"My PhD is in Organic Materials for Photovoltaics... I am horrified that [news agencies] have published this article verbatim, without even questioning the basic science behind this 'invention'... Melanin is really bad at charge separation, a basic requirement for solar cells." ~~Caesar_Dia IntroductionWhat has really happened? The Trinity College students made a cuprous oxide solar cell that is commonly used for demonstrations in school laboratories. This cell does indeed generate a small voltage and current, but is completely impractical to scale to a larger size, and the cell would work just fine without human hair. A reporter with no training in science or engineering witnessed the cuprous oxide cell working but didn't realize it wasn't generating the claimed power levels. The story was broken without being reviewed by experts, however now most news outlets are retracting the story based on feedback from scientists and engineers.
In the remainder of this article, we examine this story in detail, starting with how the story spread and why it spread. Then, we discuss the technical details of this invention and how it measures up to current science. Then we elaborate reasons for calling the invention a "hoax" based on information published so far and quotes from the inventor himself. The article ends with remarks directed at the inventor and some suggestions for more fruitful research areas. The article provides an alternative and perhaps more feasible solution in the form of a small thermoelectric generator that can be powered either by the sun or captured heat from cooking coals.
The first news article I can find in English is the Rebublica article from July 2009, though the September 2009 Daily Mail article seems to have sparked interest in the West. The Mail article has pictures of the smiling boy and his solar panel, proclaiming him as the "next Edison". One article states, "A new type of solar panel using human hair could provide the world with cheap, green electricity, believes its teenage inventor. Milan Karki, 18, who comes from a village in rural Nepal, believes he has found the solution to the developing world's energy needs. The young inventor says hair is easy to use as a conductor in solar panels and could revolutionise renewable energy."
The young man claims he has sent several units out for evaluation which, on the face of it, lends credibility to his claim: "I'm trying to produce commercially and distribute to the districts. We've already sent a couple out to the districts to test for feasibility." On the other hand, this means that he has built prototypes capable of producing 9V/18W. Based on the analysis below, this seems highly unlikely and, unfortunately, seems to indicate this is a deliberate hoax. As discussed below, the claimed output of this device does not agree with the published properties of photoelectric organic dyes, making it likely that a conventional solar cell is concealed inside the panel.
Furthermore, the article states, "Half a kilo of hair can be bought for only 16p in Nepal and lasts a few months, whereas a pack of batteries would cost 50p and last a few nights. People can replace the hair easily themselves, says Milan, meaning his solar panels need little servicing" and "The young inventor says that human hair due to the presence of melanin is sensitive to light and also acts as a type of conductor". These statements indicate that the device uses human hair directly, not purified, extracted melanin which further invalidates the claim. The melanin can't be electrically active because keratin is an insulator. Human hair is non-conductive and not photochemically active as published articles and my own experiments show.
In other online articles (July 2009) on this topic, we find additional details that explain exactly what is going on: "A group of five students of the Trinity Science and Technology Guild led by Milan Karki and Harihar Adhikari demonstrated Tuesday how they succeeded in devising such a module by making use of copper, iodine, black hair, silicon dioxide and black chart paper at a minimum cost of Rs 3,000... "Unlike the commercial solar cell, we used moist black hair as a main component in our solar cell. We replaced the silicon bridge with a natural black hair where it serves as a main agent to convert the solar radiation into electrical energy,” Milan, the main architect of the module, said while addressing a press conference in the capital, Tuesday. The hair fiber has to be immersed in salt water (NaCl solution) whereby the hair gets moist as dry hair is a bad conductor of electricity and when moist it acts as semi-conductor." A more recent Gizmag article and my response (October 2009) provides even more detail and some close-up photos of the device.
