ORCID Profile
0000-0003-2519-780X
Current Organisations
University of South Australia
,
Universiti Kebangsaan Malaysia
,
Nanyang Technological University
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Publisher: Penerbit Universiti Kebangsaan Malaysia (UKM Press)
Date: 31-07-2017
Publisher: Elsevier BV
Date: 2019
DOI: 10.1016/J.COLSURFB.2018.10.015
Abstract: As some proteins are known to interact with sulfated and phosphated biomolecules such as specific glycosaminoglycans, this study derives from the hypothesis that sulfonate and phosphonate groups on solid polymer surfaces might cause specific interfacial interactions. Such surfaces were prepared by plasma polymerization of heptylamine (HA) and subsequent grafting of sulfonate or phosphonate groups via Michael-type addition of vinylic compounds. Adsorption of the proteins fibrinogen, albumin (HSA) and lysozyme on these functionalised plasma polymer surfaces was studied by XPS and quartz crystal microbalance with dissipation (QCM-D). It was also studied whether pre-adsorption with HSA would lead to a passivated surface against further adsorption of other proteins. XPS confirmed grafting of vinyl sulfonate and vinyl phosphonate onto the amine surface and showed that the proteins adsorbed to saturation at between 1 and 2 h. QCM-D showed rapid and irreversible adsorption of albumin on all three surfaces, while lysozyme could be desorbed with PBS to substantial extents from the sulfonated and phosphonated surfaces but not from the amine surface. Fibrinogen showed rapid initial adsorption followed by slower additional mass gain over hours. Passivation with albumin led to small and largely reversible subsequent adsorption of lysozyme, whereas with fibrinogen partial displacement yielded a mixed layer, regardless of the surface chemistry. Thus, protein adsorption onto these sulfonated and phosphonated surfaces is complex, and not dominated by electrostatic charge effects.
Publisher: Elsevier BV
Date: 02-2012
Publisher: Wiley
Date: 08-09-2009
Publisher: IEEE
Date: 08-2018
Publisher: IEEE
Date: 12-2014
Publisher: IEEE
Date: 10-2016
Publisher: Springer Science and Business Media LLC
Date: 17-01-2014
Publisher: Wiley
Date: 03-2019
Publisher: Elsevier BV
Date: 11-2016
DOI: 10.1016/J.MSEC.2016.07.040
Abstract: Antibacterial coating is important to prevent the colonization of medical devices by biofilm forming bacteria that would cause infection and sepsis in patients. Current coating techniques such as immobilization of antimicrobial compounds, time-releasing antibiotic agents and silver nanoparticles, require multiple processing steps, and they have low efficacy and low stability. We proposed a single-step plasma polymerization of an essential oil known as carvone to produce a moderately hydrophobic antibacterial coating (ppCar) with an average roughness of <1nm. ppCar had a static water contact angle of 78°, even after 10days of air aging and it maintained its stability throughout 24h of LB broth immersion. ppCar showed promising results in the live-dead fluorescence assay and crystal violet assay. The biofilm assay showed an effective reduction of E. coli and S. aureus bacteria by 86% and 84% respectively. ppCar is also shown to rupture the bacteria membrane for its bactericidal effects. The cytotoxicity test indicated that the coating is not cytotoxic to the human cell line. This study would be of interest to researcher keen on producing a bacteria-resistance and biocompatible coating on different substrates in a cost-effective manner.
Publisher: MDPI AG
Date: 31-07-2017
DOI: 10.3390/MI8080236
Publisher: Springer Science and Business Media LLC
Date: 10-04-2019
Publisher: IEEE
Date: 04-2017
Publisher: Elsevier BV
Date: 05-2018
Publisher: IEEE
Date: 09-2018
Publisher: Wiley
Date: 22-07-2016
DOI: 10.1002/APP.44107
Publisher: IOP Publishing
Date: 04-2022
Abstract: In general, cold plasma treatment improves crop germination and growth. The purpose of this research is to examine the impact of low-pressure O 2 plasma treatment on the germination and growth kinetics of papaya seeds. Seeds were treated for 40 s at a discharge power of 80 W using O 2 as a monomer. Physical and chemical changes were studied to understand the mechanism of germination and growth improvement. Furthermore, changes in phytohormones and antioxidant activity that were beneficial to germination were also examined. O 2 plasma treatment improved wettability, surface etching, and oxidation, and affected other molecular-level changes leading to a 16% germination improvement in papaya.
