Guiren Wang

University of South Carolina, Columbia, South Carolina, United States

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Publications (24)39.47 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: A donut-shaped laser that is simultaneously impacted by the coma, astigmatism and spherical aberrations in a high NA focusing system is numerically simulated based on the vectorial diffraction theory. The full-width half-maximum, intensity characters, and dimensions of the dark cores of the donut-shaped laser on the focal plane are quantitatively analyzed. The results are highly consistent with the annular-shaped nano-patterns that are experimentally fabricated by our purpose-built laser direct writing system. The mechanism of asymmetric nano-patterns fabricated through laser writing lithography is also revealed.
    Journal of optics 12/2014; 16(12). · 2.01 Impact Factor
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    ABSTRACT: Nanoscale functional structures are indispensable elements in many fields of modern science. In this paper, nanopillar array with a pillar diameter far smaller than Abbe's diffraction limit is realized by a new kind of continuous wave (CW) laser direct lithography technology. With atomic force microscopy technology, the average diameter of nanopillars on thin OIR906 photoresist film is about 65 nm and the smallest diameter is 48 nm, which is about 1/11 of the incident laser wavelength. Also, the influences of coma and astigmatism effects to the shape and size of nanopillar are numerically simulated by utilizing vector integral. As far as we know, it is the first time that nanopillar array is implemented by a donut-shaped 532-nm visible CW laser. The study presents a new, simple, inexpensive, and effective approach for nanopillar/pore array fabrication.
    Nanoscale Research Letters 06/2013; 8(1):280. · 2.52 Impact Factor
  • Cuifang Kuang, Ding Luo, Xu Liu, Guiren Wang
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    ABSTRACT: With unique capability of biomedical diagnosis and chemical analysis, microfluidics has received worldwide applications in various fields. Multiple methods have been proposed to measure velocity profile of flow in microchannels, among which the laser induced fluorescence photobleaching anemometer (LIFPA) provides great performance with not only high spatial resolution but also superior temporal resolution compared with former systems. The measurement sensitivity and temporal resolution of LIFPA system is largely determined by the speed of fluorescence photobleaching effect, meaning that a half-life decay time as short as possible is required to achieve superior temporal resolution. In this paper, several experiments are done to investigate the influence over the half-life decay time by several factors, including incident laser power, dye concentration, buffer concentration and fluidic pH value. Based on the experimental results, a certain dye solution is specially designed, which demonstrates an extremely fast photobleaching effect with a half-life decay time of about 55 μs. Fluorescent dye solution with such a fast photobleaching effect is potentially applicable in the analysis of transient flows, such as the rise time of electroosmotic flow, where high temporal resolution is required.
    Measurement. 05/2013; 46(4):1393–1398.
  • Ding Luo, Cuifang Kuang, Xu Liu, Guiren Wang
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    ABSTRACT: A novel fluorescent dye named ATTO 390 is tested and verified to be applicable in STED microscopy with great performance. The experimental configuration uses a 405nm continuous wave (CW) laser as excitation beam and a 532nm CW laser as depletion beam. The two collinear beams are focused on the dye using an objective with NA=1.4 and the fluorescence is detected by avalanche photodiode detector. With short wavelength in violet band, high fluorescence quantum yield, good photostability, and relatively low Ps demonstrated in a series of experiments, ATTO 390 is proved to be a potential good choice for fluorescent dye in STED microscopy.
    Optics & Laser Technology 02/2013; · 1.37 Impact Factor
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    ABSTRACT: The present work demonstrates the use of a dielectrophoretic lab-on-a-chip device in effectively separating different cancer cells of epithelial origin for application in circulating tumor cell (CTC) identification. This study uses dielectrophoresis (DEP) to distinguish and separate MCF-7 human breast cancer cells from HCT-116 colorectal cancer cells. The DEP responses for each cell type were measured against AC electrical frequency changes in solutions of varying conductivities. Increasing the conductivity of the suspension directly correlated with an increasing frequency value for the first cross-over (no DEP force) point in the DEP spectra. Differences in the cross-over frequency for each cell type were leveraged to determine a frequency at which the two types of cell could be separated through DEP forces. Under a particular medium conductivity, different types of cells could have different DEP behaviors in a very narrow AC frequency band, demonstrating a high specificity of DEP. Using a microfluidic DEP sorter with optically transparent electrodes, MCF-7 and HCT-116 cells were successfully separated from each other under a 3.2 MHz frequency in a 0.1X PBS solution. Further experiments were conducted to characterize the separation efficiency (enrichment factor) by changing experimental parameters (AC frequency, voltage, and flow rate). This work has shown the high specificity of the described DEP cell sorter for distinguishing cells with similar characteristics for potential diagnostic applications through CTC enrichment.
