidic actuators. The innovations reported here, including concept, design, fabrication, actuation mechanisms, and applications, are expected to inspire various research areas including NEMS, nanorobotics, biomedical applications, microfluidics and lab-on-a-chip architectures.