Electrical Engineering
      and Computer Sciences

Electrical Engineering and Computer Sciences


UC Berkeley


2009 Research Summary

Phototransistor Optoelectronic Tweezers for Cell Manipulation

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

Center for Cell Control and CMISE (NASA URETI) NCC 2-1364

Optoelectronic tweezers (OET) provide a platform for massive optical manipulation of micro- and nano-particles with single particle resolution [1]. OET devices utilize optically-controlled dielectrophoresis (DEP) by exploiting a photoconductive layer that can be dynamically addressed by optical illumination. OET inherits the high-throughput properties of electrode-based DEP, while adding the high resolution and flexibility of optical control.

Utilizing amorphous silicon as photoconductive electrode, the current OET device only operates in media conductivity lower than 0.1 S/m, due to its insufficient photoconductivity. This limitation prevents experiments in cell culture media, which have typical conductivity of 1S/m or higher. Many biological experiments are desirable to be conducted in cell culture media. The goal of this project is to develop a new OET device for effective cell manipulation in a fully biocompatible environment, including highly ionic solutions.

The proposed new OET device structure is shown in Figure 1. Similar to previous OET devices, the new device consists of sandwiched layers of ITO glass, the liquid solution, and photoconductor electrodes. The photoconductive layer consists of phototransistors built on single crystalline silicon. With our new phototransistor OET device, we demonstrated HeLa cell transportation in a PBS solution and cell culture media.

Figure 1
Figure 1: Phototransistor OET device. This new device allows cell manipulation in a highly conductive solution, such as cell culture media.

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.