    Biomicrofluidics 01/2013; 7(1). · 3.39 Impact Factor
  • Guiren Wang, Fang Yang, Wei Zhao
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    ABSTRACT: We report an electrokinetically driven micro-turbulent flow phenomenon in a microchannel, where the Reynolds number (Re) based on bulk flow and channel width is in the order of 10. As we know the critical Re in a channel flow is about 2000 and a pressure driven flow with Re in the order of 10 is definitely laminar, hence, the fluid mixing is very flow. Although there have been electrokinetical micromixers published that can increase mixing, the flows are believed not to be turbulence, but chaotic. Here we design a novel electrokinetically forced pressure driven flow with Re in the order of 10 to achieve turbulence like flow. To confirm that the flow is turbulence, Laser Induced Fluorescence Photobleaching Anemometer (LIFPA) is used to measure the corresponding flow velocity features. LIFPA enables ultrahigh temporal and spatial resolution measurement. We report the measured flow features: high dissipation and diffusion rate, multiscale continuous power spectra and 3-D flow. The results open a new view of turbulence at microscale.
    12 AIChE Annual Meeting; 10/2012
  • Cuifang Kuang, Rui Qiao, Guiren Wang
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    ABSTRACT: We present a non-intrusive molecular dye based method, i.e., laser-induced fluorescence photobleaching anemometer (LIFPA), to significantly increase temporal resolution (TR) for velocity measurement of fast transient electrokinetic flows. To our knowledge, the TR has been for the first time achieved to 5–10μs, about 100 times better than that published from state-of-the-art micro particle image velocimetry (μPIV), which is currently the most widely used velocimetry in the microfluidics community. The new method provides us with new opportunities to study experimentally the fundamental phenomena of unsteady electrokinetics (EK) and to validate relevant theoretical models. One application of the new method is demonstrated by measuring the rise time of DC electroosmotic flows (EOFs) in a microcapillary of 10μm in diameter. KeywordsLaser-induced fluorescence photobleaching anemometer–LIFPA–DC electroosmotic flow–Rise time–Transient electrokinetic flow
    Microfluidics and Nanofluidics 09/2011; 11(3):353-358. · 3.22 Impact Factor
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    ABSTRACT: We have developed two new microfluidic cell sorters based on conventional negative dielectrophoresis (DEP) for continuous flow operations. The first is a cascade configuration sorter designed to increase purity of isolated target cell. The second has two staggered side channels in opposite side walls to increase sample throughput without compromising enrichment factor. Particles (carboxylate microspheres) of different sizes were first used to demonstrate the feasibility of the present DEP sorters for cell isolation. Then biological cells, i.e. human prostate cancer cell line LNCaP and human colorectal cancer cell line HCT116 were used to test the performance of the DEP sorters. In the present work, applied voltage was in the range of 0-20 V(p-p) , and frequency was from 0 to 10 MHz. Comparing to a single side channel DEP cell sorter, the isolation purity was improved from 80 to 96% by a single cascade sorter and the sample throughput was increased from 0.2 to 0.65 μL/min by a single staggered side channel sorter. In this article, we report the cell sorter designs, cell separation and enrichment factors.
    Electrophoresis 08/2011; · 3.26 Impact Factor
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    ABSTRACT: In this Letter, the nanoporous anodic alumina membranes (nanoPAAM) were first fabricated by the two-step anodic oxidisation method, and then based on these nanoPAAM master molds, polymer polymethylmethacrylate nanopillars with controllable heights and diameters were achieved by the direct casting method. Subsequently, combined with the ultraviolet lithography or electron beam lithography, a kind of useful platform of microfluidic channel that was embedded with nanopillar arrays was achieved. Finally, the transferring processes of DNA molecules around the entrance of the hybrid channel were monitored with an epi-fluorescence microscopy and electron multiplying charge coupled device camera in real time. The hybrid structure of microchannel with nanopillar arrays provides critical advantages when using the fluorescent microscopy to detect the dynamics of single DNA molecules.
    Micro & Nano Letters 06/2011; · 0.85 Impact Factor
  • Guiren Wang, An Zou, Fang Yang
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    ABSTRACT: In order to understand transport phenomena in nanofluidics, we study the flow velocity profile in a nanocapillary. Laser Induced Fluorescence Photobleaching Anemometer (LIFPA) and Stimulated Emission Depletion (STED) are combined to establish a far-field nanoscopic velocimeter for flow velocity measurement in a nanochannel. LIFPA uses molecular dye as tracer to avoid issues involved in particles as tracer in PIV, when one dimension of the channels is nearly in the same order of particle diameter. STED is applied to overcome conventional diffraction limit in physics to increase spatial resolution. To apply LIFPA, calibration is first required to establish the relationship between the fluorescence intensity signal and flow velocity. Current monitoring, time-fly of fluorescence and metering from syringe pump are used for the calibration respectively. Then the velocity profile is measured with a spatial resolution of about 70 nm in a nanocapillary with inner diameter of 360 nm. The conductivity influence on the velocity profile is investigated.
