18Fluorescence microscopy is one of the workhorses of biomedical research and laboratory diagnosis;19 however, their cost, size, maintenance, and fragility has prevented their adoption in developing countries 20 or low-resource settings. Although significant advances have decreased their size, cost and accessibility, 21 their designs and assembly remain rather complex. Here, inspired on the simple mechanism from a nut and 22 a bolt we report the construction of a portable fluorescence microscope that operates in bright field mode 23 and in three fluorescence channels: UV, green, and red. It is assembled in under 10 min from only six 3D
24printed parts and basic electronic components that can be readily purchased in most locations or online for 25 US $85. Adapting a microcomputer and a touch LCD screen, the microscope can capture time-lapse images 26 and videos. We characterized its resolution and illumination conditions and benchmarked its performance 27 against a high-end fluorescence microscope by tracking a biological process in single cells. We also 28 demonstrate its application to image cells inside a microfluidic device in bright-field and fluorescence 29 mode. Our microscope fits in a CO 2 chamber and can be operated in time-lapse mode. Our portable 30 microscope is ideal in applications where space is at a premium, such as lab-on-a-chips or space missions,
31and can find applications in clinical research, diagnostics, telemedicine and in educational settings. 32 33 3 34