| 1. |
- Anwar Zainuddin, Ahmad, et al.
(författare)
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Modeling of a Novel Biosensor with Integrated Mass and Electrochemical Sensing Capabilities
- 2016
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Ingår i: 2016 IEEE EMBS CONFERENCE ON BIOMEDICAL ENGINEERING AND SCIENCES (IECBES). - : IEEE. - 9781467377911 ; , s. 420-425
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Konferensbidrag (refereegranskat)abstract
- Rapid development in technology and society has generated diverse developments in many fields including biosensors in healthcare application. Here, the design of integrated biosensor comprises mass sensing (Quartz Crystal Microbalance) and electrochemistry sensing (Electrochemical Impedance Spectroscopy, EIS and Cyclic Voltammetry, CV) will be presented. The integrated sensor system is developed based on the innovative use of the top electrode of a quartz crystal microbalance (QCM) resonator as a working electrode for the electrochemistry technique. Integration of QCM with the electrochemistry technique is realized by fabricating a semicircular counter electrode near the upper electrode on the same side of the quartz crystal. CV and EIS measurement was conducted using finite element modeling, COMSOL (TM) 5.2 with the probe marker of 1 mmol L-1 of [Fe(CN)(6)](3-/4-). CV test was done to study the effect between increasing scan rate and peak current (anodic and cathodic) in observing the reversible electrochemical process. This observation is crucial in ensuring the electrochemical processes follow the Randles-Sevcik equation in characterizing the platform changes behavior. Later, EIS test was performed in order to measure the radius of the semicircle which reflects the charge transfer resistance (R-CT) of the redox marker. To show the effectiveness of this sensor, gold immobilization surface was electrochemically simulated and reported. Thus, an ultra-sensitive biosensor that capable to produce multi-analysis in the detection of biological targets in terms of electrochemical change of electrode interfaces, which is the crucial step towards the engineering of advanced bioelectronics.
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| 2. |
- Asri, Mohd Afiq Mohd, et al.
(författare)
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Low-cost and rapid prototyping of integrated electrochemical microfluidic platforms using consumer-grade off-the-shelf tools and materials
- 2022
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Ingår i: Lab on a Chip. - : ROYAL SOC CHEMISTRY. - 1473-0197 .- 1473-0189. ; 22:9, s. 1779-1792
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Tidskriftsartikel (refereegranskat)abstract
- We present a low-cost, accessible, and rapid fabrication process for electrochemical microfluidic sensors. This work leverages the accessibility of consumer-grade electronic craft cutters as the primary tool for patterning of sensor electrodes and microfluidic circuits, while commodity materials such as gold leaf, silver ink pen, double-sided tape, plastic transparency films, and fabric adhesives are used as its base structural materials. The device consists of three layers, the silver reference electrode layer at the top, the PET fluidic circuits in the middle and the gold sensing electrodes at the bottom. Separation of the silver reference electrode from the gold sensing electrodes reduces the possibility of cross-contamination during surface modification. A novel approach in mesoscale patterning of gold leaf electrodes can produce generic designs with dimensions as small as 250 mu m. Silver electrodes with dimensions as small as 385 mu m were drawn using a plotter and a silver ink pen, and fluid microchannels as small as 300 mu m were fabricated using a sandwich of iron-on adhesives and PET. Device layers are then fused together using an office laminator. The integrated microfluidic electrochemical platform has electrode kinetics/performance of Delta E-p = 91.3 mV, I-pa/I-pc = 0.905, characterized by cyclic voltammetry using a standard ferrocyanide redox probe, and this was compared against a commercial screen-printed gold electrode (Delta E-p = 68.9 mV, I-pa/I-pc = 0.984). To validate the performance of the integrated microfluidic electrochemical platform, a catalytic hydrogen peroxide sensor and enzyme-coupled glucose biosensors were developed as demonstrators. Hydrogen peroxide quantitation achieves a limit of detection of 0.713 mM and sensitivity of 78.37 mu A mM(-1) cm(-2), while glucose has a limit of detection of 0.111 mM and sensitivity of 12.68 mu A mM(-1) cm(-2). This rapid process allows an iterative design-build-test cycle in under 2 hours. The upfront cost to set up the system is less than USD 520, with each device costing less than USD 0.12, making this manufacturing process suitable for low-resource laboratories or classroom settings.
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| 3. |
- Khan, Muhammad Abbas, et al.
