Harikrishnan Narayanan Unni
Email Address
mpehnu@nus.edu.sg
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Publication On-chip trapping and characterization of Cryptosporidium using surface coated ITO-PDMS bonded chips(2011) Unni, H.N.; Hartono, D.; Lim, K.-M.; MECHANICAL ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERINGDielectrophoresis has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping and characterization of Cryptosporidium pathogen using a microfluidic chip fabricated through a simple, effective bonding of surface coated ITO glass and PDMS. Lithographically patterned ITO glass plates were coated with an alkoxysilane solution DMOAP (N, N - dimethyl-N-octadecyl-3- aminopropyltrimethoxysilyl chloride) prior to bonding with PDMS microchannels. The silane coating was found to enhance the bonding between ITO and PDMS and reduce cell adhesion on the electrodes. Cryptosporidium oocysts, which are 2-4 microns in size and nearly spherical in shape represent the preliminary stage of cell development. The dielectrophoretic transport of cells is dependent on electrical properties such as permittivity and conductivity of the cells. Computational simulations were performed in order to study the effects of channel height, buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip and facilitate effective cell trapping. Videomicroscopic experiments were performed using the fabricated device and the real part of Clausius-Mossotti factor of the cells was estimated from values of critical voltages of particle trapping (corresponding to various field frequencies) at the electrodes. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the Cryptosporidium oocyst cell. © (2011) Trans Tech Publications, Switzerland.Publication On-chip trapping and characterization of Cryptosporidium using surface coated ITO-PDMS bonded chips(2011) Unni, H.N.; Hartono, D.; Lim, K.-M.; MECHANICAL ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERINGDielectrophoresis has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping and characterization of Cryptosporidium pathogen using a microfluidic chip fabricated through a simple, effective bonding of surface coated ITO glass and PDMS. Lithographically patterned ITO glass plates were coated with an alkoxysilane solution DMOAP (N, N - dimethyl-N-octadecyl-3- aminopropyltrimethoxysilyl chloride) prior to bonding with PDMS microchannels. The silane coating was found to enhance the bonding between ITO and PDMS and reduce cell adhesion on the electrodes. Cryptosporidium oocysts, which are 2-4 microns in size and nearly spherical in shape represent the preliminary stage of cell development. The dielectrophoretic transport of cells is dependent on electrical properties such as permittivity and conductivity of the cells. Computational simulations were performed in order to study the effects of channel height, buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip and facilitate effective cell trapping. Videomicroscopic experiments were performed using the fabricated device and the real part of Clausius-Mossotti factor of the cells was estimated from values of critical voltages of particle trapping (corresponding to various field frequencies) at the electrodes. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the Cryptosporidium oocyst cell. © (2011) Trans Tech Publications, Switzerland.Publication Characterization and separation of Cryptosporidium and Giardia cells using on-chip dielectrophoresis(2012-03-02) Narayanan Unni, H.; Hartono, D.; Yue Lanry Yung, L.; Mah-Lee Ng, M.; Pueh Lee, H.; Cheong Khoo, B.; Lim, K.-M.; MECHANICAL ENGINEERING; CHEMICAL & BIOMOLECULAR ENGINEERINGDielectrophoresis (DEP) has been shown to have significant potential for the characterization of cells and could become an efficient tool for rapid identification and assessment of microorganisms. The present work is focused on the trapping, characterization, and separation of two species of Cryptosporidium (C. parvum and C. muris) and Giardia lambia (G. lambia) using a microfluidic experimental setup. Cryptosporidium oocysts, which are 2-4 μm in size and nearly spherical in shape, are used for the preliminary stage of prototype development and testing. G. lambia cysts are 8-12 μm in size. In order to facilitate effective trapping, simulations were performed to study the effects of buffer conductivity and applied voltage on the flow and cell transport inside the DEP chip. Microscopic experiments were performed using the fabricated device and the real part of Clausius-Mossotti factor of the cells was estimated from critical voltages for particle trapping at the electrodes under steady fluid flow. The dielectric properties of the cell compartments (cytoplasm and membrane) were calculated based on a single shell model of the cells. The separation of C. muris and G. lambia is achieved successfully at a frequency of 10 MHz and a voltage of 3 Vpp (peak to peak voltage). © 2012 American Institute of Physics.