Condensed Matter Physics Seminar
2 p.m., Thursday, January 25, 2007
Room 1201, Physics Building
The Sensitivity Limits of Nanowire Bio-Sensors
Xuan Gao
(Harvard University)
Abstract: Nanowire field effect transistors (NWFETs) are emerging
as powerful tools for biological applications such as bio-molecule detection,
yet their sensitivity limits are not understood at a fundamental level. I will
discuss the interplay of device parameters such as gate bias and NW diameter on
the operating modality and sensitivity of NWFET sensors. pH and cancer marker
detections are studied as silicon-NWFETs are tuned from linear to subthreshold
regimes by electrochemical gating. First, pH sensing data show that NWFET has
the strongest response and the best signal to noise ratio in the subthreshold
regime. Operating in the subthreshold regime also reduces the detection limit
for prostate specific antigen down to ~fM for a device with ~pM detection limit
in the linear regime. This sensitivity improvement is due to the stronger gating
effect of the molecule binding on NW surface. A quantitative model describing
these results and the intrinsic charge detection limit of NWFET sensors will be
discussed. I will also discuss future biophysics applications of such
ultra-sensitive chem/bio-sensors.
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Host: Williams/Wuttig
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