The Experts below are selected from a list of 1119 Experts worldwide ranked by ideXlab platform

Charles R. Martin - One of the best experts on this subject based on the ideXlab platform.

  • An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes
    ACS nano, 2016
    Co-Authors: Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an Electrokinetic Phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.

  • electroosmotic flow rectification in membranes with asymmetrically shaped pores effects of current and pore density
    Journal of Physical Chemistry C, 2015
    Co-Authors: Gregory W Bishop, Marcos M Lopez, Xiaojian Wu, Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    We have recently demonstrated a new Electrokinetic Phenomenon—electroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variables—current density used to drive flow through the membrane and membrane pore density—on EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio, increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories.

  • Electroosmotic Flow Rectification in Membranes with Asymmetrically Shaped Pores: Effects of Current and Pore Density
    2015
    Co-Authors: Gregory W. Bishop, Marcos M Lopez, Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    We have recently demonstrated a new Electrokinetic Phenomenonelectroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variablescurrent density used to drive flow through the membrane and membrane pore densityon EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio, increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories

  • electroosmotic flow rectification in pyramidal pore mica membranes
    Journal of the American Chemical Society, 2010
    Co-Authors: Pu Jin, Gregory W Bishop, Hitomi Mukaibo, Lloyd P Horne, Charles R. Martin
    Abstract:

    We demonstrate here a new Electrokinetic Phenomenon, Electroosmotic flow (EOF) rectification, in synthetic membranes containing asymmetric pores. Mica membranes with pyramidally shaped pores prepared by the track-etch method were used. EOF was driven through these membranes by using an electrode in solutions on either side to pass a constant ionic current through the pores. The velocity of EOF depends on the polarity of the current. A high EOF velocity is obtained when the polarity is such that EOF is driven from the larger base opening to the smaller tip opening of the pore. A smaller EOF velocity is obtained when the polarity is reversed such that EOF goes from tip to base. We show that this rectified EOF Phenomenon is the result of ion current-rectification observed in such asymmetric-pore membranes.

Pradeep Ramiah Rajasekaran - One of the best experts on this subject based on the ideXlab platform.

  • An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes
    ACS nano, 2016
    Co-Authors: Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an Electrokinetic Phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.

  • electroosmotic flow rectification in membranes with asymmetrically shaped pores effects of current and pore density
    Journal of Physical Chemistry C, 2015
    Co-Authors: Gregory W Bishop, Marcos M Lopez, Xiaojian Wu, Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    We have recently demonstrated a new Electrokinetic Phenomenon—electroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variables—current density used to drive flow through the membrane and membrane pore density—on EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio, increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories.

  • Electroosmotic Flow Rectification in Membranes with Asymmetrically Shaped Pores: Effects of Current and Pore Density
    2015
    Co-Authors: Gregory W. Bishop, Marcos M Lopez, Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    We have recently demonstrated a new Electrokinetic Phenomenonelectroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variablescurrent density used to drive flow through the membrane and membrane pore densityon EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio, increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories

Steven Danyluk - One of the best experts on this subject based on the ideXlab platform.

  • an alternative non contact planarization technique by utilizing the Electrokinetic Phenomenon
    MRS Proceedings, 2010
    Co-Authors: C. S. Leo, David Lee Butler, Steven Danyluk
    Abstract:

    In this paper, the authors introduce and present some findings on an alternative non-contact material removal technique. Material removal is made possible by utilizing the Electrokinetic and hydrodynamic effects of suspended particles to manipulate their trajectories to impact onto the surface of the workpiece. The research was previously demonstrated and reported where the removal rate can be precisely controlled by varying the electrical field and the flow rate of the slurry across the surface of the workpiece. New findings are reported on the application of the technique to different materials that will highlight the attractiveness of this alternative approach to producing surfaces with roughness in the order of nanometres.

