Optoelectrofluidic Device Research Articles

Microarray-integrated optoelectrofluidic immunoassay system.

A microarray-based analytical platform has been utilized as a powerful tool in biological assay fields. However, an analyte depletion problem due to the slow mass transport based on molecular diffusion causes low reaction efficiency, resulting in a limitation for practical applications. This paper presents a novel method to improve the efficiency of microarray-based immunoassay via an optically induced electrokinetic phenomenon by integrating an optoelectrofluidic device with a conventional glass slide-based microarray format. A sample droplet was loaded between the microarray slide and the optoelectrofluidic device on which a photoconductive layer was deposited. Under the application of an AC voltage, optically induced AC electroosmotic flows caused by a microarray-patterned light actively enhanced the mass transport of target molecules at the multiple assay spots of the microarray simultaneously, which reduced tedious reaction time from more than 30 min to 10 min. Based on this enhancing effect, a heterogeneous immunoassay with a tiny volume of sample (5 μl) was successfully performed in the microarray-integrated optoelectrofluidic system using immunoglobulin G (IgG) and anti-IgG, resulting in improved efficiency compared to the static environment. Furthermore, the application of multiplex assays was also demonstrated by multiple protein detection.

Optoelectrofluidic behavior of metal–polymer hybrid colloidal particles

Behavior of metal–polymer hybrid colloidal particles in an optoelectrofluidic device has been investigated theoretically and experimentally. In the application of hundreds of kHz ac voltage, a variety of optically induced electrokinetic and electrostatic mechanisms affect the movement of gold-coated polystyrene microspheres. The particles repel from the light pattern, and their mobility increases as the amount of gold increases. We apply this model to develop an optoelectrofluidic immunoassay, in which the corresponding metal–polymer hybrid particles are formed by a reaction of antibody-coated gold nanoparticles, antigens, and antibody-coated polystyrene microspheres.

In situ dynamic measurements of the enhanced SERS signal using an optoelectrofluidic SERS platform

A novel active surface-enhanced Raman scattering (SERS) platform for dynamic on-demand generation of SERS active sites based on optoelectrofluidics is presented in this paper. When a laser source is projected into a sample solution containing metal nanoparticles in an optoelectrofluidic device and an alternating current (ac) electric field is applied, the metal nanoparticles are spontaneously concentrated and assembled within the laser spot, form SERS-active sites, and enhance the Raman signal significantly, allowing dynamic and more sensitive SERS detection. In this simple platform, in which a glass slide-like optoelectrofluidic device is integrated into a conventional SERS detection system, both dynamic concentration of metal nanoparticles and in situ detection of SERS signal are simultaneously possible with only a single laser source. This optoelectrofluidic SERS spectroscopy allows on-demand generation of 'hot spots' at specific regions of interest, and highly sensitive, reliable, and stable SERS measurements of the target molecules in a tiny volume (∼500 nL) of liquid sample without any fluidic components and complicated systems.

Optoelectrofluidic Sandwich Immunoassays for Detection of Human Tumor Marker Using Surface-Enhanced Raman Scattering

A sandwich immunoassay is a powerful tool for identifying a specific substance in a biological sample. However, its heterogeneous strategy always requires repetitive liquid handlings and long processing time. Here an optoelectrofluidic immunoassay platform for simple, fast, and automated detection of human tumor marker based on surface-enhanced Raman scattering (SERS) has been developed. By using a conventional optoelectrofluidic device and a liquid crystal display module, simple and quantitative detection of human tumor marker, alpha-fetoprotein, in a ∼500 nL sample droplet has been automatically conducted with lower detection limit of about 0.1 ng/mL within 5 min. This study depicts the first practical application, for protein detection, of the optoelectrofluidic manipulation technology. This image-driven immunoassay platform opens a new way for simple, fast, automated, and highly sensitive detection of antigens.

Generation and manipulation of droplets in an optoelectrofluidic device integrated with microfluidic channels

This letter describes an optoelectrofluidic platform integrated with microfluidic channels for continuous generation and programmable manipulation of water-in-oil droplet emulsions. A microchannel was integrated into a film-based optoelectrofluidic device by selective perforation of poly(dimethylsiloxane) layer for simultaneously performing microfluidic generation and optoelectrofluidic manipulation of droplets in a single device. By using this device, we could continuously generate, interactively transport, and merge multiple droplets using optically induced virtual electrodes.

