Solution Revealed: Solar Powered Mosquito Repellant
The vast majority of Challenges posted by InnoCentive Seekers are of such a confidential nature that we are never permitted to reveal even the Seeker’s identity, much less the actual solution. However, we recently announced that the SunNight Solar Challenge, which was seeking a solar powered mosquito repellant to combat malaria had been awarded. We are very fortunate in this instance, that the Seeker, SunNight Solar, and the Solver, Tom Kruer, have been willing to talk about the winning solution. Below is an overview of the solution, provided by Solver Tom Kruer.
This blog entry describes, in detail the winning entry for the InnoCentive Challenge entitled “Reducing Risk of Malaria with Solar Powered Device”. The simple, passive solar device is shown in the illustration at left.
Not surprisingly, coming up with a viable solution to this Challenge involved the typical phases of product development project. Research uncovered the relatively few critical features that the product absolutely needed to have in order to be successful. The design phase generated and evaluated a number of alternative approaches which incorporated these critical features. Two of these designs broke all the rules (including the ultimate solution) which the Seeker agreed to at least look at. A couple of crude functional prototypes were constructed to prove that the concept was feasible. After that, it just was time to crunch some cost estimates and write up the submission for InnoCentive.
It must be pointed out that the Rockefeller Foundation and SunNight Solar deserve a great deal of praise for agreeing to publish this information and achieve as wide an audience as possible… with the ultimate hope of eradicating this terrible disease.
The Research
My son, Nathan, and I started this project by doing extensive reading and analysis of the published research regarding the behavior of Malaria vector mosquitoes performed by leading universities and institutions. It helped that Nathan is a student with access to a great university library and had an interest in winning some money (yes, I shared the prize with Nathan).
This literature review led us to two important conclusions that helped guide the rest of the design effort. The first conclusion was that using insecticides for eradication was probably not the best idea as these toxic chemicals kill off as many or more beneficial insects as the target pests and mosquitoes eventually develop a tolerance to whatever insecticide is employed.
The second conclusion was that mosquitoes are attracted to their human blood hosts by the combination of the following factors when inside a human habitat (2):
- The temperature of human extremities during rest (~ 29 +/-3 degrees C); and,
- Moisture emanating from the skin; and,
- The complex, multi-component scent of human sweat & resident microflora.
Once these conclusions were verified through more focused research, a device was designed to effectively attract, trap, and kill the female Anopheles mosquito by using a complete combination of the above three factors.
(1) There has been a great deal of scientific research into how carbon dioxide along with visual clues act as mosquito attractants. However, when the research is evaluated in detail, it is apparent that CO2 and visual indicators are used by the mosquito only when coming from a distance. These attractants have little, or no effect within an enclosure.
The Design
The proposal which won the challenge is quite unique in that it uses a nontoxic phase change material (PCM) to retain passive solar heat during the day (see operation). This stored heat is then released when the unit is brought indoors (when mosquitoes are feeding). Basically, the Eureka moment came when I realized that if all we needed was heat from the sun, we did not need expensive and complex photo-voltaic cells and batteries. Inexpensive wax works just fine in a passive solar mode and phase change wax can be made to closely simulate human body temperatures. Rough calculations showed that the released heat from only about 1 liter of paraffin wax, in combination with a natural convection chimney (analogous to a power plant cooling tower) distributes a water-based mosquito attractant throughout the enclosure for about 10 hours.
The black blow molded bottle which holds the phase change wax was initially configured to allow all the material to be approximately the same distance from an exterior surface. This requirement led to a tall cylindrical shape with a large cavity in the center. The shape was further tweaked to provide the shape needed to achieve natural convection air flow. A natural convection chimney was selected to achieve air flow instead of a motor-powered fan for what should be obvious reasons of reduced cost and complexity.
Phase Change Model
The third major aspect of the design was settling on which attractant to use. The attractant suggested for use in developing third world countries is simply a small amount of water combined with human sweat (collected in a sweatband during the day). It is noted that using sweat is a very simplistic approach, but it makes sense in so many ways. First of all, sweat has been scientifically and experientially proven to work.
Therefore, this simple suggestion can be implemented immediately without any further research. Secondly, there will always be a FREE supply of human sweat in the household… or from a more pungent “supplier” in the region (how about that for a job!). Thirdly, research has found more volatile compounds in adult sweat that attract mosquitoes than found in other human fluids or artificially derived compounds. And, again, its free.
The sweat attractant is located in a injection molded cup at the bottom of the unit with simple cotton wicks to expose the liquid to the rising air column. The cotton wicks could be cut from old clothing. The attractant cup snaps into a hollow in the bottom of the phase change bottle.
