We’ve covered smartphone florescence spectroscopy before, and we also have a post on building your own Lego spectrometer. In a similar vein check out a dedicated spectrophotometer detailed in a paper by Vasco Pereira and Bill Hosker. Maybe.
The paper covers a 3D-printed version and teases a Lego constructed version. Either way, you have a simple cuvette holder with an LED block that can be used with a smartphone to perform spectrophotometry. And no, that that $6 price tag does not include the smartphone, but it does get you out of buying a $1000 spectrometer.
The plans for the 3D-printed model are available on GitHub, and the supplementary material comes with a bill of materials that even includes links to pieces on Amazon. The paper includes example data and the GitHub page also includes a tutorial for assembly instructions using the 3D-printed version. There does seem to be a mild preference for Android smartphones here and uses the Shoebox Spectrophotometer App.
Since neither the paper nor the Github really covered the specifics of assembling the Lego version we reached out to Bill Hosker. Heavily paraphrasing, this is the advice he gave:
Anything that can snuggly hold a cuvette could be used, it does not have to be Lego! It could be made from quite a combination of pieces and in variations. If you are using Lego, start with a base piece that is about 5×4 lego lumps in size and build up the sides on the edges.
The design is necessarily variable, depending on the phone/tablet being used, the key things to ensure are that the anterior and posterior hole are lined up, that no external light can reach the light sensor and make sure it is firmly attached so that there is no movement when adding/removing the cuvette. It helps to have the smooth surface blocks on the inside to prevent the cuvette knocking onto the ‘lego lumps’ and moving the position of the cuvette holder when inserting/removing it.
The clip on the version in the picture was from a selfie lens from Poundland, which is a shop in the UK where everything for sale is a pound. Bulldog clips and a clothes peg have been used on different models, as long as it holds it firmly in place and can be stuck to the posterior of the holder.
Whether it is the lego version or 3D printed version, some customisation will be needed as the depth of phones/tablets and position of light sensors is variable. Edit the Github plans as needed. If you come up with an innovative design that may help others, please share!