Optoelectrofluidics, also known as optically induced electrohydrodynamics

Electrohydrodynamics

Electrohydrodynamics , also known as electro-fluid-dynamics or electrokinetics, is the study of the dynamics of electrically charged fluids. It is the study of the motions of ionised particles or molecules and their interactions with electric fields and the surrounding fluid...

, refers to the study of the motions of particles or molecules and their interactions with optically-induced electric field and the surrounding fluid.

This concept includes electrothermal vortex, electrophoresis

Electrophoresis

Electrophoresis, also called cataphoresis, is the motion of dispersed particles relative to a fluid under the influence of a spatially uniform electric field. This electrokinetic phenomenon was observed for the first time in 1807 by Reuss , who noticed that the application of a constant electric...

, dielectrophoresis, and electroosmosis induced by combination of optical and electrical energy or by optical-electrical energy transfer.

In 1995, an electrothermal vortices induced by a strong IR (infrared

Infrared

Infrared light is electromagnetic radiation with a wavelength longer than that of visible light, measured from the nominal edge of visible red light at 0.74 micrometres , and extending conventionally to 300 µm...

) laser projected into an electric field have been utilized to concentrate microparticles and molecules. In 2000, UV(ultraviolet

Ultraviolet

Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...

) pattern projected onto ITO (indium tin oxide

Indium tin oxide

Indium tin oxide is a solid solution of indium oxide and tin oxide , typically 90% In2O3, 10% SnO2 by weight. It is transparent and colorless in thin layers while in bulk form it is yellowish to grey...

) electrode has been applied for patterning colloidal particles. Illumination of the ITO electrode by UV light results in a small increase in the current from the generation of electron-hole pairs at the ITO/water interface. In 2005, optoelectronic tweezers (OET), wherein a photoconductive material was utilized to induce electric field using the optical decrement of electrical resistance on a partially illuminated area, has been reported. After that, many researches in several view-points have been performed as below.

Display Devices

1. DMD(digital micromirror device

Digital micromirror device

A digital micromirror device, or DMD, is an optical semiconductor that is the core of DLP projection technology, and was invented by Dr. Larry Hornbeck and Dr. William E. "Ed" Nelson of Texas Instruments in 1987....

)-based Optoelectronic Tweezers (OET) : P.Y. Chiou, et al., Nature 436, pp.370-372 (2005)

2. Projector

Image projector

An image projector is an optical device that projects an image onto a surface, commonly a projection screen.Most projectors creates an image by shining a light through a small transparent image, but some newer types of projectors can project the image directly, by using lasers...

-based Image Dielectrophoresis (iDEP) : Y.-s. Lu, et al., Opt. Quant. Elec. 37, pp.1385-1395 (2006)

3. LCD(liquid crystal display

Liquid crystal display

A liquid crystal display is a flat panel display, electronic visual display, or video display that uses the light modulating properties of liquid crystals . LCs do not emit light directly....

)-based Lab-on-a-Display (LOD) : W. Choi, et al., Microfluid. Nanofluid. 3, pp.217-225 (2007)

4. Lens-integrated LCD-based System : H. Hwang, et al., Electrophoresis 29, pp.1203-1212 (2008)

System Configuration

1. Interactive & Microscope-integrated System : H. Hwang, et al., Electrophoresis 29, pp.1203-1212 (2008)

2. Double Photoconductive Layers : H. Hwang, et al., Appl. Phys. Lett. 92, pp.024108 (2008)

3. Floating Electrode OET : S. Park, et al., Appl. Phys. Lett. 92, pp.151101 (2008)

4. Integration with Electrowetting

Electrowetting

Electrowetting is the modification of the wetting properties of a surface with an applied electric field.-History:...

 Device : G.J. Shah, et al., Lab Chip DOI: 10.1039/b821508a (2009)

5. Optoelectrofluidic Fluorescence Microscopy: H. Hwang and J.-K. Park, Anal. Chem. DOI: 10.1021/ac901047v (2009)

Target Materials

1. Cultured cells : A.T. Ohta, et al., IEEE J. Sel. Top. Quant. Elec. 13, pp.237-240 (2007)

2. DNA

DNA

Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...

