Tunable compound eyes with coaxial lens-on-lens ommatidia for cooperative bi-focal imaging

Compound eyes (CEs) offer a unique design paradigm for developing artificial micro-optical systems. However, current bionic CEs still fall significantly short of their insect counterparts in performance, particularly regarding ommatidial spatial arrangement, size distribution, visual field adaptability and environmental perception. Inspired by the CEs of Sympetrum frequens, we developed a tunable bionic CE with bi-focal ommatidia by integrating a flexible lens-on-lens (LoL) array with microfluidics, enabling simultaneous bi-focal imaging. The polydimethylsiloxane (PDMS) LoL array was fabricated through sequential processing steps, including femtosecond laser dual-modification of quartz glass, two-step wet etching, and soft lithography using the resulting glass template. Integration of this flexible LoL array with a microfluidic chip produced a tunable CE with bi-focal ommatidia, allowing liquid-pressure modulation of CE configurations. We systematically investigated the optical performance of both LoL ommatidia and the integrated CE, including bi-focal focusing/imaging properties, tunable field-of-view (FOV), large-FOV imaging, and moving target monitoring. This tunable CE with LoL ommatidia demonstrates significant potential for cutting-edge applications.