    11/2010;
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    Cuifang Kuang, Wei Zhao, Guiren Wang
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    ABSTRACT: Stimulated emission depletion (STED) microscopy is one of the breakthrough technologies that belong to far-field optical microscopy and can achieve nanoscale spatial resolution. We demonstrate a far-field optical nanoscopy based on continuous wave lasers with different wavelengths, i.e., violet and green lasers for excitation and STED, respectively. Fluorescent dyes Coumarin 102 and Atto 390 are used for validating the depletion efficiency. Fluorescent nanoparticles are selected for characterizing the spatial resolution of the STED system. Linear scanning of the laser beams of the STED system along one line of a microscope slide, which is coated with the nanoparticles, indicates that a spatial resolution of about 70 nm has so far been achieved. A two-dimensional image of the particle pattern of the STED system is constructed and compared with scanning confocal microscope. The present work has further extended the application of the STED microscopy into the blue regime.
    The Review of scientific instruments 05/2010; 81(5):053709. · 1.52 Impact Factor
  • Cuifang Kuang, Guiren Wang
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    ABSTRACT: For the first time we have been able to measure the flow velocity profile for nanofluidics with a spatial resolution better than 70 nm. Due to the diffraction resolution barrier, traditional optical methods have so far failed in measuring the velocity profile in a nanocapillary or a closed nanochannel without an opened sidewall. A novel optical point measurement method is presented which applies stimulated emission depletion (STED) microscopy to laser induced fluorescence photobleaching anemometer (LIFPA) techniques to measure flow velocity. Herein we demonstrate this far-field nanoscopic velocimetry method by measuring the velocity profile in a nanocapillary with an inner diameter of 360 nm. The closest measuring point to the wall is about 35 nm. This method opens up a new class of functional measuring techniques for nanofluidics and for nanoscale flows from the wall.
    Lab on a Chip 01/2010; 10(2):240-5. · 5.70 Impact Factor
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    ABSTRACT: Separation of colorectal cancer cells from other biological materials is important for stool-based diagnosis of colorectal cancer. In this paper, we use conventional dielectrophoresis in a microfluidic chip to manipulate and isolate HCT116 colorectal cancer cells. It is noticed that at a particular alternating current frequency band, the HCT116 cells are clearly deflected to a side channel from the main channel after the electric activation of an electrode pair. This motion caused by negative dielectrophoresis can be used to simply and rapidly separate cancer cells from other cells. In this manuscript, we report the chip design, flow conditions, dielectrophoretic spectrum of the cancer cells, and the enrichment factor of the colorectal cancer cells from other cells.
    Biomicrofluidics 01/2010; 4(1):13204. · 3.39 Impact Factor
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    ABSTRACT: A dynamic micropumping phenomenon has been observed, which is based on acoustic streaming generated by a piezotransducer actuated in d 31 mode without check valve. The use of d 31 mode of a piezoelectric microtransducer can significantly enhance the pumping performance for application in miniaturization. Experimental study of the maximum local velocity has been conducted to investigate the effect of actuator tip configuration on the micropumping performance. In addition, this study also shows the quantitative measurement of the pumping performance such as the pressure head generated as a function of different relevant parameters like applied electrical field, AC frequency, and length of the actuator. KeywordsDynamic micropumping-Acoustic streaming-Piezoelectric microtransducer- d 31 mode-Miniaturization-Actuator tip configuration
    Microfluidics and Nanofluidics 01/2010; 9(2):385-396. · 3.22 Impact Factor
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    ABSTRACT: Electrokinetic instability (EKI) flow can be use as an efficient tool for mixing in a lab-on-a chip system. In this report, we fabricated a quasi T channels with electrodes on the sidewall to enhance mixing with AC electrokinetics. A parametric study was conducted to explore the effectiveness of manipulating EKI waves to enhance fluid mixing inside the microchannel channel. Firstly, mixing results in two cases have been compared: electrodes are placed at the sidewall and electrodes are located at the ends of the channel. Secondly, the mixing results in the microchannel with different angle between two electrodes were assessed in terms of scalar concentration distributions. Thirdly, the effectiveness of the applied voltage phase variation between the two electrodes on the mixing process inside the quasi T channel were also explored for the further mixing enhancement. Fourthly, mixing result under high frequency was also achieved. Finally fluorescent particles in one of the two streams were used to obtain a more clear visualization of mixing process in the microchannel with 5^o angle between the two sidewalls.