 : M. Hoeb, et al., Biophys. J. 93, pp.1032-1038 (2007)

3. Blood cell

Blood cell

A blood cell, also called a hematocyte, is a cell normally found in blood. In mammals, these fall into three general categories:* red blood cells — Erythrocytes* white blood cells — Leukocytes* platelets — Thrombocytes...

 : H. Hwang, et al., Electrophoresis 29, pp.1203-1212 (2008)

4. Semiconducting nanowires : A. Jamshidi, et al., Nat. Photon. 2, pp.86-89 (2008)

5. Swimming bacteria

Bacteria

Bacteria are a large domain of prokaryotic microorganisms. Typically a few micrometres in length, bacteria have a wide range of shapes, ranging from spheres to rods and spirals...

 : W. Choi, et al., Appl. Phys. Lett. 93, pp.143901 (2008)

6. Oocyte

Oocyte

An oocyte, ovocyte, or rarely ocyte, is a female gametocyte or germ cell involved in reproduction. In other words, it is an immature ovum, or egg cell. An oocyte is produced in the ovary during female gametogenesis. The female germ cells produce a primordial germ cell which undergoes a mitotic...

 : H. Hwang, et al., Biomicrofluidics 3, pp.014103 (2009)

7. Polysaccharide

Polysaccharide

Polysaccharides are long carbohydrate molecules, of repeated monomer units joined together by glycosidic bonds. They range in structure from linear to highly branched. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure,...

, Protein

Protein

Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form, facilitating a biological function. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of...

 and Fluorophore

Fluorophore

A fluorophore, in analogy to a chromophore, is a component of a molecule which causes a molecule to be fluorescent. It is a functional group in a molecule which will absorb energy of a specific wavelength and re-emit energy at a different wavelength...

 : H. Hwang and J.-K. Park, Anal. Chem. DOI: 10.1021/ac901047v (2009)

Operating Principles

1. Dielectrophoresis (DEP) : Most of the researches above.

2. AC Electro-osmosis

Electro-osmosis

Electroosmotic flow is the motion of liquid induced by an applied potential across a porous material, capillary tube, membrane, microchannel, or any other fluid conduit...

(ACEO) : P.-Y. Chiou, et al., J. Microelectromech. Syst. 17, pp.525-531 (2008)

3. Electro-orientation : W. Choi, et al., Appl. Phys. Lett. 93, pp.143901 (2008)

4. Electrothermal flow : A. Mizuno, et al., IEEE Trans. Ind. Appl. 31,pp.464-468 (1995), S.J. Williams, A. Kumar and S. T. Wereley, Lab Chip 8,pp.1879-1882 (2008)

5. Combination of AC Electrokinetics : H. Hwang and J.-K. Park, Lab Chip 9,pp.199-206 (2009), H. Hwang and J.-K. Park, Anal. Chem. DOI: 10.1021/ac901047v (2009)

Other Phenomena

1. Surface-Particle Interactions : H. Hwang, et al., Appl. Phys. Lett. 92, pp.024108 (2008)

2. Particle-Particle Interactions : H. Hwang, et al., J. Phys. Chem. B 32, pp.9903-9908 (2008)

Applications

1. Microlens Array Fabrication : J.-Y. Huang, Y.-S. Lu and J. A. Teh, Opt. Express 14, pp.10779-10784 (2006)

2. Microparticle Separation : H. Hwang and J.-K. Park, Lab Chip 9,pp.199-206 (2009)

3. In vitro Fertilization : H. Hwang, et al., Biomicrofluidics 3, pp.014103 (2009)

4. Electroporation : J.K. Valley, et al., Lab Chip DOI: 10.1039/b821678a (2009)

5. Local Chemical Concentration Control : H. Hwang and J.-K. Park, Anal. Chem. DOI: 10.1021/ac901047v (2009)

6. Colloidal Assembly : H. Hwang, Y.-H. Park and J.-K. Park, Langmuir 25, pp.6010-6014 (2009)

Research Groups

1. Ming C. Wu's Group : Integrated Photonics Laboratory, UC Berkeley, CA, USA

2. Je-Kyun Park's Group : NanoBiotech Laboratory, KAIST, KOREA

3. P.Y. Chiou's Group : Optoelectronic Biofluidics Laboratory, UCLA, CA, USA

4. Steve Wereley's Group : Microfluidics Laboratory, Purdue University, IN, USA