Technical OverviewThis turns out to be a variation of DIY solar cells such as the cuprous oxide cell, the cuprous oxide/iodide cell, or dye-sensitized cell. A simple DIY flat cell is very similar to the student design, except it just uses salt water without the hair. In the case of the hair solar panel, the hair is serving as a sponge to replace the electrolyte container. The student's explanation is completely wrong, and I don't know how the faculty advisors didn't catch these obvious errors: the cuprous oxide is the semiconductor responsible for producing electricity from sunlight, and the salt water contained in the hair sponge is merely an electrical conductor (not a semiconductor, as claimed). Saying that hair becomes a conductor when immersed in salt water is like saying a brick becomes a conductor when you cover it with tin foil. The basic science behind this so-called invention is simply wrong.The melanin in the hair is immaterial, and the black hair has absolutely nothing to do with converting solar radiation into electrical energy as claimed - aside from the fact that it is black and, therefore, doesn't reflect light. The hair itself is not conducting electricity whether wet or dry; the salt water is the conductor, and keratin doesn't have the atomic properties to act as a semiconductor. In other words, the students could have used any dark colored synthetic or natural fiber to hold the salt solution or simply immersed the copper plate in a bowl of salt water and eliminated the hair altogether. The user of the solar panel will need to keep the hair mat wet at all times, or the cell will stop working.
I suspect the idea for a solar cell based on human hair comes from a mis-reading of some information the students found on the internet. A paper entitled Photoelectrochemical Properties of Melanin was posted in 2007. This is preliminary work that was never published in a peer-reviewed journal, not to mention that it's nonsense, as the experimenters don't seem to know the difference between a battery and a photocell. Here is a brief excerpt from the paper (I have corrected some English errors for clarity): "We started with a very simple cell where the electrolyte was a 1.3% solution of melanin in distilled water, copper and aluminum electrodes 2.5 cm apart, and copper wires (covered with silicone) attached to the electrodes with glue. We noticed that any kind of soldering affected the melanin's behavior. The cell started to generate electricity just a few minutes after being assembled."
To me, the use of dissimilar electrodes in an electrolyte solution in the Nature Precedings paper suggests, not a solar cell, but an electrochemical cell of the type used for simple demonstrations. To ensure that electricity was being generated photovoltaically, the Nature Precedings authors should have used the same metal for both electrodes. What the original paper authors probably meant to write was "covered in silicone" (final "e"), meaning simply that the wires attached to the electrodes in their cell were typical laboratory silicone insulated test leads. I believe the students who constructed the hair solar cell misunderstood "covered with silicon" from the original paper and that's why they tried to use silicon (no final "e") in their hair cell design. The referenced article states that authorities are waiting for the students to build a prototype without silicon, and "The [hair cell] experimenters claimed that silicon dioxide was used only at the edge as electrodes. They said it can be replaced with lead." The students apparently borrowed concepts from the Nature Precedings paper without fully understanding them.
Furthermore, the Nature Precedings authors used purified synthetic melanin for their experiments, and the students naively believed they could substitute human hair since it contains melanin. The final bit of misinterpretation is that melanin only enhances the photoelectric effect of organic dyes. It does not produce electricity when used by itself, but the students claim, "We replaced the silicon bridge with a natural black hair where it serves as a main agent to convert the solar radiation into electrical energy." In summary, the students found some preliminary (and faulty) research on the internet, misunderstood the research, and based their design on this misinterpretation. Direct quotes from the students describing their invention contradict well-established principles of physics and chemistry.
