Zamri Bin Radzi

Design and Development for Capacitive Humidity Sensor Applications of Lead-Free Ca,Mg,Fe,Ti-Oxides-Based Electro-Ceramics with Improved Sensing Properties via Physisorption

Despite the many attractive potential uses of ceramic materials as humidity sensors, some unavoidable drawbacks, including toxicity, poor biocompatibility, long response and recovery times, low sensitivity and high hysteresis have stymied the use of these materials in advanced applications. Therefore, in present investigation, we developed a capacitive humidity sensor using lead-free Ca,Mg,Fe,Ti-Oxide (CMFTO)-based electro-ceramics with perovskite structures synthesized by solid-state step-sintering. This technique helps maintain the submicron size porous morphology of the developed lead-free CMFTO electro-ceramics while providing enhanced water physisorption behaviour. In comparison with conventional capacitive humidity sensors, the presented CMFTO-based humidity sensor shows a high sensitivity of up to 3000% compared to other materials, even at lower signal frequency. The best also shows a rapid response (14.5 s) and recovery (34.27 s), and very low hysteresis (3.2%) in a 33%–95% relative humidity range which are much lower values than those of existing conventional sensors. Therefore, CMFTO nano-electro-ceramics appear to be very promising materials for fabricating high-performance capacitive humidity sensors.

Molecular Mechanisms of Stress-Responsive Changes in Collagen and Elastin Networks in Skin

Collagen and elastin networks make up the majority of the extracellular matrix in many organs, such as the skin. The mechanisms which are involved in the maintenance of homeostatic equilibrium of these networks are numerous, involving the regulation of genetic expression, growth factor secretion, signalling pathways, secondary messaging systems, and ion channel activity. However, many factors are capable of disrupting these pathways, which leads to an imbalance of homeostatic equilibrium. Ultimately, this leads to changes in the physical nature of skin, both functionally and cosmetically. Although various factors have been identified, including carcinogenesis, ultraviolet exposure, and mechanical stretching of skin, it was discovered that many of them affect similar components of regulatory pathways, such as fibroblasts, lysyl oxidase, and fibronectin. Additionally, it was discovered that the various regulatory pathways intersect with each other at various stages instead of working independently of each other. This review paper proposes a model which elucidates how these molecular pathways intersect with one another, and how various internal and external factors can disrupt these pathways, ultimately leading to a disruption in collagen and elastin networks.

Impact strength of an experimental polyurethane- based polymer

The impact strength of a newly developed experimental polyurethane-based polymer which is derived from palm oil (Experimental PU) was compared with denture polymers; heat-cured and self cured polymethyl methacrylate (PMMA) and Eclipse ® , light-activated urethane dimethacrylate prosthetic resin system. Ten specimens were prepared using heat-cured PMMA (Meliodent ® Heat

Uniformly Porous Nanocrystalline CaMgFe1.33Ti3O12 Ceramic Derived Electro-Ceramic Nanocomposite for Impedance Type Humidity Sensor

Since humidity sensors have been widely used in many sectors, a suitable humidity sensing material with improved sensitivity, faster response and recovery times, better stability and low hysteresis is necessary to be developed. Here, we fabricate a uniformly porous humidity sensor using Ca, Ti substituted Mg ferrites with chemical formula of CaMgFe1.33Ti3O12 as humidity sensing materials by solid-sate step-sintering technique. This synthesis technique is useful to control the grain size with increased porosity to enhance the hydrophilic characteristics of the CaMgFe1.33Ti3O12 nanoceramic based sintered electro-ceramic nanocomposites. The highest porosity, lowest density and excellent surface-hydrophilicity properties were obtained at 1050 °C sintered ceramic. The performance of this impedance type humidity sensor was evaluated by electrical characterizations using alternating current (AC) in the 33%–95% relative humidity (RH) range at 25 °C. Compared with existing conventional resistive humidity sensors, the present sintered electro-ceramic nanocomposite based humidity sensor showed faster response time (20 s) and recovery time (40 s). This newly developed sensor showed extremely high sensitivity (%S) and small hysteresis of <3.4%. Long-term stability of the sensor had been determined by testing for 30 consecutive days. Therefore, the high performance sensing behavior of the present electro-ceramic nanocomposites would be suitable for a potential use in advanced humidity sensors.

Development of biocompatible hydroxyapatite–poly(ethylene glycol) core–shell nanoparticles as an improved drug carrier: structural and electrical characterizations

Hydroxyapatite–5 wt% poly(ethylene glycol) (HA–PEG) core–shell composite nanoparticles (NPs) were synthesized using a coprecipitation technique. For the first time, the NPs are characterized for potential drug delivery applications using structural, electrical and in vitro kinetic studies. Phase quantification and the crystal structures of the NPs were analyzed using X-ray diffraction and Fourier transform infrared spectroscopy and the morphology was determined using scanning electron and transmission electron microscopies. Dielectric spectroscopy was used to analyze the polarization behaviour of the HA and HA–PEG core–shell NPs as potential drug carriers by applying an oscillating (100 Hz to 2.5 MHz) electric field. The increased intra-particle interfacial interactions in the HA–PEG NPs confirmed the significant enhancement in interfacial or space charge polarization owing to the reduction in mobility and accumulation of charge-carriers at the interfaces. Thus, HA–PEG showed better aceclofenac drug releasing properties than pristine HA NPs. An in vitro cell study confirmed that the HA and HA–PEG core–shell nanocarriers showed excellent biocompatibility on human dermis fibroblast (HDF) cells. The interaction within the HA–PEG core–shell was stronger than with pristine HA and the biodegradable PEG from the shell-layer neutralized the composite-surroundings path. Hence, it would reduce the direct interaction of aceclofenac drug with the surrounding biomolecules of the delivery paths and enhance the ability for carrying the drug precisely to the target organs.

