Side views - (i) masking of the Si wafer;. ii) coating of PMMA on the Si Wafer; (iii) Coating of the photoresist (PR) on the PMMA layer; (iv). The reliability, accuracy, reusability and fast response time of the device can be used to develop a biomedical device for ammonia and urea detection.
Graph (C) shows the variation of the rotational speed (ω) with the variation of the thermal conductivity (k) of the heated substrate. Images (G) and (H) show the FESEM image of the paper surface and AuNPs embedded on the paper surface, respectively, and image (I) shows the FESEM image of the deposited CdSNPs.
Nomenclature
Contents
Introduction
Microfluidic Sensors
CHAPTER 2: Self-spinning Nanoparticle Laden Microdroplets for Sensing and Energy Harvesting
CHAPTER 3: Droplet Based Detection of Blood α-Amylase Employing Thermal Marangoni Effect
Paper Based Electronic Sensors
Paper Based Flexible Touchpad and Hand Tremor Detection Device
Nano-Enabled Paper Humidity Sensor for Mobile Based Point-of-Care Lung Function Monitoring
Other Electronic Sensors and POC Devices
A Nano-BG-FET for Point-of-Care Estimation of Ammonia and Urea in Human Urine
A Prototype for Point-of-Care Stress Detection at Different Body Parts
Conversion of Observed Speed of a Moving Object to Diagnose Tunnel Vision
Summary and Future Scope
Introduction
Overview
In particular, the use of nanoelectronic devices integrated with specialties from smart materials and nanoscale science have opened the way in the development of sensors for health care, environmental monitoring and energy harvesting applications, to facilitate. In addition to biomedical devices, environmental monitoring with the help of POCT devices has become another front where rapid progress has been made.
Classification of Sensors
- Microfluidic Sensors
- Paper-based Sensors
- Spintronic Sensors
- Electronic Sensors
Changing the surfaces of the microchannel opened a new era in the field of sensation. This feature of the paper makes it very popular in the field of fluid mechanics and bio-sensing applications.
Objective of the Thesis
Microfluidic Sensors
Self-spinning Nanoparticle Laden Microdroplets for Sensing and Energy Harvesting
ABSTRACT
Introduction
Marangoni solute motion on the droplet surface stimulated by an external vapor source generated strong vortices within the droplet. The reduction in resistance was found to have a correlation with the change in surface tension of the vapor source and the water droplet, which in turn can be used to distinguish the vapor sources. Further, repeated exposure and withdrawal of vapor sources can also be tracked with the help of this prototype.
Surprisingly, the power density of the eddy currents was ~7 μW/cm2, which indicated the potential of the system for energy harvesting.
Experimental Section
- Materials
- Synthesis
- Methods
After this, a capillary tube filled with a volatile organic liquid, such as diethyl ether, was brought near the surface of the microdroplet. Then a 7 µl drop of the saturated salt solution was dispensed at the junction between the electrodes. Microfluidic sensors 31 were replicated by dispensing a 7 µl nanoparticle-laden microdroplet onto the junction between the Cu electrodes.
The influence of different types of volatile organic vapors, such as diethyl ether and ethanol, on the motion of the nanoparticle-laden microdroplets was also analyzed.
Results and Discussion
- Experimental Results on the Phenomenon
- Electrical Response of the Phenomenon
- Experimental Results on Energy Harvesting
- Theoretical Basis of Voltage Generation
- Computational Simulations to Estimate Potential Drop on the Electrodes
- Power Density and Conversion Efficiency
- Sensor Application
Microfluidic sensors 49 Plot (B) in Figure 2.8 shows that the presence of salt inside the droplet increases. The presence of the nanoparticles increased (decreased) the electrical conductivity (resistance) across the droplet to improve the power density. Images (A) and (B) show the schematic diagram of the experimental setup where the LED was turned off (on) in the absence (presence) of the vapor excitation.
Figure (D) shows that the percent change in resistance (R) decreases significantly as the proportion of CD in the vapor decreases.
Conclusions
The rotational motion was found to be ∼12 rpm for a 10 μL droplet when the temperature of the bottom glass surface was maintained at 40 °C while the top surface of the droplet was exposed to ambient conditions. A series of computer simulations of fluid dynamics revealed important features of circular motions derived from the Marangoni and natural conventions. A droplet filled with starch and salt showed a change in electrical resistance when placed on a hot glass surface due to an improvement in electrical conductivity due to the creation of Marangoni and natural convention vortices.
Amylase specifically broke down the starch molecules to develop lower molecular weight carbohydrates, which in turn increased the electrical conductivity of the droplet due to the combined influence of the Marangoni and natural conventional vortices.
Introduction
74 Chapter 3 Sensing, energy harvesting and biomedical applications using the specialties of fluid mechanical principles in the microfluidic devices. In view of the above, we herein discuss a single microdroplet-based sensor to detect alpha-α-amylase in blood serum. Then, the rotational speed of the droplet and the electrical conductivity across it varied with the variation in the amylase.
The reported results ensured that the prototype could be used as a biomedical device for the POCT detection of pancreatitis at the user's site.
