Ahmed Hasnain Jalal

Fabrication and calibration of Oxazine-based optic fiber sensor for detection of ammonia in water

This paper presented the fabrication and calibration of a clad-modified evanescent based plastic optical fiber (POF) sensor for the detection of ammonia in both stagnant and dynamic aqueous media. This optochemical sensor was based on Oxazine 170 perchlorate (sensing material) and polydimethylsiloxane (PDMS) (protective material) thin layers. A special chemical solution was developed for the etching removal of cladding and a methodology for trapping moisture was exercised. Experimental results on dissolved ammonia detection exhibited short response time (≤10 s), low detection limit (minimum detection limit 1.4 ppm), high sensitivity, and excellent reversibility (over 99%).

Prospects and Challenges of Volatile Organic Compound Sensors in Human Healthcare

The chemical signatures of volatile organic compounds (VOCs) in humans can be utilized for point-of-care (POC) diagnosis. Apart from toxic exposure studies, VOCs generated in humans can provide insights into ones healthy and diseased metabolic states, acting as a biomarker for identifying numerous diseases noninvasively. VOC sensors and the technology of e-nose have received significant attention for continuous and selective monitoring of various physiological and pathophysiological conditions of an individual. Noninvasive detection of VOCs is achieved from biomatrices of breath, sweat and saliva. Among these, detection from sweat and saliva can be continuous in real-time. The sensing approaches include optical, chemiresistive and electrochemical techniques. This article provides an overview of such techniques. These, however, have limitations of reliability, precision, selectivity, and stability in continuous monitoring. Such limitations are due to lack of sensor stability and complexity of samples in a multivariate environment, which can lead to false readings. To overcome selectivity barriers, sensor arrays enabling multimodal sensing, have been used with pattern recognition techniques. Stability and precision issues have been addressed through advancements in nanotechnology. The use of various forms of nanomaterial not only enhance sensing performance, but also plays a major role in detection on a miniaturized scale. The rapid growth in medical Internet of Things (IoT) and artificial intelligence paves a pathway for improvements in human theranostics.

Wearable alcohol monitoring device with auto-calibration ability for high chemical specificity

Multimodal electrochemical method comprising open circuit potential and amperometric technique has been implemented to improve the specificity of the ethanol detection in a fuel cell sensor system. A miniaturized device with LMP91000 potentiostat and a processing unit has been constructed containing simple auto-calibration algorithm. The developed processing unit consist of a low power microcontroller (MSP430F5529LP). The sensing unit composed of a three electrode proton exchange membrane (PEM) fuel cell sensor, where Nafion is the PEM. In these studies, the signal due to interference has been eliminated with the support of algorithm and multimodal electrochemical method. The results show that the sensor can detect ethanol as low as 5ppm. The constructed device was validated by comparing it with the commercially available potentiostat, and the response was similar in both devices.

Comparative analysis of the performance of polymer based opto-chemical sensor in detecting ammonia in diverse mediums

In this paper, a polymer based opto-chemical sensor is used to detect ammonia in air, stagnant water and flowing water medium. The sensor structure includes oxazine 170 per chlorate as the sensing material and Polydi-methyl-siloxane [PDMS] as the protective material. The results obtained from the sensor at different mediums are used in this paper to analyze the sensitivity variations, response time fluctuations and reversibility of this sensor in detecting the presence of ammonia. The results show that surrounding conditions impact significantly on the ammonia detection for different mediums.

Lactate biosensing: The emerging point-of-care and personal health monitoring

Lactate plays a crucial role in the anaerobic metabolic pathway of humans. In situations of oxygen deficit, its production increases; leading to several life-threatening conditions such as hemorrhage, respiratory failure, trauma or ischemia from lactate acidosis. Lactate level detection and point-of-care (POC) monitoring in a fast, accurate and non-invasive manner is ultimately important for many health care applications. Optical and electrochemical techniques are employed in lactate sensing to achieve high sensitivity and selectivity, miniaturization, portability, simplicity, and low cost. To improve the selectivity and sensitivity, two important enzymes, lactate oxidase (LOx) and lactate dehydrogenese (LDH) are employed. Conventional methods for lactate detection are not fast enough to be used in point-of-care or personal health monitoring settings. Moreover, the existing point-of-care lactate sensing tools follow invasive or partially invasive sampling protocols such as finger pricking. In this review, a comprehensive overview of different lactate biosensing devices is presented. Particularly, the state-of-the-art and prospects of wearable, non-invasive lactate sensing from different biofluids are discussed.

