Page History

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The NanoScribe GT2 Laser Lithography System is an ultramodern two-photon polymerization volumetric maskless printer. It is one of our newest acquisitions here at the Cornell NanoScale Facility (CNF). The tool was purchased in late 2019 and delivered and installed during the second week of January 2020. This was accomplished with the help of a committee of faculty and researchers, and a grant from the NSF. The NanoScribe GT2 can create three-dimensional nanostructures using a NIR femtosecond laser via direct-write onto a photosensitive resin, which is subjected to a non-linear two-photon absorption process. This process involves cross-linking the resin via UV absorption. The laser sets a focal light cone where a concentration of the light intensity defines the exposure focal spot volume or a “3D Pixel.” Using this technique, a CAD design can be broken into an X-Y-Z coordinate system to define the structure pixel by pixel and layer by layer. The exposure side of the system sits in a fine-tuned vibration isolation table and a high-speed ultra-precise piezoelectric stage for movement in X-Y-Z and uses a galvanic mirror defection system for focusing and beam rasterization. Models for printing can be designed using the stand-alone software DeScribe—which comes with the tool—or with any CAD software capable of outputting file formats DXF or STL. The DeScribe software can import these formats. 

3D Print Technology & Direct

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Write

Laser-based direct writing has been around for a few years especially in the semiconductor industry known as maskless lithography (MPL). Typically, the two-dimensional CAD design is transferred onto the substrate that is pre-coated with a photosensitive resin via reduction laser projection. The projected pattern was reduced given the tool's numerical aperture and scan across the surface of the substrate using either a raster or vector format. These techniques are the same ones utilized in 3D direct-write. The only difference is that now you are working with a thickness degree of freedom that can be scanned across the Z-axis. The NanoScribe GT2 has a Piezo Nanopositioning stage and a high-speed galvo scanner. In the case of two-photon lithography, the light source is a pulsed femtosecond fiber laser with the center wavelength being around 780 nm. 

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• Carefully remove the substrate from the sample holder.
• Place the substrate in a developer bath to wash away excess liquid 2PP resin.
• Wash away the developer.
• Transfer to IPA for at least 15 minutes.
• Gently blow-dry the sample (Optional- dependent on size and strength of your structure).
• Cure remaining liquid 2PP resin if a shell and scaffold structure was printed.

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Model Removal & Resin Stripping

Manual Interface Finding for 10X Objective

When using the 10X Objective, it is possible to use an alternate method to find an interface and begin printing on nonreflective and/or rough substrates. This method does not work with other objectives and should be used with caution.

1. Load your substrate in a sample holder. If the substrate is thicker or thinner than the holder depth (i.e. 700 microns thick for the Multi-DiLL holder), it is important to measure how much taller or shorter your substrate is.
2. Add resin to your substrate and the objective.
3. Load your sample as you would normally, select the correct holder and click OK.
   1. Do not click Approach Sample.
4. In the advanced camera settings, ensure that the light source is correct for your substrate - for opaque substrates use a Reflective Illumination, but for transparent substrates you will be better served with Transmission Illumination even though this is atypical for the 10X.
5. Approach the sample with the manual Z control. You may use coarse control initially until you reach a Z-height on the order of 9000um. For thicker substrates, it is recommended to stop earlier, substract your substrate height above the holder from 9000.
   1. During this step you should see the lens contact the resin, it will be very obvious, looking like a bubble moving across the microscope. Keeping Auto Contrast and Auto Exposure
6. Using the fine control, move the microscope slowly; you should slowly begin to resolve the substrate.
   1. For a 700um thick substrate this is typically a Z-value greater than 9800um
   2. Turning off auto-contrast and auto exposure can be helpful; ensuring short exposure times but also smaller Gain (<15) will result in a clearer image
7. Your substrate should eventually come into sharp focus, move the substrate on X and Y until you have identified where you would like to print.
8. Modify your _data.gwl file:
   1. It will contain the line FindInterfaceAt $interfacePos, comment this out by adding "%" before the line
   2. If this line is not removed or commented out, the microscope will lose the position and attempt to automatically find the interface
9. Using the fine control, move the Z axis up another 40um
   1. If your current Z-height is 10,000um, move to 10,040um
   2. Your substrate should be slightly blurry
   3. 40um is only a starting point, your actual application may require a different value
10. Load your print job and begin printing
    1. It may be valuable to have a small object (e.g. a cube) to test the print before starting a longer one. This can help validate your starting point and ensure that your print isn't floating or the laser is focused past your substrate.

~Still under construction~

Applications

• Microfluidics
• Micromechanics
• Biomedical Engineering
• Micro-electro-mechanical systems
• Mechanical metamaterials
• Micro-optics
• Photonic metamaterials and Plasmonics

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