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Anti-Virus Ideas

dougw

Fighting Germs

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Hopefully this blog will help spark good ideas to combat the Covid-19 virus and other nasty bugs. This year I have not been blogging every week and just focussing on doing projects instead, but the call for ideas to help alleviate this crisis is a good reason to try and contribute solutions. I suppose it might be possible to make money off some of these ideas, but I would rather mobilize everyone to create solutions. Rather than wait for the ideas to be developed into working devices, I wanted to get them into everyone's hands immediately. This means they will still need further work and research to become practical solutions.

This bog starts off with a few ideas and gets into a build later in the blog.

The first set of ideas is around preventing transmission by physical contact with communal surfaces.

It should be possible to retrofit many commonly contacted surfaces with hands-free mechanisms:

  • door handles - become automatic doors - using facial recognition, voice recognition, ultrasonics, radars
  • cupboard handles, refrigerator door handles, toilet flush handles can all be hands-free automated
  • phones - voice control answering of a phone which goes to speakerphone
  • light switches - hands-free voice control or gesture control
  • microwave and stove controls - voice control of settings and door opener
  • faucet taps - hands-free voice control, IR control, gesture control
  • washing machines, dryers, dish washers - voice control of settings and door opener
  • etc

The next set of ideas deals with airborne transmission at work.

Some businesses must still operate, albeit with skeleton crews, but while at work some extra distancing precautions can be taken:

  • Put arrows on the floor so everyone walks in the same direction with suitable separation and no passing in the hallway.
  • Create a scheduling app to book and use the restrooms, cafeteria and any other facilities without overlap.
  • If your employees have android 9 phones, create an app to show where everyone is in the building.

 

The last set of ideas deals with attacking airborne virus.

 

The first idea make a device that kills the virus before you can breathe it in is Germ Zapper. This device is basically just 2 bare wires wound on a frame, very close together, but not touching - conceptually like this:

The idea is to apply a voltage between the wires that is very close to the breakdown voltage of air, so when air is blown though the wires any particle will cause the gap to reduce enough to cause a breakdown. The resulting spark needs to have enough energy to fry or zap the particle. In this picture the capacitor would store enough energy to zap a virus particle. Since the spark would ionize air and create a conductive plasma, when the capacitor discharges, there would not be enough current to maintain the current flow, which would quench the spark and air would blow it away. So this system just needs a fan to blow infected air through the wires and hopefully with enough layers of wires, all virus particles would be killed on the way through.

Virus particles are approximately 0.1 micron in diameter which is really small compared to wire diameters, but this technique is very similar to the apparatus used to detect subatomic particles, which are much smaller. The breakdown voltage of air is about 30K volts per mm, so if the spacing between wires is much less than 1 mm, the system could use  less voltage. The breakdown voltage will vary with humidity, but a feedback control circuit can be used to determine the exact local breakdown voltage.

 

The second idea is to kill the virus with heat - the Germ Fryer. This system simply heats up the air long enough to kill any virus present and then cools it back down to breathable temperatures:

The system needs a fan, heater and a cooler. Several cooling technologies also have heat as a byproduct, such as Peltier effect coolers and refrigerators, so some efficiency could be realized by using such technologies. It will require some research to determine what temperatures are needed to kill Covid-19 and how long they need to last, but conceptually the technique should work.

Some people are suggesting ultraviolet light would be a good way to kill the virus. I'm not keen on this as it would take a lot of UV and UV is dangerous in its own right, and I'm worried that UV can cause mutation (as it does with melanoma), and I wouldn't want to take a chance of mutating Covid-19.

 

The third idea is to make a Germ Pulverizer. Virus particles are tiny little flimsy particles that are probably easy to crush, smash or pulverize. The concept is to blow air through some rotating mesh disks or tubes where any particles cannot get through without being hammered by a wire in the mesh.

The fan and mesh disks could have separate motors or be linked with a gear train, and there could be several disks ganged and interleaved to create a tougher gauntlet. The mesh disks would spin at high velocity to ensure destruction of virus particles. There are many ways to devise a system that will beat up the air, and anything in it, as it passes through. It is just a matter of calculating the probability of virus sized particles hitting a wire or blade, based on relative velocities.

 

The fouth idea is a way to filter air with a centrifuge type of concept. I'm calling it a CentrAirFuge.

The idea is to blow air through a rotating tube, such that all particles will be accelerated to the walls. Clean air can then be collected from the center of the tube. I built a 3D printed version of such a machine to demonstrate the principle. The main component is a tube with vanes in it to ensure all air is rotating and a fan blade at the inlet to ensure air moves through the tube. I call this tube the impeller. There is an exterior tube to hold the impeller motor and the exhaust plenum.

The tube needs to be rotating fast enough and the tube needs to be long enough that all particles have time to reach the outer wall. The walls of the 3D printed tube have a ribbed texture due to the printing method. The ribs are much larger than the virus particles and would probably do a lot of damage to the delicate particles as they tumble along the wall, so not only should the device produce clean air, any virus in the dirty air (which should be all virus particles) is likely very damaged. Research would be needed to determine what speeds work, if the concept works on the virus at all and whether the walls damage virus particles.