The Gizmag article includes a schematic provided by Milan Karki. This schematic drawing makes absolutely no sense and indicates a complete lack of technical understanding. First, the blocking diode is installed backwards -- the band (cathode) should be connected to the postive terminal of the battery, not the solar cell, as pictured. Though it might be a typo and they meant "battery", I have a feeling that the comment "a diode used to prevent discharging of the cell" means the students thought that the solar cell could discharge, which just underscores their lack of understanding. The next problem is that the negative terminal of the solar cell connects through a metallic pin to silicon dioxide "stain" on a glass substrate, and silicon dioxide is an excellent insulator (I have a feeling the teens meant to use titanium dioxide here, but just didn't know what they were doing). The negative lead cannot possibly conduct as shown. The positive terminal is cuprous oxide also connected with a metallic pin. Cuprous oxide is a semiconductor and can be used to make a solar cell, but not with an electrode connected directly to it as shown. The electrode should be connected to the underlying copper, not the cuprous oxide layer as labeled in the diagram. Finally, the hair fibers interconnecting the anode and cathode make no sense at all. Hair doesn't conduct an electric current and, even if it were generating electricity as claimed, the physical arrangement makes no sense in terms of collecting the emitted electrons. Kaeki says the hair is saturated with "organic salts" to make it conductive. Elsewhere he says the "salts" are NaCl, so I assume he means table salt, not something like sodium acetate. In any event, since he claims the hair's job is to "conduct electrons," then why not use strands of copper wire? The drawing submitted by Milan Karki is complete rubbish and his explanations are nonsensical. Using organic materials or readily available waste products such as human hair to generate solar energy has its romantic appeal, but the cost of extraction, purification, and end-product stability must be considered. For example, separating melanin from hair requires the use of harsh chemical solvents and heat, and the disposal of these chemical agents as well as the energy required to heat the solution must be considered. Also, melanin itself isn't photo-reactive, but is typically used to enhance the current-generating capability of organic dyes, so a device would require organic dyes in addition to melanin. In short, we must consider not just the initial cost of raw materials, but all factors involved in manufacturing and using any particular solution. It may be an over-simplification, but consider that the element silicon, used in solar cells, is one of the three most common elements on earth and is essentially purified sand, making silicon a cheap, stable, and relatively inexpensive solution as compared to organics such as melanin in combination with organic dyes.
While it is true that melanin can enhance the photovoltaic properties of organic dyes, the isolation of purified melanin, production of the accompanying dyes, and instability of these products makes the use of melanin for solar power generation infeasible at present - although research in the area of organics is ongoing. As regards the proposed solar panel based on human hair, it appears from photos that strands of human hair are matted beneath the front conductive cover which would require the hair itself to be a conductor or semiconductor. After my own testing and referenced tests, even hair processed in an electrolyte such as a salt solution remains, itself, nonconductive. It is possible to extract melanin from hair by dissolving the keratin (hair's structural protein) by boiling the hair in a strong acid or alkalai solution. The problem is that such harsh methods tend to destroy the pigment or alter its chemical properties. There are more concentrated sources of melanin (eumelanin) than hair available in nature, e.g. cuttlefish ink and the uveal tract and retinal pigment epithelium of bovine eyes. The most economical way to obtain melanin is to simply purchase the synthetic compound or its chemical precursors. The electrical, semiconductor, electroluminescent, and optical properties of melanin films are well-studied. The properties, which are highly variable, are a function of heat, presence of water, and other environmental factors. The use of isolated melanin to enhance the photovoltaic properties of organic dyes has been studied, for example, Dye Synthesized Photocells, Hanyz & Wrobel (2002) and especially in Solis, et al (2007). A discussion of melanin chemistry is found in Nordland, Boissy, et al., The Pigmentary System: Physiology and Pathophysiology, 2nd ed, Wiley-Blackwell, 2006, pp. 289-290. The overall conclusion is that, at present, the use of melanin for solar energy production is impractical because it requires the presence of additional expensive organic dyes and because such dyes have been shown to be unstable.
Verification of Prototype Solar Panels
Conclusion: It is not possible to use human hair in any configuration to generate electrical energy when exposed to light. Why Perpetuate a Hoax?
EpilogueA case like this saddens me on several levels, and I feel the need to preach a little. Just skip this part if you don't want to hear it. A news agency picks up an interesting story without having it fact-checked by a subject matter expert. The story spreads all over the internet and people believe it because it has a romantic element and also because the story has a kernel of truth to it. What a waste of resources just because a reporter couldn't be bothered to do a bit of checking. Even a reporter who is not a science geek should know that hair is an insulator and that static electricity is unrelated to the photoelectric effect. Just the barest amount of research would have shown that melanin must be isolated to be used in organic solar cells. If I were a reporter, I'd at least do some minimal investigation of the solar panel to verify it. Simple stuff. Does it have a battery hidden inside? Does it have a silicon solar cell hidden inside? Does the amount of power it's generating make sense? That is just good reporting.The same logic extends to other news sources picking this story up without fact checking it. It amazes me that some of the technology editors who propagated this story didn't know better. Again, you don't have to be a science geek to do a little research and at least question the claims instead of just publishing them as fact. Some of the comments on the blogs concern me a bit, too. I can't believe the number of people who seem to lack a basic familiarity with science. I hate to come off as preachy, and maybe because it's important to me personally I expect others to have the same priorities. I was just disappointed at the lack of critical thinking and analysis I saw on some of the blogs.
