Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2009 Research Summary

Optoelectronic Tweezers for Nanoparticle Manipulation

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Arash Jamshidi, Aaron Takami Ohta, Hsan-yin Hsu, Justin K Valley, Peidong Yang and Ming C. Wu

Defense Advanced Research Projects Agency Seedling grant and NIH

Optoelectronic tweezers (OET) is a non-invasive optical manipulation method for trapping, transport, and sorting of different types of beads, cells, and other bioparticles. The operation of OET is based on light-induced dielectrophoresis (DEP) force, which is the force acting on the induced dipole of a particle in a non-uniform electric field. In addition to being non-invasive, dynamic and reconfigurable, OET provides several advantages over conventional optical manipulation methods, including lower optical power density and larger working area [1].

In this study, we investigate the operation of optoelectronic tweezers for manipulation of particles at the nanoscale such as DNA, gold nanoparticles, carbon nanotubes, and nanowires. Due to the scaling of the dielectrophoresis force with the volume of the particle, the task of manipulating particles at the nanoscale becomes more challenging. However, several techniques can be used to overcome the decrease in the force with the volume, including the enhancement of the electric field gradient and scaling of the device geometry.

We have successfully demonstrated the DEP trapping and transport of silicon with 100 nm diameter and 5 µm length using optoelectronic tweezers [2]. Furthermore, formation of nanowire arrays and other arbitrary structures has been demonstrated.

Figure 1
Figure 1: Arrangement of silicon nanowires (NW) (100 nm diameter, 5 µm length) into (a) a triangular structure and (b) a diamond structure. Silicon nanowires were aligned vertically with the electric field.

P. Y. Chiou, A. T. Ohta, and M. C. Wu, "Massively Parallel Manipulation of Single Cells and Microparticles Using Optical Images," Nature, Vol. 436, 2005, pp. 370-372.
A. Jamshidi, P. J. Pauzauskie, A. T. Ohta, P. Y. Chiou, H. Hsu, P. Yang, and M. C. Wu. "Semiconductor Nanowire Manipulation Using Optoelectronic Tweezers," IEEE International Conference on MEMS, 2007.