Femtosecond Laser Micromachining of BioMEMS

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Femtosecond Laser Micromachining of BioMEMS

• BioMEMS Lab
• Mechanical and Aerospace Engineering
• University of Texas Arlington

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Comparison of Micromachining Processes
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Laser Micromachining Process
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Advantages of Laser Micromachining

• Non-contact machining
• Very high resolution, repeatability and aspect
  ratios
• Localized heating, minimal redeposition
• No pre/post processing of material
• Wide range of materials fragile, ultra-thin and
  highly reflective surfaces
• Process can be fully automated

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Effect of Laser Micromachining Process Parameters
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Characteristics of Femtosecond Laser
Micromachining

• Very high peak powers in the range 1013W/cm2
  provide for minimal thermal damage to
  surroundings
• Very clean cuts with high aspect ratios
• Sub-micron feature resolution
• Minimal redeposition
• Possible to machine transparent materials like
  glass, sapphire etc

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Ultrashort Pulses vs. Long Pulse Micromachining
Courtesy Sandia National Labs
Ti sapphire,120fs a) air b) vacuum c) NdYAG,
100ns
Extremely short pulses provide for minimal
thermal damage to surroundings
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Femtosecond Laser System at BioMEMS Lab

• Spectra Physics Hurricane Femtosecond Ti
  sapphire Laser
• Pulse width 106fs
• Wavelength range 750nm-850nm
•  
• Average energy 1mJ/pulse
•  
• Beam profile Gaussian
•  
• Polarization linear, horizontal

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Femtosecond Laser Micromachining (Preliminary
Experimental Testbed)
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Additional Equipment for Femtosecond Laser
Micromachining

• Ultra-high precision 3-axis linear stage assembly
  by Aerotech Inc .
• Ultrafast High Energy Beam Attenuator by Newport
  Corporation.
• Power Meter by Scientech Inc.
• 2GHz Oscilloscope by Hewlett Packard
• Under development
• 10-3 Torr, 1m3 Vacuum Chamber with inert gas and
  electrical and power ports
• Fully automated multiple lens changer
• LabView based control environment

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Preliminary Experimental Results
Micromachining in 18µm Thick Aluminum Foil

• Array of shots (b) Thru-hole drilled after 33
  shots at a pulse energy of 14µJ

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Single Shots in 18µm Thick Aluminum Foil
Preliminary Experimental Results
Focal position Off-focal
position
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Thru-holes Drilled in 25µm Thick Brass Foil
Preliminary Experimental Results
56µJ/pulse 27µJ/pulse
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Ablation Rate vs. Energy Density in 18?m Thick
Aluminum Foil
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Optimization of Pulse Energy Required to Drill
Thru-Holes
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Femtosecond Laser Bonding of Optically
Transparent Materials

• Explore femtosecond laser bonding of optically
• transparent PMMA or glass to a substrate
• Automatic lens changer will be used to study the
  
• effect of variable focal length on the bond
  strength

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Laser Intensity Distribution in PMMA
Focal length of 9mm Focal length
of 40mm
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Through the Thickness Intensity Distribution of
Transmitted Laser Beam in PMMA
Focal length of 9mm Focal length
of 40mm
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Automation of Laser Micromachining Process
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Conceptual Solid Model of Laser Micromachining
Setup