Fabrication of 316L stainless steel parts by Injection Moulding for Biomedical Application using a Novel Binder

This paper focuses on the usage of a novel binder system base on palm oil product to produce sintered parts of stainless steel 316L produced by vertical injection molding technique for biomedical application. The stainless steel 316L powder was mixed using z-blade mixer with the thermoplastic binder system comprising of polyethylene, paraffin wax, stearic acid and palm stearin which was derived from palm oil at different volume percent (%). The feedstock then was studied in term of viscosity and shear rate using capillary rheometer. The feedstock was molded using vertical injection molding machine. After molding, the green molded part was immersed into the solvent to extract part of the binder system followed by sintering under vacuum atmosphere at the temperature of 1360°C. The physical and mechanical properties of the sintered part such as density, hardness, shrinkage, ultimate tensile strength and elongation were measured. Biocompatibility study of in vitro test using cell osteosarcoma MG-63 was observed and discussed.

Characteristics and Young's Modulus of Collagen Fibrils from Expanded Skin Using Anisotropic Controlled Rate Self-Inflating Tissue Expander

Mechanical properties of expanded skin tissue are different from normal skin, which is dependent mainly on the structural and functional integrity of dermal collagen fibrils. In the present study, mechanical properties and surface topography of both expanded and nonexpanded skin collagen fibrils were evaluated. Anisotropic controlled rate self-inflating tissue expanders were placed beneath the skin of sheeps forelimbs. The tissue expanders gradually increased in height and reached equilibrium in 2 weeks. They were left in situ for another 2 weeks before explantation. Expanded and normal skin samples were surgically harvested from the sheep (n = 5). Youngs modulus and surface topography of collagen fibrils were measured using an atomic force microscope. A surface topographic scan showed organized hierarchical structural levels: collagen molecules, fibrils and fibers. No significant difference was detected for the D-banding pattern: 63.5 ± 2.6 nm (normal skin) and 63.7 ± 2.7 nm (expanded skin). Fibrils from expanded tissues consisted of loosely packed collagen fibrils and the width of the fibrils was significantly narrower compared to those from normal skin: 153.9 ± 25.3 and 106.7 ± 28.5 nm, respectively. Youngs modulus of the collagen fibrils in the expanded and normal skin was not statistically significant: 46.5 ± 19.4 and 35.2 ± 27.0 MPa, respectively. In conclusion, the anisotropic controlled rate self-inflating tissue expander produced a loosely packed collagen network and the fibrils exhibited similar D-banding characteristics as the control group in a sheep model. However, the fibrils from the expanded skin were significantly narrower. The stiffness of the fibrils from the expanded skin was higher but it was not statistically different.

Design and development of an in situ synthesized layered double hydroxide structure of Fe-induced hydroxyapatite for drug carriers

Iron (Fe)-induced hydroxyapatite (HA) layered double hydroxides (LDH) with different concentrations of Fe (FH95 and FH85) were prepared by a novel in situ coprecipitation method. For the first time, LDH is intercalated with calcium cations (CaI2+) by producing Frenkel defects. The LDH structure was precisely characterized by thermogravimetric analysis and X-ray diffraction study. The exfoliation in the basal planes was also confirmed by high resolution transmission electron microscopy. Hydrophilicity and change in mass in vitro swelling in phosphate buffered saline (PBS) medium were characterized to check the wettability of the pellet samples in aqueous media. The morphological and elemental study of the carriers was done before and after aceclofenac (AF) drug loading by a field emission electron microscope. Interactions of AF with LDH drug carriers (FH85 and FH95) were studied by Fourier transforms infrared spectroscopy. The AF drug-release mechanism of these novel LDH carriers was diffusion. The AF drug loading efficiency and releasing criteria were found to be better in FH95 than the carrier FH85. The FH95 LDH carrier can store the AF drug and can release the drug in a controlled manner in aqueous medium of PBS under simulated body conditions. Furthermore, the newly developed LDH material is highly biocompatible as well as a potential drug carrier. Therefore, the developed LDH drug carrier could be a potential drug scavenger for non-steroidal anti-inflammatory drugs such as AF.

The facial soft tissue simulation of orthognathic surgery using biomechanical model

This paper describes a surgical planning, simulation and prediction of facial soft tissue appearance with regard to the orthognathic surgery. The facial soft tissue prediction is done by means of mandibular advancement through the osteotomy planning system. Our approach is based on finite element method on 3D facial models of quadrilateral elements. These elements represent different tissue regions of facial bone and skin surface semi-automatically generated from segmented patient-specific computer tomography data. We describe the surface facial model reconstruction from individualized anatomy, surgical procedures and numerical solution for static postoperative facial appearance using linear elastic finite element analysis. The physical computational modeling for the prediction of soft tissue is described. Isotropic, homogeneous and linear elastic tissue models are elaborated. The simulated result which is achieved by the advancement of lower jaw bone through the contact analysis is presented. Discussion on evaluation of the simulated result is performed with the actual findings.

Validation of cone beam CT scan for measurement of palatal depth in study casts

The purpose of this study was to validate the use of digital dental study casts obtained from Cone beam CT Scan (CBCT) against gold standard; that is traditional dental study cast measured with digital caliper.