Here is a video showing the concept:

I hope these ideas inspire others to make useful items to combat Covid-19.

I had one other idea for a low cost mask - it is described here:

Corona Cap

 

Stay safe and consider others ....

Anonymous
Parents

  • Doug, you've lost some zeroes in your air breakdown sums: breakdown voltage for air is 3kV/mm.

    I have several insect killers which use the voltage between wires principle - they work OK for creatures with wingspan down to 10 - 20% of the wire gap - a virus zapper would need 1 micron spacing which is not practical.

     

    MK

Comment

  • Doug, you've lost some zeroes in your air breakdown sums: breakdown voltage for air is 3kV/mm.

    I have several insect killers which use the voltage between wires principle - they work OK for creatures with wingspan down to 10 - 20% of the wire gap - a virus zapper would need 1 micron spacing which is not practical.

     

    MK

Children
  • in reply to michaelkellett

    Thanks, I missed the k - fixed it above.

    I ran a shop that built sub-atomic particle detectors for CERN using a somewhat similar principle. Stringing the wires was a very specialized precision process, so it was not easy, but it was possible in those machines where the spacing wasn't at the submicron level, but the accuracy of placement had to be submicron. The trick would be to set the voltage so close to the breakdown voltage that any small particle would cause an avalanche breakdown.

    I hesitated to put this idea in because I know it would be tough to achieve in a garage operation, but clever people can do amazing things.

  • in reply to dougw

    The viral particle has a diameter of 120 nm, if the breakdown voltage of air is 3 kv/mm, at 120 nm you would get a breakdown voltage of 0.36 V, so you would have to supply <~0.36 V over the breakdown voltage to your wires. Also, considering that air composition/humidity changes all the time, and that using parallel wires would have to be parallel at nm scale, and also considering that ozone is toxic, and probably other sideproducts of arcing as well, I don't think its good idea.

     

    Crushing viral particles may also be harder than what you think, you may end up crushing and pulverizing your "germ pulverizing", and breathing these particles may be quite harmful. Also, at such small scale stuff behaves very differently, so particles may still be able to cross or not get damaged at all.

     

    The centrifuge may also suffer from the same issues as the pulverizer.

     

    The heater on the other side looks like an effective alternative, but would need some research to figure out what the minimum temperature to destroy the particles is. In terms of power requirement some calculations can be done. We need to compute how much power is require to heat the air breathing rate over the temperature that would destroy the particles. Let me toss some quick numbers:

     

    Constant-pressure specific heat of air: 1004.68506 J/(kg·K)

    A normal minute volume while resting is about 5–8 L/min in humans.

    At 1013.25 hPa (abs) and 15°C, air has a density of approximately 1.225 kg/m3

     

    Lets convert units to MKS:

     

    Specific heat: 1.004 J/(g·K)

    Breathing rate: 1.333E-4 m3/s (8 L/min)

    Density: 1225 g/m3

     

    To increase the temperature of air at a breathing rate by 1°K we need: 1.004 * (1.333E-4) * 1225 =  ~0.164 W.  This is quite a bit, we could make the system more efficient through passive cooling and using a peltier to do the heating (> 100% efficiency), but still would require quite a bit of power.

  • in reply to neuromodulator

    All good points. All of these ideas would need testing and development. There are certainly engineering challenges and possibly even some physics limitations. It is tough to explain a complete system in a paragraph of text. After all, the underlying theory resulted in about 5 Nobel prizes which were awarded for techniques of using sub-atomic particles to cause avalanche breakdown between conductors.

    A few more notes on the germ zapper idea:

    In this case the wires would be close together and would result in sparks less than 1 mm, Such sparks would probably not be noticeable to the human eye. I expect it would be extremely difficult to even measure the amount of ozone created by a few hundred sparks. The spark however is actually white hot air (plasma?)

    If this spark envelops a virus particle, it is only a question if it lasts long enough to impart enough energy to toast the virus particle, but since the spark (arc) will last as long as there is current available, this is an easy criterion to meet.

    This theory may not work, but it is far from clear that it won't work.

    We have all seen that it is possible to generate a visible spark in air as you short out a 9V battery, and 24V or even 12V can be used for arc welding. The 9V spark is probably way more spark than is needed. If we really want a bigger spark, we all know that spark plug technology is pretty routine.

    The bigger question in my mind is how hard is it to create a system that is sensitive enough for a virus particle to trigger a spark with tight enough tolerance that it won't create a bunch of spurious sparks. Although a few spurious sparks are not a big issue, the tolerance issue is just an engineering challenge, probably not a physics limitation. There are lots of issues to deal with when designing a practical system, but it rapidly gets to be a pretty big dissertation to deal with all of them. If you think of an issue, it would be fun to hear about how you would solve it.