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Microelectronic Pill

by Anu N on January 10, 2011


                                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.

Microelectronic Pill

 Microelectronic pill consists of 4 sensors (2) which are mounted on two silicon chips (Chip 1 & 2), a control chip (5), a radio transmitter (STD- type 1-7, type2-crystal type-10) & silver oxide batteries (8). 1-access channel, 3-capsule, 4- rubber ring, 6-PCB chip carrier.

1)    Sensor chip 1: 

                 An array consisting of both temperature sensor & pH sensor platforms were cut from the wafer & attached onto 100-µm- thick glass cover slip cured on a hot plate. The plate acts as a temporary carrier to assist handling of the device during level 1 of lithography when the electric connections tracks, electrodes bonding pads are defined. Bonding pads provide electrical contact to the external electronic circuit.

                   Lithography [2] was the first fundamentally new printing technology since the invention of relief printing in the fifteenth century. It is a mechanical Plano graphic process in which the printing and non-printing areas of the plate are all at the same level, as opposed to intaglio and relief processes in which the design is cut into the printing block. Lithography is based on the chemical repellence of oil and water. Designs are drawn or painted with greasy ink or crayons on specially prepared limestone. The stone is moistened with water, which the stone accepts in areas not covered by the crayon. Oily ink, applied with a roller, adheres only to the drawing and is repelled by the wet parts of the stone. Pressing paper against the inked drawing then makes the print


          Ion Selective Field Effect Transistor; this type of electrode contains a transistor coated with a chemically sensitive material to measure pH in solution and moist surfaces. As the potential at the chemically active surface changes with the pH, the current induced through the transistor varies. A temperature diode simultaneously monitors the temperature at the sensing surface. The pH meter to a temperature compensated pH reading correlates the change in current and temperature.

2.)      Sensor chip2:

                  Level 1 pattern was defined in 0.9 µm UV3 resist by electron beam lithography. It contains three-electrode electrochemical oxygen sensor & NiCr resistance thermometer.

Oxygen sensor detection principle: [6]