  • influence of the electrochemical dissolution effect on the material removal rate utilizing Electrokinetic Phenomenon
    Advanced Materials Research, 2010
    Co-Authors: C. S. Leo, David Lee Butler, Steven Danyluk
    Abstract:

    Recently, material removal utilising Electrokinetic Phenomenon was proposed as an alternative to create material removal at the nanometric level [1]. The concept of the introduced material removal process is to impinge particles contained in the slurry, under the influence of hydrodynamic and Electrokinetic effects, onto the workpiece with a predetermined velocity to create material removal on the surface. The material removal process proved to be feasible where the material removal rate was reported to be in the range of a few hundred nm/hr with a surface roughness of a few nm (RMS). This paper aims to look into the effect of the electrochemical dissolution on the material removal process since high voltages are involved during the material removal process. During the experimental study, electrochemical dissolution was observed and it contributed a certain proportion of the material removal process. However, the main material removal mechanism still relies on the mechanical action of the abrasive particles on the surface of the workpiece to create material removal during the process.

  • Influence of Particle Effects on the Material Removal Rate Utilizing Electrokinetic Phenomenon
    Advanced Materials Research, 2009
    Co-Authors: C. S. Leo, Travis Lee Blackburn, David Lee Butler, Chun Yang, Steven Danyluk
    Abstract:

    With the demand for precise nanometric material removal with minimal defects, several non-contact ultraprecision machining techniques were developed over recent decades. The Electrokinetic material removal technique [1] is one such method that allows material to be removed without any physical contact between the tool and the workpiece. In this work, the influence of the slurry mixture on the material removal rate for the Electrokinetic material removal process is studied. During the process, it was observed experimentally that the mixture of the slurry affected the material removal rate. The parameters varied in the slurry mixture experiments were the size and concentration of the particles. Explanations for the behaviour of the material removal rate were also suggested during the study to further understand the Electrokinetic material removal technique.

  • precision material removal using the Electrokinetic Phenomenon
    23rd Annual Meeting of the American Society for Precision Engineering ASPE 2008 and the 12th ICPE, 2008
    Co-Authors: C. S. Leo, Travis Lee Blackburn, David Lee Butler, Chun Yang, Steven Danyluk
    Abstract:

    C. S. Leo1, T. L. Blackburn3, S. H. Ng2, C. Yang1, D. L. Butler1,2,* and S. Danyluk3 1School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798 2Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore, 638075 3George W. Woodruff, School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, Georgia, USA, 30332-0405

  • Nanometric material removal using the Electrokinetic Phenomenon
    Device and Process Technologies for Microelectronics MEMS Photonics and Nanotechnology IV, 2007
    Co-Authors: Leo Cheng Seng, David Lee Butler, Travis Lee Blackburn, Yang Chun, Steven Danyluk
    Abstract:

    Material removal at the sub-micron level has been a topic of interest in the past few years, particularly with respect to the fabrication of miniaturized devices. While numerous techniques have been developed and refined from their larger mesoscale counterparts (e.g. microEDM, micromilling), most have inherent limitations such as tool dimensions restricting the minimum feature which can be produced. In this work, we are proposing a novel technique of using the Electrokinetic Phenomenon for precise material removal at rates in the order of nanometers/min. An AC electric field with a DC offset is applied to a flowing fluid containing suspended particles which will then collide with the workpiece material causing material wear and tear and thus material removal. Results showed that the technique was feasible in achieving sub-micron material removal in micro-channels up to a depth of several hundred nanometers. With no chemicals involved in the process, the technique offers the further attraction of being a benign nano-manufacturing process with potential usage in the biochip and microfluidics areas.

Gregory W Bishop - One of the best experts on this subject based on the ideXlab platform.

  • electroosmotic flow rectification in membranes with asymmetrically shaped pores effects of current and pore density
    Journal of Physical Chemistry C, 2015
    Co-Authors: Gregory W Bishop, Marcos M Lopez, Xiaojian Wu, Pradeep Ramiah Rajasekaran, Charles R. Martin
    Abstract:

    We have recently demonstrated a new Electrokinetic Phenomenon—electroosmotic flow rectification in membranes with asymmetrically shaped pores. Flow rectification means that at constant driving force the flow rate in one direction through the membrane is faster than the flow rate in the opposite direction. EOF rectification could be of practical use in microfluidic devices incorporating porous membranes, but additional research is required. We explore here the effects of two key experimental variables—current density used to drive flow through the membrane and membrane pore density—on EOF rectification. We have found that the extent of EOF rectification, as quantified by the rectification ratio, increases with increasing current density. In contrast, the rectification ratio decreases with increasing membrane pore density. We propose explanations for these results based on simple EOF and membrane-transport theories.