Measurement of Molecular Diffusion Based on Optoelectrofluidic Fluorescence Microscopy

This technical note reports a method for measuring the diffusion coefficient of molecules based on an optoelectrofluidic platform. Optoelectrofluidic fluorescence microscopy, which is constructed with an optoelectrofluidic device and a conventional fluorescence microscope, is a useful tool for controlling and detecting local molecular concentration in a fluid with a single light source. When we project a light for fluorescence excitation and apply an ac signal of a few hundred Hertz frequency around 100 Hz to the optoelectrofluidic device, a sudden decay of molecular concentration occurs within the illuminated area due to several mechanisms, including optically induced ac electroosmosis, electrostatic interaction forces among the polarized molecules, and interactions among the molecules and between the molecules and the electric double layer. After the applied voltage was turned off, the dispersed molecules diffuse into the molecular depletion area and the fluorescence signal is recovered. On the basis of these phenomena, we successfully measured the diffusion coefficient of various dextran molecules. A statistical analysis to determine the significance of our experimental values compared to the previously reported values measured using fluorescence recovery after photobleaching technology was also performed. This new technique demonstrates the first analytical measurement of diffusion based on the optoelectrofluidic platform and can be a useful tool for measuring the mobility of molecules in a simple and easy way.

Dynamic Light-Activated Control of Local Chemical Concentration in a Fluid

This article reports a method for controlling the chemical concentration in a localized region of a fluid using optoelectrofluidic mechanisms. Optoelectrofluidic fluorescence microscopy (OFM), in which an optoelectrofluidic device is integrated into a conventional fluorescence microscope, allows both modulation and detection of local chemical concentration in an easy and simple way. Here, we present the first experimental investigation of the concentration change of polysaccharides, proteins, and fluorophores, due to the frequency-dependent ac electrokinetics and electrostatic interactions in an optoelectrofluidic device. The dynamic modulation of the local concentration of biomolecules such as dextran and serum albumin was demonstrated in a temporal and spatial manner. This OFM can be a useful tool for controlling the local chemical concentration in several chemical and biological applications.

Optoelectrofluidic Control of Colloidal Assembly in an Optically Induced Electric Field

This letter reports a method for controlling the organization of colloidal particles using optoelectrofluidic mechanisms. This optoelectrofluidic colloidal assembly (OCA) can be an efficient and simple way of preparing 2D colloidal crystals. Here, we present the first investigation of 2D colloidal assembly due to the electrohydrodynamic flows in an optoelectrofluidic device. The normalized distance among the assembled particles and the assembly rate according to the applied ac signal were analyzed. This OCA allows the control of both the colloidal crystal pattern over a large area and the distance between the assembled particles by adjusting the projected light pattern and the applied ac signal.

Stamp-to-Stick Bonding 및 Microtransfer Molding 방법을 이용한 미세유체 채널이 집적된 광전기유체소자의 제작

This paper describes two methods - stamp-to-stick bonding and microtransfer molding - to integrate microfluidic channel into an optoelectrofluidic device for in-channel microparticle manipulation. We have demonstrated the optoelectronic microparticle manipulation in the channel-integrated optoelectrofluidic device using a liquid crystal display. As injecting a liquid sample containing <TEX>$15{\mu}m$</TEX>-diameter polystyrene particles into the fabricated channel, trapping and transport of individual microparticles have been successfully demonstrated. This channel-integrated optoelectrofluidic device may be useful for several in-channel applications based on the optoelectrofluidics such as optoelectronic flow control, droplet-based protein assay and bead-based immunoassay.

Rapid and selective concentration of microparticles in an optoelectrofluidic platform

We demonstrate rapid manipulation and selective concentration of microparticles using AC electrokinetics such as dielectrophoresis (DEP) and AC electro-osmosis (ACEO) in an optoelectrofluidic platform based on a liquid crystal display (LCD). When 10 V bias at 10 kHz was applied to the optoelectrofluidic device, only the 1 microm-diameter polystyrene particles were concentrated into the projected LCD image patterns and closely packed, forming the crystalline structure by ACEO flow, while the 6 microm-diameter particles were repelled by negative DEP forces. We have characterized this frequency-dependency of the optoelectrofluidic particle behavior according to the particle diameter. On the basis of these results, we can rapidly concentrate the 1 microm-diameter particles and separate them from the 6 microm particles, by applying an AC signal of 10 kHz frequency. This novel technique can be applied to rapidly concentrate, separate and pattern micro-/nanoparticles in many biological and chemical applications.