The optoelectronic tweezers (or optically induced dielectrophoresis (DEP)) have showed the ability to parallelly position a large number of colloidal microparticles without any template. The microparticles can be trapped and driven by the dielectrophoretic forces induced by the optical micropatterns in OET devices. In this chapter, the design and fabrication of flat optoelectronic devices (FOD) and hybrid optoelectronic device (HOD) are described. In the typical FOD, the manipulation modes including filtering, transporting, concentrating and focusing controlling regimes are experimentally demonstrated and analyzed. The controllable rotation of self-assembled microparticle chains in FOD has also been investigated, and a method incorporating the optically induced electrorotation (OER) and AC electroosmotic (ACEO) effects is numerically and experimentally implemented for manipulating microparticle chains. Based on the above research of FOD, a hybrid DEP microdevice HOD is conceptually and experimentally proposed. The HOD integrates with metallic microelectrode layer and the underneath photoconductive layer with projected optical virtual electrodes. FOD and HOD hybrid device enables the active driving, large-scale patterning and local position adjustment of microparticles. These techniques make up the shortcoming of low flexibility of traditional metallic microelectrodes and integrate the merits of both the metal electrode-induced and microimage-induced DEP techniques.
- optoelectronic device
- optically induced electrorotation
- AC electroosmosis
The manipulation technique based on dielectrophoresis (DEP) [1–3] is easy-to-use and requires no moving parts, thus can achieve massively paralleled and non-contact manipulation for particles or cells [4, 5]. It is becoming an important enabling technology in filtering [6–8], concentrating [9–11], transporting [12–14] and flow focusing [15, 16] for microparticles. However, these DEP technologies require design and fabrication of sophisticated electrode structures, which lack flexibility and could not provide real-time alterable electrode-patterns for diverse manipulations. Therefore, how to improve the electrodes’ flexibility and reconfigurability has become the key concern in the extended application of DEP. The proposal of optically induced DEP (ODEP) [17, 18] based on photoconductive effect in an optoelectronic device offered a potential option for the design of highly flexible and real-time reconfigurable optical microelectrodes. ODEP-based optoelectronic device offers more opportunity to develop miscellaneous particle manipulating techniques in biomedical microsystems, although ODEP device could not fully supersede the traditional physical electrode array.
Usually, the sample pretreatment process in microfluidic analysis system should include functional units capable of filtering, concentrating, transporting and focusing microparticles to be applicable to different sample handing requirements [9, 19, 20]. Filtration is essentially a separation technology, such as the insulative DEP approach for particle separation  and the DEP method for characterizing and distinguish stem cells . Once the target particles are isolated after the filtration or separation, the concentration of the target particle population is sometimes low and requires the concentrating steps for the following detection. By now various DEP concentrations of viruses, bacteria have been reported in the literature [22–24]. The function of transporting microparticles nearly runs through the whole process in the microanalysis system, and biological/chemical applications [14, 25–27]. Besides, as an important approach for the continuous single-particle detection and counting, focusing particles into a straight line are also applied in microfluidic devices. The hydrodynamic forces [28, 29] and electrokinetic force [30, 31] are usually employed to realize flow focusing. However, the above sample handling approaches require fabricating complex multi-functional electrode array or structures to achieve versatile manipulation of the micro/nano bio-particles, and the previous work also has difficulties in providing real-time alterable electrode patterns to accommodate different manipulation requirements. So, the promotion of DEP technology in the application of the micro/nano manipulation faces some restrictions. In recent years, Chiou et al. [18, 32] reported parallel manipulation of single particles using a variant of DEP mechanism—ODEP mechanism which offers the ability to trap single particles parallelly and massively. ODEP has also been used to discriminate normal oocytes at a certain frequency . However, the manipulation regimes still need more systematic study. Therefore, this chapter will experimentally verify and analyze the optical pattern and controlling regimes for filtering, transporting, concentrating and focusing based on ODEP.
In addition to the above manipulation modes for microparticle or cells, the ODEP-based optoelectronic device could serve as a more powerful tool to spatially manipulate and regulate the posture, orientation and position of microparticle chains or other microstructures. The previous methods for manipulating micro-objects usually need templates, physical or chemical reaction process involving more extra techniques . Many of the created particle chains or closely linked chains are immobilized, and their relative positions cannot be stably controlled. The ODEP (also called optoelectronic tweezers, OETs) has showed the ability to parallelly position colloidal particles without any template [18, 35]. The microparticles can be trapped and driven by the DEP forces induced by the optical micropatterns in optoelectronic devices [36, 37]. However, the rotation of assembled microparticle chains by OETs has rarely been investigated, and the degree of freedom for varying the postures, positions or orientations of the microparticle chains still has limitations. To demonstrate the promoted ability of optoelectronic devices, this chapter will experimentally demonstrate the method incorporating optically induced electrorotation (OER) and alternating current electroosmotic (ACEO) effects, for the formation and motion control of microparticle chains.
