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2011, Applied Physics Letters
https://doi.org/10.1063/1.3580760…
4 pages
1 file
Microbubbles have a variety of applications in science and biological technology. Here, we demonstrate the manipulation of the picoliter gas bubble (picobubble) based on the optoelectronic-mechanism. The organic photoconductive material, titanium oxide phthalocyanine (TiOPc), was developed to make the light-sensitive substrate of this optoelectronic chip. The virtual electrodes are formed by projecting the dynamic light pattern onto TiOPc layer for generating the desired nonuniform electric field. The picobubble suspended in silicone oil can be manipulated with the velocity of 40–50 μm/s. The driving force up to 160 pico-Newtons could be generated for manipulating a gas bubble of 300 picoliters.
Extended Abstracts of the 2013 International Conference on Solid State Devices and Materials, 2013
This paper reports the organic optoelectronic platform which integrates optoelectrowetting (OEW) and optoelectronic tweezers (OET) by spin-coating titanium oxide phthalocyanine (TiOPc) as a photoconductive layer for realizing the manipulation of cells and the actuation of droplets in a single chip.
Journal of Microelectromechanical Systems, 2007
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. [2006-0210] Index Terms-Dielectrophoresis (DEP), optical tweezers, optically induced DEP, optoelectronic tweezers (OET).
Micromachines, 2020
Optoelectrokinetics (OEK), a fusion of optics, electrokinetics, and microfluidics, has been demonstrated to offer a series of extraordinary advantages in the manipulation and fabrication of micro/nanomaterials, such as requiring no mask, programmability, flexibility, and rapidness. In this paper, we summarize a variety of differently structured OEK chips, followed by a discussion on how they are fabricated and the ways in which they work. We also review how three differently sized polystyrene beads can be separated simultaneously, how a variety of nanoparticles can be assembled, and how micro/nanomaterials can be fabricated into functional devices. Another focus of our paper is on mask-free fabrication and assembly of hydrogel-based micro/nanostructures and its possible applications in biological fields. We provide a summary of the current challenges facing the OEK technique and its future prospects at the end of this paper.
Sensors and Actuators A-physical, 2003
Optical actuation of liquid droplets has been experimentally demonstrated for the first time using a novel optoelectrowetting (OEW) principle. The optoelectrowetting surface is realized by integrating a photoconductive material underneath a two-dimensional array of electrowetting electrodes. Contact angle change as large as 308 has been achieved when illuminated by a light beam with an intensity of 65 mW/cm 2 . A micro-liter droplet of deionized water has been successfully transported by a 4 mW laser beam across a 1 cm  1 cm OEW surface. The droplet speed is measured to be 7 mm/s. Light actuation enables complex microfluidic functions to be performed on a single chip without encountering the wiring bottleneck of two-dimensional array of electrowetting electrodes. Published by Elsevier Science B.V.
Scientific reports, 2017
Light activated motion of micron-sized particles with effective forces in the range of micro-Newtons is hereby proposed and demonstrated. Our investigation shows that this exceptional amount of force results from accumulation of light-generated heat by a micron-sized particle that translates into motion due to a phase transition in the nearby water. High-speed imagery indicates the role of bubble expansion and later collapse in this event. Comparing observations with known models reveals a dynamic behavior controlled by polytropic trapped vapor and the inertia of the surrounding liquid. The potential of the proposed approach is demonstrated by realization of disordered optical media with binary light-activated switching from opacity to high transparency.