(författare)
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mmWave Four-Element MIMO Antenna for Future 5G Systems
- 2022
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Ingår i: Applied Sciences. - : MDPI AG. - 2076-3417. ; 12:9, s. 4280-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents an S-shape four-port Multiple Input Multiple Output (MIMO) wideband mmWave antenna with bandwidth of 25 GHz to 39 GHz. The antenna is designed on 0.254 mm ultra-thin RO5880 with permittivity of 2.3. The dimensions of proposed S-shape antenna are 10 x 12 mm for single element and 24 x 24 mm for four-port MIMO configuration. A decoupling network is introduced to further compress mutual coupling among MIMO elements. The peak gain achieved is 7.1 dBi and MIMO assembly delivers diversity scheme. The proposed MIMO antenna is fabricated, and simulated results are found to be in excellent agreement with simulations. Through the results obtained, the proposed MIMO antenna system can be considered as a potential candidate for future mmWave devices.
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| 4. |
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| 5. |
- Suhaimi, Muhammad Irsyad, et al.
(författare)
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Mechanical durability of screen-printed flexible silver traces for wearable devices
- 2022
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Ingår i: Sensing and Bio-Sensing Research. - : Elsevier. - 2214-1804. ; 38
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Tidskriftsartikel (refereegranskat)abstract
- There is increased usage of flexible electronics recently in various applications such as wearable devices, flexible displays and sensors. Studies on the durability of conductive metal traces under cyclic mechanical loading is crucial since these conductors will be subjected to repeated bending. In this work, the mechanical and electrical behavior of silver printed conductors was tested using cyclic three-point bend test. The samples were flexible polymer thick film (PTF) silver (Ag) ink printed on a flexible polyethylene terephthalate (PET) substrate. The durability of this PTF Ag ink, which has a hyper-elastic binder and Ag flakes, was studied by performing cyclic bending tests. Four-point resistivity measurements and imaging of the sample both before and after bending were performed. A custom tester machine was used to apply strain to the circuit and measure the resistivity of the silver trace. The results of the bending test show that the silver trace does not undergo significant deformation and the change in resistance is less than 0.6% under both tensile and compressive tests. Fatigue tests were also performed by cyclic bending tests for three trials in which batches of 10,000 cycles were completed. The printed silver wire withstood 30,000 cycles of bend tests and produced only 2.64% change in resistance. This indicates that the printed wires are very durable even after 30,000 cycles of outer bending. Imaging was also conducted on these samples to study the effect of repeated bending on the morphology of the silver conductive trace. Although there was an increase in surface roughness before and after cyclic bending, there was no obvious deformation or delamination observed in the samples.
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| 6. |
- Yunos, Muhammad Farhan Affendi Mohamad, et al.
(författare)
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RF Remote Blood Glucose Sensor and a Microfluidic Vascular Phantom for Sensor Validation
- 2021
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Ingår i: Biosensors. - : MDPI. - 2079-6374. ; 11:12
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Tidskriftsartikel (refereegranskat)abstract
- Diabetes has become a major health problem in society. Invasive glucometers, although precise, only provide discrete measurements at specific times and are unsuitable for long-term monitoring due to the injuries caused on skin and the prohibitive cost of disposables. Remote, continuous, self-monitoring of blood sugar levels allows for active and better management of diabetics. In this work, we present a radio frequency (RF) sensor based on a stepped impedance resonator for remote blood glucose monitoring. When placed on top of a human hand, this RF interdigital sensor allows detection of variation in blood sugar levels by monitoring the changes in the dielectric constant of the material underneath. The designed stepped impedance resonator operates at 3.528 GHz with a Q factor of 1455. A microfluidic device structure that imitates the blood veins in the human hand was fabricated in PDMS to validate that the sensor can measure changes in glucose concentrations. To test the RF sensor, glucose solutions with concentrations ranging from 0 to 240 mg/dL were injected into the fluidic channels and placed underneath the RF sensor. The shifts in the resonance frequencies of the RF sensor were measured using a network analyzer via its S-11 parameters. Based on the change in resonance frequencies, the sensitivity of the biosensor was found to be 264.2 kHz/mg center dot dL(-1) and its LOD was calculated to be 29.89 mg/dL.
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| 7. |
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| 8. |
- Zaidon, Nuradawiyah, et al.
