Metalens Array Parallel Two-Photon Lithography
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Solution Overview
Problem
Current two-photon lithography methods are time-consuming and inefficient for large-scale, high-resolution 3D printing due to slow printing speeds and limitations in manufacturing time, despite achieving submicron resolution.
Innovation Solution
A metalens array is used to split an optical beam into multiple focal points within a photoresist, enabling simultaneous two-photon polymerization across a large area, thereby parallelizing the lithography process and eliminating the need for high numerical aperture objectives, which allows for rapid and high-resolution 3D printing of complex structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If serial two-photon lithography using a high NA objective is used, then submicron resolution is achieved, but printing speed becomes extremely slow
Solution Approach 1:
The patent divides a single optical beam into multiple independent focal spots using a microlens array, creating parallel processing channels. Each microlens focuses light to a separate voxel, enabling simultaneous polymerization at multiple locations rather than sequential processing at a single location.
Solution Approach 2:
The patent combines multiple focal spots into a single illumination field, where all focal voxels are created simultaneously from one laser beam. This merges the processing capacity of multiple objectives into a unified parallel system, dramatically increasing throughput while maintaining submicron resolution at each focal point.
2Productivity
If projection two-photon lithography with DMD is used, then printing speed increases by eliminating raster scanning, but the focal plane thickness control requires complex temporal focusing optics
Solution Approach 1:
The patent extracts the focusing function from complex temporal focusing optics and assigns it to simpler microlens elements in an array. Each microlens naturally provides spatial confinement in the lateral directions, while the axial confinement is achieved through the two-photon absorption process itself, eliminating the need for complex temporal focusing mechanisms.
Solution Approach 2:
The patent replaces the mechanical and optical complexity of temporal focusing systems with a static microlens array structure. The focal plane thickness is controlled not by complex optics but by the inherent properties of two-photon absorption, which naturally confines polymerization to the focal region where intensity is highest.
3Productivity
If multi-foci two-photon lithography with microlens array is used, then parallel polymerization is achieved, but high NA objectives are still required which limits the field of view
Solution Approach 1:
The patent makes the microlens array serve multiple functions simultaneously: it provides parallel focusing, defines the field of view, and creates the focal spot pattern. The array geometry can be designed to match the desired printing area, making the system adaptable to different scales without requiring additional optical components.
Solution Approach 2:
The patent changes the numerical aperture parameter from high (in traditional objectives) to lower values in the microlens array elements. This allows for a larger field of view while maintaining sufficient focal intensity for two-photon polymerization. The microlens array pitch and focal length are optimized to achieve the desired balance between field of view and voxel intensity.
4Area of stationary object
If micro-stereolithography with single photon absorption is used, then printing area can be increased with demagnifying optics, but resolution is significantly less than two-photon lithography
Solution Approach 1:
The patent transitions from single-photon absorption (which polymerizes along the entire light path) to two-photon absorption, which confines polymerization to the focal plane through quadratic intensity dependence. This dimensional confinement in the axial direction enables high resolution while the microlens array provides lateral scaling for large area printing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces manufacturing time for 3D printed components by enabling the simultaneous creation of tens of thousands to millions of identical structures, improving printing resolution and quality without the need for stitching, thus making large-scale 3D printing more economical and efficient.
Implementation Method 1
The laser intensity is sufficiently high to induce two-photon polymerization
Implementation Method 2
The voxel represents a confined space from about 100 nm, or slightly less, up to a few microns in size. The laser intensity is sufficiently high to induce two-photon polymerization
Implementation Method 3
Each unit cell is configured to introduce a phase delay to a portion of the wavefront of the optical beam incident upon the unit cell
Implementation Method 4
a first metalens unit cell having a first plurality of nanoscale features, the first metalens unit cell configured to modify a first portion of a wavefront of an optical signal
Data Source
AI summary
A metalens array is disclosed for controllably modifying a phase of a wavefront of an optical beam. The metalens array may have a substrate having at least first and second metalens unit cells, and forming a single integrated structure with no stitching being required of the first and second metalens unit cells. The first metalens unit cell has a first plurality of nanoscale features and is configured to modify a phase of a first portion of a wavefront of an optical signal incident thereon in accordance with a first predetermined phase pattern to create at least one first focal voxel within an image plane. The second metalens unit cell has a second plurality of nanoscale features configured to modify the phase of a second portion of the wavefront of the optical signal incident thereon, in accordance with a second predetermined phase pattern, to simultaneously create at least one second focal voxel within the image plane. Each metalens unit cell also has an overall diameter of no more than about 200 microns.