Microelectronic Pill

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  • Topic: PH, Glass electrode, PH meter
  • Pages : 24 (8912 words )
  • Download(s) : 915
  • Published : April 17, 2012
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1.INTRODUCTION
The invention of the transistor enabled the first radio telemetry capsules, which utilized simple circuits for in vivo telemetric studies of the gastro-intestinal tract. These units could only transmit from a single sensor channel, and were difficult to assemble due to the use of discrete components. The measurement parameters consisted of temperature, pH or pressure, and the first attempts of conducting real-time noninvasive physiological measurements suffered from poor reliability, low sensitivity, and short lifetimes of the devices. The first successful pH gut profiles were achieved in 1972, with subsequent improvements in sensitivity and lifetime. Single-channel radio telemetry capsules have since been applied for the detection of disease and abnormalities in the GI tract where restricted access prevents the use of traditional endoscopy. Most radio telemetry capsules utilize laboratory type sensors such as glass pH electrodes, resistance thermometers, or moving inductive coils as pressure transducers. The relatively large size of these sensors limits the functional complexity of the pill for a given size of capsule. Adapting existing semiconductor fabrication technologies to sensor development has enabled the production of highly functional units for data collection, while the exploitation of integrated circuitry for sensor control, signal conditioning, and wireless transmission, and has extended the concept of single-channel radio telemetry to remote distributed sensing from microelectronic pills. Our current research on sensor integration and onboard data processing has, therefore, focused on the development of Microsystems capable of performing simultaneous multiparameter physiological analysis. The technology has a range of applications in the detection of disease and abnormalities in medical research. The overall aim has been to deliver enhanced functionality, reduced size and power consumption, through system-level integration on a common integrated circuit platform comprising sensors, analog and digital signal processing, and signal transmission. In this report, we present a novel analytical micro system which incorporates a four-channel micro sensor array for real-time determination of temperature, pH, conductivity and oxygen. The sensors were fabricated using electron beam and photolithographic pattern integration, and were controlled by an application specific integrated circuit (ASIC), which sampled the data with 10-bit resolution prior to communication off chip as a single interleaved data stream. An integrated radio transmitter sends the signal to a local receiver (base station), prior to data acquisition on a computer. Real-time wireless data transmission is presented from a model in vitro experimental setup, for the first time. Details of the sensors are provided in more detail later, but included: a silicon diode to measure the body core temperature, while also compensating for temperature induced signal changes in the other sensors; an ion-selective field effect transistor, ISFET, to measure pH; a pair of direct contact gold electrodes to measure conductivity; and a three-electrode electrochemical cell, to detect the level of dissolved oxygen in solution. All of these measurements will, in the future, be used to perform in 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 identify local changes associated with tissue inflammation and ulcers. Likewise, the pH sensor may be used for the determination of the presence of pathological conditions associated with abnormal pH levels, particularly those associated with pancreatic disease and hypertension, inflammatory bowel disease, the activity of fermenting bacteria, the level of...
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