Prashant R. Bhadri

A Potentiometric Sensor System with Integrated Circuitry for in situ Environmental Monitoring

The need to monitor the conditions prevailing in the external environment in order to control environmental pollution is one of the prime necessities of the modern age. This paper introduces a robust, self-contained, inexpensive integrated potentiometric sensor that can be used for in situ environmental monitoring. The primary focus is to design, implement and integrate a potentiometric CMOS circuit with the sensor device to measure the potential developed across a working probe (microelectrode sensor) and the reference probe. The magnitude of the output voltage signal is dependent on the characteristics (pH) of the solution being evaluated by the system. A Printed Circuit Board has been built to integrate the microelectrode sensor device and the sensor chip with the aim of producing a fully integrated system. The microelectrode sensor device may be replaced by a NEMS based sensor device in areas that require further miniaturization like biomedical applications.

Design of a smart optically controlled high power switch for fly-by-light applications

Fly-by-light in avionic systems reduces electromagnetic interference hence improving the clarity of the control signals. A hybrid approach combining a silicon photoreceiver module with a SiC power transistor is proposed. The resulting device uses a 5 mW optical control signal to produce a 150 A current suitable for driving an electric motor.

Potentiometric microelectrode sensors for in situ environmental monitoring

A new breed of microelectrode sensor arrays for oxidation-reduction potential (ORP) measurements in situ at environmental sites has been successfully developed. The microelectrodes were fabricated from glass using a two-step, HF-based meniscus etching process, and demonstrated electrochemical performance nearly identical to that of the commercial millielectrode, with significantly faster response times.

Characterization and performance evaluation of CMOS photodetectors implemented in optoelectronic circuits

The ability to produce a high performance monolithic CMOS photodetector could enable greater use of optics in short-distance communication systems and photonic information processing systems. The quest for a photodetector compatible with a high-volume high-yield CMOS process has yet to produce a clear winner, and has proven quite challenging. We present in this paper several different photodetector structures implemented with a conventional CMOS fabrication process that can be incorporated into optical data links and information processing systems. As a result, it combines the parallelism associated with optics and the data processing capabilities associated with CMOS logic.

Derivative spectrophotometric analysis of cerebrospinal fluid for the detection of a ruptured cerebral aneurysm

A cerebral aneurysm is a weakened portion of an artery in the brain. When a cerebral aneurysm ruptures, a specific type of bleeding known as a subarachnoid hemorrhage (SAH) occurs. No test exists currently to screen people for the presence of an aneurysm. The diagnosis of a SAH is made after an aneurysm ruptures, and the literature indicates that nearly one-third of patients with a SAH are initially misdiagnosed and subjected to the risks associated with aneurysm re-rupture. For those individuals with a suspected SAH, a computerized tomography (CT) scan of the brain usually demonstrates evidence of the bleeding. However, in a considerable portion of people, the CT scan is unable to detect the blood that has escaped from the blood vessel. For circumstances when a SAH is suspected despite a normal CT scan, physicians make the diagnosis of SAH by performing a spinal tap. A spinal tap uses a needle to sample the cerebrospinal fluid (CSF) collected from the patient’s back; CSF is tainted with blood after the aneurysm ruptures. To distinguish between a common headache and a SAH, a fast and an effective solution is required. We describe the development of an effective detection system integrating hardware and a powerful software interface solution. Briefly, CSF from the patient is aspirated and excited with an appropriate wavelength of light. The software employs spectrophotometric analysis of the output spectra and lays the foundation for the development of portable and user-friendly equipment for detection of a ruptured cerebral aneurysm.

An Integrated Amperiometric Sensor for in situ Environmental Monitoring

In the modern era, some of the most serious causes for public health problems can be attributed to environmental pollution. Proper monitoring of environmental conditions helps us to control the pollution in an effective manner. This paper introduces a robust, self-contained, inexpensive integrated amperiometric microelectrode sensor that can be used for in situ environmental monitoring. The work primarily focuses on the design, implementation and integration of an amperiometric CMOS sensor chip with a microelectrode sensor device in order to measure the current flowing through the working probe (microelectrode sensor) and the reference probe, when they are immersed in the test solution. The magnitude of the current signal, of the order of nanoamperes, is shown to be dependent on the characteristics (oxygen content) of the solution being evaluated by the system. The integration of the microelectrode sensor with the sensor chip is done with the help of a Printed Circuit Board. The microelectrode sensor device may be replaced by a NEMS based sensor device for applications requiring further miniaturization, like that in the biomedical field where the solution under test may be a biofilm.

