Aaron T. Ohta

Trap profiles of projector based optoelectronic tweezers (OET) with HeLa cells

In this paper we present trap profile measurements for HeLa cells in Optoelectronic Tweezers (OET) based on a data projector. The data projector is used as a light source to illuminate amorphous Si creating virtual electrodes which are used to trap particles through dielectrophoresis. We show that although the trap stiffness is typically greater at the edges of the optical spot it is possible to create a trap with constant trap stiffness by reducing the traps size until it is similar to the object being trapped. We have successfully created a trap for HeLa cells with a constant trap stiffness of 3 x 10(-6) Nm-1 (capable of moving the cell up to 50 microms-1) with a 12 microm diameter trap. We also calculate the depth of the potential well that the cell will experience due to the trap and find that it to be 1.6 x 10(-16)J (4 x 10(4) kBT).

Optical Manipulation of Cells

Single-cell analysis can reveal cell behaviors that are unobservable by traditional bulk measurements. The analysis of single cells is made possible by technology that enables the addressing and manipulation of microscale objects. Optical manipulators are capable of micro- and nano-manipulation and are attractive for single-cell procedures, due to their inherent flexibility and adaptability. This chapter reviews major types of optical manipulation techniques. Optical gradient and scattering forces, used in optical tweezers, holographic optical tweezers, and other optical traps, are introduced first. Next, optically controlled electrokinetic forces are discussed, with a focus on optically induced dielectrophoresis. Optically induced thermal effects are also introduced, including thermophoresis and thermocapillary force. Specific examples of applications of these techniques for procedures related to single-cell analysis are also covered, including cell culturing, cell sorting, cell surgery, and measurements of single cells.

Optoelectronic Tweezers for the Manipulation of Cells, Microparticles, and Nanoparticles

Micro- and nanoparticle manipulation capabilities can benefit researchers in a wide variety of fields, from biological research to semiconductor physics. Optoelectronic tweezers (OET) is a novel technique that complements existing manipulation technologies. OET provides optically-controlled manipulation at the single-particle level. It is a dynamic, reconfigurable, minimally-invasive tool capable of massively parallel manipulation. In this chapter, the operating principle of OET will be explained, along with device design considerations and operational regimes. The capabilities of OET will be showcased in the context of applications in biological cell handling and micro- and nanoparticle assembly.

Small satellites for rapid-response communication and situational assessment

This paper described two types of low-cost, readily deployable platforms for responsive communication and situational assessment missions. BalloonSats can be assembled and launched in just a few hours, and can provide real-time video surveillance over a disaster area. CubeSats have a longer development time, but have a longer mission time due to their orbit.

Electrically actuated liquid metal for reconfigurable RF devices

Reconfigurable RF devices can respond dynamically to complex RF environments. Liquid metals have the potential to enable reconfigurable devices that cannot be implemented by more conventional materials and technologies. This paper reviews recent progress by our research group toward the creation of reconfigurable liquid-metal RF devices that use low-power electrical actuation.