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- ''Relatively short spin chains as building blocks for an all-quantum dot quantum computer architecture''
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- A dielectric-modulated field-effect transistor for biosensing
A dielectric-modulated field-effect transistor for biosensingJournal ref: Nature Nanotechnology 2, 430 - 434 (2007)
Posted:
09 July 2007, 22:54
Abstract: Interest in biosensors based on field-effect transistors (FETs), where an electrically operated gate controls the flow of charge through a semiconducting channel, is driven by the prospect of integrating biodetection capabilities into existing semiconductor technology. In a number of proposed FET biosensors, surface interactions with biomolecules in solution affect the operation of the gate or the channel. However, these devices often have limited sensitivity. We show here that a FET biosensor with a vertical gap is sensitive to the specific binding of streptavidin to biotin. The binding of the streptavidin changes the dielectric constant (and capacitance) of the gate, resulting in a large shift in the threshold voltage for operating the FET. The vertical gap is fabricated using simple thin-film deposition and wet-etching techniques. This may be an advantage over planar nanogap FETs, which require lithographic processing. We believe that the dielectric-modulated FET (DMFET) provides a useful approach towards biomolecular detection that could be extended to a number of other systems.
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John Morton posted 00:13 10/07/07 |
 some questions
I found this a clear, well-written and interesting paper. I have a couple of few questions.
1) According to the dimensions given in the paper, it seems there are of order 1000 streptavidin molecules in the nanogap. Is this indeed the case, and what does this say about the potential sensitivity of the device? 2) You mention in the abstract the extendability of this detection moethod to other systems. Could you say a bit more about this? Does this refer to binding other biomolecules to biotin, or attaching other surface molecules to the nanogap? |
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Hyungsoon Im posted 08:14 10/07/07 |
 re : some questions
Dear Dr. Morton
Thank you for your comments. Let me answer your questions one by one. ---- 1) According to the dimensions given in the paper, it seems there are of order 1000 streptavidin molecules in the nanogap. Is this indeed the case, and what does this say about the potential sensitivity of the device? It is a good question. This question is related to the size-dependent electrical behaviors of DMFET nanogap device. First of all, it is worthwhile to note that the DMFET nanogap device is different from some open-type sensing systems which can detect very small amount of molecules. According to our experience, the nanogap size has a significant effect on electrical characteristics in the DMFET, and it would be of value for our next research work. It is very hard to calculate the number of molecules within the nanogap because dynamics of fluid flow in such one-side closed narrow (nanoscale) channels is neither understood nor developed well. We speculate that flowing of biomolecules in the fluid in the nanochannel may be fundamentally different from nominal fluid dynamics. In the current paper, we can only estimate the sensitivity from various concentrations of streptavidin solution and are working on it. We would like to continue to optimize the nanogap device design and make an effort to understand the fluid dynamics. ---- 2) You mention in the abstract the extendability of this detection moethod to other systems. Could you say a bit more about this? Does this refer to binding other biomolecules to biotin, or attaching other surface molecules to the nanogap? For the DMFET nanogap device, it is possible to detect other molecules by monitoring a shift of the threshold voltage. Here we emphasize that the detection mechanism is based on specific binding of molecules such as antigen-antibody reaction. Specified reference molecules are immobilized in the nanogap first, target molecules will be introduced into the nanogap. When a specific binding is made in the nanogap, the threshold voltage, drain current, and transconductance will be changed as a result of the specific binding of molecules to be detected. We are trying to detect C-Reactive Protein (CRP) for diagnoses of cardiac disease and Prostate Specific Antigen (PSA) for that of prostate cancer. A paper presenting results of this experiment is submitted to the 2007 IEDM (International Electron Devices Meeting) conference. Then now an array typed devices to include various kinds of designed reference molecules will be fabricated and tested. I hope our answers are satisfactory to you. Thanks. Hyungsoon Im |
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