Haibo Li

Purdue University, West Lafayette, IN, United States

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Publications (6)10.05 Total impact

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    S W Lee, Haibo Li, Rashid Bashir
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    ABSTRACT: The authors present dielectrophoresis (DEP)-based tweezers that can be used to characterize the interactions between a particle and the surface it is attached to, within a microfluidic device. As a proof of concept, 5.4 mu m polystyrene beads functionalized by carboxyl group were attached on a bare and poly-L-lysine functionalized oxide surface. Negative dielectrophoresis force was generated using interdigitated electrodes and the peak dielectrophoresis voltage where the beads were repelled away from the surface was used to characterize the strength of interaction between the particle and the surface. Electric field and DEP force calculation were used to corroborate the measured results.
    Applied Physics Letters 05/2007; · 3.79 Impact Factor
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    ABSTRACT: Since the introduction of Micro-electro-mechanical systems in the early 70’s, the significance of the biomedical applications of these miniature systems has been realized [54, 77]. BioMEMS, the abbreviation for Biomedical or Biological Micro-Electro-Mechanical- Systems, is nowa heavily researched area with a wide variety of important biomedical applications. In general, BioMEMS, and its synonym BioChip, can be defined as “Devices or systems, constructed using techniques inspired from micro/ nanoscale fabrication, that are used for processing, delivery, manipulation, analysis, or construction of biological and chemical entities”. A large number of BioMEMS devices and applications have been presented in [4, 34, 41, 57]. Technologies such as “lab-on-a-chip“ and Micro-Total-Analysis-Systems (micro-TAS or μTAS), when used for biological applications, fall into the BioMEMS category. The use of these lab-on-a-chips for cellular analysis is justified by, (i) reducing the sensor element to the scale of size of cells and smaller and hence providing a higher sensitivity, (ii) reduced reagent volumes and associated costs, (iii) reduced time to result due to small volumes resulting in higher effective concentrations, (iv) amenability of portability and miniaturization of the entire system, and (v) ability to perform large numbers of assays or measurements in parallel. Since the introduction of Micro-electro-mechanical systems in the early 70’s, the significance of the biomedical applications of these miniature systems has been realized [54, 77]. BioMEMS, the abbreviation for Biomedical or Biological Micro-Electro-Mechanical- Systems, is nowa heavily researched area with a wide variety of important biomedical applications. In general, BioMEMS, and its synonym BioChip, can be defined as “Devices or systems, constructed using techniques inspired from micro/ nanoscale fabrication, that are used for processing, delivery, manipulation, analysis, or construction of biological and chemical entities”. A large number of BioMEMS devices and applications have been presented in [4, 34, 41, 57]. Technologies such as “lab-on-a-chip“ and Micro-Total-Analysis-Systems (micro-TAS or μTAS), when used for biological applications, fall into the BioMEMS category. The use of these lab-on-a-chips for cellular analysis is justified by, (i) reducing the sensor element to the scale of size of cells and smaller and hence providing a higher sensitivity, (ii) reduced reagent volumes and associated costs, (iii) reduced time to result due to small volumes resulting in higher effective concentrations, (iv) amenability of portability and miniaturization of the entire system, and (v) ability to perform large numbers of assays or measurements in parallel.
    12/2006: pages 187-203;
  • Source
    Haibo Li, Rashid Bashir
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    ABSTRACT: Microfabricated interdigitated electrode array is a convenient form of electrode geometry for dielectrophoretic trapping of biological particles within micro-fluidic biochips. We have previously reported experimental results and finite element modeling of the holding forces for both positive and negative dielectrophoretic traps on microfabricated interdigitated electrodes within a microfluidic biochip fabricated in silicon with a 12 microm deep chamber and anodic-bonded glass cover. Based on these prior studies, we present in this paper a dynamic study to investigate the stopping capability of dielectrophoretic devices with limited electrode teeth. Simulation results on the issues of design and optimization of the dielectrophoretic devices are also presented and discussed in detail. Simulation results show that the maximum particle stopping distance in a specific device is very sensitive to the chamber height due to the near-electrode nature of DEP force. The relationship between maximum stopping distance and the applied voltage is presented, and the electrode spacing is found to be important in designing the electrode geometry. The spacing should be no less than the chamber height in order to efficiently capture the particles in a relatively short range at a given applied voltage and flow rate.
    Biomedical Microdevices 01/2005; 6(4):289-95. · 2.72 Impact Factor
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    ABSTRACT: We have used dielectrophoretic filters within microfluidic biochips to capture from a flow and image virus particles in real-time. The verification of capture was performed by fluorescently labeling the particles using dual or triple labeling. These nonmechanical filters can be very valuable in the sample preparation, purification, and concentration of viral particles from a mixed sample. The described imaging methodology can be used for real-time imaging of nanometer scale virus particles for analysis of capture, detection, and characterization of these particles within micro and nanoscale sensors.
    Nano Letters - NANO LETT. 12/2003; 4(2).
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    ABSTRACT: Lysozyme placed on the SiO2 surfaces that have previously been derivatized with C18 coating will capture both Escherichia coli and Listeria monocytogenes cells from PBS buffer at pH 7.2. This phenomenon is of significance for the design and fabrication of protein biochips that are designed to capture bacteria from buffer or water so that these can be further interrogated with respect to possible pathogenicity. Fluorescent microscopy shows that two types of bacteria (gram-negative E. coli and gram-positive Listeria spp.) will be adsorbed by lysozyme placed on the surface of the biochip but that strong adsorption of the bacteria is reduced but not eliminated when Tween 20 is present (at 0.5%) in the PBS buffer in which the cells are suspended. In comparison, Tween 20 and Bovine Serum Albumin (BSA) almost completely block adsorption of these bacteria on C18 coated surfaces. The combination of a lysozyme surface with Tween 20 gives a greater degree of adsorption of L. monocytogenes than E. coli, and hence suggests selectivity for the more hydrophobic E. coli may be reduced by the Tween 20. This paper presents protocols for preparing protein-coated, SiO2 surfaces and the effect of buffer containing Tween 20 on adsorption of bacteria by SiO2 surfaces coated with C18 to which BSA, lysozyme or C11E9 antibody is immobilized at pH 7.2 and ambient temperature.
    Enzyme and Microbial Technology. 01/2003;
  • Source
    Haibo Li, Rashid Bashir
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    ABSTRACT: Dielectrophoresis, the movement of particles in non-uniform ac electric field, was used to separate live and heat-treated Listeria innocua cells with great efficiency on the micro-fabricated devices with interdigitated electrodes by utilizing the difference of dielectric properties between alive and dead cells. Both live and dead cells are found to be only able to collect either at the centers of the electrodes in negative dielectrophoresis or at the electrode edges in positive dielectrophoresis due to the dielectrophoretic force and electrohydrodynamic force. Cell viability was verified by a rapid method using epifluorescence staining. The dependency of the applied ac signal’s frequency on the dielectrophoretic properties of Listeria cells is studied and discussed. This on-electrode manipulation and separation of cells can prove to be useful in micro-scale sample preparation and diagnostic applications in biochips.
    Sensors and Actuators B Chemical 01/2002; · 3.54 Impact Factor