By comprehensively analyzing the traditional physical electrode array and ODEP-based optoelectronic device, we further developed a hybrid optoelectronic device (HOD) that could integrate the merits of both the traditional physical electrode array and ODEP-based optoelectronic device. The ODEP-based optoelectronic device offers a flexible and real-time dynamic manipulating scheme but needs more external optic devices; the traditional physical electrode array offers a more stable working status and higher integration but lack the ability of real-time particle manipulation. In Section 5 of this chapter, HOD is conceptually proposed, and its prototype is designed and fabricated. This type of hybrid device enables the active driving, large-scale patterning and locally position adjustment of microparticles.
2. Design and fabrication of optoelectronic devices
2.1. The design and fabrication of flat optoelectronic devices
The flat optoelectronic devices (FOD) consisted of several layers, including indium tin oxide (ITO) and photoconductive layers. To fabricate photoconductive layer of FOD chip (as shown in Figure 1(a)), 50-nm doped hydrogenated amorphous silicon (n +
For the fabricated FOD chip as shown in Figure 1, the photoconductor has a high electric impedance (about 1 × 10–6 S/m, for example) prior to illumination, so at this time the majority of the applied voltage drops across the photoconductive layer, which causes a weak, uniform electric field inside the liquid layer. At this state, no ODEP force generates. When a projected light source hits the amorphous silicon layer (photoconductive layer), electron-hole pairs are excited, thus decreasing the impedance of the photoconductive layer by thousands of times (~5000 times, for example), and the electrical conductivity of the photoconductor increases to ~5 × 10-3 S/m. At this state, the virtual electrodes are formed in the photoconductor, and the voltage drop across the liquid layer in the illuminated area is much higher than that in the dark area. Consequently, the bright-dark pattern induces a non-uniform electric field inside this device. The dense electric filed lines appear at the illuminated areas, and the sparse field lines appear at the dark areas as shown in Figure 1b. Thus, a DEP force acting on microparticles can be induced in the liquid chamber(or called fluidic chamber), and the time-averaged DEP force acting on the spherical microparticle suspended inside liquid chamber can be mathematically described as follows 
2.2. The design and fabrication of hybrid optoelectronic device (HOD)
The hybrid optoelectronic device (HOD) has a more compact structure, integrating another layer of physical electrode array above the photoconductive layer. In another word, the HOD (several cm2) integrates with photoconductive layer and metal microelectrodes including the quadrupole electrodes and spiral electrodes as shown in Figures 2 and 3. Figure 2 is the schematic design diagram of this microdevice. This HOD has a hamburger-like structure. The upper plate was transparent ITO conductive glass. The lower plate included the photoconductive layer (or called photoconductor) and the bottom glass slide. The photoconductive
The microelectrode layer contains of four parallel spiral electrodes as presented in Figure 2. When the four spiral electrode elements are energized with sinusoidal voltages with relative phase differences, a travelling electric field is generated and travels along the radial direction of the spiral array. A rotating electric field is also generated in the central free-space region denoted as central region. The spiral electrodes have the advantages of equivalent driving force to the particles at an arbitrary peripheral position. The quadrupole electrodes are located in the central area of spiral electrode array. The central region is surrounded by the quadrupole electrodes as shown in Figure 3. The geometrical shape of central region somewhat influences the distribution of the electric field around, and thus the sharp geometry should be avoided.
The experimental platform was established by assembling commercial optics, projector and an upright microscope. A digital micromirror device (DMD)-based projector (SHARP XG) was used as both the light source (via its dc lamp) and the interface between DMD driver circuit and the computer. The DMD forms a light image (or called optical pattern) according to the output signal of the PC’s external monitor port. The optical image at the output of the projector lens was collimated, collected and reflected through the reflector at 45 degree to the horizontal and upward directed into a 10X driven lens from the lower location. The optical image was focused by the object lens and finally projected onto the photoconductive layer of ODEP device.