(författare)
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Serpentine Microfluidic Structures for Concentration Gradient Generators
- 2016
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Ingår i: Symposium on Design, Test, Integration and Packaging of MEMS/MOEMS (DTIP), 2016. - : Institute of Electrical and Electronics Engineers (IEEE). - 9781509014576
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Konferensbidrag (refereegranskat)abstract
- This paper presents microfluidic concentration gradient generator having tree-like structures with implementation of laminar flow concept and small-scale mixing through diffusion inside its microchannel. The microchannels aim for constant flow rate at each outlet and is achieved by optimizing the channel lengths. The generation of concentration gradients is achieved at the outlet by simply tuning the flow rate and geometries of the microfluidics network. Variations in channel dimension and geometry demonstrates possible combinations of the microfluidics network is simulated using circuit simulator, PSpice and computational fluid dynamic (CFD) analysis software, Fluent 14.5. Next, PDMS-based microfluidic chips are fabricated by using soft lithography technique. The simulation and experimental results showed that the prominent mixing behaviour can be obtained inside the serpentine channels with constant flow rate at each outlet.
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| 9. |
- Zainuddin, Ahmad Anwar, et al.
(författare)
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Integrated Multichannel Electrochemical–Quartz Crystal Microbalance Sensors for Liquid Sensing
- 2020
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Ingår i: IEEE Access. - : Institute of Electrical and Electronics Engineers (IEEE). - 2169-3536. ; 8, s. 3668-3676
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Tidskriftsartikel (refereegranskat)abstract
- This paper highlights the design, simulation and fabrication of an array of twelve integrated electrochemical - quartz crystal microbalance (IEQCM) sensors on a single substrate for liquid sensing. Integration of both measurement techniques is made possible by combining the three electrode electrochemical device with the top and bottom electrodes for the microbalance. Important design parameters such as the working electrode radius and gap spacing, were studied using both theoretical calculations and COMSOL Multiphysics® finite element simulations. The sensor’s working electrode radius affects the magnitude of the frequency response while the gap affects the capacitance and current density which are important for electrochemical measurements. It was found that the best values for the working electrode radius was 2 mm and gap spacing was 0.5 mm. The sensors were fabricated using microfabrication techniques for the gold electrode and screen printing techniques for the reference electrode. Water contact angle, atomic force microscopy, and scanning electron microscope were utilized to study the surface roughness of the IEQCM sensor. IEQCM has a low contact angle of 53.0 ± 1° and low surface roughness of 1.92nm. For liquid sensing, an array of circular chambers were fabricated using polydimethylsiloxane (PDMS) and placed on top of the quartz substrate for liquid testing. Electrochemical measurements and cyclic voltammetry were performed using the sensor in ferri-ferrocyanide and phosphate buffered saline solution to study the function of scan rates on the peak current with respect to the potential difference. For mass sensing measurements, liquid water droplets of 1uL - 10 uL were placed onto the sensing surface and the change in resonance frequencies of the sensors were measured. These resonance frequency changes can be converted in mass change/area in accordance to the advanced Sauerbrey equation. The multichannel IEQCM sensor shows good potential as a parallel sensor for both biosensing and environmental applications.
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| 10. |
- Zainuddin, Ahmad Anwar, et al.
(författare)
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Prototyping and Early Validation of an Integrated, Electrochemical and Mass Three-sensor Array for Dengue Detection
- 2021
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Ingår i: PROCEEDINGS OF THE 15TH INTERNATIONAL JOINT CONFERENCE ON BIOMEDICAL ENGINEERING SYSTEMS AND TECHNOLOGIES (BIODEVICES), VOL 1. - : SCITEPRESS. - 9789897585524 ; , s. 204-211
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Konferensbidrag (refereegranskat)abstract
- This paper presents the current progress towards a lab-on-chip biosensor for early dengue detection, consisting of an integrated sensor with dual-function working electrode that enables in-situ measurements of both electrochemical impedance spectroscopy (EIS) and quartz crystal microbalance (QCM) enclosed in a miniaturized 3D-printed package equipped with electrical contacts and sample fluid delivery to the quartz biosensor array. The sensors consist of an array of three 10 MI-lz IEQCM biosensors on a single quartz substrate. Early validation is performed for future dengue sensing application. We report the design, optimisation, and fabrication of the sensors, as well as early optimisation and validation of surface bioconjugation of antibodies. This lab-on-chip has the potential to provide accurate dengue detection due to its high sensitivity and dynamic range, as well as providing rapid and early dengue detection in point-of-care settings.
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