Inferring from Infrared

Inferring from Infrared

Imagine if there was a way to know which watermelon is sweeter? When is that avocado going to ripen? How many calories, carbs or protein is in that shake? How your plants are doing? What’s in those pills your taking? A new low-cost handheld sensor on the market promises all those answers and more, in real time ( The technology is based on near infrared spectroscopy. How does it work?

Calorific Rays: We all know that a prism can separate ordinary light into the vibrant colors of the rainbow. Back in 1800, musician and astronomer William Herschel wanted to know the temperature of each color. By placing a thermometer with a blackened bulb along the spectrum, he discovered that the red end was warmer than the blue. To his surprise, a thermometer placed just beyond the visible red part of the spectrum was even warmer. He had discovered infrared rays, although he didn’t realize it at the time. This is the same heat that you feel when you hold your hand near a fire.

Bond. Covalent Bond. Shaken and Stirred: Chemicals are arrangements of atoms, held together by bonds. You can think of these bonds as tiny springs in motion. They stretch, wiggle, rotate and twist. When they absorb energy, the natural vibrations of bonds increase. Because of quantum mechanical constraints, these increases occur only to discrete energy levels. Different bond types (C-O, or C-H) and different vibration modes result in a series of absorptions at different wavelengths. By looking at which wavelengths of light were absorbed by a compound, we can deduce what types of chemical bonds are in the sample. Absorbances in the near infrared region of the spectrum can be so complex that they give rise to unique fingerprints of different chemicals.

Citizen Science: Spectrometers built with near infrared technology used to be large, expensive and restricted to universities. That’s changing! The handheld spectrometer transmits chemical signatures to a smartphone which checks the pattern against a huge library of compounds in the “cloud” and returns the analysis to you within seconds. When you use it, not only will you be learning more about the chemical world around you but you’ll also be helping to build a database of knowledge of the stuff around us. Now that’s citizen science! 

REF: An introduction to near infrared (NIR) spectroscopy. A.M.C. Davies.

GIFS: All gifs are from Wikipedia and are in the public domain.

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87 Responses to Inferring from Infrared

  1. Good point, but the Watermelon one is easy around here. Just need to look for where the wasps have hit it.  

  2. Rajini Rao says:

    That’s funny, Jonathan Deaton ! I wonder how the wasps know? 🙂

  3. Teensy wasp-held spectrometers?

  4. Could wasps vision extend into the infrared with sufficient color resolution? 

  5. At mating time they look for the residue at the stem of melon, Just do don’t know why ,you can see small hole there from there work.  

  6. Satyr Icon says:

    Ah reminds me of the quantum spectroscopy of diatomic oxygen I slaved over in my first few postgrad years. In the 50’s & 60’s scientists were just beginning to embark on the quantum calculation of all the excitation energies for simple diatomic molecules (not individual atoms of an element). The bigger molecules were too calculation intensive back in those days.

  7. Satyr Icon says:

    If they added this device as an add-on to smart phones the item would take off. Or to utilise existing technology on smart phones to do the same.

  8. Rajini Rao says:

    Satyr Icon right now it’s a small but separate device but I can see how the sensor could be incorporated into a smart phone. 

    Re. your thesis work, I read that the NIR spectra were initially dismissed as being too calculation intensive and complicated for practical use! But an engineer working for the USDA, Karl Norris, changed all that. Apparently, no one had taught him that NIR was uninteresting, so he checked it out.

  9. Rajini Rao says:

    Tom Willingham thanks for the link! I followed up on Dr. Ozcans’ cell phone based food allergen testing device. It looks like it uses optical absorption to detect peanuts and other allergens. I’ll have to read the paper to find out more:!divAbstract

  10. Your graphic bought this to mind:

    So, so you think you can tell Heaven from Hell,

    blue skies from pain.

    Can you tell a green field from a cold steel rail?

    A smile from a veil?

    Do you think you can tell?

  11. Leland LeCuyer apparently, there’s a new hand-held sensor for that! 😀

  12. Rajini Rao says:

    Leland LeCuyer plus 100 for quoting PF 🙂

  13. Andy Payne says:

    reminds of the seek thermal camera adapter for android phones —

  14. Tau-Mu Yi says:

    Nice explanation Rajini!

