Pratyush Rai

In vitro evaluation of flexible pH and potassium ion-sensitive organic field effect transistor sensors

Acute myocardial ischemia is a state of trauma of the heart muscle caused by occlusion of oxygenated blood supply. It is accompanied by an increase in potassium and hydrogen ion concentrations in the heart muscles. A flexible substrate based ion-sensitive field effect transistor (ISFET) has been designed to measure the concentration of potassium and hydrogen ions with high specificity. Double exponential smoothing technique was used to calculate background noise and explain the dependence of drain current on reference voltage and ion concentration in saturation mode of the ISFET.

Drain Current Centric Modality: Instrumentation and Evaluation of ISFET for Monitoring Myocardial Ischemia Like Variations in pH and Potassium Ion Concentration

Variations in concentrations of ions in biological systems can be important events in the onset of a physiological disorder. In an episode of myocardial ischemia, acidosis and elevation of potassium ion concentration has been observed in the extra-cellular matrix of the myocardium. As a spectrum of markers, they can help detect onset of ischemia as well as infarctions. In this study, Flexible Organic Ion-Sensitive Field-Effect Transistors (ISFETs) have been characterized to detect Ischemia-like variations in pH and potassium ion concentration. Detection capabilities, of the sensors, have been shown as pure chemical concentration to current signal transduction of the ISFET. Independent of peripheral amplifier-converter circuits, they are standalone sensors. The sensors have been evaluated for their sensitivity and signal resolution. Calibration expression, following a thermo-electric model for device operation, represents an explicit relations between transistor drain current and ion concentrations. Signal conditioning, by normalization, has been attempted to make the calibration expression explicit in ion-concentration. Finally a reliable detection strategy, in differential mode, is proposed for a reference electrode free device.

e-Nanoflex Sensor System: Smartphone-Based Roaming Health Monitor

The growing need and market demand for point of care (POC) systems to improve patient’s quality of life are driving the development of wireless nanotechnology based smart systems for diagnosis and treatment of various chronic and life threatening diseases. POC diagnostics for neurological, metabolic, and cardiovascular disorders require constant long term untethered monitoring of individuals. Given the uncertainty associated with location and time at which immediate diagnosis and treatment may be required, constant vigilance and monitoring are the only practical solutions. What is needed is for a remote cyber-enabled health care smart system incorporating novel ideas from nanotechnology, low power embedded systems, wireless networking, and cloud computing to fundamentally advance. To meet this goal, we present e-Nanoflex platform, which is capable of monitoring patient health wherever they may be and communicating the data in real time to a physician or a hospital. Unlike state-of-the-art systems that are either local sensor systems or rely on custom relaying devices, e-Nanoflex is a highly nonintrusive and inexpensive end-to-end cyber-physical system. Using nanostructured sensors, e-Nanoflex provides nearly invisible monitoring of physiological conditions. It relies on smartphones to filter, compress, and relay geo-tagged data. Further, it ties to a backend cloud infrastructure for data storage, data dissemination, and abnormality detection using machine learning techniques. e-Nanoflex is a complete end-to-end system for physiological sensing and geo-tagged data dissemination to hospitals and caregivers. It is intended as a basic platform that can support any nanostructure based flexible sensor to monitor a variety of conditions such as body temperature, respiration air flow, oxygen consumption, bioelectric signals, pulse oximetry, muscle activity, and neural activity. Additionally, to address the cost of manufacturing sensors, e-Nanoflex uses a low cost production technique based on roll to roll gravure printing. We show the efficacy of our platform through a case study that involves acquiring electrocardiogram signals using gold nano-electrodes fabricated on a flexible substrate.

