25-11-2010, 08:48 AM
INTRODUCTION
THE invention of the transistor enabled the first radiotelemetry capsules, which utilized simple circuits for in vivotelemetric studies of the gastro-intestinal (GI) tract. These units could only transmit from a single sensor channel,and were difficult to assemble due to the use of discretecomponents. The measurement parameters consisted ofeither temperature, pH or pressure, and the first attemptsof conducting real-time noninvasive physiological measure-ments suffered from poor reliability, low sensitivity, and shortlifetimes of the devices. The first successful pH gut profileswere achieved in 1972, with subsequent improvements in sensitivity and lifetime .Single-channel radiotelemetrycapsules have since been applied for the detection of diseaseand abnormalities in the GI tract where restricted accessprevents the use of traditional endoscopy .Most radiotelemetry capsules utilize laboratory type sensorssuch as glass pH electrodes, resistance thermometers ,ormoving inductive coils as pressure transducers. The rel-atively large size of these sensors limits the functional com-plexity of the pill for a given size of capsule. Adapting existingsemiconductor fabrication technologies to sensor development has enabled the production of highly functional unitsfor data collection, while the exploitation of integrated circuitryfor sensor control, signal conditioning, and wireless transmis-sion has extended the concept of single-channel ra-diotelemetry to remote distributed sensing from microelectronicpills. Our current research on sensor integration and onboard dataprocessing has, therefore, focused on the development of mi-crosystems capable of performing simultaneous multiparameterphysiological analysis. The technology has a range of applica-tions in the detection of disease and abnormalities in medicalresearch. The overall aim has been to deliver enhanced func-tionality, reduced size and power consumption, through system-level integration on a common integrated circuit platform com-prising sensors, analog and digital signal processing, and signaltransmission. In this paper, we present a novel analytical microsystemwhich incorporates a four-channel microsensor array forreal-time determination of temperature, pH, conductivity andoxygen. The sensors were fabricated using electron beam andphotolithographic pattern integration, and were controlledby an application specific integrated circuit (ASIC), whichsampled the data with 10-bit resolution prior to communicationoff chip as a single interleaved data stream. An integrated radiotransmitter sends the signal to a local receiver (base station),prior to data acquisition on a computer. Real-time wireless datatransmission is presented from a modelin vitro experimentalsetup, for the first time. Details of the sensors are provided in more detail later, butincluded: a silicon diode to measure the body core temper-ature, while also compensating for temperature induced signalchanges in the other sensors; an ion-selective field effect tran-sistor, ISFET, to measure pH; a pair of direct contact goldelectrodes to measure conductivity; and a three-electrode elec-trochemical cell ,to detect the level of dissolved oxygenin solution. All of these measurements will, in the future, beused to performin vivo physiological analysis of the GI-tract For example, temperature sensors will not only be used to mea-sure changes in the body core temperature, but may also iden-tify local changes associated with tissue inflammation and ul-cers. Likewise, the pH sensor may be used for the determina-tion of the presence of pathological conditions associated withabnormal pH levels, particularly those associated with pancre-atic disease and hypertension, inflammatory bowel disease, theactivity of fermenting bacteria, the level of acid excretion, re-flux to the oesophagus, and the effect of GI specific drugs ontarget organs. The conductivity sensor will be used to monitorthe contents of the GI tract by measuring water and salt absorp-tion, bile secretion and the breakdown of organic componentsinto charged colloids. Finally, the oxygen sensor will measurethe oxygen gradient from the proximal to the distal GI tract. Thiswill, in future enable a variety of syndromes to be investigatedincluding the growth of aerobic bacteria or bacterial infectionconcomitant with low oxygen tension, as well as the role ofoxygen in the formation of radicals causing cellular injury andpathophysiological conditions (inflammation and gastric ulcer-ation). The implementation of a generic oxygen sensor will alsoenable the development of first generation enzyme linked am-perometric biosensors, thus greatly extending the range of futureapplications to include, e.g., glucose and lactate sensing, as wellas immunosensing protocols.