Publisher: IEEE
Date: 10-2016
Publisher: Elsevier BV
Date: 10-2017
DOI: 10.1016/J.MSEC.2017.05.091
Abstract: Our studies focused on improving the biocompatibility properties of two microfluidic prototyping substrates i.e. polyurethane methacrylate (PUMA) and off-stoichiometry thiol-ene (OSTE-80) polymer by Ar and N
Publisher: Elsevier BV
Date: 11-2017
Publisher: IEEE
Date: 08-2016
Publisher: ASME International
Date: 21-04-2016
DOI: 10.1115/1.4033069
Abstract: Sintered silver joint is a porous silver that bonds a semiconductor die to the substrate as part of the packaging process. Sintered Ag is one of the few possible bonding methods to fulfill the operating conditions of wide band-gap (WBG) power device technologies. We review the current technology development of sintered Ag as a bonding material from the perspective of patents filed by various stakeholders since late 1980s. This review addresses the formulation of sintered pastes (i.e., nano-Ag, hybrid Ag, and micron Ag fillers), innovations in the process and equipment to form this Ag joint. This review will provide the insights and confidence to engineers, scientists from universities and industry as well as investors who are developing and commercializing the sintered Ag as a bonding material for microelectronic packaging.
Publisher: Wiley
Date: 13-01-2014
Publisher: MDPI AG
Date: 29-03-2023
DOI: 10.3390/MA16072739
Abstract: Tissue engineering products have grown in popularity as a therapeutic approach for chronic wounds and burns. However, some drawbacks include additional steps and a lack of antibacterial capacities, both of which need to be addressed to treat wounds effectively. This study aimed to develop an acellular, ready-to-use ovine tendon collagen type I (OTC-I) bioscaffold with an antibacterial coating for the immediate treatment of skin wounds and to prevent infection post-implantation. Two types of crosslinkers, 0.1% genipin (GNP) and dehydrothermal treatment (DHT), were explored to optimise the material strength and biodegradability compared with a non-crosslinked (OTC) control. Carvone plasma polymerisation (ppCar) was conducted to deposit an antibacterial protective coating. Various parameters were performed to investigate the physicochemical properties, mechanical properties, microstructures, biodegradability, thermal stability, surface wettability, antibacterial activity and biocompatibility of the scaffolds on human skin cells between the different crosslinkers, with and without plasma polymerisation. GNP is a better crosslinker than DHT because it demonstrated better physicochemical properties (27.33 ± 5.69% vs. 43 ± 7.64% shrinkage), mechanical properties (0.15 ± 0.15 MPa vs. 0.07 ± 0.08 MPa), swelling (2453 ± 419.2% vs. 1535 ± 392.9%), biodegradation (0.06 ± 0.06 mg/h vs. 0.15 ± 0.16 mg/h), microstructure and biocompatibility. Similarly, its ppCar counterpart, GNPppCar, presents promising results as a biomaterial with enhanced antibacterial properties. Plasma-polymerised carvone on a crosslinked collagen scaffold could also support human skin cell proliferation and viability while preventing infection. Thus, GNPppCar has potential for the rapid treatment of healing wounds.
Publisher: MDPI AG
Date: 16-06-2023
Abstract: Medical devices are often vulnerable to colonization by nosocomial pathogens (bacteria), leading to infections. Traditional sterilization methods may not always be effective, and as a result, alternative options are being explored to prevent microbial contamination. Recently, scientists are emphasizing using plant-derived essential oils that possess inherent antibacterial properties to produce antimicrobial coatings using plasma polymerization technology carried out at atmospheric pressure (AP). This approach shows promise compared to other coating strategies that need several processing steps, including a high-vacuum system, and are laborious, such as the immobilization of antimicrobial materials on precoated layers in the low-pressure plasma polymerization approach. The present study demonstrates the potential of AP plasma polymerization for producing thin films with excellent antibacterial properties and surface characteristics. The resulting coatings are stable, smooth, and have high wettability, making them ideal for repelling bacteria. The calculated zeta potential and deposition rate for the films are also favorable. These AP plasma-polymerized thin films created from carvone show a reduction rate of more than 90% for Escherichia coli and Staphylococcus aureus bacteria. Our computational docking studies also reveal strong binding interactions between the original carvone monomer and both bacteria. The study suggests that these AP plasma-produced coatings have great potential as antibacterial coatings for biomedical devices.