Glucose Driven Nanobiopower Cells for Biomedical Applications

Power supply is an important aspect of micronanobiomedical devices. Implantable devices are required to stay inside of the body for longer period of time to provide continuous monitoring, detection, and therapeutics. The constricted areas of the human body, accessed by these devices, imply that the power source should not increase the payload significantly. Conventional on-board power sources are big, as compared with the device themselves, or involve wire-outs. Both provisions are liable to develop complications for sensor/actuator implant packaging. A plausible approach can be innovative solutions for sustainable bio-energy harvesting. Research studies have reported feasibility of miniature power sources, running on redox reactions. The device design, reported in this study, is a combination of nano-engineered composites and flexible thin film processing to achieve high density packaging. Of which, the end goal is production of energy for sensor applications. Both the bio-electrodes were successfully functionalized by amide bond cross-linkage between the carbon nanotube surface and the enzyme molecules: catalase and glucose oxidase for cathode and anode, respectively. The nanocomposite based biopower cell was evaluated as a steady power supply across the physiological range of glucose concentration. The power cell was able to deliver a steady power of 3.2 nW at 85 mV for glucose concentrations between 3 mM and 8 mM. Electron microscopy scanning of the functionalized electrode surface and spectroscopic evaluation of nanotube surface were used for evaluation of the biofunctionalization technique. Cyclic voltametric (CV) scans were performed on the cathodic and anodic half cells to corroborate bioactivity and qualitatively evaluate the power cell output against the redox peaks on the CV scans. The importance of these results has been discussed and conclusions have been drawn pertaining to further miniaturization (scale down) of the cell.

Wireless Health Monitoring Helmet for Football Players to Diagnose Concussion and Track Fatigue

Football players are regularly exposed to violent impacts. Concussions are mild traumatic brain injuries that are one of the most common injuries experienced by football players. These concussions are often overlooked by football players themselves and the clinical criteria used to diagnose them. The cumulative effect of these mild traumatic brain injuries can cause long-term residual brain dysfunctions. In addition, an athlete’s fatigue level should be monitored to prevent any secondary injuries due to over exertion. Nitric Oxide acts as a metabolic adjustment factor that controls the flow of oxygen in blood and the contraction/relaxation of muscles. Fatigue can be evaluated by measuring the concentration change of nitric oxide in blood. However, measuring the concentration of nitric oxide in blood is not feasible during exercise. Nevertheless, the degree of fatigue can be measured with SpO2 during exercise because the change of nitric oxide also influences the SpO2. In this paper, we propose a wireless health monitoring helmet to diagnose concussions and evaluate fatigue in real time and on the field. The helmet is equipped with sensors and a transmitter module. As sensors, textile based electrodes are used to sense EEG and oximeter sensors are used to derive SpO2. The sensed physiological signals are amplified and processed in the transmitter module. The processed signals are transmitted to a server using Zigbee wireless communication. The EEG signals are classified to diagnose concussion or any abnormality of brain function. In conclusion, the system can monitor and diagnose concussions and evaluate fatigue in football players in real time by measuring their EEGs and SpO2.

Smart healthcare textile sensor system for unhindered-pervasivehealth monitoring

Simultaneous monitoring of physiological parameters- multi-lead Electrocardiograph (ECG), Heart rate variability, and blood pressure- is imperative to all forms of medical treatments. Using an array of signal recording devices imply that the patient will have to be confined to a bed. Textiles offer durable platform for embedded sensor and communication systems. The smart healthcare textile, presented here, is a mobile system for remote/wireless data recording and conditioning. The wireless textile system has been designed to monitor a patient in a non-obstructive way. It has a potential for facilitating point of care medicine and streamlining ambulatory medicine. The sensor systems were designed and fabricated with textile based components for easy integration on textile platform. An innovative plethysmographic blood pressure monitoring system was designed and tested as an alternative to inflatable blood pressure sphygmomanometer. Flexible dry electrodes technology was implemented for ECG. The sensor systems were tested and conditioned to daily activities of patients, which is not permissible with halter type systems. The signal quality was assessed for it applicability to medical diagnosis. The results were used to corroborate smart textile sensor systems ability to function as a point of care system that can provide quality healthcare.

Nanocomposite electrodes for smartphone enabled healthcare garments: e-bra and smart vest

The financial burden of hospital readmissions and treatment of chronic cardiac diseases are global concerns. Point of Care (POC) has been presented as an elegant solution for healthcare cost reduction. However, large scale adoption of POC systems requires an intuitive, unobtrusive and easy to use health monitoring system from patient’s perspective. Healthcare textiles are sensor systems mounted on textile platform that function as wearable unobtrusive health monitoring systems. Although much work has been done in the development and demonstration of textile mounted monitoring systems, material and production costs are still high. Nanomaterials based devices and technology can be employed in these healthcare textiles for improved electrical characteristics of the sensors, lowered cost due to less material consumption and compatibility to varied manufacturing techniques. Carbon nanotube composite ink based printable conductive electrodes is such a textile adaptable nanomaterial technology. Screen printed Nanocomposite electrodes made of carbon nanotubes and an acrylic polymer can be used in undergarments like vests and brassieres, for cardiac biopotential (Electrocardiography, ECG) sensing. A Bluetooth module and a smartphone can then be used to provide cyber-infrastructure connectivity for the healthcare data from these healthcare garments. They can be used to monitor young or elderly recuperating /convalescent patients either in hospital or at home, or they can be used by young athletes to monitor important physiological parameters to better design their training or fitness program. In this study, we evaluate screen printed CNT-acrylic Nanocomposite electrodes for ECG signal quality and any CNT leaching hazard that might lead to skin toxicity.

