Instrumentation and Applied Physics (IAP)
https://etd.iisc.ac.in/handle/2005/48
2024-03-29T10:32:23ZAbsorption Flow-Cytometry for Point-of-Care Diagnostics
https://etd.iisc.ac.in/handle/2005/3620
Absorption Flow-Cytometry for Point-of-Care Diagnostics
Banoth, Earu
Medical devices are used widely at every stage of disease diagnosis and treatment. To eradicate certain infectious diseases, the development of highly sensitive diagnostic tools and techniques is essential. The work reported in this thesis presents a novel approach, which can be used for the diagnosis of various diseases in the field of clinical cytology. The central theme of this approach was to develop a simple, holistic and completely automated system for point-of-care (POC) diagnostics. This is realized through the Development of an Absorption Flow-Cytometer with Synergistic Integration of Microfluidic, Optics and simple Electronics. Quantitative diagnosis of malaria has been taken as test case for the characterization and validation of the developed technology.
Malaria is a life-threatening disease widely prevalent in developing countries. Approximately half the world population undergoes a test of malaria and it kills close to half a million people every year. Early detection and treatment will reduce the number of fatalities and also decrease its transmission rate. In the recent past, several diagnostic tools have been developed to detect malaria but there are varied demands on diagnostic instruments in healthcare settings and endemic contexts. The objective of this thesis is to develop an instrument capable of identifying malaria-infected red blood cells (i-RBCs) from a given few micro-liters of whole blood. The optical absorption properties of blood cells were measured at a single-cell level to diagnose malaria. The proof-of-concept for the instrument was established in four stages, after which a prototype was also developed and validated.
In the first stage, a system capable of simultaneously imaging cells and also measuring their optical absorbance properties was developed. The developed system was employed to characterize absorption properties of red blood cells (malaria-infected and healthy ones) on blood-smear. A custom-made bright-field transmission microscope in combination with a pair of laser diode and photo-detector was used to simultaneously image and measure transmittance of infected and uninfected RBCs.
In the second stage, the technique was extended to enable high-throughput measurements with the use of microfluidic sample handling and synchronous data acquisition. Using this technique, the optical absorbance and morphology of infected and healthy RBCs have been characterized in statistically significant numbers. The correlation between cell morphology (from images) and single-cell optical absorbance level helped to establish the thresholds for differentiating healthy and infected cells.
In the third stage, a portable prototype capable of assessing optical absorbance levels of single cells was fabricated. The developed prototype is capable of assessing cells at throughputs of about 1800 cells/ second. It was initially validated with sample suspensions containing infected and healthy RBCs obtained from malaria cultures. For the device to be usable at the field-level, it has to function in the presence of all other cellular components of whole blood. The optical absorbance of other cellular components of blood like white blood cells and platelets, were characterized. The device was finally tested with blood samples spiked with malaria-infected RBCs validating the overall proof-of-concept and the developed prototype. The deployment of such cost-effective, automated POC system would enable malaria diagnosis at remote locations and play a crucial role in the ongoing efforts to eradicate malaria. In future, the presented technology can be extended to develop POC diagnostic tool for other diseases as well.
As it enables quantitative estimation of malaria, the present optical absorption flow analyzer would also find application in disease prognosis monitoring, anti-malarial drug development and other studies requiring measurements on a single-cell basis. The hyper-imaging system can be used to characterize and validate the threshold information, and can be incorporated in the prototype. Thus, it is a continuous process to characterization and implementation in the prototype. The optofluidic absorption flow analyzer will help enable affordable clinical diagnostic testing in resource limited settings. This approach will be extended to diagnose other diseases, using differences in optical absorption as criteria for differentiating healthy and infected cells.
2018-05-25T00:00:00ZAdaptive Dielectric Thin Film Transistor : A Self-Configuring Device for Low Power Electrostatic Discharge Protection
https://etd.iisc.ac.in/handle/2005/4696
Adaptive Dielectric Thin Film Transistor : A Self-Configuring Device for Low Power Electrostatic Discharge Protection
Bhattacharya, Prasenjit
Large area and flexible electronic systems are widely used in applications such as displays, image sensors, wearable electronics, and energy harvesting systems. One of the fundamental functional blocks in these systems is the thin-film transistor (TFT), which suffers from poor field-effect mobility, electrical instability, etc. due to the state localization at low-temperature fabrication process, a criterion that enables system realization on glass or flexible substrate, such as plastic.