Detection of the breast cancer based on the electrical impedance myography parameters using finite element method

Electrical Impedance Myography (EIM) is a painless, non-invasive electrophysiological technique for the assessment of different disease status of the human body. In EIM, high frequency, low-intensity electrical current is injected via the surface electrode to the localized area and resulting voltage patterns are analyzed using the voltage sensing electrode to access three major parameters-resistance(R), reactance(X), and phase(θ). This method detects the abnormalities in the biological tissue based on differences in values of these three parameters between normal and malignant tissue. In this study, a finite element model of the human breast has been developed in an attempt to analyze the EIM parameters for the detection of malignant tissue. Simulations were carried out for a frequency range of 2 to 3 GHz and electrical properties of breast tissue were used. For example, at 2.45 GHz, normal breast tissue has a resistance of .961 Ω and a reactance of 4.462 Ω. At this particular frequency, malignant breast tissue with a tumor size of 7 mm had a resistance of .945 ohm and reactance of 4.365 ohm. The percentage deviation of the normal breast tissue from the 7mm malignant tissue for resistance and reactance is 1.665% and 2.174% respectively. This paper attempts to illustrate the behavior of EIM parameters for different size and location of the tumor in the breast tissue. The ultimate goal of the paper is to investigate EIM’s ability to detect early cancer cell in the breast tissue.

ZnO nanoflakes-based mediator free flexible biosensors for the selective detection of ethylglucuronide (EtG) and lactate

We report on highly sensitive and flexible biosensors for noninvasive lactate and alcohol monitoring in human perspiration based on zinc oxide (ZnO) nanostructures that does not require linker layer for surface functionalization due to the high isoelectric point of ZnO. Towards fabrication of the biosensors, two-dimensional (2D) ZnO nanoflakes (NFs) were synthesized on flexible polyethylene terephthalate (PET) substrates employing single step sonochemical method after which lactate oxidase (LOx) and anti-body for ethyl glucuronide (EtG)-a metabolite of ethanol were immobilized atop without a linker layer. The cyclic voltammetry (CV) measurements in the concentration range of 10pM-10μM for lactate and 4.5 μM-0.45 M for EtG yielded minimum limit of detection of 10 pM and 4.5 μM, respectively for the electrode area of 0.5 × 0.5 cm2. Moreover, lactate sensor with ZnO NF electrodes demonstrated four times higher sensitivity compared to the ones with gold electrode that required DTSP linker layer for surface functionalization. High isoelectric point allows a direct, stable pathway for rapid electron transport without any mediator when an analyte is immobilized on NFs and improves electron transfer rate.

Precise calibration of optical fiber sensor for ammonia sensing using multivariate analysis

Detection in chemical sensing which needs to be carried out in a specific controlled environment, becomes complex in multivariate environment. This complication is caused by chemical interference, sensor degradation or drifting of the signals with time. A minute drifting or overlapping of the signals affects the calibration, especially in the detection of sub-ppm level of concentration of any chemical species. The presence of other compounds can well interfere providing false positive readings, deterring calibration of the system in precise quantification of any compound. This problem is known to also happen in our optical fiber sensor for the detection of ammonia. A clad-modified polymer optical fiber sensor for ammonia detection is explored in this work where oxazine 170 per chlorate dye is used as a recognition element to detect ammonia. The sensor was tested in water media and the sensitivity of the sensor we found was 0.0006 ppm-1cm-2. However, the lower sensitivity causes significant overlaps in between signals corresponding to different concentrations. To resolve this problem, multivariate analysis method, such as principal component analysis (PCA) was explored to interpret the datasets for precision of measurement and classification of each concentration. PCA generates unique regression curve which represents each concentration of ammonia considering principle components. The significance of this research lies in its versatility dealing with the existing challenge of calibration of sub-ppm level measurement of any volatile compound, such as ammonia.

Thermal cycling layer by layer dip coating method for oxazine formation on clad modified optical fiber core

The paper shows plastic optical fiber of 960/1000 μm Core/Cladding as an optical waveguide by removing a portion of the cladding section of the fiber via chemical etching and then applying dip coating method to fabricate 0.0005 M Oxazine 170 per Chlorate on the bare core. It is then followed by a Poly Di-Methyl Siloxane (PDMS) layer to design an opto-chemical sensor, to be used in detection of pH-based contaminants in air and water. The thickness of PDMS layer varies between 130-145 μm and that of Oxazine layer varies between 20 - 25 μm. This paper also shows a novel moisture trapping technique, necessary to trap moisture within PDMS and Oxazine which results in proper detection of contaminants.