Nanoscribe GT2

The Nanoscribe Photonic Professional GT2 is a direct-write lithography system that uses two-photon polymerization (2PP) to create three-dimensional nanostructures.

A near-infrared (NIR) femtosecond laser is focused within a small quantity of photosensitive resin. The resin is only sensitive in the ultraviolet (UV), and does not cross-link when exposed to the NIR fundamental. It only cross-links at the laser focus, where irradiance is high enough to generate UV second harmonic (SH) by two-photon absorption. The exposed “voxel” corresponds to the SH point spread function of the laser, with its boundaries determined by the resin's exposure threshold. Structures are printed voxel by voxel and layer by layer, in blocks determined by the stage motor and piezo ranges.

Users provide their designs as STL files, which are sliced for printing with the DeScribe software. DeScribe is available at the tool, and as a free download for all GT2 users. Three objectives (10×, 25× and 63×) are available, with higher magnifications trading speed for resolution down to a minimum feature size of 0.2 μm. Each objective has its print set with specific substrate and resin selection. Resins and substrates are provided with no extra charge for all standard print sets. Standard substrates are 25 mm squares, but there are alternate trays for several other substrate sizes, including for 100 mm wafers. All prints must be developed after exposure, and a dedicated hood is provided for this purpose in 121.

There are three printing modes. In “solid”, the entirety of a structure's volume is exposed. In “shell and scaffold”, resin is left uncured within an exposed shell and must be cured after development at the provided UV curing station. “Swift” is a coarser, faster mode.

Oil immersion from the backside, only possible on very thin, transparent substrates, can be used to test user-provided resins. Coverslips are provided for this purpose, but there are other limitations which must be discussed with staff beforehand. Because of the rules on the handling of chemicals at CNF, users are not allowed to bring their own resins inside the cleanroom, and must contact staff for delivery.

Regular photolithography resists can be used by direct writing in air or with oil immersion, but require extensive characterization.

GP-silica, a resin containing fused silica beads, can be used to print glass structures. Prints with this resin are time-limited to eight hours, and after development they must undergo debinding and sintering in a furnace capable of extended operation at 1,500°C. CNF does not currently provide such a furnace.