Smartphone‐based optical sectioning (SOS) microscopy with a telecentric design for fluorescence imaging.

We propose a smartphone‐based optical sectioning (SOS) microscope based on the HiLo technique, with a single smartphone replacing a high‐cost illumination source and a camera sensor. We built our SOS with off‐the‐shelf optical, mechanical cage systems with 3D‐printed adapters to seamlessly integrate the smartphone with the SOS main body. The liquid light guide can be integrated with the adapter, guiding the smartphone's LED light to the digital mirror device (DMD) with neglectable loss. We used an electrically tuneable lens (ETL) instead of a mechanical translation stage to realise low‐cost axial scanning. The ETL was conjugated to the objective lens's back pupil plane (BPP) to construct a telecentric design by a 4f configuration to maintain the lateral magnification for different axial positions. SOS has a 571.5 µm telecentric scanning range and an 11.7 µm axial resolution. The broadband smartphone LED torch can effectively excite fluorescent polystyrene (PS) beads. We successfully used SOS for high‐contrast fluorescent PS beads imaging with different wavelengths and optical sectioning imaging of multilayer fluorescent PS beads. To our knowledge, the proposed SOS is the first smartphone‐based HiLo optical sectioning microscopy (£1965), which can save around £7035 compared with a traditional HiLo system (£9000). It is a powerful tool for biomedical research in resource‐limited areas. LAY DESCRIPTION: We have developed a new type of microscope called the Smartphone‐based Optical Sectioning (SOS) microscope, which uses a common smartphone to replace expensive traditional components. This innovative microscope is constructed from readily available parts along with 3D‐printed adapters, making it easy to assemble. The smartphone's LED light is directed precisely with minimal loss to illuminate samples, and instead of using bulky mechanical parts, we employ an adjustable lens to focus on different depths within a sample. This design allows us to maintain clear, consistent magnifications across various depths. Our SOS microscope offers a significant cost advantage, costing just under ₣2,000, compared to the ₣9,000 price tag of conventional microscopes with similar capabilities. This makes it especially valuable for conducting high‐quality biomedical research in places where resources and access to expensive equipment are limited. The microscope can produce high‐contrast images of fluorescent samples, showing details down to the cellular level. This breakthrough could greatly enhance research opportunities in many parts of the world. [ABSTRACT FROM AUTHOR]