Laser parameters:

• System laser class:  1 (en 60825-1:2007)
• Internal laser class:  3b (en 60825-1:2007)
• Center wavelength:  780 nm
• Average output power <180 mW
• Peak power:  25 kW
• Pulse duration ≈ 100 fs
• Repetition rate:  80 mHz

Approaches such as e-beam lithography, UV-lithography, focused ion beam lithography etc are not suitable for patterning multimaterial nanostructures and are inherently planar in nature. 3D Laser lithography is a femto-second laser based direct patterning technique capable of producing true three dimensional (3D) nanostructures with high throughput and large scalability. Because of nonlinear interaction between the femto-second laser pulse and the medium, the interaction is confined to the focal volume, allowing precise material modification in three dimensions in the bulk of the sample. This system will allow fabrication of high quality true 3D nano- and micrometer scaled structures of nearly arbitrary shape. The minimum feature size for 3D structures reaches below 200 nm, while sub-100 nm resolution has been realized in 2D.

3D Printing using Two Photon Polymerization (2PP)

Nanoscribe technology for the fabrication of three-dimensional micro- and nanostructures in photo-sensitive materials is based on direct laser writing (DLW): a non-linear two-photon absorption process (2PA; Figure 1). A necessary condition for two photons of near-infrared light being absorbed simultaneously is a sufficiently high light intensity that is provided by a femtosecond pulsed laser beam. Typically, the laser is focused into the resin and two-photon polymerization (2PP) is triggered only in the focal spot volume, where the light intensity exceeds a polymerization threshold. The resin is otherwise transparent to the wavelength of the photons.

The smallest printable 3D volume is termed a voxel, which is analogous to a 2D pixel. Moving the laserfocus along a trajectory in all three dimensions enables printing of structures built from multiple voxelsand printed lines (Figure 2). This technology enables printing of structures with small, medium and large feature sizes in 3D as well 2D patterns.

• Pillai MM, Ajesh S, Tayalia P*. “Two-photon polymerization based reusable master template to fabricate polymer microneedles for drug delivery”. MethodsX. 2023. 102025, ISSN 2215-0161.
• Indian patent application no.202221036495- “A method of producing a template and negative mold for microneedle array” filed on 24June 2022.

Currently the 3D lithography system is optimized for the following substrates only:

• Borosilicate substrate of 30mm diameter and 700um thickness.
• ITO substrates of 25 X 25mm and thickness 700um.
• Fused silica substrates of 25 X 25mm and thickness 700um.

Design submission:

• Users have to upload their design in .stl format, along with the online request.
• The maximum writing volume is 300μm x 300μm x 300μm. All programmed coordinates have to lie within this writing volume. If parts of the programmed structure exceed this writing volume a warning message is shown in the message pane of NanoWrite. Please note that DeScribe is not aware of hardware limits.

The 3d lithography system is optimized for the following resists only:

• IP-S
• IP-DiP
• IP-L 780

Only online registration through the IRCC webpage will be accepted. If the appointment is given but the user cannot come, a mail should be immediately sent to 3dlitho[at] iitb [dot] ac [dot] in to cancel his/her slot.