full report added by some one in http://scribddoc/37141450/Microelectronic-Pill
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THE invention of the transistor enabled the first radiotelemetry capsules, which utilized simple circuits for in vivotelemetric studies of the gastro-intestinal (GI) tract. These units could only transmit from a single sensor channel,and were difficult to assemble due to the use of discretecomponents. The measurement parameters consisted ofeither temperature, pH or pressure, and the first attemptsof conducting real-time noninvasive physiological measure-ments suffered from poor reliability, low sensitivity, and shortlifetimes of the devices. The first successful pH gut profileswere achieved in 1972, with subsequent improvements in sensitivity and lifetime .Single-channel radiotelemetrycapsules have since been applied for the detection of diseaseand abnormalities in the GI tract where restricted accessprevents the use of traditional endoscopy .Most radiotelemetry capsules utilize laboratory type sensorssuch as glass pH electrodes, resistance thermometers ,ormoving inductive coils as pressure transducers. The rel-atively large size of these sensors limits the functional com-plexity of the pill for a given size of capsule. Adapting existingsemiconductor fabrication technologies to sensor development has enabled the production of highly functional unitsfor data collection, while the exploitation of integrated circuitryfor sensor control, signal conditioning, and wireless transmis-sion has extended the concept of single-channel ra-diotelemetry to remote distributed sensing from microelectronicpills. Our current research on sensor integration and onboard dataprocessing has, therefore, focused on the development of mi-crosystems capable of performing simultaneous multiparameterphysiological analysis. The technology has a range of applica-tions in the detection of disease and abnormalities in medicalresearch. The overall aim has been to deliver enhanced func-tionality, reduced size and power consumption, through system-level integration on a common integrated circuit platform com-prising sensors, analog and digital signal processing, and signaltransmission. In this paper, we present a novel analytical microsystemwhich incorporates a four-channel microsensor array forreal-time determination of temperature, pH, conductivity andoxygen. The sensors were fabricated using electron beam andphotolithographic pattern integration, and were controlledby an application specific integrated circuit (ASIC), whichsampled the data with 10-bit resolution prior to communicationoff chip as a single interleaved data stream. An integrated radiotransmitter sends the signal to a local receiver (base station),prior to data acquisition on a computer. Real-time wireless datatransmission is presented from a modelin vitro experimentalsetup, for the first time. Details of the sensors are provided in more detail later, butincluded: a silicon diode to measure the body core temper-ature, while also compensating for temperature induced signalchanges in the other sensors; an ion-selective field effect tran-sistor, ISFET, to measure pH; a pair of direct contact goldelectrodes to measure conductivity; and a three-electrode elec-trochemical cell ,to detect the level of dissolved oxygenin solution. All of these measurements will, in the future, beused to performin vivo physiological analysis of the GI-tract For example, temperature sensors will not only be used to mea-sure changes in the body core temperature, but may also iden-tify local changes associated with tissue inflammation and ul-cers. Likewise, the pH sensor may be used for the determina-tion of the presence of pathological conditions associated withabnormal pH levels, particularly those associated with pancre-atic disease and hypertension, inflammatory bowel disease, theactivity of fermenting bacteria, the level of acid excretion, re-flux to the oesophagus, and the effect of GI specific drugs ontarget organs. The conductivity sensor will be used to monitorthe contents of the GI tract by measuring water and salt absorp-tion, bile secretion and the breakdown of organic componentsinto charged colloids. Finally, the oxygen sensor will measurethe oxygen gradient from the proximal to the distal GI tract. Thiswill, in future enable a variety of syndromes to be investigatedincluding the growth of aerobic bacteria or bacterial infectionconcomitant with low oxygen tension, as well as the role ofoxygen in the formation of radicals causing cellular injury andpathophysiological conditions (inflammation and gastric ulcer-ation). The implementation of a generic oxygen sensor will alsoenable the development of first generation enzyme linked am-perometric biosensors, thus greatly extending the range of futureapplications to include, e.g., glucose and lactate sensing, as wellas immunosensing protocols.
full report added by some one in http://scribddoc/37141450/Microelectronic-Pill
upload any raw file to download from scribd