3. Manipulation modes and controlling regimes in FOD
Usually, the impurities or non-target stuff (such as some types of microparticles) in the raw sample should be filtered firstly in the pre-treatment for the sample. The filtering experiment was implemented via an optical line scanning as shown in Figure 4. In the filtering experiment, with an applied 20 Vpp at 600 kHz, the normal pollen grains with diameters of 17–21 µm and most of the 30-µm diameter polystyrene particles were driven by the optical line with a width of ~70 µm from the upper area (Figure 4a-b) toward the bottom area of the view (Figure 4c-d). In contrast, the degenerative pollen grains and few polystyrene particles were left behind and stayed in their original positions. Therefore, the filtering function was able to be realized. This separation phenomenon is probably because the particles left behind were difficult to be polarized relative to the normal ones, which resulting in a much smaller DEP force for the abnormal ones. As long as the optical line velocity did not exceed the maximum synchronous velocity (MS-velocity) of the normal particles  (i.e., maximum filtering velocity), the filtering function could be achieved. If the optical line velocity exceeded the MS-velocity, all particles would be left behind the scanning optical line, which made the filtering unavailable. This filtering experiment demonstrated the feasibility of the ODEP filtering.
DEP can trap single particles and then transport the particles to desired positions, and the moving paths can be programed and controlled. As shown in, under the AC voltage of 20 Vpp and 1 MHz, two 30-µm diameter particles (Figure 5a) were trapped individually and moved along the programmed motion paths (two particles were marked by numbers 1 and 2 shown in Figure 5). These two particles were able to move simultaneously according to their own routings. The optical patterns can be controlled by the ODEP controlling software developed by our group. The polystyrene particles were always trapped by two optical rings those have an external diameter of ~150 µm and an interior diameter of ~40 µm during the transporting. Particle 1 and particle 2 kept moving and following the kinetic motion of the optical rings from the initial positions at the upper area (Figure 5a) to the lower area (Figure 5h) of the snapshot. The two particles moved simultaneously and always kept away from each other during the transporting, as shown in Figures 5b–g until they exchanged their positions and arrived at the terminative destinations.
In many biochemical applications, the reaction is very weak between a single bioparticle and other reagent, but a concentrated population of particles can react with other reagent intensively with much more obvious phenomena. Thus, when the raw sample was filtered and transported to the target locations, the selected particles would need concentration for the following detecting operations. The experiment presented in Figure 6 serves as a typical example for presenting the concentrating regime of ODEP.
With an applied voltage of 20 Vpp at 800 kHz, at an arbitrary area (Figure 6a), the microlight pattern with a ring-shape can be used to collect a population of particles and can move the trapped particle population to an arbitrary location. The microparticles stayed inside the optical ring with a uniformly patterned array during the concentrating process (Figure 6a-f), and the distances between adjacent particles always kept the same. At this voltage magnitude, due to the dipole-to-dipole interaction between adjacent particles, the distance between adjacent particles is difficult to eliminate. The distances between particles were obviously larger than the particle diameter (Figure 6). If the voltage increased, the ODEP force would increase, which seems to drive the particles more concentrated. However, it is not that case when the voltage was larger than 20 Vpp in this experiment, because the increased voltage also enforced the interactional repelling force between particles.
In many biochemical analyses, focusing is another important postprocessing mode apart from the procedures of concentrating particles. Focusing is mainly utilized to continuously and automatically count and detect individual particles. The ability to focus and eject particles based on ODEP is demonstrated in Figure 7.
In this study, a “drip nozzle” formed by the optical micropattern projected on the photoconductive layer was used to focus the microparticles in a straight sample flow and eject particles one by one. The optical lines forming the “drip nozzle” were set with a width of around the diameter of microparticles (Figure 7). The geometrical shape of optical pattern was real-time controlled so that the “drip nozzle” could continuously deform according to the current distribution of microparticles. The particles with 30-µm diameter moved out from the “drip nozzle” under the repelling ODEP force. This relative motion could also be regarded as the linear flow of particles relative to optical patterns. With an applied 24 Vpp at 600 kHz, the microparticles underwent negative ODEP force which always drove particles away from the virtual electrodes (optical micropattern) and thus kept particles horizontally swam in the virtual channel and then swam out of the “drip nozzle” accompany by the deformation of the optical virtual channel and “drip nozzle.” Finally, the microparticles were focused into a straight particle line and had obvious spacing distances between particles 1 and 4 (Figures 7e–f). In this operation mode, there was no substantial fluidic flow to assist the focusing of the microparticles. The focusing efficiency grew when the optical line width increased but less than twice the particle diameter.
