Microscale pH gradient generation by electrolysis on a light-addressable planar electrode

Pan

J. Microelectromech. Syst.

et al. 2015

Abstract-A technique using digital masks without ultraviolet light to rapidly print 3-D biopolymer structures with complex microarchitectures in a microfluidic chip has been demonstrated. In this approach, a customized system is used to project light images on a photoconductive substrate in order to create localized virtual electrodes when an alternating electric field is applied across the fluidic medium in an optically controlled digital electropolymerization chip. Upon these virtual electrodes, the localized electric fields are generated, which could activate the polymerization of acrylate-based molecules, such as poly(ethylene glycol) diacrylate (PEGDA), to form microstructures with the same shapes as the projected light images. We have demonstrated that the 3-D PEGDA microstructures with the customized shapes could be fabricated rapidly through a layer-by-layer process by applying a series of digital masks (projected light images). With our current projection and microscopy system, the fabrication of microhydrogel structures with a lateral resolution of 3 µm and an adjustable thickness ranging from tens of nanometers to hundreds of micrometers has been demonstrated. In summary, this novel technique provides an efficient process for the rapid printing of the 3-D biopolymer-based microstructures, and could enable many future applications in a mechanoanalysis of cancer cells, tissue engineering, and drug screening.[2015-0110]

Section: Polymerization Processmentioning

confidence: 99%

3-D Non-UV Digital Printing of Hydrogel Microstructures by Optically Controlled Digital Electropolymerization

Pan

J. Microelectromech. Syst.

et al. 2015

Micro‐ and Nanomanipulation Tools

“…For example, Starovoytov et al presented the possibility of light addressable electrical stimulation of cultured neurons with a similar structure to OEK device by replacing the transparent ITO electrode with a floating one [119,120]. Suzurikawa et al [34] reported the production of microscale pH gradient in OEK chips. Wang et al demonstrated the polymerization of prepolymer in an OEK device for the fabrication of PEGDA microstructures [121,122].…”

Section: Discussionmentioning

confidence: 99%

“…Static light patterns used to trigger the ODEP force can be generated through a photomask [22], a diaphragm [31], or a single focused laser spot [25,32]. Dynamic or programmable manipulation can be achieved by a DMD [18,33,34], a projector [35,36], or a liquid-crystalbased spatial light modulator [37,38]. Additional optical components, including an objective lens, are usually needed to focus light patterns on to the photosensitive layer to obtain a resolution of 1-20 μm [19].…”

Section: Optically Induced Electrokinetic (Oek) Forces 45mentioning

confidence: 99%

“…Since its inception in 2005, a range of OEK-based applications have been demonstrated, including manipulation of single cells [18], concentration and transport of multiple Escherichia coli cells [32], cell counting and lysis [39], microparticle counting and sorting [40], manipulation of single DNA molecules [41], parallel trapping of single-and multiwall carbon nanotubes (CNTs) [42], manipulation and patterning of single-wall CNTs [43], dynamic manipulation and separation of individual semiconducting and metallic nanowires [30], dynamic patterning of nanoparticles [44], control of local chemical concentration in [31] or the pH [34] of a fluid, selective electroporation [45], and manipulation oil-in-water emulsion droplets [46].…”

Section: Optically Induced Electrokinetic (Oek) Forces 45mentioning

confidence: 99%

See 1 more Smart Citation

Micro and Nano Manipulation and Assembly by Optically Induced Electrokinetics

Lai

et al. 2015

IntroductionIn the past 25 years, integrated circuit (IC) and microelectromechanical systems (MEMSs) technologies have moved much beyond the microdomain, and into the submicro-, nanoscopic, and, even, the molecular scales. Today, we have the capability to fabricate, manipulate, and assemble matters at the micro-, nano-, or molecular scales. This progress into "seeing" and manipulating matters that are smaller than visible light wavelength scale is impacting a range of fields including semiconductor physics, biological studies, pharmaceutical development, and many other scientific and technological applications. A range of new methods to generate physical forces have been developed in the process. For example, mechanical forces can now be applied to micro-, nano-, and biological entities using atomic force microscope probes [1], microgrippers [2], or pipettes [3]. However, disadvantages of these approaches, including inflection of mechanical damages on objects being manipulated and their relatively low manipulation speed, make manipulation of large quantities of objects difficult. In order to address these disadvantages, noncontact or noninvasive methods for micro-, nano-, and biological manipulation have also been explored in the past two decades.Manipulation devices based on magnetic forces [4], acoustic waves [5,6], hydrodynamic flows [7], light waves [8], or electrokinetic forces [9] are among the major noninvasive technologies available today. Each of them has its own advantages and disadvantages. Methods based on magnetic fields need premodification on objects with magnetic beads which constrains their application domain. In addition, movement controlled by permanent magnets is not precise enough for many proposed applications. Also, the high resistance of the magnetic coil generates significant heat during manipulation [10]. Acoustic traps show good selectivity but cannot achieve parallel manipulation of single entities. Microfluidic devices exploiting hydrodynamic flows are suitable for cell population sorting, but have difficulties in trapping or controlling specific single objects.Electrokinetic forces generated from patterned electrodes capable of inducing the desired spatial distribution of electric field have been exploited to control

“…Amplex Red reagent and reaction buffer were purchased from Molecular Probes (Grand Island, NY, UAS). 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF) was used as a fluorescence pH indicator [19]. The indicator was purchased from Sigma-Aldrich Chemicals and diluted to the final BCECF concentration of 0.2 μM before experiments.…”

Section: Methodsmentioning

confidence: 99%

Light-Addressed Electrodeposition of Enzyme-Entrapped Chitosan Membranes for Multiplexed Enzyme-Based Bioassays Using a Digital Micromirror Device

Huang

Wei

Chu

et al. 2013

Sensors

This paper describes a light-addressed electrolytic system used to perform an electrodeposition of enzyme-entrapped chitosan membranes for multiplexed enzyme-based bioassays using a digital micromirror device (DMD). In this system, a patterned light illumination is projected onto a photoconductive substrate serving as a photo-cathode to electrolytically produce hydroxide ions, which leads to an increased pH gradient. The high pH generated at the cathode can cause a local gelation of chitosan through sol-gel transition. By controlling the illumination pattern on the DMD, a light-addressed electrodeposition of chitosan membranes with different shapes and sizes, as well as multiplexed micropatterning, was performed. The effect of the illumination time of the light pattern on the dimensional resolution of chitosan membrane formation was examined experimentally. Moreover, multiplexed enzyme-based bioassay of enzyme-entrapped chitosan membranes was also successfully demonstrated through the electrodeposition of the chitosan membranes with various shapes/sizes and entrapping different enzymes. As a model experiment, glucose and ethanol were simultaneously detected in a single detection chamber without cross-talk using shape-coded chitosan membranes entrapped with glucose oxidase (GOX), peroxidase (POD), and Amplex Red (AmR) or alcohol oxidase (AOX), POD, and AmR by using same fluorescence indicator (AmR).