Publisher: IEEE
Date: 08-2016
Publisher: MDPI AG
Date: 02-07-2020
DOI: 10.3390/APP10134594
Abstract: With the aim of selecting particular frequencies of interest and rejecting others, the waveguiding and filtering properties of a two-dimensional phononic crystal slab are investigated in the context of a filtering application. To this end, we designed and manufactured a metallic device that consists of a square lattice of cylindrical pillars mounted on the top of a plate by using 3D printing technology. We respectively explored the theoretical and experimental characteristics of the device by using finite element method, a Micro System Analyzer (MSA) and a scanning laser Doppler vibrometer. The proposed device shows a complete band gap for Lamb wave around 0.3 MHz with a relative band-width of 30 % . Tailorable waveguides are realized inside this phononic crystal by inserting several space gaps to achieve a demultiplexing effect through the splitting of an acoustic signal towards three different bandpass frequency channels. The demultiplexing performance has been experimentally demonstrated by achieving rejection levels up to 60 dB. The proposed phononic platform can have a significant impact in signal processing as well as droplet manipulation for biological applications.
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Date: 06-2021
Publisher: IEEE
Date: 09-2016
Publisher: MDPI AG
Date: 15-06-2022
Abstract: In most engineering applications, the coefficients of thermal expansion (CTEs) of different materials in integrated structures are inconsistent, especially for the thin-film multilayered coatings. Therefore, mismatched thermal deformation is induced due to temperature variation, which leads to an extreme temperature gradient, stress concentration, and damage accumulation. Controlling the CTEs of materials can effectively eliminate the thermally induced stress within the layered structures and thus considerably improve the mechanical reliability and service life. In this paper, randomly distributed fibers are incorporated into the matrix material and thus utilized to tune the material CTE from the macroscopical viewpoint. To this end, finite element (FE) modeling is proposed for fiber-reinforced matrix composites. In order to overcome the challenges of creating numerical models at a mesoscale, the random distribution of fibers in three-dimensional space is realized by proposing a fiber growth algorithm with the control of the in-plane and out-of-plane angles of fibers. The homogenization method is adopted to facilitate the FE simulations by using the representative volume element (RVE) of composite materials. Periodic boundary conditions (PBC) are applied to realize the prediction of the equivalent CTE of macroscopic composite materials with randomly distributed fibers. In the established FE model, the random distribution of carbon fibers in the matrix makes it possible to tune the CTE of the composite material by considering the orientation of fibers in the matrix. The FE predictions show that the volume fraction of carbon fibers in the composite materials is found to be crucial to macroscopic CTE, but results in minor variations in Young’s modulus and shear modulus. With the developed ABAQUS plug-in program, the proposed tuning method for CTE is promising to be standardized for industrial practice.
Publisher: IEEE
Date: 11-2015
Publisher: Wiley
Date: 16-07-2018
Publisher: Elsevier BV
Date: 12-2016
Publisher: MDPI AG
Date: 06-01-2023
Abstract: Antibacterial coating is necessary to prevent biofilm-forming bacteria from colonising medical tools causing infection and sepsis in patients. The recent coating strategies such as immobilisation of antimicrobial materials and low-pressure plasma polymerisation may require multiple processing steps involving a high-vacuum system and time-consuming process. Some of those have limited efficacy and durability. Here, we report a rapid and one-step atmospheric pressure plasma polymerisation (APPP) of D-limonene to produce nano-thin films with hydrophobic-like properties for antibacterial applications. The influence of plasma polymerisation time on the thickness, surface characteristic, and chemical composition of the plasma-polymerised films was systematically investigated. Results showed that the nano-thin films deposited at 1 min on glass substrate are optically transparent and homogenous, with a thickness of 44.3 ± 4.8 nm, a smooth surface with an average roughness of 0.23 ± 0.02 nm. For its antimicrobial activity, the biofilm assay evaluation revealed a significant 94% decrease in the number of Escherichia coli (E. coli) compared to the control s le. More importantly, the resultant nano-thin films exhibited a potent bactericidal effect that can distort and rupture the membrane of the treated bacteria. These findings provide important insights into the development of bacteria-resistant and biocompatible coatings on the arbitrary substrate in a straightforward and cost-effective route at atmospheric pressure.
