Mamun Jamal

Disposable biosensor based on immobilisation of glutamate oxidase on Pt nanoparticles modified Au nanowire array electrode

Novel electrochemical platform based on Pt nanoparticle modified ordered three-dimensional gold nanowire arrays (PtNP/NAEs) for the amperometric sensing of H(2)O(2) and glutamate is developed. Pt nanoparticle (PtNP) is fabricated by electrodeposition onto the 3D nanowires and characterised using scanning electron microscopy (SEM) and cyclic voltammetry. The deposited nanoparticles have an average size of 20 nm. The PtNP/NAE shows a linear response of up to 20 mM for H(2)O(2) detection with a sensitivity of 194.60 μA mM(-1) cm(-2) at 20°C. It can detect 1 μM (S/N=3) of H(2)O(2) at normal condition without using any enzyme or mediator. Analytical performance of this electrode is tested by immobilising glutamate oxidase (GlutOx) through cross-linking in the matrix of bovine serum albumin (BSA), Nafion and glutaraldehyde. At physiological pH, the biosensor showed the sensitivity of 10.76 μA mM(-1) cm(-2), with a linear range of up to 0.8 mM.

Disposable sensor based on enzyme-free Ni nanowire array electrode to detect glutamate.

Enzyme free electrochemical sensor platform based on a vertically aligned nickel nanowire array (NiNAE) and Pt coated nickel nanowire array (Pt/NiNAE) have been developed to detect glutamate. Morphological characterisation of Ni electrodes was carried out using scanning and transmission electron microscopy combined with energy dispersive X-ray (SEM-EDX), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Cyclic voltammetry (CV) and amperometry were used to evaluate the catalytic activity of the NiNAE and the Pt/NiNAE for glutamate. It has been found that both NiNAE and Pt/NiNAE electrodes showed remarkably enhanced electrocatalytic activity towards glutamate compared to planar Ni electrodes, and showed higher catalytic activity when compared to other metallic nanostructure electrodes such as gold nanowire array electrodes (AuNAE) and Pt coated gold nanowire array electrode (Pt/AuNAE). The sensitivity of NiNAE and Pt/NiNAE has been found to be 65 and 96 μA mM(-1) cm(-2), respectively, which is approximately 6 to 9 times higher than the state of the art glutamate sensor. Under optimal detection conditions, the as prepared sensors exhibited linear behaviour for glutamate detection in the concentration up to 8mM for both NiNAE and Pt/NiNAE with a limit of detection of 68 and 83 μM, respectively. Experimental results show that the vertically aligned ordered nickel nanowire array electrode (NiNAE) has significant promise for fabricating cost effective, enzyme-less, sensitive, stable and selective sensor platform.

High-Temperature Die-Attach Technology for Power Devices Based on Thermocompression Bonding of Thin Ag Films

Wide-bandgap materials such as silicon carbide enable power electronics to face increasing demands for greater power density and high-temperature capability at the chip level. However, new packaging solutions have yet to be found to replace Pb solders in high-temperature applications. In this paper, the applicability of electrodeposited Ag thin film as a novel high-temperature die-attach material to connect power chips to direct-bonded copper substrates is investigated. Ag films were obtained by electrochemical deposition on the backmetallization of Si chips. The joint was then produced by thermocompression bonding at 350°C with a 40-N force applied for 10 min in air. A die shear strength of 1.70 MPa (twice the MIL standard) was achieved. The assembly demonstrated satisfactory resistance to thermomechanical fatigue when subjected to thermal aging and thermal cycling tests in high-temperature environments. The proposed bonding technology is thus a suitable solution for the provision of strong and reliable joints for power devices which have to operate in extreme temperature conditions (>200°C).