4. Manipulation of self-assembled microparticle chains by electroosmotic flow-assisted electrorotation in FOD
4.1. Background for microparticle chain manipulation
The microscopic particle chain is a common form of assembled particles, which involves in the colloidal, biological, electronic, photonic, magnetic fields. It plays an important role in these fields, as it serves as a link between the nanoscale world and meso- or macroscale objects. Currently, the methods for manipulating microparticle chains have become crucial for developing techniques on patterning magnetic nanoparticle arrays , forming regular superstructures by nanoparticles , constructing strings of particles , and creating multicellular assemblies  and live colloidosome structures . In order to flexibly manipulate particle chains, various methods were developed, including the physical methods based on electric field, geometric constraint, dipole-dipole interactions or surface roughness direction  and the chemical methods based on linker molecules, oriented aggregation or non-uniform stabilizer distributions . In this study, the formation and rotational manipulation of microparticle chains in real time are experimentally demonstrated by using optically induced electrorotation (OER) and ACEO flow in FOD.
4.2. Experiment setup and working principle
The structure of the OET device and the scheme for rotating particle chains are conceptually illustrated in Figure 8. The equivalent circuit of the OET device is shown in Figure 8b. The device is composed by the upper and lower indium tin oxide (ITO) slides, photoconductive layer (hydrogenated amorphous silicon,
The principle of the light-dark binary image induced rotating electric field (e-field) is indicated in Figure 8a–b. The a-Si:H layer has different impedances on light and dark sides, which leads to the amplitude and phase difference in the electric potentials at upper surface ( ), photoconductive layer/medium interface in light area ( ) and dark area ( ). In a particular frequency range, these three AC potentials can create a rotating e-field in fluidic medium around the border between light and dark regions, which will lead to self-rotating of the one-dimensional particle chains due to the interaction between the dipole moment of particle chain and rotating e-field.
According to equivalent circuit of the OET device shown in Figure 8b, and assuming that the impedance of conjunction between the light and dark regions in the a-Si:H layers is very large indicating no current flows across the border, the potential phasor at the bottom surface of fluidic chamber denoted as Φ
In (3), the subscript
is the capacitance of
ACEO flow is also induced at appropriate frequencies in the OET or ODEP device. ACEO flow is the motion of fluid due to an interaction between an e-field and the DL induced at medium/a-Si:H interface as shown in Figure 8c. The tangential e-field mainly arises around the edges of optical micropatterns. Therefore, the ACEO flow mainly occurs around the optical micropatterns projected on the photoconductive layer. ACEO flow lets the particle chains traveling in a nearly circular trajectory as shown in Figure 8c. After applying the voltage, counterions accumulate in the DL mainly within the illuminated region. Due to the distortion of electrical field induced by the optical pattern, a tangential component of e-field arises round the medium/a-Si:H interface. As a result, the ions in DL are subjected to the tangential electrostatic force along the a-Si:H surface. This force is then transmitted to the fluid and drive the boundary liquid to flow with a slip time-averaged velocity that can be calculated by using the Helmholtz–Smoluchowski equation as in Refs. [53, 54]
In experiment, the polystyrene (PS) microparticles did not form particle chains with a low voltage, but would start to form particle chains when the voltage increases to a threshold value. The PS particles with a diameter of 4 μm self-assembled into chains within the fluidic medium when the applied voltage was increased to 15 Vpp. The kinetic motion of particle chains could be enhanced with the increased voltage until 28 Vpp. The self-rotation of particle chain around its geometric center was obtained inside fluidic medium at 700 kHz because the ACEO flow can approximately be dismissed at these relatively higher frequencies. As shown in Figure 8d, the two ends of particle chains exchanged their positions after 2.8 s and had accomplished the first half-cycle of the rotation. Then, the particle chains continued to self-rotate through the other half-cycle, and it took only 1.6 s. The rotation rate of particle chain varied with time within a single period.
