An open source three-mirror laser scanning holographic two-photon lithography system

High-Throughput Two-Photon 3D Printing Enabled by Holographic Multi-Foci High-Speed Scanning

The emerging two-photon polymerization (TPP) technique enables high-resolution printing of complex 3D structures, revolutionizing micro/nano additive manufacturing. Various fast scanning and parallel processing strategies have been proposed to promote its efficiency. However, obtaining large numbers of uniform focal spots for parallel high-speed scanning remains challenging, which hampers the realization of higher throughput. We report a TPP printing platform that combines galvanometric mirrors and liquid crystal on silicon spatial light modulator (LCoS-SLM). By setting the target light field at LCoS-SLM's diffraction center, sufficient energy is acquired to support simultaneous polymerization of over 400 foci. With fast scanning, the maximum printing speed achieves 1.49 × 108 voxels s-1, surpassing the existing scanning-based TPP methods while maintaining high printing resolution and flexibility. To demonstrate the processing capability, functional 3D microstructure arrays are rapidly fabricated and applied in micro-optics and micro-object manipulation. Our method may expand the prospects of TPP in large-scale micro/nanomanufacturing.

Fast non-iterative algorithm for 3D point-cloud holography

Recently developed iterative and deep learning-based approaches to computer-generated holography (CGH) have been shown to achieve high-quality photorealistic 3D images with spatial light modulators. However, such approaches remain overly cumbersome for patterning sparse collections of target points across a photoresponsive volume in applications including biological microscopy and material processing. Specifically, in addition to requiring heavy computation that cannot accommodate real-time operation in mobile or hardware-light settings, existing sampling-dependent 3D CGH methods preclude the ability to place target points with arbitrary precision, limiting accessible depths to a handful of planes. Accordingly, we present a non-iterative point cloud holography algorithm that employs fast deterministic calculations in order to efficiently allocate patches of SLM pixels to different target points in the 3D volume and spread the patterning of all points across multiple time frames. Compared to a matched-performance implementation of the iterative Gerchberg-Saxton algorithm, our algorithm's relative computation speed advantage was found to increase with SLM pixel count, reaching >100,000x at 512 × 512 array format.

Industrial perspectives for personalized microneedles

Microneedles and, subsequently, microneedle arrays are emerging miniaturized medical devices for painless transdermal drug delivery. New and improved additive manufacturing methods enable novel microneedle designs to be realized for preclinical and clinical trial assessments. However, current literature reviews suggest that industrial manufacturers and researchers have focused their efforts on one-size-fits-all designs for transdermal drug delivery, regardless of patient demographic and injection site. In this perspective article, we briefly review current microneedle designs, microfabrication methods, and industrialization strategies. We also provide an outlook where microneedles may become personalized according to a patient's demographic in order to increase drug delivery efficiency and reduce healing times for patient-centric care.

Non-interferometric volumetric imaging in living human retina by confocal oblique scanning laser ophthalmoscopy

Three-dimensional (3D) imaging of the human retina is instrumental in vision science and ophthalmology. While interferometric retinal imaging is well established by optical coherence tomography (OCT), non-interferometric volumetric imaging in the human retina has been challenging up to date. Here, we report confocal oblique scanning laser ophthalmoscopy (CoSLO) to fill that void and harness non-interferometric optical contrast in 3D. CoSLO decouples the illumination and detection by utilizing oblique laser scanning and oblique imaging to achieve ∼4x better axial resolution than conventional SLO. By combining remote focusing, CoSLO permits the acquisition of depth signals in parallel and over a large field of view. Confocal gating is introduced by a linear sensor array to improve the contrast and resolution. For the first time, we reported non-interferometric 3D human retinal imaging with >20° viewing angle, and revealed detailed features in the inner, outer retina, and choroid. CoSLO shows potential to be another useful technique by offering 3D non-interferometric contrasts.