    11/2009;
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    ABSTRACT: A micropumping device has been developed, which may find application in different areas such as blood pumping and chemical reagents dosing in bioengineering or as an efficient thermal management solution scheme in space-constrained electronic devices, due to some of their unique properties such as lower noise generation and ease of miniaturization. In this presentation, liquid pumping effect is reported using a simple valveless piezoelectric dynamic pump in D31 mode based on acoustic streaming principle. The actuator tip configuration is found to have a significant effect on the pumping performance. Quantitative results of maximum local velocity are presented for different tip configuration of the same actuator for comparison. In addition, this work also demonstrates the quantitative measurements of the pumping performance such as the flow rate and pressure head generated as a function of different relevant parameters such as applied electrical field, AC frequency and length of the actuator.
    11/2009;
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    ABSTRACT: Separation of cancer cells from the other biological cells can be useful for clinical cancer diagnosis and cancer treatment. In this presentation, conventional dielectrophoresis (c-DEP) is used in a microfluidic chip to manipulate and collect colorectal cancer HCT116 cell, which is doped with Human Embryonic Kidney 293 cells (HEK 293). It is noticed that, the HCT116 cell are deflected to a side channel from a main channel clearly by apply electric field at particular AC frequency band. This motion caused by negative DEP can be used to separate the cancer cell from others. In this manuscript, chip design, flow condition, the DEP spectrum of the cancer cell are reported respectively, and the separation and collection efficiency are investigated as well. The sorter is microfabricated using plastic laminate technology. -/abstract- This work has been financially supported by the NSF RII funding (EP
    11/2009;
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    ABSTRACT: For the first time with a temporal resolution higher than 100 micros, we have successfully measured the risetime of electroosmotic flow (EOF) in a microcapillary using recently developed laser induced fluorescence photobleaching anemometer (LIFPA). Although there are some theoretical estimations in literature about the risetime in microcapillaries, to the best of our knowledge, this has never been experimentally validated in a microcapillary with inner diameter less than 100 microm. The LIFPA with high temporal and spatial resolution described in this paper is capable of measuring risetime distribution radially in a cylindrical microcapillary tube. The experimental results show that the risetime under a pulsed electric field decreases with the reduction of the inner diameter of a microcapillary, and the risetime also increases from the wall to the axis for a given microcapillary. These are qualitatively similar to the theoretical prediction. In addition, the initial pressure driven flow does not appear to affect risetime.
    Analytical Chemistry 08/2009; 81(16):6590-5. · 5.82 Impact Factor
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    ABSTRACT: A dynamic micropumping device has been developed, which is based on acoustic streaming generated by a piezoelectric microtransducer actuated in d31 mode without any check valve. Piezoelectric microtransducers immersed in liquid (water) are used as actuators due to some of their unique properties such as lower noise generation and ease of miniaturization. Quantitative results of maximum local velocity are presented for different tip configuration of the same actuator for comparison. In addition, this work also demonstrates the quantitative measures of the pumping performance such as the pressure head generated as a function of different relevant parameters such as applied electrical field, AC frequency and length of the actuator.
    ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer; 01/2009
  • Cuifang Kuang, Guiren Wang
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    ABSTRACT: In order to understand physical and biological phenomena in nanoscale and build functional and practical nanofluidic devices, it is important to know the flow velocity profile. Due to the Abbe's diffraction limit barrier, traditional optical methods have so far failed in measuring the velocity profile in a nanochannel. Atomic force microscopy cannot be used for nanochannels without an opened sidewall. We have, for the first time, been able to measure the flow velocity profile for nanofluidics with a spatial resolution better than 70 nm. A novel optical point measurement method is presented, which applies Stimulated Emission Depletion (STED) to Laser Induced Fluorescence Photobleaching Anemometer (LIFPA) techniques to measure flow velocity. Herein we demonstrate this far-field nanoscopic velocimetry by measuring the velocity profile in a nanocapillary with an inner diameter of 360 nm. The closest measuring point from the wall is about 35 nm. The velocity can clearly be differentiated within just a 20 nm step, even near the axial region of the nanocapillary. This method opens up a new class of functional measuring techniques for nanofluidics and for near wall flows.
    01/2009;

Publication Stats

64 Citations
39.47 Total Impact Points

Institutions

  • 2009–2013
    • University of South Carolina
      • Department of Mechanical Engineering
      Columbia, South Carolina, United States
  • 2011
    • Zhejiang University
      • State Key Lab of Modern Optical Instrumentation
      Hangzhou, Zhejiang Sheng, China
    • Northwest University
      Ch’ang-an, Shaanxi, China