A “Microelectronic pill” is a basically a multichannel sensor used for remote biomedical measurements using micro technology. This has been developed for the internal study and detection of diseases and abnormalities in the gastrointestinal (GI) tract where restricted access prevents the use of traditional endoscope. The measurement parameters for detection include real – time remote recording of temperature, pH, conductivity and dissolved oxygen in the GI tract. This paper deals with the design of the “Microelectronic pill” which mainly consists of an outer biocompatible capsule encasing 4–channel micro sensors, a control chip, a discrete component radio transmitter and 2 silver oxide cells.
| Our Body is a sensitive system.
Many times even doctors arenâ„¢t able to interpret the disease. Thus it become too late to cure it. To remove this problem scientists discovered electronic capsule in 1972. Use of discrete & relatively large componentâ„¢s, poor reliability, short lifetimes & low sensitivity makes it outdated. To overcome all these problems Professor Jon Cooper and Dr Erik Johanessen from Glasgow University , U.K has led to the development of a modern microelectronic pill. When Microelectronic pill is swallowed, then it will travel through the Gastro Intestinal Tract & simultaneously perform multiparameter in situ physiological analysis After completing its mission it will come out of the body by normal bowel movement The pill is 16mm in diameter & 55mm long weighing around 5 gram It records parameters like temperature, pH, Conductivity, & Dissolved Oxygen in real time. PARTS CONTROL CHIP RADIO TRANSMITTER 2 SILVER OXIDE CELLS BIOCOMPATIBLE CAPSULE ENCASING MICROSENSOR SILICON DIODE 3 ELECTRODE ELECTROCHEMICAL CELL DIRECT CONTACT GOLD ELECTRODE ION-SELECTIVE FIELD EFFECT TRANSISTOR (ISFET) SCHEMATIC DIAGRAM OF MICRO ELECTRONIC CAPSULE
It measures the body core temperature.
Also compensates with the temperature induced signal changes in other sensors. It also identifies local changes associated with TISSUE INFLAMMATION & ULCERS. SILICON DIODE
The ISFET measures pH.
It can reveal pathological conditions associated with abnormal pH levels These abnormalities include :
Inflammatory bowel disease
The activity of fermenting bacteria
The level of acid excretion
Reflux of oesophagus
Effect of GI specific drugs on target
ION-SELECTIVE FIELD EFFECT TRANSISTOR (ISFET)
The pair of direct contact Gold electrodes measures conductivity, by measuring the contents of water & salt absorption, bile secretion & the breakdown of organic components into charged colloids etc. in the GI tract. Since the gold has best conductivity among all the elements, Therefore it gives true value of conductivity as measured. DIRECT CONTACT GOLD ELECTRODE
The three electrode electrochemical cell detects the level of dissolved oxygen in solution. It measures the oxygen gradient from the proximal to the distal GI Tract It investigates :
Growth of aerobic or bacterial infection
Formation of radicals causing cellular injury & pathophysiological conditions like inflammation & Gastric ulceration. It develops 1 st generation enzymes linked with amperometric biosensors. 3 ELECTRODE ELECTROCHEMICAL CELL
ARRANGEMENT MICRO ELECTRONIC PILL CHIP – 1 CHIP – 2 CONTROL CHIP
The ASIC (Application Specific Integrated Circuit) is the control unit that connects together other components of the micro system. It contains an analogue signal â€œconditioning module operating the sensors, 10-bit analogue to digital (ADC) & digital to analogue (DAC) converters, & digital data processing module The temperature circuitry bias the diode at constant current so that change in temperature reflects a corresponding
change in in diode voltage. The pH ISFET sensor is biased as a simple source at constant current with the source voltage changing with threshold voltage & pH. The conductivity circuit operates at D.C. It measures the resistance across the electrode pair as an inverse function of solution conductivity. An incorporated potentiostat circuit operates the O 2 sensor with a 10 bit DAC controlling the working electrode potential w.r.t the reference Analogue signals are sequenced through a multiplexer before being digitized by ADC. ASIC & sensors consume 5.3 mW power corresponding to 1.7 mA of current. CONTROL CHIP
Size of transmitter = 8 Ãƒâ€” 5 Ãƒâ€” 3 mm
Modulation Scheme = Frequency Shift Keying (FSK)
Data Transfer Rate = 1 kbps
Frequency = 40.01 MHz at 20 Ã‚Â°C
Bandwidth of the signal generated 10 KHz
It consumes 6.8 mW power at 2.2 mA of current.
OBSERVATIONS ON RECIEVER COMPUTER
2 SR44 Ag 2 O batteries are used.
Operating Time > 40 hours.
Power Consumption = 12.1 mW
Corresponding current consumption = 3.9mA
Supply Voltage = 3.1 V
2 SILVER OXIDE BATTERIES
Temperature from 0 to 70 Ã‚Â° C
pH from 1 to 13
Dissolved Oxygen up to 8.2 mg per liter
Conductivity above 0.05 mScm -1
Full scale dynamic Range analogue signal = 2.8 V
pH channel is around 0.2 unit above the real value
Oxygen Sensor is Ã‚Â±0.4 mgL.
Temperature & Conductivity is within Ã‚Â±1%.
RANGE & ACCURACY
It is being beneficially used for disease detection & abnormalities in human body. There fore it is also called as MAGIC PILL FOR HEALTH CARE Adaptable for use in corrosive & quiescent environment It can be used in industries in evaluation of water quality, Pollution Detection, fermentation process control & inspection of pipelines. Micro Electronic Pill utilizes a PROGRAMMABLE STANDBY MODE , So Power consumption is very less. It has very small size, hence it is very easy for practical usage High sensitivity, Good reliability & Life times.
Very long life of the cells(40 hours), Less Power, Current & Voltage requirement (12.1 mW, 3.9 mA, 3.1 V) Less transmission length & hence has zero noise interference. ADVANTAGES
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* RE: MICROELECTRONIC PILLS