PIERS Online, 2008
Optical trapping and micromanipulation has developed from an interesting novelty to a powerful and widely used tool, with the capability to move or trap microscopic live biological specimens and measure forces on the order of piconewtons, typical of forces in microbiological systems. Despite this, the range of particles typically trapped or manipulated is quite small, and it is unusual to see applications involving objects other than biological specimens or homogeneous isotropic microspheres, typically polymer or silica. However, particles can be modified or specially fabricated to expand the possible applications of optical tweezers. For example, while non-absorbing homogeneous isotropic spheres cannot be rotated, optically anisotropic spheres can, and can therefore function as microscopic torque sensors, extending the usual translational micromanipulation and force measurement to rotational manipulation and torque sensing. The development of such particles has led to applications in microscale metrology and biophysics, along with potential deployment of optically-driven micromachines in lab-on-a-chip devices. We present an overview of our work on the tailoring of microparticles for versatile optical trapping and micromanipulation. This includes approaches based on controlled chemistry -nanoassembly -and optical microfabrication. Beginning with the production of anisotropic vaterite microspheres, we review some of the applications, and difficulties encountered along the way. Some of these difficulties can be overcome by coating of the vaterite microspheres. We also discuss the use of anti-reflection coating to allow strong trapping of high refractive index particles. The alternative strategy of producing arbitrarily shaped polymer microstructures through two-photon photopolymerization is also discussed. This can be used to produce optically-driven microrotors or structurally anisotropic microspheres to replace vaterites for particular applications.
ACS Nano, 2015
We report a simple yet highly efficient chemical motor that can be controlled with visible light. The motor made from a noble metal and doped silicon acts as a pump, which is driven through a lightactivated catalytic reaction process. We show that the actuation is based on electro-osmosis with the electric field generated by chemical reactions at the metal and silicon surfaces, whereas the contribution of diffusioosmosis to the actuation is negligible. Surprisingly, the pump can be operated using water as fuel. This is possible because of the large ζ-potential of silicon, which makes the electro-osmotic fluid motion sizable even though the electric field generated by the reaction is weak. The electro-hydrodynamic process is greatly amplified with the addition of reactive species, such as hydrogen peroxide, which generates higher electric fields. Another remarkable finding is the tunability of silicon-based pumps. That is, it is possible to control the speed of the fluid with light. We take advantage of this property to manipulate the spatial distribution of colloidal microparticles in the liquid and to pattern colloidal microparticle structures at specific locations on a wafer surface. Silicon-based pumps hold great promise for controlled mass transport in fluids.
Micromachines, 2012
In the last seven years, optoelectronic tweezers using optically-induced dielectrophoretic (ODEP) force have been explored experimentally with much success in manipulating micro/nano objects. However, not much has been done in terms of in-depth understanding of the ODEP-based manipulation process or optimizing the input physical parameters to maximize ODEP force. We present our work on analyzing two significant influencing factors in generating ODEP force on a-Si:H based ODEP chips: (1) the waveforms of the AC electric potential across the fluidic medium in an ODEP chip based microfluidic platform; and (2) optical spectrum of the light image projected onto the ODEP chip. Theoretical and simulation results indicate that when square waves are used as the AC electric potential instead of sine waves, ODEP force can double. Moreover, numerical results show that ODEP force increases with increasing optical frequency of the projected light on an ODEP chip following the Fermi-Dirac function, validating that the optically-induced dielectrophoresis force depends strongly on the electron-hole carrier generation phenomena in optoelectronic materials. Qualitative experimental results that validate the numerical results are also presented in this paper.
Journal of Molecular and Engineering Materials, 2014
An important challenge in the field of materials design and synthesis is to deliberately design mesoscopic objects starting from well-defined precursors and inducing directed movements in them to emulate biological processes. Recently, mesoscopic metal-oxide based Soft Oxo Metalates (SOMs) have been synthesized from well-defined molecular precursors transcending the regime of translational periodicity. Here we show that it is actually possible to controllably move such an asymmetric SOM-with the shape of a 'pea-pod' along complex paths using tailor-made sophisticated optical potentials created by spin-orbit interaction due to a tightly focused linearly polarized Gaussian beam propagating through stratified media in an optical trap. We demonstrate motion of individual trapped SOMs along circular paths of more than 15 µm in a perfectly controlled manner by simply varying the input polarization of the trapping laser. Such controlled motion can have a wide range of application starting from catalysis to the construction of dynamic mesoscopic architectures. * nghosh@iiserkol.ac.in † ayan@iiserkol.ac.in ‡ s.roy@iiserkol.ac.in 1 arXiv:1208.1602v1 [cond-mat.mes-hall]
Proceedings of the National Academy of Sciences, 2011
Noncontact optical trapping and manipulation of micrometer- and nanometer-sized particles are typically achieved by use of forces and torques exerted by tightly focused high-intensity laser beams. Although they were instrumental for many scientific breakthroughs, these approaches find few technological applications mainly because of the small-area manipulation capabilities, the need for using high laser powers, limited application to anisotropic fluids and low-refractive-index particles, as well as complexity of implementation. To overcome these limitations, recent research efforts have been directed toward extending the scope of noncontact optical control through the use of optically-guided electrokinetic forces, vortex laser beams, plasmonics, and optofluidics. Here we demonstrate manipulation of colloidal particles and self-assembled structures in nematic liquid crystals by means of single-molecule-thick, light-controlled surface monolayers. Using polarized light of intensity fro...
