Mold-free self-assembled scalable microlens arrays with ultrasmooth surface and record-high resolution

Abstract

Microlens arrays (MLAs) based on the selective wetting have opened new avenues for developing compact and miniaturized imaging and display techniques with ultrahigh resolution beyond the traditional bulky and volumetric optics. However, the selective wetting lenses explored so far have been constrained by the lack of precisely defined pattern for highly controllable wettability contrast, thus limiting the available droplet curvature and numerical aperture, which is a major challenge towards the practical high-performance MLAs. Here we report a mold-free and self-assembly approach of mass-production of scalable MLAs, which can also have ultrasmooth surface, ultrahigh resolution, and the large tuning range of the curvatures. The selective surface modification based on tunable oxygen plasma can facilitate the precise pattern with adjusted chemical contrast, thus creating large-scale microdroplets array with controlled curvature. The numerical aperture of the MLAs can be up to 0.26 and precisely tuned by adjusting the modification intensity or the droplet dose. The fabricated MLAs have high-quality surface with subnanometer roughness and allow for record-high resolution imaging up to equivalently 10,328 ppi, as we demonstrated. This study shows a cost-effective roadmap for mass-production of high-performance MLAs, which may find applications in the rapid proliferating integral imaging industry and high-resolution display.

Review of Droplet Printing Technologies for Flexible Electronic Devices: Materials, Control, and Applications

“…Sun [ 72 ] reported that the simple pre-deposition of an ethanol layer enabled a series of procedures, including homogenization, solvent exchange, post-stretching, and air drying, thereby uniformly depositing densely structured graphene nanosheets and effectively limiting and eliminating the coffee-ring effect during inkjet printing, as shown in Figure 7 b. Inkley [ 73 ] successfully used triethylene glycol for pre-wetting the powder bed before printing, significantly expanding the range of droplet spacing to produce continuous lines, as shown in Figure 7 c. Duan [ 74 ] significantly altered the fluid drying kinetics by adding surfactants during solution printing and increasing the contact-line friction between the aqueous solution and the underlying non-wetting organic crystalline film. As a result, centimeter-level highly-arranged arrays of organic crystals were successfully prepared on different substrates, as shown in Figure 7 d. Liu [ 75 ] reacted large-scale droplet arrays with controlled curvature by selectively modifying the surface using tunable oxygen plasma, promoting precise patterns by adjusting chemical contrast; they also used droplet dosage modification to achieve precise adjustment, as shown in Figure 7 e. Feng [ 76 ] proposed and verified an efficient, high-throughput method for the rapid preparation of uniform droplet arrays induced by an electric field in multiple emulsion droplets within micropores. Polydisperse emulsions were prepared through mechanical stirring and then filling them into hydrophobic micropores through screen printing.…”

“…( e ) MLA manufacturing process based on selective wetting. Reproduced with permission from [ 75 ] under the Creative Commons CC BY license. ( f ) ECDA chip-manufacturing process schematic: photolithography of micropores on ITO glass coated with Hyflon, emulsion filling, chip assembly and sealing, and micropore-constrained droplet electropolymerization.…”

“…As a result, centimeter-level highlyarranged arrays of organic crystals were successfully prepared on different substrates, as shown in Figure 7d. Liu [75] reacted large-scale droplet arrays with controlled curvature by selectively modifying the surface using tunable oxygen plasma, promoting precise patterns by adjusting chemical contrast; they also used droplet dosage modification to achieve precise adjustment, as shown in Figure 7e. Feng [76] proposed and verified an efficient, high-throughput method for the rapid preparation of uniform droplet arrays induced by an electric field in multiple emulsion droplets within micropores.…”

Two-photon polymerization lithography for imaging optics

“…Kotz et al demonstrated post-processing an MLA made of twophoton curable silica nanocomposite resin through thermal debinding and sintering to achieve a surface roughness of 6 nm [46]. Liu et al demonstrated a self-assembly-based moldfree approach of mass-production of scalable MLAs, with ultrasmooth surface (roughness of around 0.3 nm), ultrahigh resolution, and large variable curvatures [155]. The second requirement of a high fill factor is to maximize the light collection efficiency.…”

Tunable Continuous‐Variable Tripartite Entanglement via Simultaneous and Ordinal Cascaded Nonlinear Processes

“…The generation of multipartite quantum entanglement in the CV regime has attracted great interest due to its enormous potential in various applications and protocols, ranging from quantum communication, [17][18][19][20] to quantum memory, [21,22] and quantum imaging. [23,24] A large number of experimental studies on its generation has been reported. The most well-established technique for generating multipartite CV entanglement is achieved by mixing the individual squeezed states on a linear beam-splitter network.…”