Research in the micro- to nanoscale regimes is facilitated by technologies that enable the addressing of these tiny particles. In biological research, manipulation enables the study of single-cell behavior, as well as the sorting of specific target cells from a mixed population. In engineering applications, micro- and nanoparticles can be assembled to form electronic and optoelectronic devices. Several types of forces can be used to manipulate micro- and nanoscale objects, including optical and electrical forces.
A device is presented that integrates the advantages of optical and electrical manipulation, called optoelectronic tweezers (OET). The OET device combines the advantages of both optical and electrical trapping. Optical patterns are used to create manipulation patterns and particle traps in an amorphous-silicon-based semiconductor device. The optical patterns create dielectrophoretic force in the OET device, via light-induced dielectrophoresis. Thus, OET does not directly use optical energy for trapping, allowing the use of much lower optical intensities than direct optical manipulation. These low optical intensities can be achieved by a computer projector or an LED, allowing the creation of complex optical manipulation patterns. Furthermore, unlike electrical traps, OET is capable of trapping a specific single microparticle from a larger population.
In this dissertation, the optoelectronic tweezers device is discussed in detail, including the operating principle, design considerations, and fabrication processes. OET manipulation is presented in the context of three major applications: sperm sorting for improving current in vitro fertilization techniques, microdisk laser assembly for CMOS-integrated optoelectronic devices, and nanowire assembly for nanowire-based displays.
August 31, 2008
Ohta, A. T. (2008). Design and Characterization of a MEMS Piezoelectric Bi-Chevron Actuator. University of California, Berkeley.