Now showing 1 - 4 of 4
  • Publication
    Fabrication and simulation of silicon nanowire pH sensor for Diabetes Mellitus detection
    Diabetes Mellitus (DM) is a disease failed to control the balance of blood sugar level due to lack of insulin thereby it effect human health. In Malaysia, there are around 3.9 millions people aged 18 years old and above have diabetes according to National Health and Morbidity Survey 2019. Silicon Nanowire is a nanostructure which has ultra-high sensitivity and non-radioactive that has potential given good performances when applied on pH sensor and biosensor. Silicon nanowire pH sensor and biosensor is an electronic sensor that investigated to improve the sensitivity and accuracy for detecting DM. This project consists of two parts, which are fabrication of silicon nanowire pH sensor and simulation of silicon nanowire biosensor as preliminary study. In fabrication, silicon nanowire of pH sensor is fabricated by conventional lithography process, reaction ion etching (RIE) and metallization to achieved the width of 100 nm silicon nanowire. The pH6, pH7, pH10 and DI water as analytes to analysis the current-voltage (I-V) characteristics of silicon nanowire pH sensor. In second part, the silicon nanowire biosensor as preliminary study is done simulation by Silvaco ATLAS devices simulator. The silicon nanowire with 30 nm in height and 20 nm in width of biosensor is designed and simulated to analyze the performance in terms of sensitivity. I-V characteristics of silicon nanowire biosensor according to different concentration of negative interface charge is determined. The negative interface charge represent as the Retinol Binding Protein 4 (RBP4) which is used to diagnose DM. The I-V characteristic based on the change in current, resistance and conductance to determine sensitivity. Lastly, the sensitivity of silicon nanowire pH sensor obtained 23.9 pS/pH while the sensitivity of simulated silicon nanowire biosensor obtained 3.91 nS/e.cm2. The results shown the more negative charge of concentration analyte attached on surface silicon nanowire has been accumulated more current flow from drain terminal to source terminal. It leads to the resistance becomes highest and obtained good sensitivity. In summary, the silicon nanowire pH sensor exhibited good performance and high sensitivity in detection pH level. The simulated silicon nanowire biosensor is capable of detecting biomolecular interactions charges to obtained high sensitive and accuracy result.
  • Publication
    Gold-nanoparticle associated deep eutectic solution mediates early bio detection of ovarian cancer
    Gold nanoparticles (AuNPs) have indeed been extensively researched in biological and photothermal therapy applications in recent years. This study aims to enhance the sensitivity of biosensors for early detection of ovarian cancer biomarkers by investigating the efficacy of DES-mediated surface functionalization of AuNPs. Additionally, the impact of DES on the stability and dispersion of AuNPs on SiO2 support is assessed to optimize sensor performance. A simple DES-mediated synthesis method for efficient amine surface functionalization of silicon dioxide (SiO2) to incorporate tiny AuNPs for antibody biosensors. Physical characterization [Scanning Electron Microscope (SEM), Ultraviolet-Visible Spectrophotometer (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR), and 3D Profiler] and electrical characterization (Keithley) have been done to determine the functionalization of the modified IDE surface. SEM analysis indicated the resultant nanoparticles have truncated spherical shapes. There is just a peak recorded by UV-Vis at 504-540 nm with AuNPs due to the formation of monodispersed AuNPs. When the conjugation of DES with samples is measured, the curves are identical in form, and the highest peak after conjugation has remained at 230 nm but the SPR absorption peak becomes narrower and moves toward greater wavelengths, indicating the conjugation between the molecules. Furthermore, when the DES is conjugated with AuNPs, 3-Aminopropyltriethoxysilane (APTES), antibody, and protein, the peaks gradually increased and became narrower, where O-H at 3280 cm-1, C-H at 2809 cm-1 and 2933 cm-1, CH2 at 1448 cm-1, CH3 at 1268 cm-1, C-OH at 1048 cm-1 and 1110 cm-1 and C-N+ at 844 cm-1 as analyzed by FTIR. Moreover, it can be observed that the 3D profilometer revealed a few red-colored areas, which are the portion that protrudes from the IDE surface. Based on the findings, it is possible to infer that this immunosensor does have the prospective to be used in clinical investigations for the precise detection of ovarian cancer or other biomarkers. The capacitance, transmittance, and resistivity profiles of the biosensor clearly distinguished between the antibody immobilization and the affinity binding. The presence of a DES-mediated synthetic approach increased the possibility of supporting different metal nanoparticles on SiO2 as the potential platform for biosensor applications.
  • Publication
    Electrical simulation on silicon nanowire field-effect transistor biosensor at different substrate-gate voltage bias conditions for charge detection
    In this work, the impact of different substrate-gate voltage bias conditions (below and above the device threshold voltage) on current-voltage characteristics and sensitivity of a silicon nanowire field-effect transistor (SiNW-FET) biosensor was investigated. A 3-dimensional device structure with n-type SiNW channel and a substrate gate electrode was designed and electrically simulated In the Silvaco ATLAS. Next, the SiNW channel was covered with a range of interface charge density to mimic the charged target biomolecule captured by the device. The outcome was translated into a drain current versus interface charge semi-log graph and the device sensitivity was calculated using the linear regression curve’s slope of the plotted data. The device’s electrical characteristic shown higher generation of output drain current values with the increase of negative substrate-gate voltage bias due to the hole carriers’ accumulation that forms a conduction channel in the SiNW. Application of higher negative interface charge density increased the change in drain current, with the device biased with higher substrate-gate voltage shows more significant change in drain current. The device sensitivity increased when biased with higher substrate-gate voltage with highest sensitivity is 75.12 nA/dec at substrate-gate voltage bias of –1.00 V.
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  • Publication
    Fabrication of silicon nanowire sensors for highly sensitive pH and DNA hybridization detection
    ( 2022)
    Siti Fatimah Abd Rahman
    ;
    Nor Azah Yusof
    ;
    ; ; ;
    Mohd Nizar Hamidon
    A highly sensitive silicon nanowire (SiNW)-based sensor device was developed using electron beam lithography integrated with complementary metal oxide semiconductor (CMOS) technology. The top-down fabrication approach enables the rapid fabrication of device miniaturization with uniform and strictly controlled geometric and surface properties. This study demonstrates that SiNW devices are well-aligned with different widths and numbers for pH sensing. The device consists of a single nanowire with 60 nm width, exhibiting an ideal pH responsivity (18.26 × 106 Ω/pH), with a good linear relation between the electrical response and a pH level range of 4–10. The optimized SiNW device is employed to detect specific single-stranded deoxyribonucleic acid (ssDNA) molecules. To use the sensing area, the sensor surface was chemically modified using (3-aminopropyl) triethoxysilane and glutaraldehyde, yielding covalently linked nanowire ssDNA adducts. Detection of hybridized DNA works by detecting the changes in the electrical current of the ssDNA-functionalized SiNW sensor, interacting with the targeted ssDNA in a label-free way. The developed biosensor shows selectivity for the complementary target ssDNA with linear detection ranging from 1.0 × 10−12 M to 1.0 × 10−7 M and an attained detection limit of 4.131 × 10−13 M. This indicates that the use of SiNW devices is a promising approach for the applications of ion detection and biomolecules sensing and could serve as a novel biosensor for future biomedical diagnosis.
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