Ph.D. Oral Examination - Shu-Jen Han - Feb. 2, 2007

Shu-Jen Han hansj at
Thu Jan 25 15:31:50 PST 2007

"CMOS integrated biosensor array based on GMR devices
and magnetic nanoparticles"

Shu-Jen Han
Department of Materials Sci. and Eng.

Advisor: Professor Shan X. Wang

Date: Friday, February 2nd, 2007
Time: 9:45AM (Refreshment served at 9:30AM)
Place: CISX auditorium (101)


Molecular recognition is exploited in assay techniques such
as those based on DNA hybridization microarrays. Integrating
biosensor arrays and other laboratory functions on a single
CMOS chip yields a low-cost system that constitutes a promising
tool for future biological diagnostics. Magnetic biosensors are
under active development and may soon rival established biological
detection methods that use surface-bond fluorescent tags.

In a magnetoresistive biosensor detection scheme, single¡Vstranded
DNA receptors are immobilized on the surface of giant magnetoresistive
(GMR) sensors. Oligonucleotides of unknown sequence are selectively
captured by complementary probes. Streptavidin coated magnetic
nanoparticles are then introduced and bind to the biotin of the hybridized
DNA. Finally, magnetic field disturbances due to the nanoparticles are
sensed by GMR devices.

In this work, we have designed and fabricated the first GMR sensor
integrated CMOS biochip. The chip has been fabricated in a 0.25£gm BiCMOS
process, and sub-micron sized sensors were successfully integrated with the
diced chip. It contains >1000 sensing elements within 1mm^2, together with
low noise, high throughput readout channels for high sensitivity DNA
detection on the same chip. Compared to complex and expensive optical
detection systems, the GMR biochip measures electrical signal directly from
the sensor, and makes a highly portable and sensitive device feasible.

Shu-Jen Han
Materials Science and Engineering
McCullough Bldg., RM208
Stanford University

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