Non-invasive biomedical system for the quantification of bilirubin in neonates

Neonatal jaundice is a condition in new born babies, where a high level of bilirubin is present in the blood. This condition is known as hyperbilirubinemia. Bilirubin, which results from the breakdown of hemoglobin, is processed in the liver. In a significant number of cases, due to the slow development of the liver organ, a condition of excess bilirubin production occurs in the neonates. Therefore, careful attention to bilirubin levels in neonates is required to prevent serious complications. It is estimated, that about 50% of newborns have an episode of jaundice in the first few days. Approximately, 6% of them may develop hyperbilirubinemia, which can potentially cause bilirubin encephalopathy or kernicterus, a severe neonatal disease. Bilirubin is yellow in color and therefore stains the skin and other tissues if its concentration is high. Invasive procedures expose the neonates to trauma and risk of infection. Therefore, a non-invasive quantification of bilirubin in neonates has been sought by the pediatric community. Furthermore, these performing invasive tests are not always done accurately or unreliably. This paper puts forth the non-invasive approach of quantifying the bilirubin.

Detection of CT occult aneurismal subarachnoid hemorrhage using a novel spectrophotometric analysis of cerebral spinal fluid

In North America, approximately 30,000 people annually suffer an aneurismal subarachnoid hemorrhage (SAH). Using computerized tomography (CT), the blood is generally not visible after 12 hours. Currently lumbar puncture (LP) results are equivocal for diagnosing SAH largely because of technical limitations in performing a quick and objective evaluation. Having ruptured once, an aneurysm is statistically more likely to rupture again. Therefore, for those individuals with a sentinel (or warning) hemorrhage, detection within the first 12 hours is paramount. We present a diagnostic technology based on visible spectroscopy to quickly and objectively assess low-blood volume SAH from a diagnostic spinal tap. This technology provides clinicians, with the resources necessary for assessing patients with suspected aneurismal SAH beyond the current 12-hour limitation imposed by CT scans. This aids in the improvement of patient care and results in rapid and appropriate treatment of the patient. To perform this diagnosis, we quantify bilirubin and hemoglobin in human CSF over a range of concentrations. Because the bilirubin and hemoglobin spectra overlap quantification is problematic. To solve this problem, two algorithmic approaches are presented: a statistical or a random stochastic component known as Partial Least Square (PLS) and a control theory based mathematical model. These algorithms account for the noise and distortion from blood in CSF leading to the quantification of bilirubin and methemoglobin spectroscopically. The configurations for a hardware platform is introduced, that is portable and user-friendly composed of specific components designed to have the sensitivity and specificity required. This aids in measuring bilirubin in CSF, hemorrhagic-CSF and CSF-like solutions. The prototype uses purpose built algorithms contained within the platform, such that physicians can use it in the hospital and lab as a point of care diagnostic test.

Development of a diagnostic system for bilirubin detection in cerebral spinal fluid

A weakened portion of an artery in the brain leads to a medical condition known as a cerebral aneurysm. A subarachnoid hemorrhage (SAH) occurs when an aneurysm ruptures. For those individuals suspected of having a SAH, a computerized tomography (CT) scan of the brain usually demonstrates evidence of the bleeding. However, in a considerable portion of people, the CT scan is unable to detect the blood that has escaped from the blood vessel. Recent studies have indicated nearly 30% of patients with a SAH are initially misdiagnosed. For circumstances when a SAH is suspected despite a normal CT scan, physicians make the diagnosis of SAH by performing a spinal tap. A spinal tap uses a needle to sample the cerebrospinal fluid (CSF) collected from the patient’s lumbar spine. However, it is also possible for blood to be introduced into the CSF as a result of the spinal tap procedure. Therefore, an effective solution is required to help medical personnel differentiate between the blood that results from a tap and that from a ruptured aneurysm. In this paper, the development of a prototype is described which is sensitive and specific for measuring bilirubin in CSF, hemorrhagic-CSF and CSF-like solutions. To develop this instrument a combination of spectrophotometric analysis, custom data analysis software and other hardware interfaces are assembled that lay the foundation for the development of portable and user-friendly equipment suitable for assisting trained medical personnel with the diagnosis of a ruptured cerebral aneurysm.

Analysis of cerebrospinal fluid for detection of ruptured cerebral aneurysm using spectrophotometry and signal processing techniques

An accurate quantification of bilirubin in cerebrospinal fluid (CSF) will provide a simple, sensitive and rapid mechanism for detecting subarachnoid hemorrhage (SAH) and for its differentiation from a traumatic spinal tap. Derivative analysis of the spectrophotometric data provides a model for determining bilirubin in CSF where the primary contaminant is Methemoglobin. Bilirubin values are determined in the range 0-9mg/dl within a methemoglobin concentration of 4.6g/dl using the derivative analysis method. The algorithm is also implemented on test samples in which the bilirubin value is constant (4.6mg/dl) and the methemoglobin varies between 0-9g/dl. The performance of the derivative analysis method is compared to the modified minimum distance method developed in reference one. We suggest a combination of these methods for accurate bilirubin estimation in CSF/hemoglobin. This will provide the foundation for the development of a portable user friendly device for diagnosis of SAH.