SEM of a random-microlens-array-MLA-by-2GL-Two-Photon-Grayscale-Lithography SEM of a random-microlens-array-MLA-by-2GL-Two-Photon-Grayscale-Lithography

Two-Photon Grayscale Lithography (2GL)

Two-Photon Grayscale Lithography (2GL®) is a breakthrough innovation uniting the strengths of grayscale lithography with the precision and flexibility of Two-Photon Polymerization (2PP).

Basics and principles

Highest printing performance and
accurate contour control by voxel tuning

Two-Photon Grayscale Lithography (2GL®) is a new additive manufacturing technology to generate 2.5D topographies. 2GL® is subject to Nanoscribe’s intellectual property. Discrete and accurate steps as well as essentially continuous topographies are printed while scanning only one layer, resulting in drastically reduced print times. 2GL is a new family member of maskless grayscale lithography technologies that uses power-modulated laser light to shape the height profile of micro- and nanostructured functional devices.

SEM of a concave convex shape microlens array 3D-printed by two-photon grayscale lithography (2GL)
The 2GL® capability to dynamically tune the voxel size during microfabrication allows to fabricate very smooth surfaces, such as microlens arrays with excellent shape accuracy and surface roughness down to 5 nm.

Two-Photon Grayscale Lithography (2GL®) is based on Two-Photon Polymerization (2PP). 2GL® is Nanoscribe's proprietary technology that makes use of a dynamic size control over voxels. Modulating the exposure dose while scanning the laser focus across the scanning plane changes the voxel size within the photoresin, resulting in finely controllable size changes of the polymerized voxels. This is the result of synchronizing laser power modulation and high-speed galvo scanning with accurate lateral stage movement. To accomplish this, a grayscale image is converted into a spatial variation of the exposure levels, resulting in different voxel heights being printed in one plane.

Infographic high-resolution 3D printing vs two-photon grayscale lithography 2GL
A refractive lens is printed with the ordinary 3D printing approach, divided into several layers (dashed lines). Each slice is printed with a constant voxel size, resulting in a staircase effect (left and middle figure). However, with microfabrication by 2GL® the individual voxel sizes are smoothly adapted to the lens shape (right figure). The SEM images (lower row) show the corresponding printing results.

2GL printing eliminates stitching seams and tilt-related imperfections

Two-Photon Grayscale Lithography (2GL®) uses high-frequency synchronization of laser beam modulation and high-speed galvo mirrors for single voxel tuning, enabling structures in optical quality. A high-precision positioning unit and self-calibration routines are used to print with excellent accuracy when stitching adjacent print fields together to fabricate large structures. 2GL dynamically adjusts the laser dose at the print field boundaries to compensate for chemically induced shrinkage of the photopolymer and positioning imperfections. With this combination of features, truly seamless structures can be printed over an area of several cm², eliminating all stitching marks.

Even slightly tilted substrates affect print quality, resulting in visible seams when stitching individual print segments or staircases when printing tilted surfaces. The autofocus of Nanoscribe’s printers can be operated on a tight grid of points to automatically measure the substrate tilt. Using 2GL technology combined with automatic tilt compensation, deviations between print blocks and staircase effects can be compensated for. As a result, smooth surfaces without stitching seams or staircase effects are achieved even on tilted substrates.

Related product

Quantum X
Redefining microfabrication.

Mastering success.

With the performance and features of 2GL, the Quantum X system redefines the microfabrication of 2.5D freeform microoptics, microlens arrays and diffractive optical elements.

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