The electrostatic discharge (ESD) is a rapid transfer of static charge between two objects of dissimilar potentials, one of which is typically grounded. An electronic device could suffer ESD damage during different stages of its lifetime including manufacturing and product usage leading to a loss of billions of dollars annually to the electronics industry. Since the ESD phenomenon is unavoidable, on-chip ESD protection devices or circuits are required.
An ideal ESD protection device should offer a low resistance path to the surge current during an ESD event, but a high resistance path to the signal during the normal operation to minimize the power loss. In the crystalline CMOS technology, the parasitic bipolar turn-on (snapback) is effectively used to design the ESD protection device. However, most of the TFT technologies do not exhibit any bipolar turn-on owing to the poor mobility and lack of complementary devices. Hence, the conventional protection circuit uses large aspect-ratio diode-connected TFTs that offer a low resistance path to the surge current but also does the same to signals during normal system operation resulting in power loss. Additional circuits are required to keep the protection devices turned off during normal operation, but it leads to higher routing complexity, layout area, and multi-component reliability issues. This thesis investigates the feasibility of a novel idea for ESD protection involving an adaptive-dielectric TFT (adTFT) that self-configures itself to a low resistance state during an ESD event and a high resistance state during normal operation without external control.
The adTFT device is designed to differentiate between an ESD pulse, which is typically nanoseconds order, and a normal operation signal, which is either a static dc (e.g. in power line) or a pulse of width microseconds to milliseconds order (e.g. in data/address line of a switch matrix). This is achieved using a time-dependent gate field masking mechanism, which is enabled by modifying the gate dielectric of a conventional TFT to a dielectric-semiconductor-dielectric stack and attaching a charge injection/extraction terminal to the sandwiched semiconductor layer. A first-order model of the masking dynamics under a gate step-bias input is developed using the space-charge-limited-current and threshold voltage modulation. TCAD simulations are performed using poly-Si adTFT to get a detailed insight into the device operation. The HBM (human body model) ESD robustness and normal mode leakage current of the diode-connected adTFTs are evaluated and compared against that of the conventional TFTs.
Next, the adTFT and an experimental control (behaving similar to the conventional TFT) are fabricated using ZnO as the semiconductor material and Al2O3 as the dielectric material. The device operation is investigated using dc I-V, C-V, and transient pulse characterizations that eventually lead to the device layout optimization for ESD protection device design. The response of the protection device during normal circuit operation is evaluated in terms of both, the constant bias and the pulsed bias. The ESD robustness is evaluated using the transmission line pulse (TLP) measurements. Finally, the performance of the adTFT is compared to that of the conventional TFT in terms of the power to thermal breakdown during ESD and the power leakage during normal operation to highlight the primary advantage of the adTFT as an ESD protection device over the conventional one. The fabricated diode-connected adTFTs result in 1000-10000 times the power savings compared to the diode-connected conventional TFTs without sacrificing the ESD robustness. Therefore, the adTFT condenses the operation of an entire circuit into a single device and shows promise as a versatile building block for ESD protection and other circuit designs.
Advanced Instrumentation for Detection of Defects and Diseases in Sericulture
https://etd.iisc.ac.in/handle/2005/5273
Advanced Instrumentation for Detection of Defects and Diseases in Sericulture
Prasobhkumar, P P
Sericulture is the art of rearing silkworms for silk production. The matured silkworms will be spinning cocoons as a protective shield before they undergo metamorphosis. These cocoons are immersed in boiling water to soften, and raw silk yarn is reeled from them. Being silkworms are sensitive to environmental changes, they are susceptible to many diseases. The diseased and weak silkworms spin defective cocoons, which should be removed from the production of good quality silk. In developing countries, the diagnosis of diseases and defects depends mainly on subjective and unreliable methods due to the unaffordability of customized hi-fidelity support systems. Any erroneous findings will cause immense loss to the farmers and reelers. This thesis reports on advanced yet affordable instrumentation systems to detect a) the external defects and b) internal defects in cocoons, and c) pebrine in silkworms.
