Single molecule Förster Resonance Energy Transfer (smFRET) can be used to obtain a unique level of information for dynamic processes involving biological molecules, as well as revealing structural information. The Craggs Lab of The University of Sheffield has developed an open-source microscopy platform for making smFRET measurements at a fraction of the price of typical commercial systems. The smfBox system can be built for around 40,000 GBP using commercially available parts and fabrication of a simple microscope body. It requires a relatively small footprint on an optics bench or optical breadboard. When complete can be used as a class 1 laser product; all beams are enclosed, and a mechanical shutter connected to the lid prevents laser light from entering the box when the lid is open.

In a recent study smFRET was shown to be capable of reliably recovering FRET efficiencies with s.d. between ±0.02 and ±0.05. As a participant of that study, the smfBox performed on par with similiar custom and commercially available instruments worldwide. On this site we provide all information needed to fabricate and purchase the components for the smfBox, the instructions to build it, and the software required to use it.