I've been trying to come up with spectrometer to phone attachment method that can fit anything and not leave a sticky trace.
I was inspired by the Empire Universal Silicone Suction Cup Stand, shown to me by Nick Chelyapov (pictured in the gallery above). It sticks well to any phone, even when there is a textured back, like on my Samsung Galaxy S II.
I grabbed a 2cm and 4cm sizes of standard transparent PVC suction cups. They won't stick dry, but if I wet them they'll stay for several hours at least. The silicone suction cup stand stuck much better when dry.
Although fairly sturdy, there was a slight inconsistency between two takes after the spectrometer was jostled and put nose down on the table:
![two spectra between jostling](https://farm9.staticflickr.com/8376/8433701627_7f44cab459.jpg]
It would be nice to use silicone suction cups, although I can't find them for regular sale outside of glass eyeball removal suction cups. only as a specialty item. Silicone vacuum cups, used in manufacturing applications and attached to vacuum pump, are available, and they can be custom manufactured. Alibaba has them too but the search for "silicone suction cup" get NSFW really fast.