Design and fabrication of nanofluidic transistors beyond Debye screening limit
Abstract/Contents
- Abstract
- The development of microfluidic systems, which miniaturize complex laboratory pro- cedures onto small microchips, has dramatically reduced the cost and time of biologi- cal analyses. With fluidic devices scaling down to nanometer regime, new phenomena that were previously inaccessible at larger length scales arise. Particularly, electro- static force can now be used to control ionic and biomolecule transport in nanofluidic devices. Nanofluidic devices using an active gate to manipulate charged molecules called nanofluidic transistors by analogy to MOSFET transistors, have applications ranging from sample preparation in point-of-care devices to sample sorting, and sea- water desalination. In ionic solutions, the Debye Length is considered as the characteristic length scale for effective field-effect control. Hence, the state-of-the-art nanofluidic transis- tors presented in the literature have required at least one dimension comparable to or smaller than Debye Length (sub-10 nm--30 nm) to achieve sufficient electrostatic control. This limit imposes challenges and difficulties on device fabrication. Simu- lations based on coupled Poisson-Nernst-Plank-Stokes models show that strong ionic transport can overcome the Debye-screening limits, thus leading to field-effect control beyond Debye Length. This thesis therefore focuses on the design and fabrication of nanofluidic transistors with channel size 100 nm to 200 nm, far beyond Debye Length limits (typically 10 nm in 1 mM concentration solutions), while achieving efficient field effect control. Further, a novel dual-gate configuration is introduced to improve nanofluidic transistors' current modulation ratio. Two possible device structural configurations—vertical channel and lateral channel devices—are proposed and compared with regards to their fabrication feasibilities and performances; both fabrication flows are compatible with conventional semicon- ductor fabrication technologies. The measurement results of NFTs beyond Debye- screening limit demonstrate highly effective electrostatic control of ions. In vertical channel devices, current modulation rate is 6-fold by using 1 V bias; in lateral channel devices, 2.6X current modulation rate is achieved by ∼10 V bias. Both results are better than the conventional Debye Length limited nanofluidics transistors. The nanofluidic transistors beyond Debye-screening limit demonstrate a new op- erating regime. The relaxed constraint on channel sizes offers advantages in device manufacturing, testing, and reliability. Based on standard process flows for fabrica- tion, this work also opens up the possibilities of on-chip fluid system integration as well as new applications in biological sensing and sample preparation.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2015 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Ran, Qiushi |
|---|---|
| Associated with | Stanford University, Department of Electrical Engineering. |
| Primary advisor | Dutton, Robert W |
| Thesis advisor | Dutton, Robert W |
| Thesis advisor | Howe, Roger Thomas |
| Thesis advisor | Wang, Shan |
| Advisor | Howe, Roger Thomas |
| Advisor | Wang, Shan |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Qiushi Ran. |
|---|---|
| Note | Submitted to the Department of Electrical Engineering. |
| Thesis | Thesis (Ph.D.)--Stanford University, 2015. |
| Location | electronic resource |
Access conditions
- Copyright
- © 2015 by Qiushi Ran
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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