The design also needed to offer a wide range of mountings since not all mosquito species fly at the same height from the ground. Thus, the trap was design to be placed either on the ground (with the attractant cup providing an insulating thermal break for the heating element), on a tabletop, hung by a wire hook, or a pole up through the center of the attractant cup and the cavity in the heat element bottle.
Heat, moisture and scent are all present, thus meeting the critical requirements found in the research phase. The mosquitoes are trapped in a simple tortuous path container placed on top and eventually die by dehydration.
Total manufactured cost was estimated to be roughly US $5.00 of material with assembly labor of an additional US $1.25.
An alternative design was also considered for this product. This version positioned the phase change material in a plastic pouch which wrapped around a liquid trap. The trap mimicked nature’s pitcher plant which my son had seen in his travels to the rainforests of Peru . Although equally unique as the final design, this design was deemed not as effective at distributing the scent nor trapping the attracted mosquitoes.
Operation
At the start of each day, the heating element/clear chimney assembly is removed from the attractant cup and placed on the ground, roof, or table outside the home where it can be exposed to the full sun. At the same time, the sweatband is put around the ankle of the adult resident who is most frequently bitten by mosquitoes(2).
The phase change material within the black bottle melts during the day by absorbing heat from the sun. The phase change assembly can be stood upright or laid on its side. If stood upright, the flat surface of the chimney resting on the surface cuts off air flow through the hyperbolic gap and diminishes any cooling effect of wind or breezes. Nothing will be damaged if it rains or tips over!
As the PCM heats up in the sun, the sweatband (or, alternatively, a cotton sock) will collect some sweat and foot odor from the “donor”.
At the end of the day, prior to dusk, the sweat band is washed with a few CC’s of water and wrung into the attractant cup. The warmed heating element assembly would be placed back on top of the attractant cup with the conical surfaces ensuring proper alignment. The trap would be placed on top of the heating element, if it had been removed. Note that leaving the trap in place while the unit is heated by the sun may hasten the death of any entrapped mosquitoes.
At this point, it is recommended that the heated unit be placed in a dark corner downwind of beds or people in the habitat. The reason for this is that the traps should be located in inconspicuous locations where they will not be disturbed or vandalized. Furthermore, the research shows that mosquitoes search for hosts by traveling upwind, guided by scent.
Once inside the habitat, the heating element will begin to release its stored heat. Heated air, laced with the moisture and scent from the cotton wicks, flows up through the hyperbolic gap between the bottle and chimney. The air exits through the openings in the top of the trap and is distributed downwind to start attracting local mosquitoes. Very intentionally, there is no CO2 present in the air so as to avoid attracting more distant mosquitoes to the habitat.
The mosquitoes track the scent upwind to the trap rather than to the humans. They find their way to the wicks only to find no host. The mosquito then takes off vertically and follows and/or are forced by the natural convective air flow up through the gap between the bottle and the chimney. They pass through the trap holes into the trap assembly. Once inside the trap, they cannot escape due to the tortuous path.
It is important to continually monitor the number of mosquitoes in the trap day to day. If after several days the trap does not appear productive, it should be moved to an alternate location, or height. Remember the primary goal is to trap blood-feeding mosquitoes. It is less of a priority to maintain consistent sites that may have poor yields.
(2) Note that the ankle is the preferred site for the cotton/elastic sweatband as a number of researchers have proven the effectiveness of foot odor as an attractant over other human scents.
A prototype of this solution will be built and tested by SunNight Solar. If it is effective, SunNight Solar expects to begin production as early as this Spring. For more on SunNight Solar and the malaria Challenge, click here.
Tags: malaria, mosquito, Rockefeller, SunNight Solar, Tom Kruer
February 6th, 2009 at 12:29 pm
wow, this is amazing. They could be on the brink of making a fortune. malaria is a massive problem in fact the biggest killer on man there is. I really hope this works out. I’d love to invest in it myself
February 6th, 2009 at 8:55 pm
This is a great invention;it will save millions of people across the world.
February 6th, 2009 at 9:10 pm
Interesting concept. Was the device tested against actual malaria mosquitoes? What species, when and where?
February 7th, 2009 at 6:03 pm
Thank you all for the compliments. Dacarls, due to the obvious risk of introducing the Anopheles mosquito to midwest United States, no actual testing with mosquitoes was required or performed. However, it is interesting to note that, while testing a rough prototype of the design, I unintentionally attracted and trapped a mosquito. (Sorry, I am not a Biologist so I could not place the species nor the sex of said mosquito.)
We all share the hope that this concept proves to be very effective in upcoming field field testing… and then in actual global use.
Personally, it would thrill my heart to know that I had some impact on eraticating this disease from the planet. We shall see.
