Introduction
Direct laser lithography or direct laser writing using two-photon deep ultraviolet laser for additive 3d manufacturing using conventional resin sensitive to two-photon absorption resulting in two-photon polymerization to create volumetric prints from CAD models.
Exposure System
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 wright
Laser-based direct writing has been around for a few years especially in the semiconductor industry know 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 know 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.
Hardware Overview
Diagram of a simplified optical path of a Two-Photon Lithography System.
Two-photon Light Source
Hight Performance NIR femtosecond laser
NanoScribe's Subsystems
Electronics Cabinet
Optics Cabinet [contains the laser, optics, and Galvo]
Emergency Off (EMO) switch
Printing Cabinet [Microscope, Piezo, and Stage]
Power Supply 232
System Controller
System Computer
Laser System Controller
Galvo Stage Power Supply
Monitor, Keyboard, and Mouse
Manual Microscope Controller
Joystick
Power UP and Power DOWN Procedures
Power UP Procedure
Warning!
"Disregard of the guidelines concerning power-up of the Photonic Professional GT2 may cause damage to the system!"
Apply the following sequence in order to power up the Photonic Professional GT2 (See Fig)
Turn the mains power switch to position 1.
Wait some seconds until the reset and open buttons blink in alternation and the attention indicator is lit up.
Press the reset button, the attention indicator switches off.
Switch on the Photonic Professional GT2 Controller by activating the key switch.
Switch on the Control PC: Let it boot completely before proceeding, wait until the long on-screen shows up.
Switch on the laser controller by activating the key switch. The button
start/stopdoes not have to be pushed (the backlight of the button should be off). The laser emission is controlled via the Photonic Professional GT2 control software NanoWrite.Switch on the GT power supply.
Switch on the z-drive power supply.
Switch on the computer monitor.
Press the open button in order to release the safety lock and to open the printing cabinet. As long as the safety lock is released the open button is blinking white.
Note: The laser gives acoustic feedback, as soon as its start-up is finished. This can take up to 30 s. After that, the control software NanoWrite may be launched. Make sure that the laser is operational when starting NanoWrite. The laser emission is switched on automatically when NanoWrite starts. The status of laser emission is indicated by the backlight of the button
start/stopon the front panel of the laser controller. If the light is activated, the emission is on. You can manually switch on/off the emission by pressing this button. A power calibration of the laser is performed automatically before the first print starts or when NanoWrite receives the first script command.
Power Down Procedure
Warning!
"Disregard of the guidelines concerning power-up of the Photonic Professional GT2 may cause damage to the system!"
Apply the following sequence in order to shut down the Photonic Professional GT2 (See Fig)
Exit NanoWrite. Wait until NanoWrite is shut down. Otherwise, error messages may occur. In general, the laser emission is switched off automatically when exiting NanoWrite.
Shut down the computer.
Make sure the objective lens is in the lowermost position. Check for the message
lower z-limit reachedon the touch panel.Switch off the z-drive power supply.
Switch off the GT power supply.
Check the status of the laser emission; if the backlight of the button
start/stopis activated, press it to switch off the emission.Switch off the laser controller by deactivating the key switch.
Switch off the Photonic Professional GT2 controller by deactivating the key switch.
Switch off the Photonic Professional GT2 by turning the mains power switch to position 0.
Warning!