Mahmoud Al Ahmad

RF Microalgal lipid content characterization

Most conventional techniques for the determination of microalgae lipid content are time consuming and in most cases are indirect and require excessive sample preparations. This work presents a new technique that utilizes radio frequency (RF) for rapid lipid quantification, without the need for sample preparation. Tests showed that a shift in the resonance frequency of a RF open-ended coaxial resonator and a gradual increase in its resonance magnitude may occur as the lipids content of microalgae cells increases. These response parameters can be then calibrated against actual cellular lipid contents and used for rapid determination of the cellular lipids. The average duration of lipid quantification using the proposed technique was of about 1 minute, which is significantly less than all other conventional techniques, and was achieved without the need for any time consuming treatment steps.

Virus detection and quantification using electrical parameters.

Here we identify and quantitate two similar viruses, human and feline immunodeficiency viruses (HIV and FIV), suspended in a liquid medium without labeling, using a semiconductor technique. The virus count was estimated by calculating the impurities inside a defined volume by observing the change in electrical parameters. Empirically, the virus count was similar to the absolute value of the ratio of the change of the virus suspension dopant concentration relative to the mock dopant over the change in virus suspension Debye volume relative to mock Debye volume. The virus type was identified by constructing a concentration-mobility relationship which is unique for each kind of virus, allowing for a fast (within minutes) and label-free virus quantification and identification. For validation, the HIV and FIV virus preparations were further quantified by a biochemical technique and the results obtained by both approaches corroborated well. We further demonstrate that the electrical technique could be applied to accurately measure and characterize silica nanoparticles that resemble the virus particles in size. Based on these results, we anticipate our present approach to be a starting point towards establishing the foundation for label-free electrical-based identification and quantification of an unlimited number of viruses and other nano-sized particles.

Piezoelectric energy droplet harvesting and modeling

Vibrational harvested energy using piezoelectric cantilevers provides sufficient output for small power applications. This work reports on free falling droplet energy harvesting using piezoelectric cantilevers. The harvester incorporates a bimorph cantilever that composite of two layers of lead zirconate titanate (PZT) materials. During the drop impact a transfer of kinetic energy from the drop to the piezoelectric cantilever occurs in the form of mechanical stress forcing the piezoelectric structure to vibrate. Experimental results show an instantaneous water droplet power of around 2.15 mWcm3g-1, i.e. this is 37 times higher than what previously has been reported.

Pulse electrodeposited RuO2 electrodes for high-performance supercapacitor applications

ABSTRACT The present work addresses high-performance Ruthenium Oxide (RuO2) electrodes prepared by using a simple pulse electrodeposition method. For the comparison purpose, two different precursors, namely, ruthenium (III) nitrosyl sulphate (RuNS) and ruthenium trichloride (RuCl3), were used in this study. The coatings were subjected to material characterisation such as Field Emission Scanning Electron Microscopy and Energy-Dispersive X-ray Spectroscopy, X-ray diffraction and Transmission electron microscopy as well as electrochemical characterisation such as Cyclic Voltammetry, Electrochemical Impedance Spectroscopy and charge/discharge. The RuNS–RuO2 coating exhibited excellent specific capacitance (1724 F/g at 5 A/g) with a remarkable rate capability. This value is significantly higher (52%) than the value obtained for RuCl3–RuO2 electrode material at 5 A/g. The findings provide valuable information on the potential use of RuNS as a precursor for synthesising RuO2 and pulse electrodeposition process to produce electrodes for supercapacitors.

Electrical characterization of DNA supported on nitrocellulose membranes.

Integrated DNA-based nanoscale electronic devices will enable the continued realization of Moore’s Law at the level of functional devices and systems. In this work, the electrical characterization of single and complementary base paired DNA has been directly measured and investigated via the use of nitrocellulose membranes. A radio frequency DAKS-3.5 was used to measure the reflection coefficients of different DNA solutions dotted onto nitrocellulose membranes. Each DNA solution was exposed to a radio frequency signal with a power of 10 dBm and with a sweep from 200 MHz up to 13.6 GHz. The conducted measurements show some distinctions between the homomeric and complementary bases due to their different electrical polarization. As revealed from the measurements conducted, with the addition of DNA oligonucleotides, the measured capacitance increased when compared with buffer medium alone. The DNA molecules could be modeled as dielectric material that can hold electrical charges. Furthermore, the complementary paired DNA molecule-based inks solutions had a higher capacitance value compared with single DNA molecules (A, C, G and T) solutions.