Experimental Section
- Materials
- Sensor Fabrication and Set-up
- Experimental Method for Microfluidics
- Experimental Method for Electrical Characterization
The camera setup is illustrated in images (C – D) of Figure 3.1 A ~200 um particle was placed inside and then the droplet to quantify fluid movement. Initially, 10% (w/v) starch solution and 1 M FeSO4 was prepared by dissolving appropriate amounts of solvents in DI water. A 10 μL drop of the well-stirred reaction mixture of DI water, saline, starch, and amylase solution was distributed symmetrically between the electrodes.
The adhesive tape was used to make the surface hydrophobic and prevent it from spreading out of the droplet.
Results and Discussion
- Experimental Study on Effect of Temperature
- Computational Analysis
- Experimental Analysis
The top wall of the computational domain is assumed to be non-slip and impermeable. While, near the top of the drop the temperature remains almost equal to the ambient temperature (20⁰C), which ensures that there is a surface tension gradient and natural convection created inside the water drop due to the hot substrate (50⁰C) located on down. dots. The first, second, and third columns of the figure show the rotational motions within the droplet due to thermal Marangoni, natural convection, and the combined effect of thermal Marangoni and natural convection, respectively.
Image (C) shows the response of the system to different concentrations of α-amylase at 3 different temperatures.
Conclusions
The dot system was further extended to biomedical application to detect α-amylase in blood serum. Experimental studies showed the detection ability of blood serum in the range of 20 – 110 U/L, which is suitable for diagnosing pancreatitis at an early stage. Analyzes were also performed with human blood serum and the results were in the range of pathological data.
Therefore, the proposed system can be used for biomedical application to diagnose pancreatitis in its early stages.
Paper Based Electronic Sensors
Paper Based Flexible Touchpad and Hand Tremor Detection Device
Introduction
The design and development of modern electronic touch sensors have an important analogy with the sensations of "touch" generated by hypodermal nerves in the epidermal layer of human skin1. For example, to identify the (X, Y) coordinates of the "touch" position on a 4-wire display, a voltage in the Y direction is initially applied upon receiving a touch sensation. The concept then extends to the development of a hand tremor monitoring device to detect neurological disorders in the early stages.
In this direction, we are extending the principle of the resistive pad to develop a proof-of-concept prototype that can be used at the user site for regular hand tremor monitoring.
Materials and Methods
- Materials
- Characterizations
Figure (A) shows the view of the outer surface with PDMS coating and Cu connection of the top surface, Figure (B) shows the configuration. Figure (D) shows an optical microscopic image of a cross-section of a touchpad with three different layers. Figure (E) shows the current (I) vs. voltage (V) characteristics of graphite coatings at various locations 1 through 4 on the wafer.
Image (F) shows the variations in the electrical response at different locations over time, highlighting the stability of the sensors.
Results and Discussion
- Resistive Touchpad
Image (I) shows the theoretical (solid line) and experimental (scattered points) response of the sensor to the bend. Images (G) and (H) show the actual images of the sensor in relaxed and bent state, respectively. Here R0 refers to the base resistance of the sensor and ΔR is the variation in the resistance.
Figure (E) shows the stability of the sensor over time, and Figure (F) shows the advantages of the four different sensors.
Conclusions
Paper-Based Electronic Sensors 123 The results obtained in Figure 4.8 led us to test the prototype to detect the hand tremors of the real patients. The calibration was performed by measuring the sensor's response and severity as shown in image (D) in Figure 4.8. 124 Chapter 4 A minor tweak to the pad's design led to a POCT device to detect hand tremors from neurological disorders such as Parkinson's disease.
The variation in the response of the resistive sensor was able to distinguish between mild, moderate and high hand tremor levels in the human fingers.
Nano-Enabled Paper Humidity Sensor for Mobile Based Point-of-Care Lung Function Monitoring
Introduction
134 Chapter 5 In view of the above, we report the development of a paper-based LFM-POCT device, which may bring about a paradigm shift in lung fitness measurement. In the current work, we have developed a humidity sensor, which can monitor the moisture content of exhaled air coming from human breathing. The integration of the LFM-POCT device and application into the mobile phone helped in real-time testing, monitoring, analysis and data storage of the lung function parameters via smartphones.
The image shows the coating of the CdSNPs and the Ag electrodes, which were integrated with the micro-heating arrangement.
Experimental Section
- Materials
- Synthesis and Characterizations of Nanoparticles
- Fabrication of the Sensor, Micro-heater and their Integration
- Experiments to Create Environment with different relative humidity
- Methods
The integration of a battery through an external circuit in the Cu connections of the micro-heater helped to supply the current for the joule heating. The frequency and duty cycle of the micro-heater was maintained by adjusting the values of resistors R1, R2 and a capacitor C. In the case of figure (A), FR is below the desired level (S) as indicated by the peak expiratory flow meter of imaginary scale (PEF).
It can be noted here that Rise is more for image (B) than for image (A).
Results and Discussion
- Response of Paper Humidity Sensor
- LFM-POCT Device Architecture
- Experimental and Simulation to Study the Dependence of Flowrate
- Computational Analysis of Adsorption
Image (D) shows the change in ∆R of the sensor due to the pulsed exposure to ~97% moist air at different Q. Image (C) shows the variation in R due to different peak exhaled air flow rates (FR). sky. Importantly, we used a commercial peak flow meter to obtain the peak flow rate (FR), which was then correlated with the change in electrical resistance (R) of the paper sensor, as shown in Figure 5.11C.
The resistances in the circuit of the LFM-POCT device were then adjusted using the calibration graph shown in Figure 5.11C.