Carbon nanotubes polymer nanoparticles inks for healthcare textile

Healthcare textiles are ambient health monitoring systems that can contribute towards medical aid as well as general fitness of the populace. These are textile based products that have sensor systems mounted on them or are electrically functionalized to act as sensors. While embedded sensor chipsets and connection wires have been shown as working prototypes of this concept, there is a need for seamless integration of sensor technologies without hindering the inherent properties of the textile. Screen printing or stamping with electrically conductive inks have been demonstrated as technologies for fabricating electronics on flexible substrates. They are applicable to textile manufacturing as well. Printing technology allows for fabrication of nanocomposite based electronics elements in a bottom-up fashion. This has advantages such as low material consumption, high speed fabrication and low temperature processing. In this research, Multi-Wall Carbon Nanotubes (MWCNTs) and polyaniline nanoparticles (PANP) core shell based nanocomposites were synthesized and formulated into colloidal ink. Printed MWCNTs-PANP traces were electrically characterized and compared with traces made with those made by other composites such as Silver, and Carbon Black. The nanocomposite based inks are compared for proposed applications as sensor systems and conductive tracks on smart textile for pervasive wireless healthcare system that can be mass produced using low cost printing processes.

Smart real-time cardiac diagnostic sensor systems for football players and soldiers under intense physical training

Sudden cardiac death (SCD) and acute myocardial infarctions (AMIs) have been reported to be up to 7.6 times higher in rate of occurrence during intense exercise as compared to sedentary activities. The risk is high in individuals with both diagnosed as well as occult heart diseases. Recently, SCDs have been reported with a high rate of occurrence among young athletes and soldiers who routinely undergo vigorous training. Prescreening Electrocardiograms (ECG) and echocardiograms have been suggested as potential means of detecting any cardiac abnormalities prior to intense training to avoid the risk of SCDs, but the benefits of this approach are widely debated. Moreover, the increased risk of SCDs and AMIs during training or exercise suggests that ECGs are of much greater value when acquired real-time during the actual training. The availability of immediate diagnostic data will greatly reduce the time taken to administer the appropriate resuscitation. Important factors to consider in the implementation of this solution are: - cost of overall system, accuracy of signals acquired and unobtrusive design. In this paper, we evaluate a system using printed sensors made of inks with functional properties to acquire ECGs of athletes and soldiers during physical training and basic military training respectively. Using Zigbee, we show that athletes and soldiers can be monitored in real time, simultaneously.

Wireless Glucose Monitoring Watch enabled by an Implantable Self- sustaining Glucose Sensor System

Implantable glucose sensors can measure real time blood glucose as compared to conventional techniques involving drawing blood samples and in-vitro processing. An implantable sensor requires energy source for operation with wire inout provision for power and sending signals. Implants capable of generation-transmission of sensory signals, with minimal or no power requirement, can solve this problem. An implantable nanosensor design has been presented here, which can passively detect glucose concentration in blood stream and transmit data to a wearable receiver-recorder system or a watch. The glucose sensitive component is a redox pair of electrodes that generates voltage proportional to glucose concentration. The bio-electrode, made of carbon nanotubes-enzyme nanocluster, has been investigated because of the large surface area for taping electrical signals. This glucose sensor can charge a capacitor, which can be a part of a LCR resonance/inductive coupling based radio frequency (RF) sensor telemetry. Such a system can measure change in glucose concentration by the induced frequency shift in the LCR circuit. A simultaneous power transmission and signal transmission can be achieved by employing two separate LCR oscillating loops, one for each operation. The corresponding coupling LCR circuits can be housed in the wearable receiving watch unit. The data logged in this glucose monitoring watch can be instrumental in managing blood glucose as trigger for an insulin dispensing payload worn on person or implanted.