LED flashlight used as fluorescence microscopy light source

Mercury gas discharge lamps, the traditional light sources for

fluorescence microscopy, come with several disadvantages. They have a limited lifetime, a fluctuating intensity, give off heat, and can sometimes explode. LED illumination overcomes these limitations, but most commercial LED illumination systems are expensive because they are made to excite at many different wavelength ranges.

Researchers from Vanderbilt University wanted to find a cheaper way, so they tried an off-the-shelf LED flashlight as an illumination source for fluorescence microscopy. They picked out the brightest flashlight available at a camping store, which was a $50 Inova Bolt 4.6 W/6 V flashlight. It had a strong emission in the 440 to 480 nm range, which is useful for excitation of several common fluorescence probes including enhanced GFP. They hooked up the flashlight to a power supply so that it could be turned off and on from outside the light-tight box they were using and also created an adaptor to fit the flashlight to the microscope’s fluorescence lamp port.

Although the flashlight was less intense than a mercury light source, they did achieve images with the LEDs that were comparable to those from a mercury light source by increasing the CCD camera exposure to four to five times that used for a 100 W mercury lamp. The researchers say that the power supply and flashlight together costs around $90, less than a single replacement mercury lamp.

Read more about this work in the paper:

J.B. Robertson, Y. Zhang & C.H. Johnson. Light-emitting diode flashlights as effective and inexpensive light sources for fluorescence microscopy, Journal ofMicroscopy, Vol. 236, Pt 1 2009, pp. 1–4, doi: 10.1111/j.1365-2818.2009.03208.x