Hey fellow engineers, I now live in the north of Sweden where we typically have some really incredible quantities of mosquitoes. It's mind blowing really. Also midges as well that can leave a drip of blood going down your leg after they bite. They leave sores on your skin that can last for a couple weeks! I want something to protect my camp site when I go camping up north.
So I'm sure many of you have read about laser walls for killing insects before they can even get near you.
Here are some links for your reading so you know a bit what I'm trying to talk about:http://en.wikipedia.org/wiki/Mosquito_laser
http://spectrum.ieee.org/consumer-electronics/gadgets/backyard-star-wars
http://www.intellectualventures.com/index.php/inventions-patents/our-inventions/photonic-fence
These ideas were mainly for protecting people against malaria.
I like the ideas that are described but they seem overly complicated to me. The idea of using cameras and tracking software seems like a lot of work to me, mainly because I'm a mechanical engineer. Also, I don't care what insect it is that is invading my camp site, I just don't want ANY insects flying into my face when I'm around my camp fire. Here, about 99% of the flying insects are either mosquitoes or midges.
Concept:
My idea is this. You have a small mirror mounted 45 degrees on a rotating shaft turned by a motor. There would be two lasers pointed at the mirror such that there is a low power high frequency (just say a hundred kilohertz for sake of concept) pulsed laser which is pointed at a slight angle with respect to the other high power laser such that once bounced off the mirror, the pulsed laser is in a slight advanced timing in comparison. You could encircle the lasers with sensitive photodetectors that are sensitive to that pulsed laser and use some clever programming or hardware filtering to pay attention to when it gets that 100 kilohertz signal in response. If it does, it tells the device that something is reflecting that signal. An accurate position sensor could be used to tell not to fire straight into the ground or wall or whatever.
Since the mirror is rotating at a known velocity and the angular difference is known the timing is also known. If rotating fast enough, the difference in time shouldn't be enough for the insect to fly past the laser. From what I read, even if you just clip a wing or leg, it might be enough to disable the mosquito. I'm sure you could optimize the laser wavelengths such that the wavelength for the sensing laser is more reflective off the insect and the power laser absorbs well on the insect.
I did some math to see how easy this would be for a laser could do this in concept:
Please give a polite correction if you think the concepts are wrong. Knowing that mosquitoes only fly top speed of about 0.55 m/s and are 5mm long and maximum weigh about 2.5 mg we can figure some things out. The "interception time" would be how long it takes to travel one body length at max speed (0.09 seconds).
The minimum RPM of the rotating laser to catch every insect would be the reciprocal times 60 seconds. (660 rpm). That seems easy.
Assuming the mosquito body is about 2mm wide and is flying perpendicular to the wall and is also 2 meters away, the laser angle for the above numbers would be about 0.05 degrees and the contact time would be 14.5 microseconds.
At first I thought that in order to kill them quickly the laser would have to boil them. I knew the heating would be incredibly uneven due to the high power, short time and low thermal conductivity but I wanted to check anyways. I checked my heat transfer textbook and did some calculations to see how uneven the heating would be. The duration of time is so fast and the power is so high that the surface of the insect would become very hot and the inside cold so the delta T would be very high. The IEEE article above says that only a few tens of millijoules is enough to kill the insect with enough time after the laser pulse due to "heat stroke." I calculated to heat the insect 40C higher than ambient (say lowest ambient is 10C) it would take ~4 joules which is way too much for a small cheap laser in 14 microseconds. But assuming IEEE is right, maybe 100 mJ is enough to kill it. In that case, only a 7 watt laser is needed for 14 microseconds. A 1 watt laser could pulse 7 watts for short periods of time. It should be enough to burn wings off at least if hit.
Safety:
Blinding people and animals is obviously a concern. We could use the same ultrasonic range finder devices used in car parking sensors. Those are pretty cheap. Mount those on your devices. Once you set up your laser wall, you calibrate them to "tell" your programmable module that anything closer than these range values is considered something that shouldn't be there, whether it's a person, your pet or a car. Since the laser is in a plane, it should be relatively safe as long as nothing is reflected into someone's eyes. Also, a "shake" sensor could easily be implemented in case something is bumped slightly so it automatically turns off if it is moved. Obviously, I don't want it bumped and burning tiny holes into my tent or face! Also, a simple remote control to turn it on and off would be easy to implement.
I'd like to know what you guys think about this idea! If it sounds feasible, I'd be interested in working with someone in order to make a working prototype. When it comes to building things, I'm pretty good but I'm lacking in the electrical engineering aspect of things.
"Photonic Fence" Laser Wall Mosquito Defense
Re: "Photonic Fence" laser wall mosquito defense :)
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