  15. Rajini Rao says:

    Thanks, Tau-Mu Yi 🙂

    Tarek Abuaita I think a hand held device that can detect chemical composition by infrared spectroscopy is amazing! 🙂

  16. SCIO  -This device is very close to release:

    Out of the box, when you get your SCiO, you will be able to analyze food, plants, and medications.

    For example, you can:

    Get nutritional facts about different kinds of food: Dairy products, Fruits and vegetables. Other apps for drinks, meats, ripeness, salad dressing and more will be released on a regular basis as our database expands.

    Know the well-being of popular plants.

    Identify capsules containing medicine and nutritional supplements.

    Help build the world’s first database of matter.

    These are just a few of the starter applications that you can use upon receiving your SCiO. After SCiO is released, new applications will be developed and released regularly.

    The possibilities of SCiO applications are endless. For example in the future you can use SCiO to measure properties of cosmetics, clothes, flora, soil, jewels and precious stones, leather, rubber, oils, plastics, and even your pet!

    Quoted from website

  17. Mary T says:

    Pink Floyd and a device to pick the perfect nectarine.  Doesn’t get much better than that :).

  18. Rajini Rao says:

     Mara Rose  You saw through my excuse of writing a science post just to share this gif, didn’t you? 😉

  19. Mary T says:

    Laughing, yes, Rajini Rao ~ It’s just too perfect :))).

  20. Re: watermelon, looking for “bee stings” or “wasp stings” (dark spots/streaks or scars where it looks like dried fluid has oozed out) is a common method of choosing watermelons. Bees and wasps have nothing to do with it though, the “stings” are just a folk explanation.

  21. Rajini Rao says:

    Ah, I hadn’t heard of the tale anyway Steve Esterly . I’ve seen people knocking on them and sniffing. I’d rather use a NIR spec! 

  22. Bill Collins says:

    Excellent article. Well explained for the lay person. There are labs that have been working on “fingerprinting” chemicals for years – Dr. Armstrong in Texas was invaluable for a case of mine – and yet that’s a tad of a simplification. Still it more than suffices.

    The handheld spectrometer now is genius and I look forward to finding out more as they become available.

  23. Fascinating Rajini, the mechanism is eloquent. thank you.

    A spectrometer in a cell phone would be nice too – then people could quit obsessing over contrails.

  24. Rajini Rao says:

    Bill Collins it helped that the topic is out of my field so I wrote it as I understood it. There are some terrific articles that go step by step through the spectra of simple compounds like chloroform and explain what each blip tells us. Let me know if there’s anything I missed or oversimplified. 

  25. Rajini Rao says:

    David Andrews or formaldehyde in GMO and any number of “toxins”!

  26. Cynthia Bush says:

    Rahini, thanks for the fascinating article!

    I love it when someone so bright as you shares great information ☆☆☆☆☆

    (I still thump watermelons as any rural-grown person is supposed to do!😉)

  27. Bill Collins says:

    Not that I could tell Rajini Rao . I am however simply a scholar with no claim of degree or distinction in this field or honestly most others. I know, for example, that manufacturers of dynamite and other explosives have had to include specific chemical tracers for a long time. We also know, anecdotally, that each person has a unique chemical signature, and often has children by someone with the opposite immune system or biochemistry. So such mechanisms already exist in small areas, however the ability to identify, store and replicate the knowledge is huge?

  28. Rajini Rao says:

    Chemical tracers in explosives are a clever idea. As for people, I suppose we have very many unique chemical signatures, ranging from genetic to immunological to microbial. That’s an interesting thought!

  29. Cynthia Bush says:

    Rajini Rao​ yes, we all do… a Mother can distinguish her child by odor alone, people can pick out someone by a T-shirt worn by them…I know I can still recognize my 33yo twins by scent, & dogs not only pick out people, but cancer on their breath as well! 

  30. Rajini Rao says:

    We have so much more to learn, Cynthia Bush !

  31. I want this technology. My plants are begging for it. My brilliant surgeon husband cannot take care of flowers to safe his life! How fabulous. Can we use it on humans to tell if they are mean????

  32. Rajini Rao says:

    Could you persuade your surgeon husband to prune your shrubs? I’m much too tender hearted to take the pruner to my plants. Right now, we have to skirt an overgrown border and step around floppy, badly behaved perennials to get to our front door 🙂

    I don’t know if there is a chemical signature for mean Giselle Minoli , but perhaps we can have a modernized quantitative version of the mood rings from the sixties?! 

