Fast and accurate detection and monitoring of alcohol consumption have significant importance for safety and clinical applications. The excessive consumption of alcohol causes many health issues, such as colon, rectum, mouth, and throat cancers, liver cirrhosis, stroke, cardiovascular disease, and several psychiatric comorbidities. Alcohol addiction treatments also require close monitoring of the consumption. The correlation of alcohol concentration levels in sweat with the blood alcohol content (BAC) encourages developing a wearable sensing platform for alcohol detection noninvasively, continuously, and in real-time. Moreover, sweat is considered one of the most useful body fluids for biosensing applications since it contains several biomarkers with crucial medical information and is easy to collect. ZnO has exclusive chemical and physical characteristics to enhance chemical stability in physiological environments. Moreover, it has higher catalytic activity, biocompatibility, and a higher isoelectric point (IEP) of 9.5. Such a high IEP of ZnO nanoflakes (NFs) improves any biomolecules' immobilization. Hence, there is no necessity for an additional binding layer between the enzyme and the sensing electrode. A single-step sonochemical approach was developed to synthesize a thin layer of ZnONFs virtually on any substrate. This technique is fast, catalyst-free, less expensive, and ecologically benign, which enables a well-oriented growth on polyethylene terephthalate (PET) over an extensive range. In this study, an electrochemical biosensor was fabricated by immobilization of alcohol oxidase (AOX) on ZnO nanoflakes with a thickness of 20nm, synthesized on Au-coated PET. The results demonstrated a fast response within 5s. The sensor was tested in the range of 1 mg – 400 mg, which covers the entire physiological range, and the sensitivity of the sensor was determined by 3.47 nA/mg/dL/cm2.
KEYWORDS: Multiplexing, Analog electronics, Safety, Receivers, Mobile devices, Glucose, Digital electronics, Dielectric spectroscopy, Data conversion, Data acquisition
A miniaturized potentiostat integrated with a three-electrode system to monitor different analytes is presented. The potentiostat circuit has been designed to have the feature of four-channel multiplexing to operate different electrochemical cells simultaneously. It is Bluetooth-connected to a user-controlled mobile app through which the system is wirelessly controlled and data is acquired. The personalized data from the analysis are displayed and analyzed in the mobile app. The system is comprised of four units: digital to analog converter (DAC), multiplexing unit, control unit, and current to voltage converter (CVC). The circuit is run by Arduino NANO 33 BLE. The Arduino's digital pulse width modulator (PWM) signal is converted into an analog signal through the DAC unit to run the scanning in the voltage range of -1V to 2V. This output of the DAC unit is then fed into the multiplexing unit to distribute it to all four control units one at a time. Later, each control unit of the respective cells performs scanning through the three-electrode system connected to the control unit. The real-time scanning data collected from the cell, sent to the CVC unit, and converted into a voltage to be readable by the Arduino. With its small form factor, low power, and low cost the presented system can be used wearable health monitoring platforms.
Ambient energy harvesting is a promising route to achieve self-powered electronic devices. A nanogenerator scavenges mechanical energy from surrounding and converts it into electrical energy to supply power to a self-powered system. Using piezoelectric, thermoelectric, and triboelectric effects, several nanogenerators have been developed. Piezoelectric nanogenerators harvest kinetic energy to provide power for portable and small electronics. The kinetic energy generated from human body motions is an excellent energy source to power wearable devices. Biocompatibility, flexibility, high efficiency, and small volume are the main attributes for applications related to the human body. Piezoelectric nanogenerators based on thin films are desirable for their ability to scavenge irregular mechanical energies from bending. The power generation mechanism of a thin film based piezoelectric nanogenerator is determined by the coupled piezoelectric and semiconducting properties of the thin film.
ZnO is an appealing material for piezoelectric nanogenerators thanks to its coupling effect of semiconducting and piezoelectrical properties, extremely high elasticity, high power density, low-cost and controlled growth, and biocompatibility. Herein, a flexible piezoelectric nanogenerator with ZnO nanoflakes-polyethylene terephthalate (PET) is reported. The direct synthesis of ZnO nanoflakes on flexible PET substrate was achieved via a simple, fast, low-temperature, low-cost, highly stable, and reproducible sonochemical method. The synthesized ZnO thin films were characterized in detail. The results show that ZnO nanoflakes were grown with high purity and highly crystallinity along [0001] direction. Our piezoelectric device generated a peak voltage of 62 mV with great reproducibility (p-value of 0.0212). The fabrication of ZnO nanoflakes-PET piezoelectric nanogenerators helps us to develop more flexible and bio-compatible nanogenerators particularly self-powered wearable electronics.
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.
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.
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.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.