Opto-Electronic Advances (光电进展)•2026•DOI: 10.29026/oea.2026.250197
Artificial compound eyes (CEs) remain inferior to insect counterparts in ommatidial spatial arrangement, size distribution, visual field adaptability, and environmental perception. This work presents a tunable bionic CE with coaxial lens-on-lens (LoL) ommatidia, inspired by Sympetrum frequens, integrating a flexible polydimethylsiloxane (PDMS) LoL array with a microfluidic chip to achieve simultaneous bi-focal imaging. The LoL array was fabricated via femtosecond laser dual-modification of quartz glass, two-step wet etching, and soft lithography, yielding a concave template of approximately 2.6 mm². Integration with a microfluidic chamber enabled liquid-pressure modulation of CE configurations, producing a complete curved bi-focal plane that overcomes the limitations of single-focal-plane and regionalized nonuniform ommatidia CEs. Optical characterization confirmed stable focusing performance for both large and small ommatidia within their theoretical fields of view (FOVs). Cooperative bi-focal imaging was achieved by regulating FOV and relative positions of different LoL ommatidia through controlled injection of PDMS precursor. Large-FOV imaging and moving target monitoring were demonstrated, with reconstructed trajectories of triangular and dragonfly targets in 3D coordinates. The tunable CE with LoL ommatidia offers significant potential for particle image velocimetry, robotic vision, and virtual endoscopy, providing a scalable route to advanced micro-optical systems with adaptive visual field and depth perception.
Int. Journal of Minerals, Metallurgy and Materials (矿物冶金与材料学报)•2025•DOI: 10.1007/s12613-024-3047-9
Low- to medium-maturity oil shale resources display substantial reserves, offering promising prospects for in-situ conversion in China. Investigating the evolution of the mechanical properties of the reservoir and caprock under in-situ high-temperature and confinement conditions is of considerable importance. Compared to conventional mechanical experiments on rock samples after high-temperature treatment, in-situ high-temperature experiments can more accurately characterize the behavior of rocks in practical engineering, thereby providing a more realistic reflection of their mechanical properties. In this study, an in-situ high-temperature triaxial compression testing machine is developed to conduct in-situ compression tests on sandstone at different temperatures (25, 200, 400, 500, and 650°C) and confining pressures (0, 10, and 20 MPa). Based on the experimental results, the temperature-dependent changes in compressive strength, peak strain, elastic modulus, Poisson’s ratio, cohesion, and internal friction angle are thoroughly analyzed and discussed. Results indicate that the mass of sandstone gradually decreases as the temperature increases. The thermal conductivity and thermal diffusivity of sandstone exhibit a linear relationship with temperature. Peak stress decreases as the temperature rises, while it increases with higher confining pressures. Notably, the influence of confining pressure on peak stress diminishes at higher temperatures. Additionally, as the temperature rises, the Poisson’s ratio of sandstone decreases. The internal friction angle also decreases with increasing temperature, with 400°C acting as the threshold temperature. Interestingly, under uniaxial conditions, the damage stress of sandstone is less affected by temperature. However, when the confining pressure is 10 or 20 MPa, the damage stress decreases as the temperature increases. This study enhances our understanding of the influence of in-situ high-temperature and confinement conditions on the mechanical properties of sandstone strata. The study also provides valuable references and experimental data that support the development of low- to medium-maturity oil shale resources.