Fig. 1. Schematics of the microsphere-lens template assembly and lithography process. (a) UV-curable adhesive patterned template fabricated using an E-jet printing system. (b) Process of using the UV-curable-adhesive-assisted assembly of microsphere-lens arrays for projection lithography. (c) Magnified microsphere-lens lithography.

Fig. 2. Simulation and numerical analysis of the optical-field distribution of microsphere lenses assembled with the assistance of a UV-curable adhesive. (a) Schematic of the focused optical field of the microsphere lens. (b)–(d) Schematic of the microsphere lens assembled with three different sizes of UV-curable adhesive. (e) Simulation of the focused optical field of a single microsphere lens that was not assembled on a UV-curable adhesive. (f)–(h) Simulation of the focused optical field of the microsphere lens assembled with three different sizes of UV-curable adhesive corresponding to (b)–(d). (i) Intensity distribution along the z-axis, which is the central axis of the microsphere lens in (e)–(h). Here, z=0 is the bottom of the microsphere. (j) Intensity distribution along the y-axis, which is located at the field maximum in (e)–(h).

Fig. 3. Fabrication and characterization of UV-curable-adhesive-printed microsphere lenses assembled in situ. (a) Schematic of the UV-curable adhesive templates printed using the E-jet system. (b), (c) SEM images of UV-curable-adhesive-patterned templates printed using the E-jet system. (d) Schematic of the in situ assembly of patterned microsphere lenses on UV-curable adhesive. (e), (f) SEM images of patterned microsphere arrays assembled on UV-curable adhesive templates corresponding to (b), (c), respectively. (g) SEM images of the assembled arrayed microspheres. (h) SEM images of the assembly of microspheres of three different sizes and materials, with a scale bar of 10 μm shown in the inset. (i) Optical image of patterned fluorescent microsphere arrays assembled over a large area.

Fig. 4. Characterization of the imaging performance of microspheres assembled on the UV-curable adhesive. (a) Schematic of the microsphere-lens imaging system. (b) Optical image of the “+” pattern projected by an array of 5×5 microsphere lenses assembled on the UV-curable adhesive. The inset in the upper-right corner shows the magnified projected image of a single microsphere lens. (c) Normalized light-intensity mapping image corresponding to the imaging of a single microsphere lens. (d) Images of the focal spots focused by the microsphere-lens array. (e) Distribution of the normalized light intensity corresponding to the five focal spot images circled in (d). (f) Optical image of the “+” pattern projected by a 5×5 microlens array. The inset in the upper-right corner shows the magnified projected image of a single microlens. (g) Normalized light-intensity mapping image corresponding to the imaging of a single microlens. (h) Images of the focal spots focused by the microlens array. (i) Distribution of the normalized light intensity corresponding to the five focal spot images circled in (h).

Fig. 5. Characterization of microsphere-lens projection lithography. (a) Optical image of the microsphere-lens projection-lithography system. (b) Schematic of microsphere-lens array projection lithography. (c)–(f) SEM images of structures fabricated by the microsphere-lens array projection lithography, which have been mirrored. The insets in the upper-right corners show the results of a magnified individual structure. (g)–(j) AFM images corresponding to the structures in (c)–(f), respectively.

Fig. 6. An example of microspheres with a diameter of 10 μm is used to illustrate the effect of different sizes of UV-curable adhesives on the assembled microspheres.

Fig. 7. (a) Scanning electron microscopy (SEM) image of UV-curable-adhesive-patterned spiral array template. (b) SEM image of patterned microsphere arrays assembled on UV-curable adhesive spiral array template, corresponding to (a).

Fig. 8. (a) Optical image of UV-curable-adhesive-patterned number array template. (b), (c) Atomic force microscopy (AFM) image of the UV-curable adhesive in (a) and the corresponding profile curves. (d) Optical image of UV-curable-adhesive-patterned letter array template. (e), (f) AFM image of the UV-curable adhesive in (d) and the corresponding profile curves. (g) Optical image of UV-curable-adhesive-patterned spiral array template. (h), (i) AFM image of the UV-curable adhesive in (g) and the corresponding profile curves.

Fig. 9. (a)–(c) SEM images of the assembled arrayed microspheres with different spacings.

Fig. 10. (a)–(c) SEM images of different periods of UV-curable adhesive templates printed by E-jet.

Fig. 11. (a)–(c) Optical fluorescent images of patterned fluorescent microsphere arrays assembled over a large area. (d)–(f) Optical images of UV-curable adhesive templates for “Puppy,” “Rose,” and “Beach,” corresponding to the fluorescent images in (a)–(c). (g)–(l) Blue and red fluorescent images of fluorescent microsphere patterns.