a) The proposed system for detecting cocoons' external defects consists of an image acquisition and processing unit made using a smart-camera. The LED strip and cardboard box are used for conditioned illumination. The cocoons are rolled over a slope, and their whole surfaces are imaged and processed utilizing the smart-camera. An image processing algorithm, exploiting the techniques such as morphological operations, image enhancement and ellipse fitting, is developed for quantitative measurements of the cocoon's size, shape and colour. These values are compared against each category's thresholds, and identified the cocoon category (good, externally stained, double, urinated and uzi pierced). A graphical user interface is designed for helping farmers and reelers to visualize the quality of cocoons easily. The developed system is tested on 137 cocoons, and the results showed that it could evaluate 96 cocoons per second with 100% accuracy.
b) The instrument developed for the automated detection of cocoons' internal defects is designed to have a plastic arm attached to an Arduino-driven servo motor to vibrate the cocoons. Two microphones with specific separation are used to record the vibration induced acoustic emission (VIAE) from cocoons and ambient noise. A spectral analysis algorithm is developed to identify the cocoon category (good, dried and mute) based on the area under VIAE's power spectral density curve. This system classified 86 cocoons with 100% accuracy at a speed of 20 seconds/cocoon. These two defect detection systems are compatible to be integrated for the detection of external and internal defects of all cocoons in a given lot.
c) In the developed pebrine diagnostic instrument, a machine learning algorithm classifies the quantitative phase images of test spores in silkworm's body fluid as pebrine and Metarhizium anisopliae (MA), which resembles pebrine spore in microscopic examination. Its hardware consists of a custom-made motorized brightfield microscope to acquire a pair of (focused and defocused) images of spores. A transport of intensity equation based algorithm is developed to produce phase images, which carry information of spores' internal features. Further, the histogram of oriented gradients (HOG) feature of the phase images is extracted and used to train a machine learning algorithm. This system is tested on 92 pebrine and 185 MA spores and found to offer a classification accuracy of 97%. This instrument can be used for diagnosing other silkworm diseases such as nuclear polyhedrosis and septicemia.
Advanced Light Sheet Volume Flow Cytometry (VFC/iLIFE) and Spectroscopy System for Cell Biophysics and Clinical Biology
https://etd.iisc.ac.in/handle/2005/6458
Advanced Light Sheet Volume Flow Cytometry (VFC/iLIFE) and Spectroscopy System for Cell Biophysics and Clinical Biology
Kumar, Prashant
Optical imaging is paramount for disease diagnosis and to access its progression over time. The developed light sheet-based optical flow imaging techniques, known as Volume Flow Cytometry(VFC/iLIFE), and related techniques (Multicolor Volume Flow Cytometry, and High-throughput Multichannel Multi-sheet Multicolor Imaging Cytometry) offer a range of advanced capabilities for disease diagnosis and monitoring disease progression over time. Unlike existing point-illumination-based biomedical imaging methods, these developed techniques use light sheet illumination, which enables single-shot sectional visualization, high throughput analysis, real-time parameter estimation, and instant volume reconstruction with an organelle-level resolution for live specimens. The detection is carried out in an orthogonal configuration. On the other hand, Spectral Integrated Light-sheet imaging and flow-based inquiry (Spectral iLIFE) is an innovative imaging/spectroscopy system that combines the benefits of spectroscopy and optical microscopy. The technique provides valuable insights into molecular interactions and other critical information alongside imaging. By utilizing the spectral characteristics of fluorophores, Spectral iLIFE enables the identification and analysis of specific molecular components within a biological sample. This integration can allow researchers to not only visualize cellular structures and organelles but also study molecular interactions, such as protein-protein interactions or the binding of specific molecules. The ability to simultaneously obtain imaging data and spectral information enhances our understanding of complex biological processes and provides a more comprehensive view of molecular dynamics within living systems.
The stages of system development include the fabrication of a multichannel microfluidic chip, light sheet illumination, and multicolor widefield 4f detection. The experimentation involves the preparation of fluorescently-labeled cells, determination of flow-variant PSF, calibration of the light sheet, image deconvolution, and separation of spectrally-distinct fluorescent signals. The system offers the determination of physiologically relevant cell parameters (organelle count, morphology, and organelle distribution) on the go. Moreover, it facilitates changes over time, thereby revealing the metastatic progression of diseases. Overall, the developed imaging cytometry technique and its variants allow for real-time monitoring of sub-cellular organelle organization with high throughput and high-content capacity, enhancing our ability to understand disease progression and facilitate drug therapy.