February 8th, 2009 at 11:21 am
Tom,
Congratulations on this interesting concept and innovative design from an engineering perspective. My background in mosquito biology (including having tested many dozens of different trap designs) leaves me skeptical that this device will actually work for the desired purpose. Why would a mosquito be attracted to this device in preference to a living and breathing human being in the same room or house? The human(s) there would produce far more heat, moisture, a complex cocktail of odors and carbon dioxide (an important component lacking from your trap). A few simple tests (by those who can identify mosquitoes) should be performed before expending too much money. I’d enjoy being proven wrong. As for the comment by ’solar panel diy’, one shouldn’t expect too much of a return on an investment in this field. Those who most need to be protected from mosquitoes rarely could afford the meager sum to purchase such a device. The rewards, if any, might be measured in less tangible ways.
February 9th, 2009 at 9:24 am
Anopheles:
I understand your skepticism and I think we can fully agree that the next obvious step is quantitative testing of the device. Which is now being arranged. Am I hearing an offer to help?
However, the underlying question becomes….does one do this testing in a lab and pay thousands of dollars for it or use the same money to make up thousands of units and “crowd-source” the testing in the field? I do not know, nor do I have the authority to decide, but I suspect that some combination of lab testing, along with involving the shareholders (those actually being bitten) in the testing and debug may shorten the timeline and increase the ultimate acceptance.
Perhaps I have bought into this open innovation too intently, but one of InnoCentive’s key and most fascinating strengths is bringing in divergent perspectives to achieve unexpected results. Enough said on that subject, given the nature of this blog. Moving forward…
Assuming that you would indeed be willing to share your expertise…. I suggested that the trap should be placed downwind of any occupants in the enclosure so that it is the first “host” found. The humans may still be bitten, but less often. I would let the occupants decide if that is an acceptable result.
Secondly, please confirm that I am correct in my conclusion that “when the research is evaluated in detail, it is apparent that CO2 is used by the mosquito only when coming from a distance. These attractants have little, or no effect within an enclosure. (Gilles, M.T., “The Role of Carbon Dioxide in Host-Finding by Mosquitoes (Diptera: Culicidae) a review”, Bulletin of Entomological Research, 70 (1), 525-532, (Mar. 1980). )
P.S. I love the “Anopheles” moniker
February 9th, 2009 at 11:04 am
Tom,
Testing is costly, no matter whether you pursue it in the lab or ‘in nature’. Based on what you’ve described, it would make far more sense to take a few baby steps to test the concept before rolling out thousands of devices.
I agree that InnoCentive seeks to bring to the table folks with diverse backgrounds and who have not been jaded with the conclusion that ‘it can’t be done’. As I said, I’d be pleased if you proved me wrong.
You asked whether the devices should be placed downwind of occupants. I suppose that this makes sense, but what direction is ‘downwind’ within a house? Traditional homes in malaria endemic regions have doorways and windows (usually without screens), but also open eaves and many other openings that offer easy entry for mosquitoes.
Mosquitoes can and do certainly detect and orient with respect to CO2 concentrations, whether within enclosures or outside. So, press ahead, but start with a few well-conceived and performed lab tests. The results should help guide you on how to proceed. Finally, partner with someone with appropriate expertise in mosquito biology. Good luck.
February 10th, 2009 at 5:05 pm
Anopheles:
Regarding testing…. note that some of the suggested “baby steps” have already been taken by the RTP process of building and testing two feasibility prototypes for the original challenge. Granted, those rough prototypes were NOT tested for attractiveness to the female Anopheles mosquito, which is the direction that I assume you are now suggesting. So, toward that end, are you (or anyone else out there for that matter) offering to help? Be aware that I have NO problem seeking help from anyone who might prove me “wrong”, or you “wrong”, or best of all, come up with improvements to make this thing even better.
Regarding optimized placement of the trap within an enclosure without screens….. I propose that crowd sourcing broad testing out in the field will help quickly determine the best location for the device within various habitats. As a very simplified example, let’s give a thousand of these things away to shareholders (again, those being bit) in exchange for them taking data every morning on how many mosquitoes were trapped. We would also need to know where the device was placed the prior night. We might even give them a second unit to be placed in a common location, like on the hearth, to serve as a control. Thousands of data points per day obtained in this manner for a month might show the trend. We then tell everyone involved in the testing to put the trap in the “optimum” location to prove the results. Done in two months…. resulting in 100,000 less victims. Testing continues for years with results fed back to one of the funded NGO’s to compile results for distribution.
The only unknown in this testing becomes, is there an easy way to visually distinguish between Malaria Vector mosquitoes and other species in the field?
BTW, Thank you for the discussion… and thank you in advance for any feedback you may offer.
February 12th, 2009 at 2:08 am
The design looks promising.