At lower frequencies, the particle chains circularly travelled around the center of fluid roll generated by the optically induced ACEO effect. As indicated in Figure 8e, the ACEO flow assisted particle chain rotation can be decomposed into two component motions: the self-rotation and orbital movement of the entire particle chain. Figure 8f shows the optically projected ring-shaped micropattern and the formed microparticle chains around the optical ring. The ACEO flow assisted microparticle chain rotation at 480 kHz is shown in Figure 8g. The particle chains were moving closer to the edge of optical pattern and turned around through the vertical planes after a short time (less than one second or a few seconds). Then, the particle chains were moving away from the optical ring along the circular path. They continued to turn around at the other corner of the circular path and then moved closer to optical ring again. The orbital moving of particle chains was not uniform motion and the vertical plane in which the circularly orbital movement occurred was approximate parallel to the diametrical dimension of optical ring. The complex movement of particle chains exhibited a three-dimensional (3D) movement of distributed particle chains that had more degrees of freedom than the 2D motion. These results offer more opportunities for spatially controlling the position, posture and orientation of particle chains for the applications regarding electrics, mechanics, optics and biodevices.
5. Manipulation of microparticles in a prototypical HOD
5.1. Integrated design and fabrication of metal electrode array and photoconductive layer
The virtual electrode is actually the microlight image in which we project in vertical direction on the photoconductive layer. It can precisely locate single microparticles and dynamically drive them. On the silicon nitride layer, we fabricated the planar microelectrode structure by photolithography. The microlight pattern could be designed according to specific experimental or application requirement, and it may be, for example, a linear or a spiral microelectrode array. In practical operations, we usually imposed low voltage to prevent insulating layer from breaking down by strong electric field. The spacer to mechanically support the fluidic chamber can be fabricated by polydimethylsiloxane (PDMS) or just double-sided tapes. The electric pads of microelectrodes were led out and connected to external PCB by gold wires. Then, the connectors on PCB were further connected to the external signal generator. The HODs were finally fabricated as shown in Figure 9.
The microelectrode array was fabricated by the depositing about 2000nm-thick layer of aluminum or gold on top of the insulating layer through electron beam evaporation. Then, the spiral pattern (Figure 9) was produced by standard or “lift-off” lithography process. In the standard lithography process, the corrosion rate needs to be strictly controlled in order to prevent possible damage to the insulating layer as well as the photoconductive layer. In our study, we had also sputtered gold over the silicon carbide layer (insulating layer) and then fabricated microelectrodes. Sputtering process and standard lithography process had a certain impact on the layer-to-layer electrical connections. In general, after the deposition by electron beam evaporations, the insulating property between the aluminum layer and the substrate is better. This usually could meet the insulating requirement of layers in this device. On the other hand, depositing gold by sputtering method onto the photoconductive film usually involved a relatively higher sputtering power or higher temperature in vacuum chamber (typically the sputtering involved a much higher temperature than the electron beam evaporation). These process features may result in that the
5.2. Experiment result of the distribution of particles when light pattern is off
In this experiment, a 10 V peak-to-peak (Vpp) AC bias with a frequency of 1 MHz is applied between the top and bottom ITO electrodes, and the light pattern is not projected onto the HOD. The metal electrodes might be connected to the bottom ITO layer by a very low resistance through the Schottky contact between the metal and photoconductive layer and/or through the local defects of
5.3. Experiment result of the particle’s assembly under the assistance of light pattern
Before the microlight pattern was projected onto the HOD, the particles had distributed along the trend of spiral electrodes (Figure 10). The particles could be actuated by moving the microlight pattern when the light pattern (the diameter was nearly 120μm in this experiment) was projected as shown in Figure 11. The light pattern produced by LED can meet the needs of the power for operation. The spatial interval between the particles can be manipulated by adjusting the magnitude of the voltage applied between the upper and lower ITO layers, and the increase in voltage leads to larger separation between the particles. The metallic electrode array was not electrically energized. As shown in Figure 11, the DEP forces acting on microparticles were generated due to the participation of both the planar metal electrodes and microlight pattern in the electric field generated by the voltage applied between the upper and lower ITO layers. The curve arrow indicated the moving track of the light spot. Particles along spiral electrode and away from the white dotted arc were gradually moving closer to the position marked by the dotted arc due to the repulsive force from the light spot. This HOD can meet the need of the large-scale particles manipulation requiring the particles to form specific geometrical array. In this device, incorporation of metal microelectrode array was more suitable for the situation that the required separation between particles was small, and the tracks of particle distribution are more elaborate than the virtual electrode produced by light projection system. That is because microlight pattern needs to be produced by using even more complex and higher cost optical device, and the Gaussian distribution of light pattern border, the diffraction and the scattering may also limit the light pattern to have the smaller, finer and sharper geometry. This combination of metal microelectrode and light-induced virtual electrode in HOD is appropriate for the situation that the area for arranging particles is compact, and the particular geometric form (like curve shape distribution) is expected. This technique may also have the potential for manipulating large number of cells and be incorporated into the self-organization scheme for constructing multicellular structure [55, 56], in order to develop biomaterials applied in regenerative medicine.