Then we come to the kids. I blame their teachers for a lack of guidance and for not teaching the kids the basics of the scientific method. For example, did they even test the panel with other fibers besides human hair to see the effect? Why didn't the advisor teach the students to use experimental controls? Did the advisor not question the student's claim about human hair that "when moist it acts as a semiconductor".
And finally, there's scientific fraud. I know that in some countries the pressure to succeed in school is enormous. Students compete on exams to make the top couple of percent in order to gain admittance to a university. Professional scientists and academics all over the world commit fraud because of the pressure to publish results. I don't know for sure if these students committed fraud, though I strongly suspect they did because they claim to have sent out working prototypes. As I have shown above, it is not possible for a device of that size and technology to produce the claimed power levels. Again, I blame the faculty advisors for not vetting the design. The advisors should have questioned whether a home made solar panel could produce the kind of voltage and current claimed by the students. If the students were caught cheating, it was the adult advisor's responsibility to detect the fraud and discipline the students.
I have only kind words for Milan Karki and his colleagues. Mr. Karki, if what you have produced isn't valid, then drop it and take another path. That's how science works. Dye sensitized cells are a hot topic. Start with this source which discusses the use of natural organic dyes (berry juices) in solar cells. Order some lab grade melanin (or synthesize it) and combine it in a controlled manner to see what results you get. You need to start with pure melanin to do controlled studies, because extracting melanin from hair will produce impurities and variable quality unsuitable for research. Bear in mind that melanin alone won't generate electricity because melanin only acts as a "frequency shifter" for light. You will need to combine melanin with a large variety of organic dyes and vary the concentration of melanin. To determine the starting melanin concentration, consult current publications starting with the Gratzel Cell and working your way forward. It may take you hundreds or even thousands of trials, but that's how Edison worked! You might also consider thermo-electric generation, using wind to turn a generator, a solar stirling engine generator, and fuel cells. If you need electricity during load shedding, investigate energy storage methods such as batteries in addition to power generation. If you need light, investigate lighting methods like luminescence or pyrognomic materials.
In your application, thermoelectric seems to be a good choice because the generator can be made out of junk: scrap metal for a heat collector/radiator, wire (copper, aluminum, steel, nichrome from old toasters) and stones or glass for insulators. Some examples here seem to provide enough energy to charge batteries, but it would take a lot of experimentation to build something practical. Here's a rough design I came up with to get you started. If you try it, drop me an email and let me know what happens. Here's a young man in Malawi who's the real deal: he builds windmills to power pumps and generators.
My message is this: Don't worry about glamour. Focus on practicality, maintainability, and using what is inexpensive and available to you. Contact me for advice and guidance. I will be happy to assist you. Correct your mistakes. Educate yourself. Keep working. You are a big fan of Thomas Edison and so am I. His words still ring true:
"Genius is one percent inspiration and ninety-nine percent perspiration." -Thomas Edison
Notes
Contact and PressContact me at craighyatt@live.com with your comments. Comments from subject-matter experts are especially welcome, and if you find mistakes, I will gladly fix them.
Press release and photos: press release in doc format, press release in html format, hair test photo, hair test photo with text overlay, author photo
Credits: Photo of Milan Karki above is (c)Tom van Cakenberghe/Barcroft Media; solar cell schematic courtesy of Milan Karki via Gizmag; T-shirt image courtesy of Reddit.com.
|