  33. Rajini Rao  I think it would be perfect a sensor like this integrated into a smartwatch (or maybe google glass?) and in the near future… in some kind of contact lenses 😉

  34. Rajini Rao says:

    I love the idea of incorporating tech into everyday wearables, al pistacchio !

  35. Yes! Rajini Rao seamless integration of really useful technology is the perfect match 🙂

  36. Also related: coming soon, small cheap spectroscopy tools based on ink quantum dots. Tech paper was published recently in Nature, here is a G+ discussion (article includes link to the paper):

  37. Jan Moren says:

    A commenter on Reddit that designs spectroscopy equipment took this idea apart. Basically there are physical constraints on the size that limits your resolution, speed and accuracy. It will be able to tell you some simple things, especially as you apparently need to tell the service what item you’re measuring, but it won’t really work as a general spectrometer.

  38. Jan Moren – of course none of the tiny cheap spectrometers can compete with the high performance models. I think, though, there are plenty of applications where the high performance is not necessary, and price/convenience issues trump performance.

  39. Jan Moren says:

    Steve Esterly Absolutely. I just think people maybe are rather overestimating what this thing will be capable of. Resolution is very limited, and calibration is practically impossible. The thing you measure needs to be in their online database (no measuring THC content of anything, for instance).

    I suspect, for instance, that you can say if something is sweet or not, but not really by how much unless your sample happens to be very similar to those they compare to.

  40. Nick James says:

    Rajini Rao “Right now, we have to skirt an overgrown border and …”   I get out the hedge trimmer about every 18 months and get brutally enthusiastic.  They still come back.

  41. Nick James says:

    Rajini Rao Some friends of mine developed a system, used by several UK supermarkets, for selecting ripe avocados..” ready to eat” etc.  I will tease them that they have been replaced by a phone app.

  42. Rajini Rao says:

    Jan Moren the average household user is not going to need laboratory-grade sensitivity and the device specifically warns against medical use (such as to detect life-threatening allergens). The chief limitation in detection is that the hand held spectrometer is not using transmission spectrometry, as would be used in a lab instrument. Instead, it is detecting reflected radiation.  Online databases are not likely to be limiting in my opinion, since they are already quite large. Even NASA has a massive online database devoted only to polycyclic hydrocarbons for use by the astrophysics community ( Also the point is that the database will increase with public use. 

    Not having used one, we don’t know how sensitive the SCIO is, but it would be odd if the instrument is specifically advertised as giving concentrations of sugars, including caloric and carbohydrate information, but be incapable of doing so. It makes no sense to market a device that one can point at a watermelon and have it say, yes, there are sugars in it! 

  43. Rajini Rao says:

    Nick James I’m really weak willed when it comes to keeping my garden in check. I now pay the lawn guys to hack at my shrubbery each year, and mourn their brutality when they leave.

    So what is this avocado ripening detection trick that your friends developed? I’ve only heard of the stem “stub” looking “just so”, which is still pretty mysterious to me. 🙂 

  44. Rajini Rao says:

    Steve Esterly thanks for the link to Yonatan’s post, I missed it and it was a great read. Interestingly, there is already a substantive discussion on the sensitivity of SCIO in that thread (mostly by Olivier Malinur)  so I will refer people to it: 

    I’m using the SCIO as a jumping off point to talk about NIR here, rather than the specifics of any one particular commercial device. 

  45. Nick James says:

    Rajini Rao I’m just lazy!  Funny, my neighbours pass by when I’m hacking and they all say how they like my somewhat unkempt but natural front garden.  As do the bees, the butterflies and some things I have not identified.

    My friends used NDT techniques they developed for testing undersea oil pipes and the like.  Ultrasound signals were the core technique, which was amenable to automated fruit selection.  To be honest, I don’t know if that is still used, but I was impressed when they did it.  They always had loads of avocados they were just begging to give away.

  46. Rajini Rao I would somehow think that we can/will be able to “map” a chemical signature for “mean,” “sincere,” “non-threatening,” etc. Dogs seems to be able to tell such things and are even used to assist people who are prone to seizures. True that dogs’ noses are infinitely more powerful than humans noses, but they do sense something and it would be interesting, chemically, to know what that is.