In this chapter,
This work was supported by grants from the National Natural Science Foundation of China (51505127), the Natural Science Foundation of Jiangsu Province (BK20161197), the Changzhou Sci&Tech Program (CE20165029), and the Fundamental Research Funds for the Central Universities of China (2015B04414). Parts of this chapter are reproduced from authors’ recent conference publication [40, 48].
Medoro G, Nastruzzi C, Guerrieri R, Gambari R, and Manaresi N. Lab on a chip for live-cell manipulation. IEEE Design & Test of Computers. 2007; 24(1): 26-36.
Vahey MD and Voldman J. An equilibrium method for continuous-flow cell sorting using dielectrophoresis. Analytical Chemistry. 2008; 80(9): 3135-3143.
Wang X-B, Huang Y, Gascoyne PRC, and Becker FF. Dielectrophoretic manipulation of particles. IEEE Transactions on Industry Applications. 1997; 33(3): 660-669.
Gascoyne PRC and Vykoukal JV. Dielectrophoresis-based sample handling in general-purpose programmable diagnostic instruments. Proceedings of the IEEE. 2004; 92(1): 22-42.
Small WR, Stoyanov SD, and Paunov VN. Scaffold free fabrication of linear multicellular assemblies by dielectrophoretic hydrogel trapping technique. Biomaterials Science. 2013; 1(9): 996-1002.
Flanagan LA, Lu J, Wang L, Marchenko SA, Jeon NL, Lee AP, and Monuki ES. Unique dielectric properties distinguish stem cells and their differentiated progeny. Stem Cells. 2008; 26(3): 656-65.
Iliescu C, Tresset G, and Xu G. Dielectrophoretic field-flow method for separating particle populations in a chip with asymmetric electrodes. Biomicrofluidics. 2009; 3(4): 044104-10.
Eguchi M, Imasato H, Yamakawa T, and Ieee, Separation of blood cells by employing dielectrophoresis and traveling-wave electric fields. 2012 World Automation Congress; 2012.
Schonfeld F, Griebel A, Konrad R, Rink S, and Karlsen F. Development of a [mu]-concentrator using dielectrophoretic forces. Journal of the Association for Laboratory Automation. 2002; 7(6): 130-134.
Yokokawa R, Manta Y, Namura M, Takizawa Y, Le NCH, and Sugiyama S. Individual evaluation of DEP, EP and AC-EOF effects on lambda DNA molecules in a DNA concentrator. Sensors and Actuators B-Chemical. 2010; 143(2): 769-775.
Cheng IF, Chang HC, Chen TY, Hu CM, and Yang FL. Rapid (<5 min) identification of pathogen in human blood by electrokinetic concentration and surface-enhanced raman spectroscopy. Scientific Reports. 2013; 3: 2365. DOI: 10.1038/srep02365
Crews N, Darabi J, Voglewede P, Guo F, and Bayoumi A. An analysis of interdigitated electrode geometry for dielectrophoretic particle transport in micro-fluidics. Sensors and Actuators B: Chemical. 2007; 125(2): 672-679.
Dos Santos MVP, Lima LPB, Mayer RA, Beron F, Pirota KR, and Diniz JA. Dielectrophoretic manipulation of individual nickel nanowires for electrical transport measurements. Journal of Vacuum Science & Technology B. 2015; 33(3): 031804.
Hossan MR, Dutta P, Dillon R, and ASME. Numerical investigation of DC dielectrophoretic particle transport. ASME Fluids Engineering Division Summer Meeting—2014, Vol 2: Fora; 2014.
Fu LM, Yang RJ, Lin CH, Pan YJ, and Lee GB. Electrokinetically driven micro flow cytometers with integrated fiber optics for on-line cell/particle detection. Analytica Chimica Acta. 2004; 507(1): 163-169.
Yao B, Luo GA, Feng X, Wang W, Chen LX, and Wang YM. A microfluidic device based on gravity and electric force driving for flow cytometry and fluorescence activated cell sorting. Lab on a Chip. 2004; 4(6): 603-607.