Publisher: Springer Science and Business Media LLC
Date: 03-2015
Publisher: IEEE
Date: 08-2014
Publisher: Wiley
Date: 27-07-2017
Publisher: MDPI AG
Date: 14-02-2021
Abstract: In general, seed germination is improved by low-pressure plasma (LPP) treatment using precursors such as air, nitrogen, argon, or water (H2O). Here, H2O-based LPP treatment using the optimized parameters of 10 W and 10 s improves the germination of Bambara groundnut seeds by 22%. LPP increases the wettability and roughness of the seed hilum while oxidizing the surface with carboxyl and amine groups. In this H2O-based treatment of Bambara groundnut seeds, combinatory etching and chemical modification facilitated the imbibition process and increased the germination percentage. The success of this method has the potential to be scaled up to solve food security with seeds otherwise facing germination-related issues.
Publisher: Wiley
Date: 15-08-2006
Abstract: Summary: This review surveys methods for the fabrication, by plasma surface treatments or plasma polymerization, of polymeric surfaces and thin plasma polymer coatings that contain reactive chemical groups useful for the subsequent covalent immobilization, by solution chemical reactions or vapor phase grafting, of molecules or polymers that can exert bio‐specific interfacial responses. Surfaces containing amine, carboxy, hydroxy, and aldehyde groups are the subject of this review. Aminated surfaces have been fabricated using various plasma vapors or mixtures and have found wide use for bio‐interface applications. However, in many cases the amine surfaces have a rather limited shelf life, with post‐plasma oxidation reactions and surface adaptation leading to the disappearance of amine groups from the surface. Aging is a widespread phenomenon that often has not been recognized, particularly in some of the earlier studies on the use of plasma‐fabricated surfaces for bio‐interfacial applications, and can markedly alter the surface chemistry. Plasma‐fabricated surfaces that contain carboxy groups have also been well documented. Fewer reports exist on hydroxy and aldehyde surfaces prepared by plasma methods. Hydroxy surfaces can be prepared by water plasma treatment or the plasma polymerization of alkyl alcohol vapors. Water plasma treatment on many polymer substrates suffers from aging, with surface adaptation leading to the movement of surface modification effects into the polymer. Both hydroxy and aldehyde surfaces have been used for the covalent immobilization of biologically active molecules. Aging effects are less well documented than for amine surfaces. This review also surveys studies using such surfaces for cell colonization assays. Generally, these surface chemistries show good ability to support cell colonization, though the effectiveness seems to depend on the process vapor and the plasma conditions. Carboxylate co‐polymer surfaces have shown excellent ability to support the colonization of some human cell lines of clinical interest. Immobilization of proteins onto plasma‐carboxylated surfaces is also well established. XPS O/C ratios (0 0 emission) as a function of storage time, of plasma‐polymerized methyl methacrylate deposited at power levels of 5 and 40 W. magnified image XPS O/C ratios (0 0 emission) as a function of storage time, of plasma‐polymerized methyl methacrylate deposited at power levels of 5 and 40 W.
