Thermal-responsive high-quality hydrogel microlens arrays with tunable focal lengths

Microlens arrays (MLAs) have seen significant advancements in optical imaging, three-dimensional (3D) displays, and laser applications. However, conventional fixed-focus MLAs face limitations in scenarios requiring dynamic focal length adjustments. This work demonstrates a high-throughput fabrication strategy for spherical hydrogel-based microlens arrays (HMLAs) with tunable focal length and ultra-low surface roughness. Under thermal actuation, the HMLAs enable isotropic 3D deformation that preserves precise spherical lens geometry, ensuring excellent focusing capability. In addition, the HMLAs exhibit excellent optical transmittance and reversible focal length modulation over a range spanning from 7.0 to 10.0 mm, which allows for a simulated endoscopic depth-scanning imaging system with designable scanning depths. These advancements pave the way for next-generation adaptive optics technologies, particularly in medical endoscopy, where space-constrained, depth-variable imaging proves essential for tissue differentiation and minimally invasive procedures.