A rapid, low-cost approach to solid immersion lens fabrication for enhanced resolution in optical microscopy

Solid immersion lenses (SILs) enhance the spatial resolution of an optical microscope by increasing the effective numerical aperture (NA) without physical modification of the objective lens. However, SIL application remains limited by cost, fragility, and accessibility. We present a rapid, single-step fabrication process to create optical quality hemispherical SILs using consumer-grade UV-curable transparent resin which reduces material costs by over five orders of magnitude relative to commercial glass counterparts. Our method produced resin SILs within seconds which can be easily implemented into conventional microscopy setups for increasing the effective NA. Quantitative imaging of USAF resolution targets and histology muscle preparations demonstrated a resolution enhancement approaching theoretical limits and comparable performance to N-BK7 glass SILs. This enabled visualisation of features usually below the diffraction limit of low NA dry objectives at a fraction of the cost of otherwise required high-powered objective lenses. To demonstrate accessibility and translational potential, our workflow was taught in a practical tutorial of an international microscopy course, where non-expert participants successfully fabricated, characterised, and applied SILs within a single session, reporting high confidence in independent implementation. We established ultra-low-cost resin SILs as a practical, scalable option to enhance the spatial resolution of routine optical microscopes and as an accessible and cost-effective platform for optics education.