Publisher: Springer Science and Business Media LLC
Date: 20-02-2019
Publisher: IEEE
Date: 11-2012
Publisher: Elsevier BV
Date: 05-2023
Publisher: Penerbit Universiti Kebangsaan Malaysia (UKM Press)
Date: 31-08-2018
Publisher: Wiley
Date: 02-09-2014
Publisher: Springer Science and Business Media LLC
Date: 30-01-2023
DOI: 10.1038/S41598-023-28811-W
Abstract: Cold plasma (low pressure) technology has been effectively used to boost the germination and growth of various crops in recent decades. The durability of these plasma-treated seeds is essential because of the need to store and distribute the seeds at different locations. However, these ageing effects are often not ascertained and reported because germination and related tests are carried out within a short time after the plasma-treatment. This research aims to fill that knowledge gap by subjecting three different types of seeds (and precursors): Bambara groundnuts (water), chilli (oxygen), and papaya (oxygen) to cold plasma-treatment. Common mechanisms found for these erse seed types and treatment conditions were the physical and chemical changes induced by the physical etching and the cold plasma on the seeds and subsequent oxidation, which promoted germination and growth. The high glass transition temperature of the lignin-cellulose prevented any physical restructuring of the surfaces while maintaining the chemical changes to continue to promote the seeds germination and growth. These changes were monitored over 60 days of ageing using water contact angle (WCA), water uptake, electrical conductivity, field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS). The vacuum effect was also investigated to separate its effect from cold plasma (low pressure). This finding offers a framework for determining how long agricultural seeds that have received plasma treatment can be used. Additionally, there is a need to transfer this research from the lab to the field. Once the impact of plasma treatment on seeds has been estimated, it will be simple to do so.
Publisher: Emerald
Date: 02-2001
DOI: 10.1108/00035590110365309
Abstract: This study showed the complex interactions of alloying elements and their prevailing microstructure on the pitting corrosion. This interaction was illustrated by electrochemical tests of three grades of wrought duplex stainless steels. It was shown that SAF2507 had the highest pitting potential, followed by SAF2205 and SAF2304. However, SAF2205 had higher corrosion potential than SAF2507. SAF2205 and SAF2507 were immune to pitting, while SAF2304 was susceptible to pitting. It was also found in the experiment that the austenite‐ferrite interface was the most susceptible to corrosion, followed by the austenite and finally the ferrite phase.
Publisher: AIP Publishing
Date: 12-2016
DOI: 10.1063/1.4968609
Abstract: Pillar-based phononic crystals exhibit some unique wave phenomena due to the interaction between surface acoustic modes of the substrate and local resonances supported by pillars. In this paper, we extend the investigations by taking into account the presence of a liquid medium. We particularly demonstrate that local resonances dramatically decrease the phase velocity of Scholte-Stoneley wave, which leads to a slow wave at the solid/fluid interface. Moreover, we show that increasing the height of pillars introduces a new set of branches of interface modes and drastically affects the acoustic energy localization. Indeed, while some modes display a highly confined pressure between pillars, others exponentially decay in the fluid or only propagate in the solid without disturbing the fluid pressure. These theoretical results, performed by finite element method, highlight a new acoustic wave confinement suitable in various applications such as acoustophoresis, lab on chip and microfluidics.
Publisher: Penerbit Universiti Kebangsaan Malaysia (UKM Press)
Date: 31-03-2018
Publisher: ASME International
Date: 25-05-2016
DOI: 10.1115/1.4033633
Publisher: Elsevier BV
Date: 09-2005
Publisher: IEEE
Date: 08-2018
Publisher: World Scientific Pub Co Pte Lt
Date: 08-2005
DOI: 10.1142/S0219581X05003358
Abstract: The microstructural characteristics and mechanical property of the Nanocrystalline Nickel ( Nc -Nickel), produced by Electrodeposition (ED) and Mechanical milling (MM), were investigated in the present work. From the nanoindentation study, we observed that MM - Nc - Ni showed lower hardness than ED - Nc - Ni and Microcrystalline ( Mc )- Ni . ED - Nc - Ni showed a significant improvement in hardness. All the Nc -Nickel s les, regardless of processing methods and grain sizes, showed comparable elastic moduli. The lower hardness of MM - Nc - Ni is due to the presence of microcrystalline Nc - Ni .
Publisher: Springer Science and Business Media LLC
Date: 06-07-2017
Publisher: IEEE
Date: 2006
No related grants have been discovered for Kim Siow.