Motion control platform for accurate measurement of nano-structures

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Motion control platform for accurate measurement
of nano-structures

• Hua Yang and Richard Seugling
• Advisors
• Dr. Stuart Smith
• Dr. Robert Hocken
• Dr. David Trumper

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Project Info.

• Project funded by NSF
• Award DMI-0210543
• 3 year project.
• Collaborative work UNC-Charlotte, NIST and MIT.

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Overview

• Objectives
• Project Requirements
• Conceptual design of the motion control platform
• Polymer bearing tester (summer work)
• Horizontal/Vertical motion
• Results
• Current work

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Objectives

• Development of integrated position measurement
  system with nanometer uncertainties traceable to
  national standards.
• Translation mechanism for multi degree-of-freedom
  motion control.
• Integration of fine motion controllers into
  long-range instrumentation for nano-scale
  manipulation in centimeter-sized workspaces.
• Integration of combined uncertainty analyses for
  determination of system error budget.
• Integration of cascaded multi degree-of-freedom
  control systems.

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Requirements

• Vacuum Compatibility
• 10-3 to 10-4 Torr
• Range
• 50 mm ? 50 mm ? 10 mm
• Velocity
• 5 mm/sec max velocity
• Resolution
• 25 nm positioning
• 10 nm accuracy

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Conceptual design of motion control platform
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Bearing Test Design, Why?

• Characterize coefficient of friction for UHMWPE
  thin film slideway bearings.
• Derive model for normal stresses for polymer
  bearings during sliding.(Ajith Ramesh)
• Test the durability of UHMWPE bearings over time
  and distance.
• Assess thin film polymer bearing in a vacuum
  environment. (10-3 Torr)

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Nanometer Repeatability (Eric Buice)
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Thin Film Bearing Model (Ajith Ramesh)
Load 2.44 N Film thickness 100 microns
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Bearing Test Setup, Pin-on-disk
Velocity at polymer tip
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Calibration Curve
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Static and Dynamic Friction Coeff. 2.5 N _at_ 4.2
mms-1
Before
? 0.1679 rads-1
After
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Reversal of direction 2.5 N _at_ 4.2 mms-1
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Dwell Time (after 24 Hours) 2.5 N _at_ 4.2 mms-1
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Variation in velocitywith 6.65 N load (r 19
mm to 50 mm)
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Durability Test
6.65 N load _at_ 4.2 mms-1 for 11 hours
11.55 N load _at_ 4.2 mms-1 for 70 hours
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Larger bearing diameter

• Bearing diameter increase from 3/16?1/2
• 61 increase in area of contact
• 37 decrease of normal stress
• New Bearing
• Load of 27.8 N _at_ 4.2 mms-1
• Over 145 hours run 2.2 km

Old bearing design
New bearing design
Final bearing design (Eric Buice)
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Current work Design of Linear Slide-way
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Future work (cont.)

• Vacuum system procurement
• Optical systems specification and component
  identification
• Verify polymer bearing performance and vacuum
  compatibility
• Finalize linear slide-way design
• Finalize coarse stage design
• Identification of calibration methodology and
  comparative assessment with competing systems

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Questions?Comments?Suggestions?