Lab Chip, 2010
Optoelectronic tweezers (OET), based on light-induced dielectrophoresis, has been shown as a versatile tool for parallel manipulation of micro-particles and cells (P. Y. Chiou, A. T. Ohta and M. C. Wu, Nature, 2005, 436, 370-372). 1 However, the conventional OET device cannot operate in cell culture media or other high-conductivity physiological buffers due to the limited photoconductivity of amorphous silicon. In this paper, we report a new phototransistor-based OET (Ph-OET). Consisting of single-crystalline bipolar junction transistors, the Ph-OET has more than 500Â higher photoconductivity than amorphous silicon. Efficient cell trapping of live HeLa and Jurkat cells in Phosphate Buffered Saline (PBS) and Dulbecco's Modified Eagle's Medium (DMEM) has been demonstrated using a digital light projector, with a cell transport speed of 33 mm/sec, indicating a force of 14.5 pN. Optical concentration of cells and real-time control of individually addressable cell arrays have also been realized. Precise control of separation between two cells has also been demonstrated. We envision a new platform for single cell studies using Ph-OET.
Applied Physics Letters, 2010
This manuscript presents an approach for selective manipulation of microparticles using polymer-based optically induced dielectrophoretic ͑ODEP͒ devices. A thin film of a bulk-heterojunction polymer ͓a mixture of regioregular poly͑3-hexylthiophene͒ ͑P3HT͒ and ͓6,6͔-phenyl C61-butyric acid methyl ester ͑PCBM͔͒ is used as a light active layer. The ODEP force is generated by "virtual" electrodes ͑the optical images͒ created from a computer-programmable projector to manipulate polystyrene particles. The magnitude of the ODEP force is found to be dependant on the color of illumination light, due to the variation of the absorption coefficient in the P3HT:PCBM film. A noncontact approach is then demonstrated to separate or collect the polymer particles by shrinking one of the two light rings with different colors and diameters. The development of this promising platform may provide a cost-effective approach for ODEP applications.
Optics Letters, 2012
We introduce a method for trapping and arranging microparticles in arbitrary two-dimensional patterns with high flexibility. For this purpose, optoelectronic tweezers based on lithium niobate as photoconductor are used to create virtual electrodes through modulated illumination. The evolving field gradients arrange microparticles due to dielectrophoretic (DEP) forces and enable an all-optical approach for DEP. In order to increase flexibility further, we investigate multiplexed electrode structures for in situ reconfiguration of particle arrangements. Using the alloptical erasure of previously written virtual electrodes, we demonstrate electrode switching and sequential particle trapping in a microchannel for microfluidic applications.