  • electroosmotic flow rectification in pyramidal pore mica membranes
    Journal of the American Chemical Society, 2010
    Co-Authors: Pu Jin, Gregory W Bishop, Hitomi Mukaibo, Lloyd P Horne, Charles R. Martin
    Abstract:

    We demonstrate here a new Electrokinetic Phenomenon, Electroosmotic flow (EOF) rectification, in synthetic membranes containing asymmetric pores. Mica membranes with pyramidally shaped pores prepared by the track-etch method were used. EOF was driven through these membranes by using an electrode in solutions on either side to pass a constant ionic current through the pores. The velocity of EOF depends on the polarity of the current. A high EOF velocity is obtained when the polarity is such that EOF is driven from the larger base opening to the smaller tip opening of the pore. A smaller EOF velocity is obtained when the polarity is reversed such that EOF goes from tip to base. We show that this rectified EOF Phenomenon is the result of ion current-rectification observed in such asymmetric-pore membranes.

C. S. Leo - One of the best experts on this subject based on the ideXlab platform.

  • an alternative non contact planarization technique by utilizing the Electrokinetic Phenomenon
    MRS Proceedings, 2010
    Co-Authors: C. S. Leo, David Lee Butler, Steven Danyluk
    Abstract:

    In this paper, the authors introduce and present some findings on an alternative non-contact material removal technique. Material removal is made possible by utilizing the Electrokinetic and hydrodynamic effects of suspended particles to manipulate their trajectories to impact onto the surface of the workpiece. The research was previously demonstrated and reported where the removal rate can be precisely controlled by varying the electrical field and the flow rate of the slurry across the surface of the workpiece. New findings are reported on the application of the technique to different materials that will highlight the attractiveness of this alternative approach to producing surfaces with roughness in the order of nanometres.

  • influence of the electrochemical dissolution effect on the material removal rate utilizing Electrokinetic Phenomenon
    Advanced Materials Research, 2010
    Co-Authors: C. S. Leo, David Lee Butler, Steven Danyluk
    Abstract:

    Recently, material removal utilising Electrokinetic Phenomenon was proposed as an alternative to create material removal at the nanometric level [1]. The concept of the introduced material removal process is to impinge particles contained in the slurry, under the influence of hydrodynamic and Electrokinetic effects, onto the workpiece with a predetermined velocity to create material removal on the surface. The material removal process proved to be feasible where the material removal rate was reported to be in the range of a few hundred nm/hr with a surface roughness of a few nm (RMS). This paper aims to look into the effect of the electrochemical dissolution on the material removal process since high voltages are involved during the material removal process. During the experimental study, electrochemical dissolution was observed and it contributed a certain proportion of the material removal process. However, the main material removal mechanism still relies on the mechanical action of the abrasive particles on the surface of the workpiece to create material removal during the process.

  • Influence of Particle Effects on the Material Removal Rate Utilizing Electrokinetic Phenomenon
    Advanced Materials Research, 2009
    Co-Authors: C. S. Leo, Travis Lee Blackburn, David Lee Butler, Chun Yang, Steven Danyluk
    Abstract:

    With the demand for precise nanometric material removal with minimal defects, several non-contact ultraprecision machining techniques were developed over recent decades. The Electrokinetic material removal technique [1] is one such method that allows material to be removed without any physical contact between the tool and the workpiece. In this work, the influence of the slurry mixture on the material removal rate for the Electrokinetic material removal process is studied. During the process, it was observed experimentally that the mixture of the slurry affected the material removal rate. The parameters varied in the slurry mixture experiments were the size and concentration of the particles. Explanations for the behaviour of the material removal rate were also suggested during the study to further understand the Electrokinetic material removal technique.

  • precision material removal using the Electrokinetic Phenomenon
    23rd Annual Meeting of the American Society for Precision Engineering ASPE 2008 and the 12th ICPE, 2008
    Co-Authors: C. S. Leo, Travis Lee Blackburn, David Lee Butler, Chun Yang, Steven Danyluk
    Abstract:

    C. S. Leo1, T. L. Blackburn3, S. H. Ng2, C. Yang1, D. L. Butler1,2,* and S. Danyluk3 1School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore, 639798 2Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore, 638075 3George W. Woodruff, School of Mechanical Engineering, Georgia Institute of Technology, 801 Ferst Drive, Atlanta, Georgia, USA, 30332-0405