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  4. An experimental investigation of capillary driven flow in open rectangular channels: a method to create PDMS microfilaments for pN scale force measurements
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An experimental investigation of capillary driven flow in open rectangular channels: a method to create PDMS microfilaments for pN scale force measurements

Full metadata

Description

The flow of liquid PDMS (10:1 v/v base to cross-linker ratio) in open, rectangular silicon micro channels, with and without a hexa-methyl-di-silazane (HMDS) or poly-tetra-fluoro-ethylene (PTFE) (120 nm) coat, was studied. Photolithographic patterning and etching of silicon wafers was used to create micro channels with a range of widths (5-50 μm) and depths (5-20 μm). The experimental PDMS flow rates were compared to an analytical model based on the work of Lucas and Washburn. The experimental flow rates closely matched the predicted flow rates for channels with an aspect ratio (width to depth), p, between one and two. Flow rates in channels with p less than one were higher than predicted whereas the opposite was true for channels with p greater than two. The divergence between the experimental and predicted flow rates steadily increased with increasing p. These findings are rationalized in terms of the effect of channel dimensions on the front and top meniscus morphology and the possible deviation from the no-slip condition at the channel walls at high shear rates.

In addition, a preliminary experimental setup for calibration tests on ultrasensitive PDMS cantilever beams is reported. One loading and unloading cycle is completed on a microcantilever PDMS beam (theoretical stiffness 0.5 pN/ µm). Beam deflections are actuated by adjusting the buoyancy force on the beam, which is submerged in water, by the addition of heat. The expected loading and unloading curve is produced, albeit with significant noise. The experimental results indicate that the beam stiffness is a factor of six larger than predicted theoretically. One probable explanation is that the beam geometry may change when it is removed from the channel after curing, making assumptions about the beam geometry used in the theoretical analysis inaccurate. This theory is bolstered by experimental data discussed in the report. Other sources of error which could partially contribute to the divergent results are discussed. Improvements to the experimental setup for future work are suggested.

Date Created
2014
Contributors
  • Sowers, Timothy Wayne (Author)
  • Rajagopalan, Jagannathan (Thesis advisor)
  • Herrmann, Marcus (Committee member)
  • Huang, Huei-Ping (Committee member)
  • Arizona State University (Publisher)
Topical Subject
  • Mechanical Engineering
  • capillary
  • force sensor
  • meniscus morphology
  • microchannel
  • Microfluidics
  • PDMS
  • Polydimethylsiloxane
  • Cytoplasmic filaments
Genre
Masters Thesis
Academic theses
Extent
ix, 53 p. : ill. (some col.)
Language
eng
Copyright Statement
In Copyright
Reuse Permissions
All Rights Reserved
Primary Member of
ASU Electronic Theses and Dissertations
Peer-reviewed
No
Open Access
No
Handle
https://hdl.handle.net/2286/R.I.25941
Statement of Responsibility
by Timothy Wayne Sowers
Description Source
Viewed on December 17, 2014
Level of coding
full
Note
Partial requirement for: M.S., Arizona State University, 2014
Note type
thesis
Includes bibliographical references (p. 47-50)
Note type
bibliography
Field of study: Mechanical engineering
System Created
  • 2014-10-01 08:03:32
System Modified
  • 2021-08-26 09:47:01
  •     
  • 1 year 6 months ago
Additional Formats
  • OAI Dublin Core
  • MODS XML

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