Sensor and biosensor to detect vascular graft infection: diagnosis and challenges

Vascular graft implantation is a very common practice in clinics; however, one of the major limitations of synthetic vascular grafts is that they are prone to infection, which has drastic implications. In severe stages of infection, this requires removal of the graft, if left untreated the mortality is almost definite. Therefore, it is important to detect the graft infection early in the disease process to manage and eliminate the graft infection with appropriate drug delivery. However, current infection detection methods are time consuming, not reliable and expensive. Therefore, researchers recently geared their effort toward developing sensor/biosensor technology to detect infection. In recent years, biochemical sensors and biosensors have emerged as a dynamic technique to perform qualitative and quantitative analysis of various analytes in the clinical environment. The need for a low cost, reliable, sensitive and biocompatible sensor device is crucial in the complex biological environment. In this review, we examine the different types of vascular graft infections and the major cause of such infections associated with implantation. Routine detection methods along with their limitations are also discussed. With the growing number of vascular graft infections being diagnosed worldwide and the increased number of fatalities due to late detection, there is a need to have such a device that can ensure in vivo continuous monitoring. As point-of-care diagnostic devices present a viable option for the rapid and sensitive detection and analysis, it is another option in the early diagnosis of prosthetic vascular graft infections (PVGIs), to use a reliable and cost effective sensor. For this reason, specific biomarkers to detect graft infection along with their detection using sensor or biosensor is the main focus of this review. This review provides an overview of the in vivo implantable devices available today, areas which are currently being developed and researched for in vivo implantation and a consideration of future prospects of the technology with their challenges.

Novel pH sensor based on anthraquinone–ferrocene modified free standing gold nanowire array electrode

A novel electrochemical pH sensor was fabricated through the use of an anthraquinone–ferrocene (AQ–Fc) complex based on a vertically aligned gold nanowire array electrode (AuNAE). The sensing capability was achieved by monitoring the variation in peak potential of the redox active/pH active anthraquinone moiety with respect to the redox active ferrocene moiety. The pH sensor, based on AQ–Fc/AuNAE, was characterised using scanning electron microscopy (SEM) and cyclic voltammetry (CV). The difference in peak potential of the ferrocene and anthraquinone moieties was measured using square wave voltammetry (SWV) and was found to be linear over the range of pH 2–11, with a sensitivity of 1.38 V pH−1 cm−2 at 25 °C. The electrode was found to respond both in the presence and absence of oxygen, further expanding the potential applications to include de-oxygenated environments. The sensor showed a potential drift of 1.0–3.3% after three hours and 95% of the signal was retained after one week. Such single molecular complex (AQ–Fc) based pH sensors should provide easy manufacturing and long term stability when incorporated into the sensor designs.

Thermocompression bonding of Ag-MWCNTs nanocomposite films as an alternative die-attach solution for high temperature packaging of SiC devices

Power electronics faces increasing demands for greater power density and high temperature handling capability. Wide band gap materials were shown to enable improved performance at the chip level, however, new packaging solutions that replace Pb solders at high temperatures have yet to be found. This work investigates the use of a Ag-MWCNTs composite as a novel die-attach material to bond SiC Schottky diodes to DBC substrates. Ag and MWCNTs are co-deposited to form a thin film on the backside of a chip. The joint is then produced by thermocompression flip-chip bonding at 350°C for 10 min with a 40 N applied force, in air. Die shear tests demonstrate that a joint strength of 2 MPa on average can be achieved, over twice the MIL standard. Thermal cycling and thermal aging tests in high temperature environments also demonstrated the good resistance of the bonded assembly to thermomechanical fatigue. It was thus found that strong and reliable joints, that are able to operate at high temperatures, can be created using the developed bonding technology.

Robust Design for High Temperature and High Voltage Applications

The automotive industry developments in the electrification of power train systems (i.e. HEVs and EVs), chassis systems (i.e. X-by wire systems) and auxiliaries (e.g. HVAC) have created a rapidly growing demand of advanced high temperature robust and reliable power electronics systems. This will require further efforts both in nanoelectronics semiconductor basic technologies and in system integration: power electronic system coming from industrial segments, need to be qualified against automotive requirements in term of reliability, robustness, safety and dependability. The paper gives an overview of the semiconductor technologies and integrated electronics for electrical power systems in particular for electric vehicles (EVs) and hybrid electric vehicles (HEVs). In addition it will discuss the mapping of the semiconductor technologies to the module electronics requirements aiming to the highest levels of reliability (target zero defects).