Kwun Lun Cho
University of Melbourne
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Publication
Featured researches published by Kwun Lun Cho.
Advanced Materials | 2015
Kwun Lun Cho; Anita J. Hill; Frank Caruso; Sandra E. Kentish
Crosslinked polyelectrolyte multilayer membranes are synthesized with salt rejection values approaching those of commercial desalination membranes, but with increased chlorine resistance. The membranes are fabricated directly onto porous commercial substrates. Subsequent crosslinking of the polycation layers with glutaraldehyde leads to NaCl rejections of up to 97%, while the incorporation of a highly sulfonated polysulfone polyanion leads to high chlorine resistance.
Biointerphases | 2013
Alex Wu; Kenichi Nakanishi; Kwun Lun Cho; Robert N. Lamb
Surfaces consisting of sub micron holes (0.420-0.765 μm) engineered into nanoparticle (12 nm) coatings were examined for marine antifouling behaviour that defines early stage settlement. Immersed surfaces were found to be resistant to a 5-hour attachment assay of Amphora coffeaeformis, a marine organism commonly found in abundance on fouled substrates such as foul-releasing paints and self-polishing coatings. Attachment inhibition was attributed to the accessibility of diatoms to the surface. This was governed by the size and morphology of trapped interfacial air pockets measured in-situ using synchrotron small angle x-ray scattering. Surfaces containing larger pores (0.765 μm) exhibited the highest resistance. Macroscopic wettability via contact angle measurements however remained at 160° and sliding angle of < 5° and was found to be independent of pore size and not indicative of early stage fouling behaviour. The balance of hierarchical nano/micro length scales was critical in defining the early stage stability of biofouling character of the interface.
Langmuir | 2015
Joel K.J. Yong; Jiwei Cui; Kwun Lun Cho; Geoff W. Stevens; Frank Caruso; Sandra E. Kentish
Carbonic anhydrase (CA) is a native enzyme that facilitates the hydration of carbon dioxide into bicarbonate ions. This study reports the fabrication of thin films of active CA enzyme onto a porous membrane substrate using layer-by-layer (LbL) assembly. Deposition of multilayer films consisting of polyelectrolytes and CA was monitored by quartz crystal microgravimetry, while the enzymatic activity was assayed according to the rates of p-nitrophenylacetate (p-NPA) hydrolysis and CO2 hydration. The fabrication of the films onto a nonporous glass substrate showed CO2 hydration rates of 0.52 ± 0.09 μmol cm(-2) min(-1) per layer of bovine CA and 2.6 ± 0.7 μmol cm(-2) min(-1) per layer of a thermostable microbial CA. The fabrication of a multilayer film containing the microbial CA on a porous polypropylene membrane increased the hydration rate to 5.3 ± 0.8 μmol cm(-2) min(-1) per layer of microbial CA. The addition of mesoporous silica nanoparticles as a film layer prior to enzyme adsorption was found to increase the activity on the polypropylene membranes even further to a rate of 19 ± 4 μmol cm(-2) min(-1) per layer of microbial CA. The LbL treatment of these membranes increased the mass transfer resistance of the membrane but decreased the likelihood of membrane pore wetting. These results have potential application in the absorption of carbon dioxide from combustion flue gases into aqueous solvents using gas-liquid membrane contactors.
Soft Matter | 2013
James P. Best; Sameen Javed; Joseph J. Richardson; Kwun Lun Cho; Marloes M. J. Kamphuis; Frank Caruso
We report engineered hydrogel thin-films with varying degrees of covalent crosslinking, which demonstrate enhanced HeLa cell adhesion with decreasing film stiffness. This trend is contrary to previous findings for tumour cell adhesion on hydrogel substrates, and is attributed to the extremely soft nature of the films studied, allowing for a greater cell–film contact area and the development of adhesive focal contacts. Adhesion based on mechanical tuning of the film was decoupled from chemical effects through characterisation and analysis of film surface roughness, hydrophobicity and charge.
