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 <i>in vivo</i> and <i>in vitro</i> 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.