    Nick James I get pretty brutal too. I believe it’s good for the plants, keeps them healthier and – this is big plus – allows you to discover if a (ahem….) groundhog is living under the house, having made it’s way through Rajini Rao’s wildly overgrown, but I imagine beautiful, badly behaved though they may be, perennials (typical typical typical). But I digress, because, I think that if you were to “measure” Rajini’s chemicals, the groundhog would know she’s a pushover. Just sayin’.

  47. Rajini Rao says:

    Giselle Minoli I’m not going to be able to sleep if I laugh so much 😛

  48. I don’t think you sleep anyway Rajini Rao. Nick James please send avocados Fed Ex. BTW…there is nothing lovelier than drooping day lilies and tulips. Love them love them love them love them. Flowers are often more beautiful when they are older. Like women!

  49. It was very interesting and educative Rajini Rao​​. Thanks for the knowledge.

  50. I would like to purchase one when they become available.

  51. Thanks for the (as usual) stellar post. It prompted me thinking about microbiology and food. Spoilage of foods (usually) ends up being growth of undesirables. Faster growers dominate. And apparently fancy footwork (FT IR) has been used to interpret for subtyping of bacteria also, using IR spectroscopy. This indeed could be a nice test for such a device. ABSTRACT: Detection and identification of bacteria in a juice matrix with Fourier transform-near infrared spectroscopy and multivariiate analysis.

  52. It’s hard to answer more than one question at a time but il say this the elephant ears are doing well the trees are pretty the bushes I cannot name are very green . I’m a bit hungry but I am not complaining one bit.

  53. Does an array of these in the form of a bigger handheld be useful for scientists amateurs or professionnals giving a better resolution and/or scanning distance? What about robotic applications?

  54. This seems like a description of the tricorder from StarTrek Rajini Rao I am surprised no one has mentioned it in the comments thus far.

  55. Nick James says:

    Debashish Samaddar Sorry, Tom Willingham beat you to that one – 8th comment in.

  56. Nick James says:

    Jan Moren Damn smart idea…thc.  Self protection!

    And also protection against spiked drinks in clubs?

  57. Nick James says:

    Giselle Minoli I found mice under mine!

  58. Nick James yeah, close but no.

    1. you have to say the actual word

    2. McCoy used a medical tricorder, not an engineering one, so it was a wrong reference anyway

    3. what’s with the blue head?

  59. Nick James says:

    Debashish Samaddar  As you struggle so much, I’ll give it to you:-) I’ll still leave you Tom to argue that one;-)

    Hey, I like blue.  Much better than so many of the fake names and fake pictures and somebody else’s pictures you see around here. Not, I’m glad to say, on Rajini’s posts very much.  A better class of people here.

  60. to measure fructose for a melon meter or know the ripeness of fruit you would not use IR but NIR

  61. Rajini Rao says:

    Alan DeRossett that’s right, NIR is referenced in the opening paragraph of this post 🙂

  62. Rajini Rao says:

    chaitanya athale thanks for the link to the  paper on FT-NIR (“fancy footwork”!) to detect bacterial species in juices. It was a good trick to concentrate bacteria on a membrane filter to increase the signal. That’s quite a technical breakthrough compared to the old days of microscopic analysis, staining or culturing bacteria.

  63. A Cheap NIR would be something very important. 

  64. Rajini Rao says:

    Rashid Moore the RjR device may not be new fangled, nor quite as small as the hand held (!), but it does come with a satisfaction guarantee 😀 

  65. just fyi: SCIO was panned by CNET and appears more conceptual, than a workable device.

  66. Thanks Rajini Rao for getting to the bottom of this technique. I read a while ago that there are mobile drug testing labs in Gujarat, India to test for the authenticity of drugs. Those vans have the same equipment. 

  67. Citizen science has such a great potential! 🙂

  68. Nice! I saw mention of SCiO in passing, but didn’t have time to see if it was a true product. I could have so much fun with SCiO…

  69. Joy Ogene says:

    Got the importance of eating fresh fruits and vegetables.

  70. Tay Slay says:

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  71. Ricky Purcell You and me both 🙂  

  72. A aranha da foto a cima e a aranha pavão .

  73. There is a way we can make watermelon sweeter! In google, it says add salt

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