Faraday Discussions | 2010
Alex Wu; Kwun Lun Cho; Irving I. Liaw; Grainne Moran; Nigel Kirby; Robert N. Lamb
Two scales of roughness are imparted onto silicon surfaces by isotropically patterning micron sized pillars using photolithography followed by an additional nanoparticle coating. Contact angles of the patterned surfaces were observed to increase with the addition of the nanoparticle coating, several of which, exhibited superhydrophobic characteristics. Freeze fracture atomic force microscopy and in situ synchrotron SAXS were used to investigate the micro- and nano-wettability of these surfaces using aqueous liquids of varying surface tension. The results revealed that scaling different roughness morphologies result in unique wetting characteristics. It indicated that surfaces with micro, nano or dual scale roughness induced channels for the wetting liquid as per capillary action. With the reduction of liquid surface tension, nano-wetting behaviour differed between superhydrophobic and non-superhydrophobic dual-scale roughness surfaces. Micro-wetting behaviour, however, remained consistent. This suggests that micro- and nano-wetting are mutually exclusive, and that the order in which they occur is ultimately governed by the energy expenditure of the entire system.
Faraday Discussions | 2009
Derek Y. C. Chan; Md. Hemayet Uddin; Kwun Lun Cho; Irving I. Liaw; Robert N. Lamb; Geoffrey W. Stevens; Franz Grieser; Raymond R. Dagastine
We used atomic force microscopy to study dynamic forces between a rigid silica sphere (radius approximately 45 microm) and a silica nano-particle super-hydrophobic surface (SNP-SHS) in aqueous electrolyte, in the presence and absence of surfactant. Characterization of the SNP-SHS surface in air showed a surface roughness of up to two microns. When in contact with an aqueous phase, the SNP-SHS traps large, soft and stable air pockets in the surface interstices. The inherent roughness of the SNP-SHS together with the trapped air pockets are responsible for the superior hydrophobic properties of SNP-SHS such as high equilibrium contact angle (> 140 degrees) of water sessile drops on these surfaces and low hydrodynamic friction as observed in force measurements. We also observed that added surfactants adsorbed at the surface of air pockets magnified hydrodynamic interactions involving the SNP-SHS. The dynamic forces between the same silica sphere and a laterally smooth mica surface showed that the fitted Navier slip lengths using the Reynolds lubrication model were an order of magnitude larger than the length scale of the sphere surface roughness. The surface roughness and the lateral heterogeneity of the SNP-SHS hindered attempts to characterize the dynamic response using the Reynolds lubrication model even when augmented with a Navier slip boundary.
Langmuir | 2015
Kwun Lun Cho; Axel Rosenhahn; Richard Thelen; Michael Grunze; Matthew Lobban; Markus Leopold Karahka; H. Jürgen Kreuzer
In this work we experimentally and theoretically analyze the detachment of microscopic polystyrene beads from different self-assembled monolayer (SAM) surfaces in a shear flow in order to develop a mechanistic model for the removal of cells from surfaces. The detachment of the beads from the surface is treated as a thermally activated process applying an Arrhenius Ansatz to determine the activation barrier and attempt frequency of the rate determing step in bead removal. The statistical analysis of the experimental shear detachment data obtained in phosphate-buffered saline buffer results in an activation energy around 20 kJ/mol, which is orders of magnitude lower than the adhesion energy measured by atomic force microscopy (AFM). The same order of magnitude for the adhesion energy measured by AFM is derived from ab initio calculations of the van der Waals interaction energy between the polystyrene beads and the SAM-covered gold surface. We conclude that the rate determing step for detachment of the beads is the initiation of rolling on the surface (overcoming static friction) and not physical detachment, i.e., lifting the particle off the surface.
Chemistry of Materials | 2014
Md. Arifur Rahim; Hirotaka Ejima; Kwun Lun Cho; Kristian Kempe; Markus Müllner; James P. Best; Frank Caruso
Journal of Physical Chemistry C | 2010
Kwun Lun Cho; Irving I. Liaw; Alex Wu; Robert N. Lamb
Journal of Physical Chemistry C | 2012
Kwun Lun Cho; Alex Wu; Irving I. Liaw; David Cookson; Robert N. Lamb
Collaboration
Dive into the Kwun Lun Cho's collaboration.
Commonwealth Scientific and Industrial Research Organisation
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