Aaron T. Ohta

Bio: Aaron T. Ohta is an academic researcher from University of Hawaii at Manoa. The author has contributed to research in topics: Tweezers & Dielectrophoresis. The author has an hindex of 27, co-authored 143 publications receiving 4259 citations. Previous affiliations of Aaron T. Ohta include University of Hawaii & Lawrence Livermore National Laboratory.

Massively parallel manipulation of single cells and microparticles using optical images.

Abstract: The ability to manipulate biological cells and micrometre-scale particles plays an important role in many biological and colloidal science applications. However, conventional manipulation techniques--including optical tweezers, electrokinetic forces (electrophoresis, dielectrophoresis, travelling-wave dielectrophoresis), magnetic tweezers, acoustic traps and hydrodynamic flows--cannot achieve high resolution and high throughput at the same time. Optical tweezers offer high resolution for trapping single particles, but have a limited manipulation area owing to tight focusing requirements; on the other hand, electrokinetic forces and other mechanisms provide high throughput, but lack the flexibility or the spatial resolution necessary for controlling individual cells. Here we present an optical image-driven dielectrophoresis technique that permits high-resolution patterning of electric fields on a photoconductive surface for manipulating single particles. It requires 100,000 times less optical intensity than optical tweezers. Using an incoherent light source (a light-emitting diode or a halogen lamp) and a digital micromirror spatial light modulator, we have demonstrated parallel manipulation of 15,000 particle traps on a 1.3 x 1.0 mm2 area. With direct optical imaging control, multiple manipulation functions are combined to achieve complex, multi-step manipulation protocols.

Dynamic manipulation and separation of individual semiconducting and metallic nanowires

Abstract: The synthesis of nanowires has advanced in the past decade to the point where a vast range of insulating, semiconducting and metallic materials1 are available for use in integrated, heterogeneous optoelectronic devices at nanometre scales2. However, a persistent challenge has been the development of a general strategy for the manipulation of individual nanowires with arbitrary composition. Here we report that individual semiconducting and metallic nanowires with diameters below 20 nm are addressable with forces generated by optoelectronic tweezers3. Using 100,000 times less optical power density than optical tweezers, optoelectronic tweezers are capable of transporting individual nanowires with speeds four times greater than the maximum speeds achieved by optical tweezers. A real-time array of silver nanowires is formed using photopatterned virtual electrodes, demonstrating the potential for massively parallel assemblies. Furthermore, optoelectronic tweezers enable the separation of semiconducting and metallic nanowires, suggesting a broad range of applications for the separation and heterogeneous integration of one-dimensional nanoscale materials.

EWOD-driven droplet microfluidic device integrated with optoelectronic tweezers as an automated platform for cellular isolation and analysis

Abstract: We report the integration of two technologies: droplet microfluidics using electrowetting-on-dielectric (EWOD) and individual particle manipulation using optoelectronic tweezers (OET)—in one microfluidic device. The integrated device successfully demonstrates a sequence involving both EWOD and OET operations. We encountered various challenges during integration of the two different technologies and present how they are addressed. To show the applicability of the device in cellular biology, live HeLa cells are used in the experiments. The unique advantages of EWOD and OET make their integration a significant step towards a powerful tool for many applications, such as single cell studies involving multiplexed environmental stimuli.

Dynamic Cell and Microparticle Control via Optoelectronic Tweezers

Abstract: This paper reports on cell and microparticle manipulation using optically induced dielectrophoresis. Our novel optoelectronic tweezers (OET) device enables optically controlled trapping, transportation, and sorting via dielectrophoretic forces. By integrating a spatial light modulator and using direct imaging, arbitrary dynamic manipulation patterns are obtained. Here, we demonstrate manipulation functions, including particle collectors, single-particle traps, individually addressable single-particle arrays, light-defined particle channels, and size-based particle sorting. OET-induced particle manipulation velocities are analyzed as a function of the applied voltage, optical pattern linewidth, and single-particle trap dimensions.

Micro-assembly using optically controlled bubble microrobots

Abstract: Bubbles controlled by optically induced heating were made to function as novel microrobots for micromanipulation and micro-assembly. Using light patterns generated by a commercial computer projector, bubble microrobots were controlled and used to manipulate glass microbeads and perform the micro-assembly of micro-blocks and cell-encapsulating hydrogel beads. Two manipulation modes, pulling and pushing, were used to move micro-objects into place and manipulate glass beads with a velocity of up to 350 μm/s. The simultaneous independent control of three bubble robots was also demonstrated.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Synthetic molecular motors and mechanical machines.

Abstract: The widespread use of controlled molecular-level motion in key natural processes suggests that great rewards could come from bridging the gap between the present generation of synthetic molecular systems, which by and large rely upon electronic and chemical effects to carry out their functions, and the machines of the macroscopic world, which utilize the synchronized movements of smaller parts to perform specific tasks. This is a scientific area of great contemporary interest and extraordinary recent growth, yet the notion of molecular-level machines dates back to a time when the ideas surrounding the statistical nature of matter and the laws of thermodynamics were first being formulated. Here we outline the exciting successes in taming molecular-level movement thus far, the underlying principles that all experimental designs must follow, and the early progress made towards utilizing synthetic molecular structures to perform tasks using mechanical motion. We also highlight some of the issues and challenges that still need to be overcome.

Single-molecule force spectroscopy: optical tweezers, magnetic tweezers and atomic force microscopy

Abstract: Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.

Developing optofluidic technology through the fusion of microfluidics and optics

Abstract: We describe devices in which optics and fluidics are used synergistically to synthesize novel functionalities. Fluidic replacement or modification leads to reconfigurable optical systems, whereas the implementation of optics through the microfluidic toolkit gives highly compact and integrated devices. We categorize optofluidics according to three broad categories of interactions: fluid–solid interfaces, purely fluidic interfaces and colloidal suspensions. We describe examples of optofluidic devices in each category.