Bio-sensors - Medical Applications

The Sensors and microsystems session at ISSCC included microwave radar chips for remote medical monitoring, and a CMOS DNA-screening system.

Remote Medical Monitoring Chip
The single-chip, direct conversion 1.6GHz Doppler radars, using 0.25pm CMOS and BiCMOS, were described by researchers from Stanford University, Bell Labs and Agere Systems.

The devices, claimed to be the first of their type to be integrated in low-cost silicon, use an active balanced amplifier to split a voltage controlled oscillator (VCO) signal into an RF output and a local oscillator (LO) signal.

The reflected RF signal is mixed with the LO, and since they are derived from the same source, the mixer downconverts the RF signal to baseband. The output is proportional to the movement of the target - in this case displacement due to breathing and heartbeat. The transceivers detected these vital signs 500mm from the subject.

DNA Sensor Array Chip

A DNA sensor array chip based on 0.5pm CMOS, with some extra steps to add gold electrodes, was presented by German researchers from Infineon and Siemens, among others.

The active sensor array is made from pairs of gold electrodes in a circular compartment, onto which DNA strands with known sequences (probes) are fixed. A solution of unknown sequence (target) DNA strands is washed across the chip, and compatible strands bind to the fixed probes. Unreacted strands are washed off.

After enzyme labels on the target DNA are chemically converted to charge-carrying species, potentials are applied to the interleaving electrode grids.

A pixel circuit on the 16x8the generator and collector electrodes. The currents of both electrodes are amplified using dual current irrors in series with each branch. A dynamic range of five array reads current from both decades of current is needed.


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