The prototype could be vary in size and nos. Also it is possible to
change the design in trial. It is observed that the mosquito try to find the
immovable area of body or where it could easily bite.
is it possible that the insect sends a signal like honey bees to others?
then it would be better killed inside the trap. Also it is possible to develop
similar trap where the mosquito find safe place to rest and get trapped
during day time?
February 13th, 2009 at 8:33 am
Hi Tom,
As suggested by you in CR4 Forum, I would like to give my comments as under:-
If you have funding problem then I think you can get funds for your projects such as WHO and other NGOs.
1) I read about your winning Innovation in Innocentive blog and felt I should recommend my friends at CR4 to read it.
2) I am not a expert on the subject but an affected party (Share Holder).
3) I live in Mumbai,India where there various types mosquitos creating havoc in summer and spreading Malaria. Municipal Corporations spends hell of money in getting rid of them and treating patients.
4) Here we do have some type ropellants such as, burning coils of herbal chemicals, liquid chemical fumes emitted from wick heated by electricity, pads heated by the electric heaters, etc. All of them are not 100% effective.
5) If you feel the testing in lab is expensive then you you should test your prototypes in field trials in your city or other places.
6) I would suggest instead of targeting poor African villages without power you should also target big and small cities where electric power is available. In this case you can eliminate Solar portion but will have to add electric heating element which will enable device to work in rainy days too. It may increase the price but it will be better product for city dwellers.
7) I am giving you web site address of local mfr. here:-www.godrejsaralee.com.
February 13th, 2009 at 10:08 am
Sameer,
Thanks for your interesting comments and suggestions.
The academic research does suggest that mosquitoes tend to prefer lower extremities that are not moving (De Jong & Knols)…. as does our personal experience at summer picnics. Based upon this, I suspect that we will find that placing the trap on the floor of the dwelling while the occupants sleep on elevated beds may lead to the best results. We shall see.
In regard to your suggestion of trapping during the day, we did find some interesting research being done on trapping mosquitoes for study when they settle down to rest. see: http://www.rci.rutgers.edu/~insects/restbox.htm This day trapping approach was beyond the scope of the InnoCentive Challenge but is still worth pursuing. In other words, putting simple dark boxes with a lining of sticky paper in a still corner of the dwelling to trap the little buggers could lead to a 24 hour control scheme.
Any additional thoughts on this concept, Anopheles?
February 17th, 2009 at 5:12 pm
Suresh:
Great to hear from an actual Share Holder (perhaps not an expert, but clearly a valuable voice).
Indeed, a lot of money has been ,and is being spent trying to deal with mosquito control, globally. Wouldn’t it be great to direct some or all of those funds to truly effective control devices that do not containment the environment. Furthermore, I personally tend to feel that it is in some way unfair to use repellents or even bed netting – that merely divert the feeding female mosquito to another, less privileged blood meal host – rather than actually trapping the bugger.
In regard to electrically-powered small city device versus a passive solar rural villages, why not do both? Per your suggestion, we can contact Sara Lee Corporation (the voint venture partner with Godre) to see if there is any interest on their part for a product that is a departure from their current household incecticide products.
In regard to funding…. again, it must be mentioned that the Rockefeller Foundation was key to bringing this project to InnoCentive by providing the funding of this challenge. Of course, support of other NGO’s and agencies could be key to implementation.
June 27th, 2009 at 2:25 am
Nice writing : will visit
November 17th, 2009 at 11:11 am
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December 13th, 2009 at 7:35 pm
Wow, truly an impressive innovation, solar powered mosquito repellent who would have thought?
Thanks to InnoCentive for providing the means for tomorrow’s biggest innovations.
February 6th, 2010 at 8:27 am
Hi, After reading all of this, One thing pops into my head regarding the capture using sent; Instead of using actual “ankle” sweat …one should use a high concentration of same so that the mosquito will go for the ’steak’(trap) in the dwelling instead of the hamburger(person). So that way, in a 25 foot area-no matter what level- the little bugger would go for the most allured concentrated scent.
April 15th, 2010 at 12:23 pm
I look forward to more earth-friendly forms of mosquito control. Gone are the days where we can decimate wetlands and wear DEET to solve our mosquito problems. After some research, I also found Mosquito Magnets, which convert butane into harmless CO2 to lure mosquitoes into traps.
May 31st, 2010 at 8:17 pm
These days, solar power is the way to go. Aside from it being earth friendly, it can also lessen electric bills. . . The solar powered mosquito repellent is really a great innovation.
June 9th, 2010 at 5:50 pm
this is crazy awesome. i really love these more greener approaches.
I liked the reviews of mosquito traps on this blog. http://mosquito-trap-review.blogspot.com/
Sometimes it’s nicer to have something permanent, instead of something on your skin.
July 2nd, 2010 at 7:21 am
Just thought i’d comment and say neat theme, did you code it yourself? Looksgood.