Jamshidi A, Pauzauskie PJ, Schuck PJ, Ohta AT, Chiou PY, Chou J, Yang PD, and Wu MC. Dynamic manipulation and separation of individual semiconducting and metallic nanowires. Nature Photonics. 2008; 2(2): 85-89.
Chiou PY, Ohta AT, and Wu MC. Massively parallel manipulation of single cells and microparticles using optical images. Nature. 2005; 436(7049): 370-372.
Tsutsui H and Ho CM. Cell separation by non-inertial force fields in microfluidic systems. Mechanics Research Communications. 2009; 36(1): 92-103.
Cheng IF, Chang HC, Hou D, and Chang HC. An integrated dielectrophoretic chip for continuous bioparticle filtering, focusing, sorting, trapping, and detecting. Biomicrofluidics. 2007; 1(2): 021503.
Hawkins BG, Smith AE, Syed YA, and Kirby BJ. Continuous-flow particle separation by 3D insulative dielectrophoresis using coherently shaped, dc-biased, ac electric fields. Analytical Chemistry. 2007; 79(19): 7291-7300.
Yeo WH, Lee HB, Kim JH, Lee KH, and Chung JH. Nanotip analysis for dielectrophoretic concentration of nanosized viral particles. Nanotechnology. 2013; 24(18):185502. DOI: 10.1088/0957-4484/24/18/185502
Maruyama H, Kotani K, Masuda T, Honda A, Takahata T, and Arai F. Nanomanipulation of single influenza virus using dielectrophoretic concentration and optical tweezers for single virus infection to a specific cell on a microfluidic chip. Microfluidics and Nanofluidics. 2011; 10(5): 1109-1117.
Cho YK, Kim TH, and Lee JG. On-chip concentration of bacteria using a 3D dielectrophoretic chip and subsequent laser-based DNA extraction in the same chip. Journal of Micromechanics and Microengineering. 2010; 20(6): 1023-1035.
Sen AK and Sajeesh P. Electrokinetic transport and separation of droplets in a microchannel. Microfluidics and Nanofluidics. 2014; 17(1): 97-106.
Wang CH, Wang XZ, and Jiang ZD. Dielectrophoretic driving of blood cells in a microchannel. Biotechnology & Biotechnological Equipment. 2011; 25(2): 2405-2411.
Khoshmanesh K, Nahavandi S, Baratchi S, Mitchell A, and Kalantar-Zadeh K. Dielectrophoretic platforms for bio-microfluidic systems. Biosensors & Bioelectronics. 2011; 26(5): 1800-1814.
Zhang JM, Aguirre-Pablo AA, Li EQ, Buttner U, and Thoroddsen ST. Droplet generation in cross-flow for cost-effective 3D-printed “plug-and-play” microfluidic devices. RSC Advances. 2016; 6(84): 81120-81129.
Pittermannova A, Ruberova Z, Zadrazil A, Bremond N, Bibette J, and Stepanek F. Microfluidic fabrication of composite hydrogel microparticles in the size range of blood cells. RSC Advances. 2016; 6(105): 103532-103540.
Song YX, Wang CF, Li MQ, Pan XX, and Li DQ. Focusing particles by induced charge electrokinetic flow in a microchannel. Electrophoresis. 2016; 37(4): 666-675.
Li D, Lu XY, Song YX, Wang JS, Li DQ, and Xuan XC. Sheathless electrokinetic particle separation in a bifurcating microchannel. Biomicrofluidics. 2016; 10(5): 1-13.
Park S, Pan C, Wu T-H, Kloss C, Kalim S, Callahan CE, Teitell M, and Chiou EPY. Floating electrode optoelectronic tweezers: light-driven dielectrophoretic droplet manipulation in electrically insulating oil medium. Applied Physics Letters. 2008; 92(15): 151101.
Hwang H, Lee D-H, Choi W, and Park J-K. Enhanced discrimination of normal oocytes using optically induced pulling-up dielectrophoretic force. Biomicrofluidics. 2009; 3(1): 14103.
Kitching H, Shiers MJ, Kenyon AJ, and Parkin IP. Self-assembly of metallic nanoparticles into one dimensional arrays. Journal of Materials Chemistry A. 2013; 1(24): 6985-6999.
Hwang H and Park JK. Optoelectrofluidic platforms for chemistry and biology. Lab Chip. 2011; 11(1): 33-47.
Zhu XL, Yin ZF, and Ni ZH. Dynamics simulation of positioning and assembling multi-microparticles utilizing optoelectronic tweezers. Microfluidics and Nanofluidics. 2012; 12(1-4): 529-544.