2009
The synthesis of nanostructures has advanced in the last decade to a point where a vast range of insulating, semiconducting, and metallic materials are available in a variety of forms and shapes such as wires, tubes, ribbons, sheets, and spheres. These nanostructures display exceptional physical properties that can be used to realize novel devices such as high-speed electronics, efficient photovoltaics and thermoelectrics, sensitive chemical and biological sensors, nano-light sources such as lasers and light-emitting diodes, and high-frequency resonators. However, a persistent challenge has been the development of a general strategy for manipulation and heterogeneous integration of individual nanostructures with arbitrary shapes and compositions. Development of such methods is essential in transforming nano-sciences into successful nano-technologies that can ultimately affect the society. Several techniques such as microcontact printing, microfluidics, Langmuir-Blodgett, mechanical nano-manipulators, optical tweezers, and fixed-electrode dielectrophoresis have been developed to address this challenge. However, these techniques either lack the capability to manipulate single nanostructures or are unable to do so in a dynamic and large-scale fashion. Optoelectronic tweezers (OET) has emerged as a powerful tool for massively parallel manipulation of polymer-beads and living cells at micron length-scales via optically-induced dielectrophoresis. By combining the optical and electrical trapping capabilities, OET is able to manipulate particles with much lower optical intensities than optical tweezers and unlike fixed electrode dielectrophoresis, OET is capable of dynamic manipulation of single particles over large areas. In this dissertation, we will first introduce OET as an optofluidic platform and characterize the various electrokinetic forces that can be generated in the OET device. Next, we will use these forces for manipulation, sorting, assembly, and patterning of various nanostructures such as semiconducting and metallic nanowires, carbon nanotubes, and metallic spherical nanocrystals. Though the initial demonstrations of OET were limited to manipulation of microscale objects, 2 here, we will explore the capabilities of OET for manipulation of nanoscale particles, establishing it as an important tool for post-synthesis organization and heterogeneous integration of nanostructures. i TABLE OF CONTENTS TABLE OF CONTENTS.
Journal of Microelectromechanical Systems, 2003
We present the results of a device that uses controllable microbubble actuation to manipulate bioparticles. In order to create a useful device for controlling the position of bioparticles, predictable microfluidic actuation is crucial. The goal of this project was to develop fundamental technology that can be used to manipulate single bioparticles (e.g., cells). We use a thermal bubble actuation method to accomplish this goal. Microbubbles have the advantages of relatively simple electronics and fabrication but can be difficult to control. In this paper, we describe two specific accomplishments: the use of micromachined nucleation cavities to precisely localize thermal bubbles and to achieve controllable bubble formation temperatures and bubble dissipation and the demonstration of controllable microbubbles in a new device for particle sorting.
Applied Sciences
The advancement of micro-robotics in recent years has permitted a vast field of active research and application in the biomedical sector. Latest developments in microrobotics point to some ground-breaking work using light for manufacturing as well as actuation. Optical manipulation in three-dimensional space for living biological cells in a minimally invasive manner is crucial for different biomedical applications. This article attempts to provide an overview of the accomplishments and future possibilities of light-powered microbots. An overview of the feasibility of different fabrication techniques and control modalities is compared, along with prospective applications and design considerations of light-powered microbots. A variety of challenges that still prohibit polymeric light-powered microbots from attaining their full potential are pointed out, and viable ways to overcome such challenges are proposed. This study will help future researchers to study and develop the next gener...
Recent Optical and Photonic Technologies, 2010
Particle & Particle Systems Characterization, 2019
Advanced Functional Materials, 2010
Titanium dioxide (TiO 2 ) possesses high photocatalytic activity, which can be utilized to power the autonomous motion of microscale objects. This paper presents the first examples of TiO 2 micromotors and micropumps. UVinduced TiO 2 reversible microfireworks phenomenon was observed and diffusiophoresis has been proposed as a possible mechanism.
Small (Weinheim an der Bergstrasse, Germany), 2016
An electrochemical approach for manufacturing light-driven nanostructured titanium dioxide (TiO2 ) microengines with controlled spatial architecture for improved performance is reported. The microengines based on microscale arrays of TiO2 nanotubes with variable (50-120 nm) inner diameter show a quasi-ordered arrangement of nanotubes, being the smallest tubular entities for catalytic microengines reported to date. The nanotubes exhibit well defined crystalline phases depending upon the postfabrication annealing conditions that determine the microengines' efficiency. When exposed to UV-light, the microarrays of TiO2 nanotubes exhibiting conical internal shapes show directed motion in confined space, both in the presence and absence of hydrogen peroxide. In the former case, two different motion patterns related to diffusiophoresis and localized nanobubble generation inside of the tubes due to the photocatalytic decomposition of H2 O2 are disclosed. Controlled pick-up, transport, a...
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