Lensless light guide-coupled LED illumination for low-cost microscopy

Solid-state LED illumination systems for microscopy are generally expensive, often containing multiple LED drivers, excitation filters, and mirrors. High intensity illumination and precise timing are important for in vivo and in vitro microscopy, fluorescence imaging, and for optical stimulation. Here we present a low-cost, simplified single-wavelength LED mount with 3D printed components that achieves nearly 300 mW optical power through a plastic PMMA light guide, and 40-60 mW excitation intensity with ∼95 % flatfield uniformity at the sample, for under $70 USD. By keeping the LED light beam within the diameter of the light guide, no collecting or collimating lenses are needed. Illumination performance of the low-cost 3 W red and blue systems with passive cooling and plastic light guide match 7 W to 15 W commercial systems with active fan cooling and a liquid-filled light guide, while reducing cost over 20-fold. Additionally, low electrical power use (5 W) and small physical size enable its use in resource-limited environments and compact, battery-powered imaging devices.