Visualization and quantification of oil in single microalgal cells

Microalgae are considered a promising source of oil for biodiesel production. This work reports an estimation method of oil content inside living microalgal cells by visualization and image processing techniques. This approach was used to analyze the time course of oil accumulation patterns in Nile Red-stained microalgal cells of Scenedesmus sp. cultivated in nitrogen-deficient medium used to induce oil accumulation in microalgal cells. Nile Red staining is a widely used technique for studying oil content of microalgal cells. The intracellular oil content was estimated by mathematically evaluating the oil volume inside the stained cell. This novel visualization approach has the potential to be used in ex vivo studies of oil content at the level of single microalgal cells. This method can also be applied to other types of oil-producing microorganisms because of its accuracy, precision, and reduction in the time and effort required for optimization.

Piezoelectric extraction of ECG signal

The monitoring and early detection of abnormalities or variations in the cardiac cycle functionality are very critical practices and have significant impact on the prevention of heart diseases and their associated complications. Currently, in the field of biomedical engineering, there is a growing need for devices capable of measuring and monitoring a wide range of cardiac cycle parameters continuously, effectively and on a real-time basis using easily accessible and reusable probes. In this paper, the revolutionary generation and extraction of the corresponding ECG signal using a piezoelectric transducer as alternative for the ECG will be discussed. The piezoelectric transducer pick up the vibrations from the heart beats and convert them into electrical output signals. To this end, piezoelectric and signal processing techniques were employed to extract the ECG corresponding signal from the piezoelectric output voltage signal. The measured electrode based and the extracted piezoelectric based ECG traces are well corroborated. Their peaks amplitudes and locations are well aligned with each other.

Piezoelectric self-biased energy harvesting circuit for smart city applications

This paper presents a novel energy harvesting circuitry for a self-biased piezoelectric suitable for battery-less sensors in remote applications. The presented self-biased energy harvesting circuit does not require any external DC bias. The DC bias required to switch a transistor is granted from the electronic oscillator that is biased through the piezoelectric converted energy. The amplified output voltage utilizing a DC to DC boost converter with maximum power efficiency at the output has been fabricated using PCB board. The circuit is composed of a full wave bridge rectifier, smoothing capacitor, switch mode DC/DC Boost converter and a storage component at the output terminal. The measured harvested power is of 300 micro watts at load of 1.2M ohms used for ultra-low power applications.

Electromechanical analogy for d 33 piezoelectric harvester power calculations

This paper combines both the well-known power transfer and electromechanical coupling analogy theories for calculating the electrical power output of d33-based piezoelectric harvesters. The proposed methodology utilized the direct mechanical-to-electrical analogy, electromagnetic and power system theories to develop analytical models to compute the power output taking into account the dimensions and material properties of the piezoelectric generator. The developed method has been experimentally validated and it was found that the current technique provides significant additional information that crucial for enhancing the device design and operation in a straightforward manner when compared to other conventional reported methods.

Label-free capacitance-based identification of viruses.

This study was undertaken to quantitate a single virus suspension in culture medium without any pre-processing. The electrical capacitance per virus particle was used to identify the kind of virus present by measuring the suspension (virus plus medium) capacitance, de-embedding the medium contribution, and dividing by the virus count. The proposed technique is based on finding the single virus effective dielectric constant which is directly related to the virus composition. This value was used to identify the virus type accordingly. Two types of viruses thus tested were further quantified by a biochemical technique to validate the results. Furthermore, non-organic nanoparticles with known concentration and capacitance per particle were identified using the proposed method. The selectivity of the method was demonstrated by performing electrical measurements on a third virus, revealing that the proposed technique is specific and sensitive enough to permit detection of a few hundred virus particles per milliliter within a few minutes.