Yang YJ, Mao YF, Shin KS, Chui CO, and Chiou PY. Self-locking optoelectronic tweezers for single-cell and microparticle manipulation across a large area in high conductivity media. Scientific Reports. 2016; 6: 22630. DOI: 10.1038/srep22630
Morgan H and Green NG. AC electrokinetics: colloids and nanoparticles. Microtechnologies and Microsystems Series, 2. 2003, Philadelphia, PA: Research Studies Press.
Zhu XL, Yin ZF, Gao ZQ, and Ni ZH. Experimental study on filtering, transporting, concentrating and focusing of microparticles based on optically induced dielectrophoresis. Science China-Technological Sciences. 2010; 53(9): 2388-2396.
Zhu XL, Yi H, Ni ZH, and IEEE. Novel design of multiphase optoelectronic microfluidic device for dielectric characterization of single biological or colloidal particles. 2009 ICME International Conference on Complex Medical Engineering. 2009. 542-547.
Zhu XL, Yi H, and Ni ZH. Frequency-dependent behaviors of individual microscopic particles in an optically induced dielectrophoresis device. Biomicrofluidics. 2010; 4(1) :013202. DOI:10.1063/1.3279788
Schelhas LT, Farrell RA, Halim U, and Tolbert SH. Directed self-assembly as a route to ferromagnetic and superparamagnetic nanoparticle arrays. Advanced Functional Materials. 2014; 24(44): 6956-6962.
Zhou F, Xie MX, and Chen DY. Structure and ultrasonic sensitivity of the superparticles formed by self-assembly of single chain janus nanoparticles. Macromolecules. 2014; 47(1): 365-372.
Termonia Y. Entropy-driven self-assembly of nanoparticles into strings. Colloids and Surfaces A: Physicochemical and Engineering Aspects. 2014; 447: 23-27.
Brandy M-L, Cayre OJ, Fakhrullin RF, Velev OD, and Paunov VN. Directed assembly of yeast cells into living yeastosomes by microbubble templating. Soft Matter. 2010; 6(15): 3494-3498.
Fakhrullin RF, Brandy M-L, Cayre OJ, Velev OD, and Paunov VN. Live celloidosome structures based on the assembly of individual cells by colloid interactions. Physical Chemistry Chemical Physics. 2010; 12(38): 11912-11922.
Kraft DJ, Ni R, Smallenburg F, Hermes M, Yoon K, Weitz DA, van Blaaderen A, Groenewold J, Dijkstra M, and Kegel WK. Surface roughness directed self-assembly of patchy particles into colloidal micelles. Proceedings of the National Academy of Sciences of the United States of America. 2012; 109(27): 10787-10792.
Zhu X. Electroosmotic flow assisted rotation of self-assembled microparticle chains using optoelectronic tweezers. in IEEE International Conference on Nano/micro Engineered and Molecular Systems. 2015.
Zhu X. Manipulation of self-assembled microparticle chains by electroosmotic flow assisted electrorotation in an optoelectronic device. Micromachines. 2015; 6(9): 1387-1405.
Jones TB. Electromechanics of Particles. 1995, New York: Cambridge University Press.
Jones TB. Basic theory of dielectrophoresis and electrorotation. IEEE Engineering in Medicine and Biology Magazine. 2003; 22(6): 33-42.
Jiang ZH, He XD, Han JC, Zhang BM, and Du SY. Fractal characterization of the dipole moments of dielectric particle chains. Journal of Electrostatics. 1998; 44(1-2): 47-51.
Ramos A, Morgan H, Green NG, Gonzalez A, and Castellanos A. Pumping of liquids with traveling-wave electroosmosis. Journal of Applied Physics. 2005; 97(8): 084906.
Lyklema J. Fundamentals of Interface and Colloid Science, Volume II: Solid–Liquid Interfaces. Vol. 2. New York: Academic Press; 1995.
Zhu X, Gojgini S, Chen T-H, Teng F, Fei P, Dong S, Segura T, and Ho C-M. Three dimensional tubular structure self-assembled by vascular mesenchymal cells at stiffness interfaces of hydrogels. Biomedicine & Pharmacotherapy. 2016; 83: 1203-1211.
Zhu X and Yang H. In-silico constructing three-dimensional hollow structure via self-organization of vascular mesenchymal cells. in The 16th International Conference on Nanotechnology (IEEE NANO 2016). 2016. Sendai, Japan: IEEE.