DIλ spectrophotometer


A spectrophotometer measures how much light passes through the sample at a given wavelength. To produce light at the right wavelength, most spectrophotometers use a mechano-optical system to position a monochromator at the right angle from the light source, and a slit to only select the right wavelength.

A spectrophotometer: a) Light source b) Monochromator c) Sample holder with slits d) Photosensor e) Microcontroller and display

(Monochromator can be located either before of after the sample)

Spectrophotometers are used in many fields of science, ranging from physics to biochemistry and molecular biology.


DIλ is an Open Hardware spectrophotomter, designed to be accurate, easy to modify, and extremely cheap. We achieve this by using LEDs instead of an optical refraction system.

DIλ: a) LED b) Sample holder with slits c) Digital light sensor d) Microcontroller e) Computer

This design choice means that the device is limited to one or a few pre-selected wavelengths, but most biological applications only use a few. It is also possible to select a different wavelength by populating a spare LED board, but since it's so cheap, it might be easier to just buy one for each task.

An other disadvantage is large spectral width of LEDs, typically 15-25nm, compared to 1-5nm for traditional spectrophotometers.

All this means that DIλ is not always able to replace a traditional spectrophotometer, but works great for a majority of biological applications.


Fluorescence is hard. We need to excite the sample at wevelengt X and measure light emitted at wavlength Y, while filtering out X. The problem is, X and Y are usually very close together, and emission at Y is much weaker than the exciting light. In practice this means:

  • Excitation light source should not emit light at wavelength Y, only X.
  • A filter needs to filter our all X, and let Y pass.

While there are very affordable filters to the second part, getting a light source that does not emit at Y is problematic. Lasers are expensive. For GFP, 470-485nm lasers cost in the range of thousands. A cheaper 450nm laser exists, but it's quite a bit off the GFP excitation peack, and it still costs in the range of 20-30 euro.

Blue LEDs seem all to be made using Indium-Gallium nitrite technology. They emit around 470 nm, but leack considerably into the 520+ nm range where GFP emission happens.

One solution is to use an emission filter that stops light above 500nm. Unfortunately, affordable quality filters are not very easy to find, and we are currently researching this topic.

See Tools/DI-Lambda/Fluorescense?


The development is still in progress. A number of working prototype designs exist, and we are heading towards a production version.

Source code:

DIλ Paris

See Tools/DI-Lambda/Paris

DIλ Paris is the current production prototype. It offers 3 channels. While it is open, it is not intended to be built from scratch, as a laser cutter and very good soldering skills are required. That said, the wavelengths can still be easily modified by populating an spare LED board with the right LEDs.

DIλ Test rig

See Tools/DI-Lambda/Test_rig?

The rig is intended to test various parameters, used to develop later versions that match the readings from professional lab equipment. It allows to tune the distance between the LED, sensor and the cuvette, as well as the size of the slit.

DIλ Spirulina

See Tools/DI-Lambda/Spirulina?

DIλ Spirulina was quickly designed and built for the SPIRIS group at the CRI, and is largely based on the test rig, minus the ability to tune the parameters. While an early prototype, it produced results that matched expectations, thus suggesting that we are on the right path.

DIλ Luna

See Tools/DI-Lambda/Luna?

A version designed specifically for the NightScience 2015 workshop. Largely based on the test rig, with some added elegance. It is easy to build, and can be used for Do-It-yourself workshops.

Existing equipment

Commercially available equipment


Maker Name Wavelengths (nm)ChannelsFluorescensePrice (shipping not included)Description
NanoDrop 2000c 190 - 840 1 No 13000 Euro While mostly knows for the microvolume feature, nanodrop 2000c also offers a cuvette interface.
Thermoscientific Orion™ AquaMate 7000 325-1100 1 No 3650 $
Thermoscientific Orion AQUAfast AQ3700 LED 430, 530, 560, 580, 610, 660 1 No 950 $ Designed for water-related field tests. Portable, waterproof
LABORATORY SKY SHANGHAI 721, 722, 723, 725, etc 320-1020 4 No ~250 $ Cheapest option from China. Manual wavelength selection knob.
LABORATORY SKY SHANGHAI UV-7502, 7404, etc 200-1000 4 No 2000-4500$ ?
Bio-rad SmartSpec Plus 200–800 1 No 5900 $
Eppendorf Eppendorf BioSpectrometer 200-830 1? Optional, GFP only (470 -> 520 / 560 nm)
YSI YSI 9300 LED 450, 500, 550, 575, 600, 650 1 No 1000 $ Water-related tests, field tests. Water-proof. +300$ for USB interface
Jenway Jenway 63 series 190 - 1000 1-4 (+?) No 2100 $
Jenway Jenway 67 series 190 - 1000 1-8 No 4500 $+


Maker Name Wavelengths (nm)ChannelsFluorescensePrice (shipping not included)Description
Extech CL500 LED, 525 1 No 600 $ Portable Free and Total Chlorine Meter
Extech TB400 LED, 850 1 No Portable Turbidity Meter
YSI 900 LED 530 1 No 390 $ Portable Chlorine Colorimeter , waterproof
YSI 910 LED 430, 610 1 No 560 $ Portable COD (organic stuff in water) Colorimeter


Lots and lots. Just a few promising examples.

One that looks kind of similar to this project: . We have ordered one, but it did not quite work - it looks like the slit was out of alignment. Overall, design somewhat similar to DIλ, includes slits, something that is missing from most other projects. They also have some documentation and assays for the device available online. , which is a spectrometer, not a spectrophotometer. It looks simple and elegant, produces results, and has a community of users. Well done! It's a different device, and it's made out of cardboard, but unlike the vast majority of DIY "designs", it's a finished product, that can be built cheaply and provide reproducible results.

3D printable Raman Spectrometer. Completely unrelated, but absolutely fabulous: .

96 well plate reader. Quite impressive. . They need to tune it to get the results to match reality, but nice overall design.

Double channel, intended to measure pH with an indicator: . The data looks great. Design files unfortunately do not really seem to be available. Should we contact them?

And iGEM Aachen 2014. Design somewhat similar to DIλ. .

Overall, while there are very promising projects, it looks like they most have been abandoned at early stages, after the initial limited success. The Publiclab spectrometer and the IORodeo spectrophotometer stand out here, have build instructions, are open-source, and can be purchased as a kit.

Last modified 16 months ago Last modified on Jul 13, 2016, 12:50:54 PM

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